diff --git a/Microsoft.Dotnet.Wpf.sln b/Microsoft.Dotnet.Wpf.sln
index 712d90ca334..d79c7150d1c 100644
--- a/Microsoft.Dotnet.Wpf.sln
+++ b/Microsoft.Dotnet.Wpf.sln
@@ -252,6 +252,7 @@ EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "PresentationFramework.Fluent", "src\Microsoft.DotNet.Wpf\src\Themes\PresentationFramework.Fluent\PresentationFramework.Fluent.csproj", "{3F2C0E0E-BB13-46D9-8D9A-08256A49ECA9}"
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "PresentationFramework.Fluent-ref", "src\Microsoft.DotNet.Wpf\src\Themes\PresentationFramework.Fluent\ref\PresentationFramework.Fluent-ref.csproj", "{3C43C553-2C1F-4EB9-8BF8-371D4A42E0FD}"
+Project("{6FFF8BB3-74D1-4860-BEF1-5B307BCDBB95}") = "WindowsBase.Tests", "src\Microsoft.DotNet.Wpf\tests\UnitTests\WindowsBase.Tests\WindowsBase.Tests.csproj", "{A5DC575D-EC10-445B-94C1-98015F926FFA}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
@@ -1978,6 +1979,28 @@ Global
 		{3C43C553-2C1F-4EB9-8BF8-371D4A42E0FD}.Release|x64.Build.0 = Release|x64
 		{3C43C553-2C1F-4EB9-8BF8-371D4A42E0FD}.Release|x86.ActiveCfg = Release|Any CPU
 		{3C43C553-2C1F-4EB9-8BF8-371D4A42E0FD}.Release|x86.Build.0 = Release|Any CPU
+		{A5DC575D-EC10-445B-94C1-98015F926FFA}.Debug|Any CPU.ActiveCfg = Debug|Win32
+		{A5DC575D-EC10-445B-94C1-98015F926FFA}.Debug|Any CPU.Build.0 = Debug|Win32
+		{A5DC575D-EC10-445B-94C1-98015F926FFA}.Debug|Any CPU.Deploy.0 = Debug|Win32
+		{A5DC575D-EC10-445B-94C1-98015F926FFA}.Debug|ARM64.ActiveCfg = Debug|ARM64
+		{A5DC575D-EC10-445B-94C1-98015F926FFA}.Debug|ARM64.Build.0 = Debug|ARM64
+		{A5DC575D-EC10-445B-94C1-98015F926FFA}.Debug|x64.ActiveCfg = Debug|x64
+		{A5DC575D-EC10-445B-94C1-98015F926FFA}.Debug|x64.Build.0 = Debug|x64
+		{A5DC575D-EC10-445B-94C1-98015F926FFA}.Debug|x64.Deploy.0 = Debug|x64
+		{A5DC575D-EC10-445B-94C1-98015F926FFA}.Debug|x86.ActiveCfg = Debug|Win32
+		{A5DC575D-EC10-445B-94C1-98015F926FFA}.Debug|x86.Build.0 = Debug|Win32
+		{A5DC575D-EC10-445B-94C1-98015F926FFA}.Debug|x86.Deploy.0 = Debug|Win32
+		{A5DC575D-EC10-445B-94C1-98015F926FFA}.Release|Any CPU.ActiveCfg = Release|Win32
+		{A5DC575D-EC10-445B-94C1-98015F926FFA}.Release|Any CPU.Build.0 = Release|Win32
+		{A5DC575D-EC10-445B-94C1-98015F926FFA}.Release|Any CPU.Deploy.0 = Release|Win32
+		{A5DC575D-EC10-445B-94C1-98015F926FFA}.Release|ARM64.ActiveCfg = Release|ARM64
+		{A5DC575D-EC10-445B-94C1-98015F926FFA}.Release|ARM64.Build.0 = Release|ARM64
+		{A5DC575D-EC10-445B-94C1-98015F926FFA}.Release|x64.ActiveCfg = Release|x64
+		{A5DC575D-EC10-445B-94C1-98015F926FFA}.Release|x64.Build.0 = Release|x64
+		{A5DC575D-EC10-445B-94C1-98015F926FFA}.Release|x64.Deploy.0 = Release|x64
+		{A5DC575D-EC10-445B-94C1-98015F926FFA}.Release|x86.ActiveCfg = Release|Win32
+		{A5DC575D-EC10-445B-94C1-98015F926FFA}.Release|x86.Build.0 = Release|Win32
+		{A5DC575D-EC10-445B-94C1-98015F926FFA}.Release|x86.Deploy.0 = Release|Win32
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -2100,6 +2123,7 @@ Global
 		{B2F2A89C-55C9-41B1-A645-0948609BD8BE} = {A48B585E-6AB0-4F8D-8484-77F37CB44437}
 		{3F2C0E0E-BB13-46D9-8D9A-08256A49ECA9} = {5ACFB055-649D-4A01-98C2-B0BFE7E543D6}
 		{3C43C553-2C1F-4EB9-8BF8-371D4A42E0FD} = {60F4058B-D35B-42D2-B276-D44B3AC579BD}
+		{A5DC575D-EC10-445B-94C1-98015F926FFA} = {A48B585E-6AB0-4F8D-8484-77F37CB44437}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {B4340004-DAC0-497D-B69D-CFA7CD93F567}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/Helpers.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/Helpers.cs
new file mode 100644
index 00000000000..3f9646d19ed
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/Helpers.cs
@@ -0,0 +1,125 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Specialized;
+using System.ComponentModel;
+using System.IO;
+using System.Runtime.ExceptionServices;
+using System.Text;
+using System.Threading;
+using System.Windows;
+using System.Windows.Media;
+using Xunit.Sdk;
+
+public static class Helpers
+{
+#pragma warning disable xUnit1013
+    public static string GetResourcePath(string name) => Path.GetFullPath(Path.Combine("Resources", name));
+
+    public static void ExecuteOnDifferentThread(Action action, ApartmentState? state = null)
+    {
+        ExceptionDispatchInfo? edi = null;
+        var t = new Thread(() =>
+        {
+            try
+            {
+                action();
+            }
+            catch (Exception e)
+            {
+                edi = ExceptionDispatchInfo.Capture(e);
+            }
+        });
+        if (state is not null)
+        {
+            t.SetApartmentState(state.Value);
+        }
+        t.Start();
+        t.Join();
+
+        if (edi is not null)
+        {
+            edi.Throw();
+        }
+    }
+    
+    public static T ExecuteOnDifferentThread<T>(Func<T> action, ApartmentState? state = null)
+    {
+        T? result = default;
+        ExceptionDispatchInfo? edi = null;
+        var t = new Thread(() =>
+        {
+            try
+            {
+                result = action();
+            }
+            catch (Exception e)
+            {
+                edi = ExceptionDispatchInfo.Capture(e);
+            }
+        });
+        if (state is not null)
+        {
+            t.SetApartmentState(state.Value);
+        }
+        t.Start();
+        t.Join();
+
+        if (edi is not null)
+        {
+            edi.Throw();
+            throw new Exception("Not reachable.");
+        }
+        else
+        {
+            return result!;
+        }
+    }
+    
+    public static void AssertEqualRounded(Matrix expected, Matrix actual, int precision = 5)
+    {
+        if (expected.Equals(actual))
+        {
+            return;
+        }
+
+        try
+        {
+            Assert.Equal(expected.M11, actual.M11, precision);
+            Assert.Equal(expected.M12, actual.M12, precision);
+            Assert.Equal(expected.M21, actual.M21, precision);
+            Assert.Equal(expected.M22, actual.M22, precision);
+            Assert.Equal(expected.OffsetX, actual.OffsetX, precision);
+            Assert.Equal(expected.OffsetY, actual.OffsetY, precision);
+        }
+        catch (Exception)
+        {
+            // Throw main AssertException with formatting.
+            //Assert.Equal(expected, actual);
+        }
+    }
+
+    public static void AssertEqualRounded(Rect expected, Rect actual, int precision)
+    {
+        if (expected.Equals(actual))
+        {
+            return;
+        }
+
+        try
+        {
+            Assert.Equal(expected.X, actual.X, precision);
+            Assert.Equal(expected.Y, actual.Y, precision);
+            Assert.Equal(expected.Width, actual.Width, precision);
+            Assert.Equal(expected.Height, actual.Height, precision);
+        }
+        catch (Exception)
+        {
+            // Throw main AssertException with formatting.
+            Assert.Equal(expected, actual);
+        }
+    }
+#pragma warning restore xUnit1013
+}
\ No newline at end of file
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Collections/Specialized/CollectionChangedEventManagerTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Collections/Specialized/CollectionChangedEventManagerTests.cs
new file mode 100644
index 00000000000..14782fcea44
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Collections/Specialized/CollectionChangedEventManagerTests.cs
@@ -0,0 +1,574 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Windows;
+
+namespace System.Collections.Specialized.Tests;
+
+public class CollectionChangedEventManagerTests
+{
+    public static IEnumerable<object?[]> AddHandler_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset) };
+    }
+
+    [Theory]
+    [MemberData(nameof(AddHandler_TestData))]
+    public void AddHandler_InvokeWithHandler_CallsCollectionChanged(NotifyCollectionChangedEventArgs e)
+    {
+        var source = new CustomNotifyCollectionChanged();
+        int callCount1 = 0;
+        var listener1 = new CustomWeakEventListener();
+        listener1.HandlerAction += (actualSender, actualE) =>
+        {
+            Assert.Same(source, actualSender);
+            Assert.Same(e, actualE);
+            callCount1++;
+        };
+        EventHandler<NotifyCollectionChangedEventArgs> handler1 = (EventHandler<NotifyCollectionChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<NotifyCollectionChangedEventArgs>), listener1, nameof(CustomWeakEventListener.Handler));
+        int callCount2 = 0;
+        var listener2 = new CustomWeakEventListener();
+        listener2.HandlerAction += (actualSender, actualE) =>
+        {
+            Assert.Same(source, actualSender);
+            Assert.Same(e, actualE);
+            callCount2++;
+        };
+        EventHandler<NotifyCollectionChangedEventArgs> handler2 = (EventHandler<NotifyCollectionChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<NotifyCollectionChangedEventArgs>), listener2, nameof(CustomWeakEventListener.Handler));
+
+        // Add.
+        CollectionChangedEventManager.AddHandler(source, handler1);
+
+        // Call.
+        source.OnCollectionChanged(source, e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Call invalid source.
+        source.OnCollectionChanged(listener1, e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        
+        source.OnCollectionChanged(new object(), e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        
+        source.OnCollectionChanged(null!, e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Add again.
+        CollectionChangedEventManager.AddHandler(source, handler1);
+        source.OnCollectionChanged(source, e);
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Add another.
+        CollectionChangedEventManager.AddHandler(source, handler2);
+        source.OnCollectionChanged(source, e);
+        Assert.Equal(5, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove second.
+        CollectionChangedEventManager.RemoveHandler(source, handler2);
+        source.OnCollectionChanged(source, e);
+        Assert.Equal(7, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove first.
+        CollectionChangedEventManager.RemoveHandler(source, handler1);
+        source.OnCollectionChanged(source, e);
+        Assert.Equal(8, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove again.
+        CollectionChangedEventManager.RemoveHandler(source, handler1);
+        source.OnCollectionChanged(source, e);
+        Assert.Equal(8, callCount1);
+        Assert.Equal(1, callCount2);
+    }
+
+    [Fact]
+    public void AddHandler_InvokeMultipleTimes_Success()
+    {
+        var source1 = new CustomNotifyCollectionChanged();
+        var source2 = new CustomNotifyCollectionChanged();
+        var target1 = new CustomWeakEventListener();
+        int callCount1 = 0;
+        target1.HandlerAction += (actualSender, actualE) => callCount1++;
+        EventHandler<NotifyCollectionChangedEventArgs> handler1 = (EventHandler<NotifyCollectionChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<NotifyCollectionChangedEventArgs>), target1, nameof(CustomWeakEventListener.Handler));
+        var target2 = new CustomWeakEventListener();
+        int callCount2 = 0;
+        target2.HandlerAction += (actualSender, actualE) => callCount2++;
+        EventHandler<NotifyCollectionChangedEventArgs> handler2 = (EventHandler<NotifyCollectionChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<NotifyCollectionChangedEventArgs>), target2, nameof(CustomWeakEventListener.Handler));
+        var target3 = new CustomWeakEventListener();
+        int callCount3 = 0;
+        target3.HandlerAction += (actualSender, actualE) => callCount3++;
+        EventHandler<NotifyCollectionChangedEventArgs> handler3 = (EventHandler<NotifyCollectionChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<NotifyCollectionChangedEventArgs>), target3, nameof(CustomWeakEventListener.Handler));
+
+        // Add.
+        CollectionChangedEventManager.AddHandler(source1, handler1);
+        source1.OnCollectionChanged(source1, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        source2.OnCollectionChanged(source2, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+
+        // Add again.
+        CollectionChangedEventManager.AddHandler(source1, handler1);
+        source1.OnCollectionChanged(source1, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        source2.OnCollectionChanged(source2, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+
+        // Add another handler.
+        CollectionChangedEventManager.AddHandler(source1, handler2);
+        source1.OnCollectionChanged(source1, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(5, callCount1);
+        Assert.Equal(1, callCount2);
+        Assert.Equal(0, callCount3);
+        source2.OnCollectionChanged(source2, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(5, callCount1);
+        Assert.Equal(1, callCount2);
+        Assert.Equal(0, callCount3);
+
+        // Add another source.
+        CollectionChangedEventManager.AddHandler(source2, handler3);
+        source1.OnCollectionChanged(source1, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(7, callCount1);
+        Assert.Equal(2, callCount2);
+        Assert.Equal(0, callCount3);
+        source2.OnCollectionChanged(source2, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(7, callCount1);
+        Assert.Equal(2, callCount2);
+        Assert.Equal(1, callCount3);
+    }
+
+    [Fact]
+    public void AddHandler_InvokeNoSource_Success()
+    {
+        var target1 = new CustomWeakEventListener();
+        EventHandler<NotifyCollectionChangedEventArgs> handler1 = (EventHandler<NotifyCollectionChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<NotifyCollectionChangedEventArgs>), target1, nameof(CustomWeakEventListener.Handler));
+        var target2 = new CustomWeakEventListener();
+        EventHandler<NotifyCollectionChangedEventArgs> handler2 = (EventHandler<NotifyCollectionChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<NotifyCollectionChangedEventArgs>), target2, nameof(CustomWeakEventListener.Handler));
+
+        // Add.
+        Assert.Throws<NullReferenceException>(() => CollectionChangedEventManager.AddHandler(null, handler1));
+
+        // Add again.
+        CollectionChangedEventManager.AddHandler(null, handler1);
+
+        // Add another.
+        CollectionChangedEventManager.AddHandler(null, handler2);
+    }
+
+    [Fact]
+    public void AddHandler_NullHandler_ThrowsArgumentNullException()
+    {
+        var source = new CustomNotifyCollectionChanged();
+        Assert.Throws<ArgumentNullException>("handler", () => CollectionChangedEventManager.AddHandler(null, null));
+        Assert.Throws<ArgumentNullException>("handler", () => CollectionChangedEventManager.AddHandler(source, null));
+    }
+
+    public static IEnumerable<object?[]> AddListener_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset) };
+    }
+
+    [Theory]
+    [MemberData(nameof(AddListener_TestData))]
+    public void AddListener_InvokeWithHandler_CallsCollectionChanged(NotifyCollectionChangedEventArgs e)
+    {
+        var source = new CustomNotifyCollectionChanged();
+        int callCount1 = 0;
+        var listener1 = new CustomWeakEventListener();
+        listener1.ReceiveWeakEventAction += (actualManagerType, actualSender, actualE) =>
+        {
+            Assert.Equal(typeof(CollectionChangedEventManager), actualManagerType);
+            Assert.Same(source, actualSender);
+            Assert.Same(e, actualE);
+            callCount1++;
+            return true;
+        };
+        int callCount2 = 0;
+        var listener2 = new CustomWeakEventListener();
+        listener2.ReceiveWeakEventAction += (actualManagerType, actualSender, actualE) =>
+        {
+            Assert.Equal(typeof(CollectionChangedEventManager), actualManagerType);
+            Assert.Same(source, actualSender);
+            Assert.Same(e, actualE);
+            callCount2++;
+            return true;
+        };
+
+        // Add.
+        CollectionChangedEventManager.AddListener(source, listener1);
+
+        // Call.
+        source.OnCollectionChanged(source, e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Call invalid source.
+        source.OnCollectionChanged(listener1, e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        
+        source.OnCollectionChanged(new object(), e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        
+        source.OnCollectionChanged(null!, e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Add again.
+        CollectionChangedEventManager.AddListener(source, listener1);
+        source.OnCollectionChanged(source, e);
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Add another.
+        CollectionChangedEventManager.AddListener(source, listener2);
+        source.OnCollectionChanged(source, e);
+        Assert.Equal(5, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove second.
+        CollectionChangedEventManager.RemoveListener(source, listener2);
+        source.OnCollectionChanged(source, e);
+        Assert.Equal(7, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove first.
+        CollectionChangedEventManager.RemoveListener(source, listener1);
+        source.OnCollectionChanged(source, e);
+        Assert.Equal(8, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove again.
+        CollectionChangedEventManager.RemoveListener(source, listener1);
+        source.OnCollectionChanged(source, e);
+        Assert.Equal(8, callCount1);
+        Assert.Equal(1, callCount2);
+    }
+
+    [Fact]
+    public void AddListener_InvokeMultipleTimes_Success()
+    {
+        var source1 = new CustomNotifyCollectionChanged();
+        var source2 = new CustomNotifyCollectionChanged();
+        var listener1 = new CustomWeakEventListener();
+        int callCount1 = 0;
+        listener1.ReceiveWeakEventAction += (t, s, e) =>
+        {
+            callCount1++;
+            return true;
+        };
+        var listener2 = new CustomWeakEventListener();
+        int callCount2 = 0;
+        listener2.ReceiveWeakEventAction += (t, s, e) =>
+        {
+            callCount2++;
+            return true;
+        };
+        var listener3 = new CustomWeakEventListener();
+        int callCount3 = 0;
+        listener3.ReceiveWeakEventAction += (t, s, e) =>
+        {
+            callCount3++;
+            return true;
+        };
+
+        // Add.
+        CollectionChangedEventManager.AddListener(source1, listener1);
+        source1.OnCollectionChanged(source1, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        source2.OnCollectionChanged(source2, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+
+        // Add again.
+        CollectionChangedEventManager.AddListener(source1, listener1);
+        source1.OnCollectionChanged(source1, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        source2.OnCollectionChanged(source2, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+
+        // Add another listener.
+        CollectionChangedEventManager.AddListener(source1, listener2);
+        source1.OnCollectionChanged(source1, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(5, callCount1);
+        Assert.Equal(1, callCount2);
+        Assert.Equal(0, callCount3);
+        source2.OnCollectionChanged(source2, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(5, callCount1);
+        Assert.Equal(1, callCount2);
+        Assert.Equal(0, callCount3);
+
+        // Add another source.
+        CollectionChangedEventManager.AddListener(source2, listener3);
+        source1.OnCollectionChanged(source1, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(7, callCount1);
+        Assert.Equal(2, callCount2);
+        Assert.Equal(0, callCount3);
+        source2.OnCollectionChanged(source2, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(7, callCount1);
+        Assert.Equal(2, callCount2);
+        Assert.Equal(1, callCount3);
+    }
+
+    [Fact]
+    public void AddListener_NullSource_ThrowsArgumentNullException()
+    {
+        var listener = new CustomWeakEventListener();
+        Assert.Throws<ArgumentNullException>("source", () => CollectionChangedEventManager.AddListener(null, listener));
+    }
+
+    [Fact]
+    public void AddListener_NullListener_ThrowsArgumentNullException()
+    {
+        var source = new CustomNotifyCollectionChanged();
+        Assert.Throws<ArgumentNullException>("listener", () => CollectionChangedEventManager.AddListener(source, null));
+    }
+
+    [Fact]
+    public void RemoveHandler_Invoke_Success()
+    {
+        var source = new CustomNotifyCollectionChanged();
+        var target = new CustomWeakEventListener();
+        int callCount = 0;
+        target.HandlerAction += (actualSender, actualE) => callCount++;
+        EventHandler<NotifyCollectionChangedEventArgs> handler = (EventHandler<NotifyCollectionChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<NotifyCollectionChangedEventArgs>), target, nameof(CustomWeakEventListener.Handler));
+        CollectionChangedEventManager.AddHandler(source, handler);
+
+        // Remove.
+        CollectionChangedEventManager.RemoveHandler(source, handler);
+        source.OnCollectionChanged(source, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(0, callCount);
+
+        // Remove again.
+        CollectionChangedEventManager.RemoveHandler(source, handler);
+        source.OnCollectionChanged(source, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void RemoveHandler_InvokeNoSource_Success()
+    {
+        var target = new CustomWeakEventListener();
+        EventHandler<NotifyCollectionChangedEventArgs> handler = (EventHandler<NotifyCollectionChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<NotifyCollectionChangedEventArgs>), target, nameof(CustomWeakEventListener.Handler));
+        CollectionChangedEventManager.AddHandler(null, handler);
+
+        // Remove.
+        CollectionChangedEventManager.RemoveHandler(null, handler);
+
+        // Remove again.
+        CollectionChangedEventManager.RemoveHandler(null, handler);
+    }
+
+    [Fact]
+    public void RemoveHandler_InvokeNoSuchSource_Nop()
+    {
+        var source1 = new CustomNotifyCollectionChanged();
+        var source2 = new CustomNotifyCollectionChanged();
+        var target = new CustomWeakEventListener();
+        int callCount = 0;
+        target.HandlerAction += (actualSender, actualE) => callCount++;
+        EventHandler<NotifyCollectionChangedEventArgs> handler = (EventHandler<NotifyCollectionChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<NotifyCollectionChangedEventArgs>), target, nameof(CustomWeakEventListener.Handler));
+        CollectionChangedEventManager.AddHandler(source1, handler);
+
+        // Remove.
+        CollectionChangedEventManager.RemoveHandler(source2, handler);
+        source1.OnCollectionChanged(source1, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(1, callCount);
+        source2.OnCollectionChanged(source2, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(1, callCount);
+
+        // Remove again.
+        CollectionChangedEventManager.RemoveHandler(source2, handler);
+        source1.OnCollectionChanged(source1, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(2, callCount);
+        source2.OnCollectionChanged(source2, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void RemoveHandler_InvokeNoSuchHandler_Nop()
+    {
+        var source = new CustomNotifyCollectionChanged();
+        var target1 = new CustomWeakEventListener();
+        int callCount1 = 0;
+        target1.HandlerAction += (actualSender, actualE) => callCount1++;
+        EventHandler<NotifyCollectionChangedEventArgs> handler1 = (EventHandler<NotifyCollectionChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<NotifyCollectionChangedEventArgs>), target1, nameof(CustomWeakEventListener.Handler));
+        var target2 = new CustomWeakEventListener();
+        int callCount2 = 0;
+        target2.HandlerAction += (actualSender, actualE) => callCount2++;
+        EventHandler<NotifyCollectionChangedEventArgs> handler2 = (EventHandler<NotifyCollectionChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<NotifyCollectionChangedEventArgs>), target2, nameof(CustomWeakEventListener.Handler));
+        CollectionChangedEventManager.AddHandler(source, handler1);
+
+        // Remove.
+        CollectionChangedEventManager.RemoveHandler(source, handler2);
+        source.OnCollectionChanged(source, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Remove again.
+        CollectionChangedEventManager.RemoveHandler(source, handler2);
+        source.OnCollectionChanged(source, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(2, callCount1);
+        Assert.Equal(0, callCount2);
+    }
+
+    [Fact]
+    public void RemoveHandler_NullHandler_ThrowsArgumentNullException()
+    {
+        var source = new CustomNotifyCollectionChanged();
+        Assert.Throws<ArgumentNullException>("handler", () => CollectionChangedEventManager.RemoveHandler(null, null));
+        Assert.Throws<ArgumentNullException>("handler", () => CollectionChangedEventManager.RemoveHandler(source, null));
+    }
+
+    [Fact]
+    public void RemoveListener_Invoke_Success()
+    {
+        var source = new CustomNotifyCollectionChanged();
+        var listener = new CustomWeakEventListener();
+        int callCount = 0;
+        listener.ReceiveWeakEventAction += (t, s, e) =>
+        {
+            callCount++;
+            return true;
+        };
+        CollectionChangedEventManager.AddListener(source, listener);
+
+        // Remove.
+        CollectionChangedEventManager.RemoveListener(source, listener);
+        source.OnCollectionChanged(source, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(0, callCount);
+
+        // Remove again.
+        CollectionChangedEventManager.RemoveListener(source, listener);
+        source.OnCollectionChanged(source, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void RemoveListener_InvokeNoSuchSource_Nop()
+    {
+        var source1 = new CustomNotifyCollectionChanged();
+        var source2 = new CustomNotifyCollectionChanged();
+        var listener = new CustomWeakEventListener();
+        int callCount = 0;
+        listener.ReceiveWeakEventAction += (t, s, e) =>
+        {
+            callCount++;
+            return true;
+        };
+        CollectionChangedEventManager.AddListener(source1, listener);
+
+        // Remove.
+        CollectionChangedEventManager.RemoveListener(source2, listener);
+        source1.OnCollectionChanged(source1, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(1, callCount);
+        source2.OnCollectionChanged(source2, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(1, callCount);
+
+        // Remove again.
+        CollectionChangedEventManager.RemoveListener(source2, listener);
+        source1.OnCollectionChanged(source1, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(2, callCount);
+        source2.OnCollectionChanged(source2, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void RemoveListener_InvokeNoSuchListener_Nop()
+    {
+        var source = new CustomNotifyCollectionChanged();
+        var listener1 = new CustomWeakEventListener();
+        int callCount1 = 0;
+        listener1.ReceiveWeakEventAction += (t, s, e) =>
+        {
+            callCount1++;
+            return true;
+        };
+        var listener2 = new CustomWeakEventListener();
+        int callCount2 = 0;
+        listener2.ReceiveWeakEventAction += (t, s, e) =>
+        {
+            callCount2++;
+            return true;
+        };
+        CollectionChangedEventManager.AddListener(source, listener1);
+
+        // Remove.
+        CollectionChangedEventManager.RemoveListener(source, listener2);
+        source.OnCollectionChanged(source, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Remove again.
+        CollectionChangedEventManager.RemoveListener(source, listener2);
+        source.OnCollectionChanged(source, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        Assert.Equal(2, callCount1);
+        Assert.Equal(0, callCount2);
+    }
+
+    [Fact]
+    public void RemoveListener_NullListener_ThrowsArgumentNullException()
+    {
+        var source = new CustomNotifyCollectionChanged();
+        Assert.Throws<ArgumentNullException>("listener", () => CollectionChangedEventManager.RemoveListener(source, null));
+    }
+
+    private class CustomNotifyCollectionChanged : INotifyCollectionChanged
+    {
+        #pragma warning disable CS0067
+        public event NotifyCollectionChangedEventHandler? CollectionChanged;
+        #pragma warning restore CS0067
+
+        public void OnCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
+        {
+            CollectionChanged?.Invoke(sender, e);
+        }
+    }
+
+    private class CustomWeakEventListener : IWeakEventListener
+    {
+        public Func<Type, object, EventArgs, bool>? ReceiveWeakEventAction { get; set; }
+
+        public bool ReceiveWeakEvent(Type managerType, object sender, EventArgs e)
+        {
+            if (ReceiveWeakEventAction is null)
+            {
+                return true;
+            }
+
+            return ReceiveWeakEventAction(managerType, sender, e);
+        }
+
+        public Action<object, NotifyCollectionChangedEventArgs>? HandlerAction { get; set; }
+
+        public void Handler(object sender, NotifyCollectionChangedEventArgs e)
+        {
+            HandlerAction?.Invoke(sender, e);
+        }
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/CurrentChangedEventManagerTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/CurrentChangedEventManagerTests.cs
new file mode 100644
index 00000000000..751f7b6d389
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/CurrentChangedEventManagerTests.cs
@@ -0,0 +1,633 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections;
+using System.Collections.ObjectModel;
+using System.Collections.Specialized;
+using System.Globalization;
+using System.Windows;
+
+namespace System.ComponentModel.Tests;
+
+public class CurrentChangedEventManagerTests
+{
+    public static IEnumerable<object?[]> AddHandler_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { new EventArgs() };
+        yield return new object?[] { EventArgs.Empty };
+    }
+
+    [Theory]
+    [MemberData(nameof(AddHandler_TestData))]
+    public void AddHandler_InvokeWithHandler_CallsCurrentChanged(EventArgs e)
+    {
+        var source = new CustomCollectionView();
+        int callCount1 = 0;
+        var listener1 = new CustomWeakEventListener();
+        listener1.HandlerAction += (actualSender, actualE) =>
+        {
+            Assert.Same(source, actualSender);
+            Assert.Same(e, actualE);
+            callCount1++;
+        };
+        EventHandler<EventArgs> handler1 = (EventHandler<EventArgs>)Delegate.CreateDelegate(typeof(EventHandler<EventArgs>), listener1, nameof(CustomWeakEventListener.Handler));
+        int callCount2 = 0;
+        var listener2 = new CustomWeakEventListener();
+        listener2.HandlerAction += (actualSender, actualE) =>
+        {
+            Assert.Same(source, actualSender);
+            Assert.Same(e, actualE);
+            callCount2++;
+        };
+        EventHandler<EventArgs> handler2 = (EventHandler<EventArgs>)Delegate.CreateDelegate(typeof(EventHandler<EventArgs>), listener2, nameof(CustomWeakEventListener.Handler));
+
+        // Add.
+        CurrentChangedEventManager.AddHandler(source, handler1);
+
+        // Call.
+        source.OnCurrentChanged(source, e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Call invalid source.
+        source.OnCurrentChanged(listener1, e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        
+        source.OnCurrentChanged(new object(), e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        
+        source.OnCurrentChanged(null!, e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Add again.
+        CurrentChangedEventManager.AddHandler(source, handler1);
+        source.OnCurrentChanged(source, e);
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Add another.
+        CurrentChangedEventManager.AddHandler(source, handler2);
+        source.OnCurrentChanged(source, e);
+        Assert.Equal(5, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove second.
+        CurrentChangedEventManager.RemoveHandler(source, handler2);
+        source.OnCurrentChanged(source, e);
+        Assert.Equal(7, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove first.
+        CurrentChangedEventManager.RemoveHandler(source, handler1);
+        source.OnCurrentChanged(source, e);
+        Assert.Equal(8, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove again.
+        CurrentChangedEventManager.RemoveHandler(source, handler1);
+        source.OnCurrentChanged(source, e);
+        Assert.Equal(8, callCount1);
+        Assert.Equal(1, callCount2);
+    }
+
+    [Fact]
+    public void AddHandler_Invoke_Success()
+    {
+        var source1 = new CustomCollectionView();
+        var source2 = new CustomCollectionView();
+        var target1 = new CustomWeakEventListener();
+        int callCount1 = 0;
+        target1.HandlerAction += (sender, e) => callCount1++;
+        EventHandler<EventArgs> handler1 = (EventHandler<EventArgs>)Delegate.CreateDelegate(typeof(EventHandler<EventArgs>), target1, nameof(CustomWeakEventListener.Handler));
+        var target2 = new CustomWeakEventListener();
+        int callCount2 = 0;
+        target2.HandlerAction += (sender, e) => callCount2++;
+        EventHandler<EventArgs> handler2 = (EventHandler<EventArgs>)Delegate.CreateDelegate(typeof(EventHandler<EventArgs>), target2, nameof(CustomWeakEventListener.Handler));
+        int callCount3 = 0;
+        var target3 = new CustomWeakEventListener();
+        target3.HandlerAction += (sender, e) => callCount3++;
+        EventHandler<EventArgs> handler3 = (EventHandler<EventArgs>)Delegate.CreateDelegate(typeof(EventHandler<EventArgs>), target3, nameof(CustomWeakEventListener.Handler));
+
+        // Add.
+        CurrentChangedEventManager.AddHandler(source1, handler1);
+        source1.OnCurrentChanged(source1, EventArgs.Empty);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        source2.OnCurrentChanged(source2, EventArgs.Empty);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+
+        // Add again.
+        CurrentChangedEventManager.AddHandler(source1, handler1);
+        source1.OnCurrentChanged(source1, EventArgs.Empty);
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        source2.OnCurrentChanged(source2, EventArgs.Empty);
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+
+        // Add another handler.
+        CurrentChangedEventManager.AddHandler(source1, handler2);
+        source1.OnCurrentChanged(source1, EventArgs.Empty);
+        Assert.Equal(5, callCount1);
+        Assert.Equal(1, callCount2);
+        Assert.Equal(0, callCount3);
+        source2.OnCurrentChanged(source2, EventArgs.Empty);
+        Assert.Equal(5, callCount1);
+        Assert.Equal(1, callCount2);
+        Assert.Equal(0, callCount3);
+
+        // Add another source.
+        CurrentChangedEventManager.AddHandler(source2, handler3);
+        source1.OnCurrentChanged(source1, EventArgs.Empty);
+        Assert.Equal(7, callCount1);
+        Assert.Equal(2, callCount2);
+        Assert.Equal(0, callCount3);
+        source2.OnCurrentChanged(source2, EventArgs.Empty);
+        Assert.Equal(7, callCount1);
+        Assert.Equal(2, callCount2);
+        Assert.Equal(1, callCount3);
+    }
+
+    [Fact]
+    public void AddHandler_InvokeNoSource_Success()
+    {
+        var target1 = new CustomWeakEventListener();
+        EventHandler<EventArgs> handler1 = (EventHandler<EventArgs>)Delegate.CreateDelegate(typeof(EventHandler<EventArgs>), target1, nameof(CustomWeakEventListener.Handler));
+        var target2 = new CustomWeakEventListener();
+        EventHandler<EventArgs> handler2 = (EventHandler<EventArgs>)Delegate.CreateDelegate(typeof(EventHandler<EventArgs>), target2, nameof(CustomWeakEventListener.Handler));
+
+        // Add.
+        Assert.Throws<NullReferenceException>(() => CurrentChangedEventManager.AddHandler(null, handler1));
+
+        // Add again.
+        CurrentChangedEventManager.AddHandler(null, handler1);
+
+        // Add another.
+        CurrentChangedEventManager.AddHandler(null, handler2);
+    }
+
+    [Fact]
+    public void AddHandler_NullHandler_ThrowsArgumentNullException()
+    {
+        var source = new CustomCollectionView();
+        Assert.Throws<ArgumentNullException>("handler", () => CurrentChangedEventManager.AddHandler(null, null));
+        Assert.Throws<ArgumentNullException>("handler", () => CurrentChangedEventManager.AddHandler(source, null));
+    }
+
+    public static IEnumerable<object?[]> AddListener_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset) };
+    }
+
+    [Theory]
+    [MemberData(nameof(AddListener_TestData))]
+    public void AddListener_InvokeWithHandler_CallsCurrentChanged(NotifyCollectionChangedEventArgs e)
+    {
+        var source = new CustomCollectionView();
+        int callCount1 = 0;
+        var listener1 = new CustomWeakEventListener();
+        listener1.ReceiveWeakEventAction += (actualManagerType, actualSender, actualE) =>
+        {
+            Assert.Equal(typeof(CurrentChangedEventManager), actualManagerType);
+            Assert.Same(source, actualSender);
+            Assert.Same(e, actualE);
+            callCount1++;
+            return true;
+        };
+        int callCount2 = 0;
+        var listener2 = new CustomWeakEventListener();
+        listener2.ReceiveWeakEventAction += (actualManagerType, actualSender, actualE) =>
+        {
+            Assert.Equal(typeof(CurrentChangedEventManager), actualManagerType);
+            Assert.Same(source, actualSender);
+            Assert.Same(e, actualE);
+            callCount2++;
+            return true;
+        };
+
+        // Add.
+        CurrentChangedEventManager.AddListener(source, listener1);
+
+        // Call.
+        source.OnCurrentChanged(source, e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Call invalid source.
+        source.OnCurrentChanged(listener1, e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        
+        source.OnCurrentChanged(new object(), e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        
+        source.OnCurrentChanged(null!, e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Add again.
+        CurrentChangedEventManager.AddListener(source, listener1);
+        source.OnCurrentChanged(source, e);
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Add another.
+        CurrentChangedEventManager.AddListener(source, listener2);
+        source.OnCurrentChanged(source, e);
+        Assert.Equal(5, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove second.
+        CurrentChangedEventManager.RemoveListener(source, listener2);
+        source.OnCurrentChanged(source, e);
+        Assert.Equal(7, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove first.
+        CurrentChangedEventManager.RemoveListener(source, listener1);
+        source.OnCurrentChanged(source, e);
+        Assert.Equal(8, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove again.
+        CurrentChangedEventManager.RemoveListener(source, listener1);
+        source.OnCurrentChanged(source, e);
+        Assert.Equal(8, callCount1);
+        Assert.Equal(1, callCount2);
+    }
+
+    [Fact]
+    public void AddListener_InvokeMultipleTimes_Success()
+    {
+        var source1 = new CustomCollectionView();
+        var source2 = new CustomCollectionView();
+        var listener1 = new CustomWeakEventListener();
+        int callCount1 = 0;
+        listener1.ReceiveWeakEventAction += (managerType, sender, e) =>
+        {
+            callCount1++;
+            return true;
+        };
+        var listener2 = new CustomWeakEventListener();
+        int callCount2 = 0;
+        listener2.ReceiveWeakEventAction += (managerType, sender, e) =>
+        {
+            callCount2++;
+            return true;
+        };
+        var listener3 = new CustomWeakEventListener();
+        int callCount3 = 0;
+        listener3.ReceiveWeakEventAction += (managerType, sender, e) =>
+        {
+            callCount3++;
+            return true;
+        };
+
+        // Add.
+        CurrentChangedEventManager.AddListener(source1, listener1);
+        source1.OnCurrentChanged(source1, EventArgs.Empty);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        source2.OnCurrentChanged(source2, EventArgs.Empty);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+
+        // Add again.
+        CurrentChangedEventManager.AddListener(source1, listener1);
+        source1.OnCurrentChanged(source1, EventArgs.Empty);
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        source2.OnCurrentChanged(source2, EventArgs.Empty);
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+
+        // Add another listener.
+        CurrentChangedEventManager.AddListener(source1, listener2);
+        source1.OnCurrentChanged(source1, EventArgs.Empty);
+        Assert.Equal(5, callCount1);
+        Assert.Equal(1, callCount2);
+        Assert.Equal(0, callCount3);
+        source2.OnCurrentChanged(source2, EventArgs.Empty);
+        Assert.Equal(5, callCount1);
+        Assert.Equal(1, callCount2);
+        Assert.Equal(0, callCount3);
+
+        // Add another source.
+        CurrentChangedEventManager.AddListener(source2, listener3);
+        source1.OnCurrentChanged(source1, EventArgs.Empty);
+        Assert.Equal(7, callCount1);
+        Assert.Equal(2, callCount2);
+        Assert.Equal(0, callCount3);
+        source2.OnCurrentChanged(source2, EventArgs.Empty);
+        Assert.Equal(7, callCount1);
+        Assert.Equal(2, callCount2);
+        Assert.Equal(1, callCount3);
+    }
+
+    [Fact]
+    public void AddListener_NullSource_ThrowsArgumentNullException()
+    {
+        var listener = new CustomWeakEventListener();
+        Assert.Throws<ArgumentNullException>("source", () => CurrentChangedEventManager.AddListener(null, listener));
+    }
+
+    [Fact]
+    public void AddListener_NullListener_ThrowsArgumentNullException()
+    {
+        var source = new CustomCollectionView();
+        Assert.Throws<ArgumentNullException>("listener", () => CurrentChangedEventManager.AddListener(source, null));
+    }
+
+    [Fact]
+    public void RemoveHandler_Invoke_Success()
+    {
+        var source = new CustomCollectionView();
+        var target = new CustomWeakEventListener();
+        int callCount = 0;
+        target.HandlerAction += (sender, e) => callCount++;
+        EventHandler<EventArgs> handler = (EventHandler<EventArgs>)Delegate.CreateDelegate(typeof(EventHandler<EventArgs>), target, nameof(CustomWeakEventListener.Handler));
+        CurrentChangedEventManager.AddHandler(source, handler);
+
+        // Remove.
+        CurrentChangedEventManager.RemoveHandler(source, handler);
+        source.OnCurrentChanged(source, EventArgs.Empty);
+        Assert.Equal(0, callCount);
+
+        // Remove again.
+        CurrentChangedEventManager.RemoveHandler(source, handler);
+        source.OnCurrentChanged(source, EventArgs.Empty);
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void RemoveHandler_InvokeNoSource_Success()
+    {
+        var target = new CustomWeakEventListener();
+        EventHandler<EventArgs> handler = (EventHandler<EventArgs>)Delegate.CreateDelegate(typeof(EventHandler<EventArgs>), target, nameof(CustomWeakEventListener.Handler));
+        CurrentChangedEventManager.AddHandler(null, handler);
+
+        // Remove.
+        CurrentChangedEventManager.RemoveHandler(null, handler);
+
+        // Remove again.
+        CurrentChangedEventManager.RemoveHandler(null, handler);
+    }
+
+    [Fact]
+    public void RemoveHandler_InvokeNoSuchSource_Nop()
+    {
+        var source1 = new CustomCollectionView();
+        var source2 = new CustomCollectionView();
+        var target = new CustomWeakEventListener();
+        int callCount = 0;
+        target.HandlerAction += (sender, e) => callCount++;
+        EventHandler<EventArgs> handler = (EventHandler<EventArgs>)Delegate.CreateDelegate(typeof(EventHandler<EventArgs>), target, nameof(CustomWeakEventListener.Handler));
+        CurrentChangedEventManager.AddHandler(source1, handler);
+
+        // Remove.
+        CurrentChangedEventManager.RemoveHandler(source2, handler);
+        source1.OnCurrentChanged(source1, EventArgs.Empty);
+        Assert.Equal(1, callCount);
+        source2.OnCurrentChanged(source2, EventArgs.Empty);
+        Assert.Equal(1, callCount);
+
+        // Remove again.
+        CurrentChangedEventManager.RemoveHandler(source2, handler);
+        source1.OnCurrentChanged(source1, EventArgs.Empty);
+        Assert.Equal(2, callCount);
+        source2.OnCurrentChanged(source2, EventArgs.Empty);
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void RemoveHandler_InvokeNoSuchHandler_Nop()
+    {
+        var source = new CustomCollectionView();
+        var target1 = new CustomWeakEventListener();
+        int callCount1 = 0;
+        target1.HandlerAction += (sender, e) => callCount1++;
+        EventHandler<EventArgs> handler1 = (EventHandler<EventArgs>)Delegate.CreateDelegate(typeof(EventHandler<EventArgs>), target1, nameof(CustomWeakEventListener.Handler));
+        var target2 = new CustomWeakEventListener();
+        int callCount2 = 0;
+        target2.HandlerAction += (sender, e) => callCount2++;
+        EventHandler<EventArgs> handler2 = (EventHandler<EventArgs>)Delegate.CreateDelegate(typeof(EventHandler<EventArgs>), target2, nameof(CustomWeakEventListener.Handler));
+        CurrentChangedEventManager.AddHandler(source, handler1);
+
+        // Remove.
+        CurrentChangedEventManager.RemoveHandler(source, handler2);
+        source.OnCurrentChanged(source, EventArgs.Empty);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Remove again.
+        CurrentChangedEventManager.RemoveHandler(source, handler2);
+        source.OnCurrentChanged(source, EventArgs.Empty);
+        Assert.Equal(2, callCount1);
+        Assert.Equal(0, callCount2);
+    }
+
+    [Fact]
+    public void RemoveHandler_NullHandler_ThrowsArgumentNullException()
+    {
+        var source = new CustomCollectionView();
+        Assert.Throws<ArgumentNullException>("handler", () => CurrentChangedEventManager.RemoveHandler(null, null));
+        Assert.Throws<ArgumentNullException>("handler", () => CurrentChangedEventManager.RemoveHandler(source, null));
+    }
+
+    [Fact]
+    public void RemoveListener_Invoke_Success()
+    {
+        var source = new CustomCollectionView();
+        var listener = new CustomWeakEventListener();
+        int callCount = 0;
+        listener.ReceiveWeakEventAction += (managerType, sender, e) =>
+        {
+            callCount++;
+            return true;
+        };
+        CurrentChangedEventManager.AddListener(source, listener);
+
+        // Remove.
+        CurrentChangedEventManager.RemoveListener(source, listener);
+        source.OnCurrentChanged(source, EventArgs.Empty);
+        Assert.Equal(0, callCount);
+
+        // Remove again.
+        CurrentChangedEventManager.RemoveListener(source, listener);
+        source.OnCurrentChanged(source, EventArgs.Empty);
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void RemoveListener_NoSuchSource_Success()
+    {
+        var source1 = new CustomCollectionView();
+        var source2 = new CustomCollectionView();
+        var listener = new CustomWeakEventListener();
+        int callCount = 0;
+        listener.ReceiveWeakEventAction += (managerType, sender, e) =>
+        {
+            callCount++;
+            return true;
+        };
+        CurrentChangedEventManager.AddListener(source1, listener);
+
+        // Remove.
+        CurrentChangedEventManager.RemoveListener(source2, listener);
+        source1.OnCurrentChanged(source1, EventArgs.Empty);
+        Assert.Equal(1, callCount);
+        source2.OnCurrentChanged(source2, EventArgs.Empty);
+        Assert.Equal(1, callCount);
+
+        // Remove again.
+        CurrentChangedEventManager.RemoveListener(source2, listener);
+        source1.OnCurrentChanged(source1, EventArgs.Empty);
+        Assert.Equal(2, callCount);
+        source2.OnCurrentChanged(source2, EventArgs.Empty);
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void RemoveListener_InvokeNoSuchListener_Nop()
+    {
+        var source = new CustomCollectionView();
+        var listener1 = new CustomWeakEventListener();
+        int callCount1 = 0;
+        listener1.ReceiveWeakEventAction += (managerType, sender, e) =>
+        {
+            callCount1++;
+            return true;
+        };
+        var listener2 = new CustomWeakEventListener();
+        int callCount2 = 0;
+        listener2.ReceiveWeakEventAction += (managerType, sender, e) =>
+        {
+            callCount2++;
+            return true;
+        };
+        CurrentChangedEventManager.AddListener(source, listener1);
+
+        // Remove.
+        CurrentChangedEventManager.RemoveListener(source, listener2);
+        source.OnCurrentChanged(source, EventArgs.Empty);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Remove again.
+        CurrentChangedEventManager.RemoveListener(source, listener2);
+        source.OnCurrentChanged(source, EventArgs.Empty);
+        Assert.Equal(2, callCount1);
+    }
+
+    [Fact]
+    public void RemoveListener_NullListener_ThrowsArgumentNullException()
+    {
+        var source = new CustomCollectionView();
+        Assert.Throws<ArgumentNullException>("listener", () => CurrentChangedEventManager.RemoveListener(source, null));
+    }
+
+    private class CustomCollectionView : ICollectionView
+    {
+        public bool CanFilter => throw new NotImplementedException();
+
+        public bool CanGroup => throw new NotImplementedException();
+
+        public bool CanSort => throw new NotImplementedException();
+
+        public CultureInfo Culture
+        {
+            get => throw new NotImplementedException();
+            set => throw new NotImplementedException();
+        }
+
+        public object CurrentItem => throw new NotImplementedException();
+
+        public int CurrentPosition => throw new NotImplementedException();
+
+        public Predicate<object> Filter
+        {
+            get => throw new NotImplementedException();
+            set => throw new NotImplementedException();
+        }
+
+        public ObservableCollection<GroupDescription> GroupDescriptions => throw new NotImplementedException();
+
+        public ReadOnlyObservableCollection<object> Groups => throw new NotImplementedException();
+
+        public bool IsCurrentAfterLast => throw new NotImplementedException();
+
+        public bool IsCurrentBeforeFirst => throw new NotImplementedException();
+
+        public bool IsEmpty => throw new NotImplementedException();
+
+        public SortDescriptionCollection SortDescriptions => throw new NotImplementedException();
+
+        public IEnumerable SourceCollection => throw new NotImplementedException();
+
+        #pragma warning disable CS0067
+        public event EventHandler? CurrentChanged;
+        public event CurrentChangingEventHandler? CurrentChanging;
+        public event NotifyCollectionChangedEventHandler? CollectionChanged;
+        #pragma warning restore CS0067
+
+        public bool Contains(object item) => throw new NotImplementedException();
+
+        public IDisposable DeferRefresh() => throw new NotImplementedException();
+
+        public IEnumerator GetEnumerator() => throw new NotImplementedException();
+
+        public bool MoveCurrentTo(object item) => throw new NotImplementedException();
+
+        public bool MoveCurrentToFirst() => throw new NotImplementedException();
+
+        public bool MoveCurrentToLast() => throw new NotImplementedException();
+
+        public bool MoveCurrentToNext() => throw new NotImplementedException();
+
+        public bool MoveCurrentToPosition(int position) => throw new NotImplementedException();
+
+        public bool MoveCurrentToPrevious() => throw new NotImplementedException();
+
+        public void Refresh() => throw new NotImplementedException();
+
+        public void OnCurrentChanged(object sender, EventArgs e) => CurrentChanged?.Invoke(sender, e);
+    }
+
+    private class CustomWeakEventListener : IWeakEventListener
+    {
+        public Func<Type, object, EventArgs, bool>? ReceiveWeakEventAction { get; set; }
+
+        public bool ReceiveWeakEvent(Type managerType, object sender, EventArgs e)
+        {
+            if (ReceiveWeakEventAction is null)
+            {
+                return true;
+            }
+
+            return ReceiveWeakEventAction(managerType, sender, e);
+        }
+
+        public Action<object, EventArgs>? HandlerAction { get; set; }
+
+        public void Handler(object sender, EventArgs e)
+        {
+            HandlerAction?.Invoke(sender, e);
+        }
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/CurrentChangingEventArgsTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/CurrentChangingEventArgsTests.cs
new file mode 100644
index 00000000000..9ed2ed10c9e
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/CurrentChangingEventArgsTests.cs
@@ -0,0 +1,63 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.ComponentModel.Tests;
+
+public class CurrentChangingEventArgsTests
+{
+    [Fact]
+    public void Ctor_Default()
+    {
+        var args = new CurrentChangingEventArgs();
+        Assert.True(args.IsCancelable);
+        Assert.False(args.Cancel);
+    }
+    
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void Ctor_Bool(bool isCancelable)
+    {
+        var args = new CurrentChangingEventArgs(isCancelable);
+        Assert.Equal(isCancelable, args.IsCancelable);
+        Assert.False(args.Cancel);
+    }
+
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void Cancel_Set_GetReturnsExpected(bool value)
+    {
+        var args = new CurrentChangingEventArgs();
+
+        // Set.
+        args.Cancel = value;
+        Assert.Equal(value, args.Cancel);
+
+        // Set same.
+        args.Cancel = value;
+        Assert.Equal(value, args.Cancel);
+
+        // Set different.
+        args.Cancel = !value;
+        Assert.Equal(!value, args.Cancel);
+    }
+
+    [Fact]
+    public void Cancel_SetFalseNotCancellable_Success()
+    {
+        var args = new CurrentChangingEventArgs(false);
+
+        // Set.
+        args.Cancel = false;
+        Assert.False(args.Cancel);
+    }
+
+    [Fact]
+    public void Cancel_SetTrueNotCancellable_ThrowsInvalidOperationException()
+    {
+        var args = new CurrentChangingEventArgs(false);
+        Assert.Throws<InvalidOperationException>(() => args.Cancel = true);
+    }
+}
\ No newline at end of file
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/CurrentChangingEventManagerTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/CurrentChangingEventManagerTests.cs
new file mode 100644
index 00000000000..f6daebc9528
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/CurrentChangingEventManagerTests.cs
@@ -0,0 +1,631 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections;
+using System.Collections.ObjectModel;
+using System.Collections.Specialized;
+using System.Globalization;
+using System.Windows;
+
+namespace System.ComponentModel.Tests;
+
+public class CurrentChangingEventManagerTests
+{
+    public static IEnumerable<object?[]> AddHandler_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { new CurrentChangingEventArgs(false) };
+    }
+
+    [Theory]
+    [MemberData(nameof(AddHandler_TestData))]
+    public void AddHandler_InvokeWithHandler_CallsCurrentChanging(CurrentChangingEventArgs e)
+    {
+        var source = new CustomCollectionView();
+        int callCount1 = 0;
+        var listener1 = new CustomWeakEventListener();
+        listener1.HandlerAction += (actualSender, actualE) =>
+        {
+            Assert.Same(source, actualSender);
+            Assert.Same(e, actualE);
+            callCount1++;
+        };
+        EventHandler<CurrentChangingEventArgs> handler1 = (EventHandler<CurrentChangingEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<CurrentChangingEventArgs>), listener1, nameof(CustomWeakEventListener.Handler));
+        int callCount2 = 0;
+        var listener2 = new CustomWeakEventListener();
+        listener2.HandlerAction += (actualSender, actualE) =>
+        {
+            Assert.Same(source, actualSender);
+            Assert.Same(e, actualE);
+            callCount2++;
+        };
+        EventHandler<CurrentChangingEventArgs> handler2 = (EventHandler<CurrentChangingEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<CurrentChangingEventArgs>), listener2, nameof(CustomWeakEventListener.Handler));
+
+        // Add.
+        CurrentChangingEventManager.AddHandler(source, handler1);
+
+        // Call.
+        source.OnCurrentChanging(source, e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Call invalid source.
+        source.OnCurrentChanging(listener1, e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        
+        source.OnCurrentChanging(new object(), e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        
+        source.OnCurrentChanging(null!, e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Add again.
+        CurrentChangingEventManager.AddHandler(source, handler1);
+        source.OnCurrentChanging(source, e);
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Add another.
+        CurrentChangingEventManager.AddHandler(source, handler2);
+        source.OnCurrentChanging(source, e);
+        Assert.Equal(5, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove second.
+        CurrentChangingEventManager.RemoveHandler(source, handler2);
+        source.OnCurrentChanging(source, e);
+        Assert.Equal(7, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove first.
+        CurrentChangingEventManager.RemoveHandler(source, handler1);
+        source.OnCurrentChanging(source, e);
+        Assert.Equal(8, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove again.
+        CurrentChangingEventManager.RemoveHandler(source, handler1);
+        source.OnCurrentChanging(source, e);
+        Assert.Equal(8, callCount1);
+        Assert.Equal(1, callCount2);
+    }
+
+    [Fact]
+    public void AddHandler_InvokeMultipleTimes_Success()
+    {
+        var source1 = new CustomCollectionView();
+        var source2 = new CustomCollectionView();
+        var target1 = new CustomWeakEventListener();
+        int callCount1 = 0;
+        target1.HandlerAction += (s, e) => callCount1++;
+        EventHandler<CurrentChangingEventArgs> handler1 = (EventHandler<CurrentChangingEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<CurrentChangingEventArgs>), target1, nameof(CustomWeakEventListener.Handler));
+        var target2 = new CustomWeakEventListener();
+        int callCount2 = 0;
+        target2.HandlerAction += (s, e) => callCount2++;
+        EventHandler<CurrentChangingEventArgs> handler2 = (EventHandler<CurrentChangingEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<CurrentChangingEventArgs>), target2, nameof(CustomWeakEventListener.Handler));
+        var target3 = new CustomWeakEventListener();
+        int callCount3 = 0;
+        target3.HandlerAction += (s, e) => callCount3++;
+        EventHandler<CurrentChangingEventArgs> handler3 = (EventHandler<CurrentChangingEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<CurrentChangingEventArgs>), target3, nameof(CustomWeakEventListener.Handler));
+
+        // Add.
+        CurrentChangingEventManager.AddHandler(source1, handler1);
+        source1.OnCurrentChanging(source1, new CurrentChangingEventArgs(false));
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        source2.OnCurrentChanging(source2, new CurrentChangingEventArgs(false));
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+
+        // Add again.
+        CurrentChangingEventManager.AddHandler(source1, handler1);
+        source1.OnCurrentChanging(source1, new CurrentChangingEventArgs(false));
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        source2.OnCurrentChanging(source2, new CurrentChangingEventArgs(false));
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+
+        // Add another handler.
+        CurrentChangingEventManager.AddHandler(source1, handler2);
+        source1.OnCurrentChanging(source1, new CurrentChangingEventArgs(false));
+        Assert.Equal(5, callCount1);
+        Assert.Equal(1, callCount2);
+        Assert.Equal(0, callCount3);
+        source2.OnCurrentChanging(source2, new CurrentChangingEventArgs(false));
+        Assert.Equal(5, callCount1);
+        Assert.Equal(1, callCount2);
+        Assert.Equal(0, callCount3);
+
+        // Add another source.
+        CurrentChangingEventManager.AddHandler(source2, handler3);
+        source1.OnCurrentChanging(source1, new CurrentChangingEventArgs(false));
+        Assert.Equal(7, callCount1);
+        Assert.Equal(2, callCount2);
+        Assert.Equal(0, callCount3);
+        source2.OnCurrentChanging(source2, new CurrentChangingEventArgs(false));
+        Assert.Equal(7, callCount1);
+        Assert.Equal(2, callCount2);
+        Assert.Equal(1, callCount3);
+    }
+
+    [Fact]
+    public void AddHandler_InvokeNoSource_Success()
+    {
+        var target1 = new CustomWeakEventListener();
+        EventHandler<CurrentChangingEventArgs> handler1 = (EventHandler<CurrentChangingEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<CurrentChangingEventArgs>), target1, nameof(CustomWeakEventListener.Handler));
+        var target2 = new CustomWeakEventListener();
+        EventHandler<CurrentChangingEventArgs> handler2 = (EventHandler<CurrentChangingEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<CurrentChangingEventArgs>), target2, nameof(CustomWeakEventListener.Handler));
+
+        // Add.
+        Assert.Throws<NullReferenceException>(() => CurrentChangingEventManager.AddHandler(null, handler1));
+
+        // Add again.
+        CurrentChangingEventManager.AddHandler(null, handler1);
+
+        // Add another.
+        CurrentChangingEventManager.AddHandler(null, handler2);
+    }
+
+    [Fact]
+    public void AddHandler_NullHandler_ThrowsArgumentNullException()
+    {
+        var source = new CustomCollectionView();
+        Assert.Throws<ArgumentNullException>("handler", () => CurrentChangingEventManager.AddHandler(null, null));
+        Assert.Throws<ArgumentNullException>("handler", () => CurrentChangingEventManager.AddHandler(source, null));
+    }
+
+    public static IEnumerable<object?[]> AddListener_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { new CurrentChangingEventArgs(false) };
+    }
+
+    [Theory]
+    [MemberData(nameof(AddListener_TestData))]
+    public void AddListener_InvokeWithHandler_CallsCurrentChanging(CurrentChangingEventArgs e)
+    {
+        var source = new CustomCollectionView();
+        int callCount1 = 0;
+        var listener1 = new CustomWeakEventListener();
+        listener1.ReceiveWeakEventAction += (actualManagerType, actualSender, actualE) =>
+        {
+            Assert.Equal(typeof(CurrentChangingEventManager), actualManagerType);
+            Assert.Same(source, actualSender);
+            Assert.Same(e, actualE);
+            callCount1++;
+            return true;
+        };
+        int callCount2 = 0;
+        var listener2 = new CustomWeakEventListener();
+        listener2.ReceiveWeakEventAction += (actualManagerType, actualSender, actualE) =>
+        {
+            Assert.Equal(typeof(CurrentChangingEventManager), actualManagerType);
+            Assert.Same(source, actualSender);
+            Assert.Same(e, actualE);
+            callCount2++;
+            return true;
+        };
+
+        // Add.
+        CurrentChangingEventManager.AddListener(source, listener1);
+
+        // Call.
+        source.OnCurrentChanging(source, e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Call invalid source.
+        source.OnCurrentChanging(listener1, e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        
+        source.OnCurrentChanging(new object(), e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        
+        source.OnCurrentChanging(null!, e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Add again.
+        CurrentChangingEventManager.AddListener(source, listener1);
+        source.OnCurrentChanging(source, e);
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Add another.
+        CurrentChangingEventManager.AddListener(source, listener2);
+        source.OnCurrentChanging(source, e);
+        Assert.Equal(5, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove second.
+        CurrentChangingEventManager.RemoveListener(source, listener2);
+        source.OnCurrentChanging(source, e);
+        Assert.Equal(7, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove first.
+        CurrentChangingEventManager.RemoveListener(source, listener1);
+        source.OnCurrentChanging(source, e);
+        Assert.Equal(8, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove again.
+        CurrentChangingEventManager.RemoveListener(source, listener1);
+        source.OnCurrentChanging(source, e);
+        Assert.Equal(8, callCount1);
+        Assert.Equal(1, callCount2);
+    }
+
+    [Fact]
+    public void AddListener_InvokeMultipleTimes_Success()
+    {
+        var source1 = new CustomCollectionView();
+        var source2 = new CustomCollectionView();
+        var listener1 = new CustomWeakEventListener();
+        int callCount1 = 0;
+        listener1.ReceiveWeakEventAction += (t, s, e) =>
+        {
+            callCount1++;
+            return true;
+        };
+        var listener2 = new CustomWeakEventListener();
+        int callCount2 = 0;
+        listener2.ReceiveWeakEventAction += (t, s, e) =>
+        {
+            callCount2++;
+            return true;
+        };
+        var listener3 = new CustomWeakEventListener();
+        int callCount3 = 0;
+        listener3.ReceiveWeakEventAction += (t, s, e) =>
+        {
+            callCount3++;
+            return true;
+        };
+
+        // Add.
+        CurrentChangingEventManager.AddListener(source1, listener1);
+        source1.OnCurrentChanging(source1, new CurrentChangingEventArgs(false));
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        source2.OnCurrentChanging(source2, new CurrentChangingEventArgs(false));
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+
+        // Add again.
+        CurrentChangingEventManager.AddListener(source1, listener1);
+        source1.OnCurrentChanging(source1, new CurrentChangingEventArgs(false));
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        source2.OnCurrentChanging(source2, new CurrentChangingEventArgs(false));
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+
+        // Add another listener.
+        CurrentChangingEventManager.AddListener(source1, listener2);
+        source1.OnCurrentChanging(source1, new CurrentChangingEventArgs(false));
+        Assert.Equal(5, callCount1);
+        Assert.Equal(1, callCount2);
+        Assert.Equal(0, callCount3);
+        source2.OnCurrentChanging(source2, new CurrentChangingEventArgs(false));
+        Assert.Equal(5, callCount1);
+        Assert.Equal(1, callCount2);
+        Assert.Equal(0, callCount3);
+        
+        // Add another source.
+        CurrentChangingEventManager.AddListener(source2, listener3);
+        source1.OnCurrentChanging(source1, new CurrentChangingEventArgs(false));
+        Assert.Equal(7, callCount1);
+        Assert.Equal(2, callCount2);
+        Assert.Equal(0, callCount3);
+        source2.OnCurrentChanging(source2, new CurrentChangingEventArgs(false));
+        Assert.Equal(7, callCount1);
+        Assert.Equal(2, callCount2);
+        Assert.Equal(1, callCount3);
+    }
+
+    [Fact]
+    public void AddListener_NullSource_ThrowsArgumentNullException()
+    {
+        var listener = new CustomWeakEventListener();
+        Assert.Throws<ArgumentNullException>("source", () => CurrentChangingEventManager.AddListener(null, listener));
+    }
+
+    [Fact]
+    public void AddListener_NullListener_ThrowsArgumentNullException()
+    {
+        var source = new CustomCollectionView();
+        Assert.Throws<ArgumentNullException>("listener", () => CurrentChangingEventManager.AddListener(source, null));
+    }
+
+    [Fact]
+    public void RemoveHandler_Invoke_Success()
+    {
+        var source = new CustomCollectionView();
+        var target = new CustomWeakEventListener();
+        int callCount = 0;
+        target.HandlerAction += (s, e) => callCount++;
+        EventHandler<CurrentChangingEventArgs> handler = (EventHandler<CurrentChangingEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<CurrentChangingEventArgs>), target, nameof(CustomWeakEventListener.Handler));
+        CurrentChangingEventManager.AddHandler(source, handler);
+
+        // Remove.
+        CurrentChangingEventManager.RemoveHandler(source, handler);
+        source.OnCurrentChanging(source, new CurrentChangingEventArgs(false));
+        Assert.Equal(0, callCount);
+
+        // Remove again.
+        CurrentChangingEventManager.RemoveHandler(source, handler);
+        source.OnCurrentChanging(source, new CurrentChangingEventArgs(false));
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void RemoveHandler_InvokeNoSource_Success()
+    {
+        var target = new CustomWeakEventListener();
+        EventHandler<CurrentChangingEventArgs> handler = (EventHandler<CurrentChangingEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<CurrentChangingEventArgs>), target, nameof(CustomWeakEventListener.Handler));
+        Assert.Throws<NullReferenceException>(() => CurrentChangingEventManager.AddHandler(null, handler));
+
+        // Remove.
+        Assert.Throws<NullReferenceException>(() => CurrentChangingEventManager.RemoveHandler(null, handler));
+
+        // Remove again.
+        CurrentChangingEventManager.RemoveHandler(null, handler);
+    }
+
+    [Fact]
+    public void RemoveHandler_InvokeNoSuchSource_Nop()
+    {
+        var source1 = new CustomCollectionView();
+        var source2 = new CustomCollectionView();
+        var target = new CustomWeakEventListener();
+        int callCount = 0;
+        target.HandlerAction += (s, e) => callCount++;
+        EventHandler<CurrentChangingEventArgs> handler = (EventHandler<CurrentChangingEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<CurrentChangingEventArgs>), target, nameof(CustomWeakEventListener.Handler));
+        CurrentChangingEventManager.AddHandler(source1, handler);
+
+        // Remove.
+        CurrentChangingEventManager.RemoveHandler(source2, handler);
+        source1.OnCurrentChanging(source1, new CurrentChangingEventArgs(false));
+        Assert.Equal(1, callCount);
+        source2.OnCurrentChanging(source2, new CurrentChangingEventArgs(false));
+        Assert.Equal(1, callCount);
+
+        // Remove again.
+        CurrentChangingEventManager.RemoveHandler(source2, handler);
+        source1.OnCurrentChanging(source1, new CurrentChangingEventArgs(false));
+        Assert.Equal(2, callCount);
+        source2.OnCurrentChanging(source2, new CurrentChangingEventArgs(false));
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void RemoveHandler_InvokeNoSuchHandler_Nop()
+    {
+        var source = new CustomCollectionView();
+        var target1 = new CustomWeakEventListener();
+        int callCount1 = 0;
+        target1.HandlerAction += (s, e) => callCount1++;
+        EventHandler<CurrentChangingEventArgs> handler1 = (EventHandler<CurrentChangingEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<CurrentChangingEventArgs>), target1, nameof(CustomWeakEventListener.Handler));
+        var target2 = new CustomWeakEventListener();
+        int callCount2 = 0;
+        target2.HandlerAction += (s, e) => callCount2++;
+        EventHandler<CurrentChangingEventArgs> handler2 = (EventHandler<CurrentChangingEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<CurrentChangingEventArgs>), target2, nameof(CustomWeakEventListener.Handler));
+        CurrentChangingEventManager.AddHandler(source, handler1);
+
+        // Remove.
+        CurrentChangingEventManager.RemoveHandler(source, handler2);
+        source.OnCurrentChanging(source, new CurrentChangingEventArgs(false));
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Remove again.
+        CurrentChangingEventManager.RemoveHandler(source, handler2);
+        source.OnCurrentChanging(source, new CurrentChangingEventArgs(false));
+        Assert.Equal(2, callCount1);
+        Assert.Equal(0, callCount2);
+    }
+
+    [Fact]
+    public void RemoveHandler_NullHandler_ThrowsArgumentNullException()
+    {
+        var source = new CustomCollectionView();
+        Assert.Throws<ArgumentNullException>("handler", () => CurrentChangingEventManager.RemoveHandler(null, null));
+        Assert.Throws<ArgumentNullException>("handler", () => CurrentChangingEventManager.RemoveHandler(source, null));
+    }
+
+    [Fact]
+    public void RemoveListener_Invoke_Success()
+    {
+        var source = new CustomCollectionView();
+        var listener = new CustomWeakEventListener();
+        int callCount = 0;
+        listener.ReceiveWeakEventAction += (t, s, e) =>
+        {
+            callCount++;
+            return true;
+        };
+        CurrentChangingEventManager.AddListener(source, listener);
+
+        // Remove.
+        CurrentChangingEventManager.RemoveListener(source, listener);
+        source.OnCurrentChanging(source, new CurrentChangingEventArgs(false));
+        Assert.Equal(0, callCount);
+
+        // Remove again.
+        CurrentChangingEventManager.RemoveListener(source, listener);
+        source.OnCurrentChanging(source, new CurrentChangingEventArgs(false));
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void RemoveListener_InvokeNoSuchSource_Nop()
+    {
+        var source1 = new CustomCollectionView();
+        var source2 = new CustomCollectionView();
+        var listener = new CustomWeakEventListener();
+        int callCount = 0;
+        listener.ReceiveWeakEventAction += (t, s, e) =>
+        {
+            callCount++;
+            return true;
+        };
+        CurrentChangingEventManager.AddListener(source1, listener);
+
+        // Remove.
+        CurrentChangingEventManager.RemoveListener(source2, listener);
+        source1.OnCurrentChanging(source1, new CurrentChangingEventArgs(false));
+        Assert.Equal(1, callCount);
+        source2.OnCurrentChanging(source2, new CurrentChangingEventArgs(false));
+        Assert.Equal(1, callCount);
+
+        // Remove again.
+        CurrentChangingEventManager.RemoveListener(source2, listener);
+        source1.OnCurrentChanging(source1, new CurrentChangingEventArgs(false));
+        Assert.Equal(2, callCount);
+        source2.OnCurrentChanging(source2, new CurrentChangingEventArgs(false));
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void RemoveListener_InvokeNoSuchListener_Nop()
+    {
+        var source = new CustomCollectionView();
+        var listener1 = new CustomWeakEventListener();
+        int callCount1 = 0;
+        listener1.ReceiveWeakEventAction += (t, s, e) =>
+        {
+            callCount1++;
+            return true;
+        };
+        var listener2 = new CustomWeakEventListener();
+        int callCount2 = 0;
+        listener2.ReceiveWeakEventAction += (t, s, e) =>
+        {
+            callCount2++;
+            return true;
+        };
+        CurrentChangingEventManager.AddListener(source, listener1);
+
+        // Remove.
+        CurrentChangingEventManager.RemoveListener(source, listener2);
+        source.OnCurrentChanging(source, new CurrentChangingEventArgs(false));
+        Assert.Equal(1, callCount1);
+
+        // Remove again.
+        CurrentChangingEventManager.RemoveListener(source, listener2);
+        source.OnCurrentChanging(source, new CurrentChangingEventArgs(false));
+        Assert.Equal(2, callCount1);
+    }
+
+    [Fact]
+    public void RemoveListener_NullListener_ThrowsArgumentNullException()
+    {
+        var source = new CustomCollectionView();
+        Assert.Throws<ArgumentNullException>("listener", () => CurrentChangingEventManager.RemoveListener(source, null));
+    }
+
+    private class CustomCollectionView : ICollectionView
+    {
+        public bool CanFilter => throw new NotImplementedException();
+
+        public bool CanGroup => throw new NotImplementedException();
+
+        public bool CanSort => throw new NotImplementedException();
+
+        public CultureInfo Culture
+        {
+            get => throw new NotImplementedException();
+            set => throw new NotImplementedException();
+        }
+
+        public object CurrentItem => throw new NotImplementedException();
+
+        public int CurrentPosition => throw new NotImplementedException();
+
+        public Predicate<object> Filter
+        {
+            get => throw new NotImplementedException();
+            set => throw new NotImplementedException();
+        }
+
+        public ObservableCollection<GroupDescription> GroupDescriptions => throw new NotImplementedException();
+
+        public ReadOnlyObservableCollection<object> Groups => throw new NotImplementedException();
+
+        public bool IsCurrentAfterLast => throw new NotImplementedException();
+
+        public bool IsCurrentBeforeFirst => throw new NotImplementedException();
+
+        public bool IsEmpty => throw new NotImplementedException();
+
+        public SortDescriptionCollection SortDescriptions => throw new NotImplementedException();
+
+        public IEnumerable SourceCollection => throw new NotImplementedException();
+
+        #pragma warning disable CS0067
+        public event EventHandler? CurrentChanged;
+        public event CurrentChangingEventHandler? CurrentChanging;
+        public event NotifyCollectionChangedEventHandler? CollectionChanged;
+        #pragma warning restore CS0067
+
+        public bool Contains(object item) => throw new NotImplementedException();
+
+        public IDisposable DeferRefresh() => throw new NotImplementedException();
+
+        public IEnumerator GetEnumerator() => throw new NotImplementedException();
+
+        public bool MoveCurrentTo(object item) => throw new NotImplementedException();
+
+        public bool MoveCurrentToFirst() => throw new NotImplementedException();
+
+        public bool MoveCurrentToLast() => throw new NotImplementedException();
+
+        public bool MoveCurrentToNext() => throw new NotImplementedException();
+
+        public bool MoveCurrentToPosition(int position) => throw new NotImplementedException();
+
+        public bool MoveCurrentToPrevious() => throw new NotImplementedException();
+
+        public void Refresh() => throw new NotImplementedException();
+
+        public void OnCurrentChanging(object sender, CurrentChangingEventArgs e) => CurrentChanging?.Invoke(sender, e);
+    }
+
+    private class CustomWeakEventListener : IWeakEventListener
+    {
+        public Func<Type, object, EventArgs, bool>? ReceiveWeakEventAction { get; set; }
+
+        public bool ReceiveWeakEvent(Type managerType, object sender, EventArgs e)
+        {
+            if (ReceiveWeakEventAction is null)
+            {
+                return true;
+            }
+
+            return ReceiveWeakEventAction(managerType, sender, e);
+        }
+
+        public Action<object, CurrentChangingEventArgs>? HandlerAction { get; set; }
+
+        public void Handler(object sender, CurrentChangingEventArgs e)
+        {
+            HandlerAction?.Invoke(sender, e);
+        }
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/DependencyPropertyDescriptorTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/DependencyPropertyDescriptorTests.cs
new file mode 100644
index 00000000000..834c1bed942
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/DependencyPropertyDescriptorTests.cs
@@ -0,0 +1,79 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Reflection;
+using System.Windows;
+
+namespace System.ComponentModel.Tests;
+
+public class DependencyPropertyDescriptorTests
+{
+    // TODO:
+    // FromProperty - success
+
+    [Fact]
+    public void FromProperty_InvokeNotDependencyObjectPropertyDescriptor_Success()
+    {
+        var component = new NotDependencyObject();
+        PropertyDescriptor property = TypeDescriptor.GetProperties(component)[nameof(NotDependencyObject.Property)]!;
+        
+        // Get descriptor.
+        Assert.Null(DependencyPropertyDescriptor.FromProperty(property));
+        
+        // Get descriptor again.
+        Assert.Null(DependencyPropertyDescriptor.FromProperty(property));
+    }
+
+    [Fact]
+    public void FromProperty_NullProperty_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("property", () => DependencyPropertyDescriptor.FromProperty(null));
+    }
+
+    [Fact]
+    public void FromProperty_InvokeTypeDependencyProperty_ReturnsNull()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyPropertyDescriptorTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject));
+
+        // Get descriptor.
+        Assert.Null(DependencyPropertyDescriptor.FromProperty(property, typeof(DependencyProperty)));
+        
+        // Get descriptor again.
+        Assert.Null(DependencyPropertyDescriptor.FromProperty(property, typeof(DependencyProperty)));
+    }
+
+    [Fact]
+    public void FromProperty_InvokeTypeNotDependencyProperty_ReturnsNull()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyPropertyDescriptorTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject));
+
+        // Get descriptor.
+        Assert.Null(DependencyPropertyDescriptor.FromProperty(property, typeof(int)));
+        
+        // Get descriptor again.
+        Assert.Null(DependencyPropertyDescriptor.FromProperty(property, typeof(int)));
+    }
+    
+    [Fact]
+    public void FromProperty_NullDependencyProperty_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("dependencyProperty", () => DependencyPropertyDescriptor.FromProperty(null, typeof(object)));
+    }
+    
+    [Fact]
+    public void FromProperty_NullTargetType_ThrowsArgumentNullException()
+    {
+        DependencyProperty property = DependencyProperty.Register(MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        Assert.Throws<ArgumentNullException>("targetType", () => DependencyPropertyDescriptor.FromProperty(property, null));
+    }
+
+    public class NotDependencyObject
+    {
+        public int Property { get; set; }
+    }
+
+    private class SubDependencyObject : DependencyObject
+    {
+    }
+}
\ No newline at end of file
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/ErrorsChangedEventManagerTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/ErrorsChangedEventManagerTests.cs
new file mode 100644
index 00000000000..9ec413fc584
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/ErrorsChangedEventManagerTests.cs
@@ -0,0 +1,293 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections;
+using System.Windows;
+
+namespace System.ComponentModel.Tests;
+
+public class ErrorsChangedEventManagerTests
+{
+    public static IEnumerable<object?[]> AddHandler_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { new DataErrorsChangedEventArgs(null) };
+        yield return new object?[] { new DataErrorsChangedEventArgs("") };
+        yield return new object?[] { new DataErrorsChangedEventArgs("propertyName") };
+    }
+
+    [Theory]
+    [MemberData(nameof(AddHandler_TestData))]
+    public void AddHandler_InvokeWithHandler_CallsErrorsChanged(DataErrorsChangedEventArgs e)
+    {
+        var source = new CustomNotifyDataErrorInfo();
+        int callCount1 = 0;
+        var listener1 = new CustomWeakEventListener();
+        listener1.HandlerAction += (actualSender, actualE) =>
+        {
+            Assert.Same(source, actualSender);
+            Assert.Same(e, actualE);
+            callCount1++;
+        };
+        EventHandler<DataErrorsChangedEventArgs> handler1 = (EventHandler<DataErrorsChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<DataErrorsChangedEventArgs>), listener1, nameof(CustomWeakEventListener.Handler));
+        int callCount2 = 0;
+        var listener2 = new CustomWeakEventListener();
+        listener2.HandlerAction += (actualSender, actualE) =>
+        {
+            Assert.Same(source, actualSender);
+            Assert.Same(e, actualE);
+            callCount2++;
+        };
+        EventHandler<DataErrorsChangedEventArgs> handler2 = (EventHandler<DataErrorsChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<DataErrorsChangedEventArgs>), listener2, nameof(CustomWeakEventListener.Handler));
+
+        // Add.
+        ErrorsChangedEventManager.AddHandler(source, handler1);
+
+        // Call.
+        source.OnErrorsChanged(source, e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Call invalid source.
+        source.OnErrorsChanged(listener1, e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        
+        source.OnErrorsChanged(new object(), e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        
+        source.OnErrorsChanged(null!, e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Add again.
+        ErrorsChangedEventManager.AddHandler(source, handler1);
+        source.OnErrorsChanged(source, e);
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Add another.
+        ErrorsChangedEventManager.AddHandler(source, handler2);
+        source.OnErrorsChanged(source, e);
+        Assert.Equal(5, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove second.
+        ErrorsChangedEventManager.RemoveHandler(source, handler2);
+        source.OnErrorsChanged(source, e);
+        Assert.Equal(7, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove first.
+        ErrorsChangedEventManager.RemoveHandler(source, handler1);
+        source.OnErrorsChanged(source, e);
+        Assert.Equal(8, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove again.
+        ErrorsChangedEventManager.RemoveHandler(source, handler1);
+        source.OnErrorsChanged(source, e);
+        Assert.Equal(8, callCount1);
+        Assert.Equal(1, callCount2);
+    }
+
+    [Fact]
+    public void AddHandler_InvokeMultipleTimes_Success()
+    {
+        var source1 = new CustomNotifyDataErrorInfo();
+        var source2 = new CustomNotifyDataErrorInfo();
+        var target1 = new CustomWeakEventListener();
+        int callCount1 = 0;
+        target1.HandlerAction += (sender, e) => callCount1++;
+        EventHandler<DataErrorsChangedEventArgs> handler1 = (EventHandler<DataErrorsChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<DataErrorsChangedEventArgs>), target1, nameof(CustomWeakEventListener.Handler));
+        var target2 = new CustomWeakEventListener();
+        int callCount2 = 0;
+        target2.HandlerAction += (sender, e) => callCount2++;
+        EventHandler<DataErrorsChangedEventArgs> handler2 = (EventHandler<DataErrorsChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<DataErrorsChangedEventArgs>), target2, nameof(CustomWeakEventListener.Handler));
+        var target3 = new CustomWeakEventListener();
+        int callCount3 = 0;
+        target3.HandlerAction += (sender, e) => callCount3++;
+        EventHandler<DataErrorsChangedEventArgs> handler3 = (EventHandler<DataErrorsChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<DataErrorsChangedEventArgs>), target3, nameof(CustomWeakEventListener.Handler));
+
+        // Add.
+        ErrorsChangedEventManager.AddHandler(source1, handler1);
+        source1.OnErrorsChanged(source1, new DataErrorsChangedEventArgs(null));
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        source2.OnErrorsChanged(source2, new DataErrorsChangedEventArgs(null));
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+
+        // Add again.
+        ErrorsChangedEventManager.AddHandler(source1, handler1);
+        source1.OnErrorsChanged(source1, new DataErrorsChangedEventArgs(null));
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        source2.OnErrorsChanged(source2, new DataErrorsChangedEventArgs(null));
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+
+        // Add another handler.
+        ErrorsChangedEventManager.AddHandler(source1, handler2);
+        source1.OnErrorsChanged(source1, new DataErrorsChangedEventArgs(null));
+        Assert.Equal(5, callCount1);
+        Assert.Equal(1, callCount2);
+        Assert.Equal(0, callCount3);
+        source2.OnErrorsChanged(source2, new DataErrorsChangedEventArgs(null));
+        Assert.Equal(5, callCount1);
+        Assert.Equal(1, callCount2);
+        Assert.Equal(0, callCount3);
+
+        // Add another source.
+        ErrorsChangedEventManager.AddHandler(source2, handler3);
+        source1.OnErrorsChanged(source1, new DataErrorsChangedEventArgs(null));
+        Assert.Equal(7, callCount1);
+        Assert.Equal(2, callCount2);
+        Assert.Equal(0, callCount3);
+        source2.OnErrorsChanged(source2, new DataErrorsChangedEventArgs(null));
+        Assert.Equal(7, callCount1);
+        Assert.Equal(2, callCount2);
+        Assert.Equal(1, callCount3);
+    }
+
+    [Fact]
+    public void AddHandler_NullSource_ThrowsArgumentNullException()
+    {
+        var target = new CustomWeakEventListener();
+        EventHandler<DataErrorsChangedEventArgs> handler = (EventHandler<DataErrorsChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<DataErrorsChangedEventArgs>), target, nameof(CustomWeakEventListener.Handler));
+        Assert.Throws<ArgumentNullException>("source", () => ErrorsChangedEventManager.AddHandler(null, handler));
+    }
+
+    [Fact]
+    public void AddHandler_NullHandler_ThrowsArgumentNullException()
+    {
+        var source = new CustomNotifyDataErrorInfo();
+        Assert.Throws<ArgumentNullException>("handler", () => ErrorsChangedEventManager.AddHandler(source, null));
+    }
+
+    [Fact]
+    public void RemoveHandler_Invoke_Success()
+    {
+        var source = new CustomNotifyDataErrorInfo();
+        var target = new CustomWeakEventListener();
+        int callCount = 0;
+        target.HandlerAction += (sender, e) => callCount++;
+        EventHandler<DataErrorsChangedEventArgs> handler = (EventHandler<DataErrorsChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<DataErrorsChangedEventArgs>), target, nameof(CustomWeakEventListener.Handler));
+        ErrorsChangedEventManager.AddHandler(source, handler);
+
+        // Remove.
+        ErrorsChangedEventManager.RemoveHandler(source, handler);
+        source.OnErrorsChanged(source, new DataErrorsChangedEventArgs(null));
+        Assert.Equal(0, callCount);
+
+        // Remove again.
+        ErrorsChangedEventManager.RemoveHandler(source, handler);
+        source.OnErrorsChanged(source, new DataErrorsChangedEventArgs(null));
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void RemoveHandler_InvokeNoSuchSource_Nop()
+    {
+        var source1 = new CustomNotifyDataErrorInfo();
+        var source2 = new CustomNotifyDataErrorInfo();
+        var target = new CustomWeakEventListener();
+        int callCount = 0;
+        target.HandlerAction += (sender, e) => callCount++;
+        EventHandler<DataErrorsChangedEventArgs> handler = (EventHandler<DataErrorsChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<DataErrorsChangedEventArgs>), target, nameof(CustomWeakEventListener.Handler));
+        ErrorsChangedEventManager.AddHandler(source1, handler);
+
+        // Remove.
+        ErrorsChangedEventManager.RemoveHandler(source2, handler);
+        source1.OnErrorsChanged(source1, new DataErrorsChangedEventArgs(null));
+        Assert.Equal(1, callCount);
+        source2.OnErrorsChanged(source1, new DataErrorsChangedEventArgs(null));
+        Assert.Equal(1, callCount);
+
+        // Remove again.
+        ErrorsChangedEventManager.RemoveHandler(source2, handler);
+        source1.OnErrorsChanged(source1, new DataErrorsChangedEventArgs(null));
+        Assert.Equal(2, callCount);
+        source2.OnErrorsChanged(source1, new DataErrorsChangedEventArgs(null));
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void RemoveHandler_InvokeNoSuchHandler_Nop()
+    {
+        var source = new CustomNotifyDataErrorInfo();
+        var target1 = new CustomWeakEventListener();
+        int callCount = 0;
+        target1.HandlerAction += (sender, e) => callCount++;
+        EventHandler<DataErrorsChangedEventArgs> handler1 = (EventHandler<DataErrorsChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<DataErrorsChangedEventArgs>), target1, nameof(CustomWeakEventListener.Handler));
+        var target2 = new CustomWeakEventListener();
+        EventHandler<DataErrorsChangedEventArgs> handler2 = (EventHandler<DataErrorsChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<DataErrorsChangedEventArgs>), target2, nameof(CustomWeakEventListener.Handler));
+        ErrorsChangedEventManager.AddHandler(source, handler1);
+
+        // Remove.
+        ErrorsChangedEventManager.RemoveHandler(source, handler2);
+        source.OnErrorsChanged(source, new DataErrorsChangedEventArgs(null));
+        Assert.Equal(1, callCount);
+
+        // Remove again.
+        ErrorsChangedEventManager.RemoveHandler(source, handler2);
+        source.OnErrorsChanged(source, new DataErrorsChangedEventArgs(null));
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void RemoveHandler_NullSource_ThrowsArgumentNullException()
+    {
+        var target = new CustomWeakEventListener();
+        EventHandler<DataErrorsChangedEventArgs> handler = (EventHandler<DataErrorsChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<DataErrorsChangedEventArgs>), target, nameof(CustomWeakEventListener.Handler));
+        Assert.Throws<ArgumentNullException>("source", () => ErrorsChangedEventManager.RemoveHandler(null, handler));
+    }
+
+    [Fact]
+    public void RemoveHandler_NullHandler_ThrowsArgumentNullException()
+    {
+        var source = new CustomNotifyDataErrorInfo();
+        Assert.Throws<ArgumentNullException>("handler", () => ErrorsChangedEventManager.RemoveHandler(source, null));
+    }
+
+    private class CustomNotifyDataErrorInfo : INotifyDataErrorInfo
+    {
+        public bool HasErrors => throw new NotImplementedException();
+
+        #pragma warning disable CS0067
+        public event EventHandler<DataErrorsChangedEventArgs>? ErrorsChanged;
+        #pragma warning restore CS0067
+
+        public IEnumerable GetErrors(string? propertyName) => throw new NotImplementedException();
+
+        public void OnErrorsChanged(object sender, DataErrorsChangedEventArgs e) => ErrorsChanged?.Invoke(sender, e);
+    }
+
+    private class CustomWeakEventListener : IWeakEventListener
+    {
+        public Func<Type, object, EventArgs, bool>? ReceiveWeakEventAction { get; set; }
+
+        public bool ReceiveWeakEvent(Type managerType, object sender, EventArgs e)
+        {
+            if (ReceiveWeakEventAction is null)
+            {
+                return true;
+            }
+
+            return ReceiveWeakEventAction(managerType, sender, e);
+        }
+
+        public Action<object, DataErrorsChangedEventArgs>? HandlerAction { get; set; }
+
+        public void Handler(object sender, DataErrorsChangedEventArgs e)
+        {
+            HandlerAction?.Invoke(sender, e);
+        }
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/GroupDescriptionTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/GroupDescriptionTests.cs
new file mode 100644
index 00000000000..c6e6c1532a1
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/GroupDescriptionTests.cs
@@ -0,0 +1,625 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections;
+using System.Collections.ObjectModel;
+using System.Globalization;
+using System.Linq;
+
+namespace System.ComponentModel.Tests;
+
+public class GroupDescriptionTests
+{
+    [Fact]
+    public void Ctor_Default()
+    {
+        var description = new SubGroupDescription();
+        Assert.Null(description.CustomSort);
+        Assert.Empty(description.GroupNames);
+        Assert.Same(description.GroupNames, description.GroupNames);
+        Assert.Empty(description.SortDescriptions);
+        Assert.Same(description.SortDescriptions, description.SortDescriptions);
+    }
+
+    public static IEnumerable<object?[]> CustomSort_Set_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { StringComparer.CurrentCulture };
+    }
+
+    [Theory]
+    [MemberData(nameof(CustomSort_Set_TestData))]
+    public void CustomSort_Set_GetReturnsExpected(IComparer? value)
+    {
+        var description = new SubGroupDescription
+        {
+            CustomSort = value
+        };
+        Assert.Same(value, description.CustomSort);
+        Assert.Empty(description.SortDescriptions);
+
+        // Set same.
+        description.CustomSort = value;
+        Assert.Same(value, description.CustomSort);
+        Assert.Empty(description.SortDescriptions);
+    }
+
+    [Theory]
+    [MemberData(nameof(CustomSort_Set_TestData))]
+    public void CustomSort_SetNonNullOldValue_GetReturnsExpected(IComparer? value)
+    {
+        var description = new SubGroupDescription
+        {
+            CustomSort = StringComparer.Ordinal
+        };
+
+        description.CustomSort = value;
+        Assert.Same(value, description.CustomSort);
+        Assert.Empty(description.SortDescriptions);
+
+        // Set same.
+        description.CustomSort = value;
+        Assert.Same(value, description.CustomSort);
+        Assert.Empty(description.SortDescriptions);
+    }
+
+    [Theory]
+    [MemberData(nameof(CustomSort_Set_TestData))]
+    public void CustomSort_SetWithSortDescriptions_GetReturnsExpected(IComparer? value)
+    {
+        var description = new SubGroupDescription();
+        description.SortDescriptions.Add(new SortDescription("Name", ListSortDirection.Ascending));
+
+        // Set.
+        description.CustomSort = value;
+        Assert.Same(value, description.CustomSort);
+        Assert.Empty(description.SortDescriptions);
+
+        // Set same.
+        description.CustomSort = value;
+        Assert.Same(value, description.CustomSort);
+        Assert.Empty(description.SortDescriptions);
+    }
+
+    [Theory]
+    [MemberData(nameof(CustomSort_Set_TestData))]
+    public void CustomSort_SetWithEmptySortDescriptions_GetReturnsExpected(IComparer? value)
+    {
+        var description = new SubGroupDescription();
+        Assert.Empty(description.SortDescriptions);
+
+        // Set.
+        description.CustomSort = value;
+        Assert.Same(value, description.CustomSort);
+        Assert.Empty(description.SortDescriptions);
+
+        // Set same.
+        description.CustomSort = value;
+        Assert.Same(value, description.CustomSort);
+        Assert.Empty(description.SortDescriptions);
+    }
+
+    [Fact]
+    public void CustomSort_SetWithHandler_CallsPropertyChanged()
+    {
+        var description = new SubGroupDescription();
+        int callCount = 0;
+        PropertyChangedEventHandler handler = (sender, e) =>
+        {
+            Assert.Same(description, sender);
+            Assert.Equal("CustomSort", e.PropertyName);
+            callCount++;
+        }; ;
+        ((INotifyPropertyChanged)description).PropertyChanged += handler;
+
+        // Set.
+        description.CustomSort = StringComparer.CurrentCulture;
+        Assert.Equal(StringComparer.CurrentCulture, description.CustomSort);
+        Assert.Equal(1, callCount);
+
+        // Set same.
+        description.CustomSort = StringComparer.CurrentCulture;
+        Assert.Equal(StringComparer.CurrentCulture, description.CustomSort);
+        Assert.Equal(2, callCount);
+
+        // Remove handler.
+        ((INotifyPropertyChanged)description).PropertyChanged -= handler;
+        description.CustomSort = null;
+        Assert.Null(description.CustomSort);
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void CustomSort_SetWithSortDescriptionsWithHandler_CallsPropertyChanged()
+    {
+        var description = new SubGroupDescription();
+        description.SortDescriptions.Add(new SortDescription("Name", ListSortDirection.Ascending));
+
+        int callCount = 0;
+        var properties = new List<string>();
+        PropertyChangedEventHandler handler = (sender, e) =>
+        {
+            Assert.Same(description, sender);
+            properties.Add(e.PropertyName!);
+            callCount++;
+        }; ;
+        ((INotifyPropertyChanged)description).PropertyChanged += handler;
+
+        // Set.
+        description.CustomSort = StringComparer.CurrentCulture;
+        Assert.Equal(StringComparer.CurrentCulture, description.CustomSort);
+        Assert.Equal(2, callCount);
+        Assert.Equal(new[] { "SortDescriptions", "CustomSort" }, properties);
+
+        // Set same.
+        description.CustomSort = StringComparer.CurrentCulture;
+        Assert.Equal(StringComparer.CurrentCulture, description.CustomSort);
+        Assert.Equal(3, callCount);
+        Assert.Equal(new[] { "SortDescriptions", "CustomSort", "CustomSort" }, properties);
+
+        // Remove handler.
+        ((INotifyPropertyChanged)description).PropertyChanged -= handler;
+        description.CustomSort = null;
+        Assert.Null(description.CustomSort);
+        Assert.Equal(3, callCount);
+        Assert.Equal(new[] { "SortDescriptions", "CustomSort", "CustomSort" }, properties);
+    }
+
+    [Fact]
+    public void CustomSort_SetWithEmptySortDescriptionsWithHandler_CallsPropertyChanged()
+    {
+        var description = new SubGroupDescription();
+        Assert.Empty(description.SortDescriptions);
+
+        int callCount = 0;
+        var properties = new List<string>();
+        PropertyChangedEventHandler handler = (sender, e) =>
+        {
+            Assert.Same(description, sender);
+            properties.Add(e.PropertyName!);
+            callCount++;
+        }; ;
+        ((INotifyPropertyChanged)description).PropertyChanged += handler;
+
+        // Set.
+        description.CustomSort = StringComparer.CurrentCulture;
+        Assert.Equal(StringComparer.CurrentCulture, description.CustomSort);
+        Assert.Equal(2, callCount);
+        Assert.Equal(new[] { "SortDescriptions", "CustomSort" }, properties);
+
+        // Set same.
+        description.CustomSort = StringComparer.CurrentCulture;
+        Assert.Equal(StringComparer.CurrentCulture, description.CustomSort);
+        Assert.Equal(3, callCount);
+        Assert.Equal(new[] { "SortDescriptions", "CustomSort", "CustomSort" }, properties);
+
+        // Remove handler.
+        ((INotifyPropertyChanged)description).PropertyChanged -= handler;
+        description.CustomSort = null;
+        Assert.Null(description.CustomSort);
+        Assert.Equal(3, callCount);
+        Assert.Equal(new[] { "SortDescriptions", "CustomSort", "CustomSort" }, properties);
+    }
+
+    [Fact]
+    public void CustomSort_GetFirstTime_DoesNotCallPropertyChanged()
+    {
+        var description = new SubGroupDescription();
+        int callCount = 0;
+        ((INotifyPropertyChanged)description).PropertyChanged += (sender, e) => callCount++;
+
+        // Get.
+        Assert.Null(description.CustomSort);
+        Assert.Equal(0, callCount);
+
+        // Get again.
+        Assert.Null(description.CustomSort);
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void GroupNames_GetFirstTime_DoesNotCallPropertyChanged()
+    {
+        var description = new SubGroupDescription();
+        int callCount = 0;
+        ((INotifyPropertyChanged)description).PropertyChanged += (sender, e) => callCount++;
+
+        // Get.
+        ObservableCollection<object> collection = description.GroupNames;
+        Assert.Empty(collection);
+        Assert.Same(collection, description.GroupNames);
+        Assert.Equal(0, callCount);
+
+        // Get again.
+        Assert.Empty(description.GroupNames);
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void GroupNames_Change_CallsPropertyChanged()
+    {
+        var description = new SubGroupDescription();
+        int callCount = 0;
+        PropertyChangedEventHandler handler = (sender, e) =>
+        {
+            Assert.Same(description, sender);
+            Assert.Equal("GroupNames", e.PropertyName);
+            callCount++;
+        };
+        ((INotifyPropertyChanged)description).PropertyChanged += handler;
+
+        // Clear.
+        description.GroupNames.Clear();
+        Assert.Empty(description.GroupNames);
+        Assert.Equal(1, callCount);
+
+        // Clear again.
+        description.GroupNames.Clear();
+        Assert.Empty(description.GroupNames);
+        Assert.Equal(2, callCount);
+
+        // Remove handler.
+        ((INotifyPropertyChanged)description).PropertyChanged -= handler;
+        description.GroupNames.Clear();
+        Assert.Empty(description.GroupNames);
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void GroupNames_ShouldSerialize_ReturnsExpected()
+    {
+        var description = new SubGroupDescription();
+        PropertyDescriptor property = TypeDescriptor.GetProperties(typeof(GroupDescription))[nameof(GroupDescription.GroupNames)]!;
+        Assert.False(property.ShouldSerializeValue(description));
+
+        Assert.Empty(description.GroupNames);
+        Assert.False(property.ShouldSerializeValue(description));
+
+        description.GroupNames.Add("Name");
+        Assert.True(property.ShouldSerializeValue(description));
+
+        description.GroupNames.Clear();
+        Assert.False(property.ShouldSerializeValue(description));
+    }
+
+    [Fact]
+    public void SortDescriptions_GetFirstTime_CallsPropertyChanged()
+    {
+        var description = new SubGroupDescription();
+        int callCount = 0;
+        ((INotifyPropertyChanged)description).PropertyChanged += (sender, e) =>
+        {
+            Assert.Same(description, sender);
+            Assert.Equal("SortDescriptions", e.PropertyName);
+            callCount++;
+        };
+
+        // Get.
+        SortDescriptionCollection collection = description.SortDescriptions;
+        Assert.Empty(collection);
+        Assert.Same(collection, description.SortDescriptions);
+        Assert.Equal(1, callCount);
+
+        // Get again.
+        Assert.Empty(description.SortDescriptions);
+        Assert.Equal(1, callCount);
+    }
+
+    [Fact]
+    public void SortDescriptions_GetFirstTimeWithCustomSort_CallsPropertyChanged()
+    {
+        var description = new SubGroupDescription();
+        description.CustomSort = StringComparer.CurrentCulture;
+        Assert.Equal(StringComparer.CurrentCulture, description.CustomSort);
+
+        int callCount = 0;
+        ((INotifyPropertyChanged)description).PropertyChanged += (sender, e) =>
+        {
+            Assert.Same(description, sender);
+            Assert.Equal("SortDescriptions", e.PropertyName);
+            callCount++;
+        };
+
+        // Get.
+        SortDescriptionCollection collection = description.SortDescriptions;
+        Assert.Empty(collection);
+        Assert.Same(collection, description.SortDescriptions);
+        Assert.Equal(1, callCount);
+
+        // Get again.
+        Assert.Empty(description.SortDescriptions);
+        Assert.Equal(1, callCount);
+    }
+
+    [Fact]
+    public void SortDescriptions_GetRemovedHandler_DoesNotCallPropertyChanged()
+    {
+        var description = new SubGroupDescription();
+        int callCount = 0;
+        PropertyChangedEventHandler handler = (sender, e) => callCount++;
+        ((INotifyPropertyChanged)description).PropertyChanged += handler;
+        ((INotifyPropertyChanged)description).PropertyChanged -= handler;
+
+        // Get.
+        SortDescriptionCollection collection = description.SortDescriptions;
+        Assert.Empty(collection);
+        Assert.Same(collection, description.SortDescriptions);
+        Assert.Equal(0, callCount);
+
+        // Get again.
+        Assert.Empty(description.SortDescriptions);
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void SortDescriptions_ChangeCount_ClearsCustomSort()
+    {
+        var description = new SubGroupDescription();
+        var description1 = new SortDescription("Name1", ListSortDirection.Ascending);
+        var description2 = new SortDescription("Name2", ListSortDirection.Ascending);
+
+        description.CustomSort = StringComparer.CurrentCulture;
+        Assert.Equal(StringComparer.CurrentCulture, description.CustomSort);
+
+        // Add.
+        description.SortDescriptions.Add(description1);
+        Assert.Equal(new[] { description1 }, description.SortDescriptions.Cast<SortDescription>());
+        Assert.Null(description.CustomSort);
+    }
+
+    [Fact]
+    public void SortDescriptions_ChangeNoCount_DoesNotClearCustomSort()
+    {
+        var description = new SubGroupDescription();
+        var description1 = new SortDescription("Name1", ListSortDirection.Ascending);
+        var description2 = new SortDescription("Name2", ListSortDirection.Ascending);
+
+        description.CustomSort = StringComparer.CurrentCulture;
+        Assert.Equal(StringComparer.CurrentCulture, description.CustomSort);
+
+        // Clear.
+        description.SortDescriptions.Clear();
+        Assert.Empty(description.SortDescriptions);
+        Assert.Equal(StringComparer.CurrentCulture, description.CustomSort);
+    }
+
+    [Fact]
+    public void SortDescriptions_Change_CallsPropertyChanged()
+    {
+        var description = new SubGroupDescription();
+        var description1 = new SortDescription("Name1", ListSortDirection.Ascending);
+        var description2 = new SortDescription("Name2", ListSortDirection.Ascending);
+        Assert.Empty(description.SortDescriptions);
+
+        int callCount = 0;
+        PropertyChangedEventHandler handler = (sender, e) =>
+        {
+            Assert.Same(description, sender);
+            Assert.Equal("SortDescriptions", e.PropertyName);
+            callCount++;
+        };
+        ((INotifyPropertyChanged)description).PropertyChanged += handler;
+
+        // Add.
+        description.SortDescriptions.Add(description1);
+        Assert.Equal(new[] { description1 }, description.SortDescriptions.Cast<SortDescription>());
+        Assert.Null(description.CustomSort);
+        Assert.Equal(1, callCount);
+
+        // Clear.
+        description.SortDescriptions.Clear();
+        Assert.Empty(description.SortDescriptions);
+        Assert.Null(description.CustomSort);
+        Assert.Equal(2, callCount);
+
+        // Remove handler.
+        ((INotifyPropertyChanged)description).PropertyChanged -= handler;
+        description.SortDescriptions.Add(description2);
+        Assert.Equal(new[] { description2 }, description.SortDescriptions.Cast<SortDescription>());
+        Assert.Null(description.CustomSort);
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void SortDescriptions_ChangeWithCustomSort_CallsPropertyChanged()
+    {
+        var description = new SubGroupDescription();
+        var description1 = new SortDescription("Name1", ListSortDirection.Ascending);
+        var description2 = new SortDescription("Name2", ListSortDirection.Ascending);
+        description.CustomSort = StringComparer.CurrentCulture;
+        Assert.Empty(description.SortDescriptions);
+
+        int callCount = 0;
+        var properties = new List<string>();
+        PropertyChangedEventHandler handler = (sender, e) =>
+        {
+            Assert.Same(description, sender);
+            properties.Add(e.PropertyName!);
+            callCount++;
+        };
+        ((INotifyPropertyChanged)description).PropertyChanged += handler;
+
+        // Add.
+        description.SortDescriptions.Add(description1);
+        Assert.Equal(new[] { description1 }, description.SortDescriptions.Cast<SortDescription>());
+        Assert.Null(description.CustomSort);
+        Assert.Equal(2, callCount);
+        Assert.Equal(new[] { "CustomSort", "SortDescriptions" }, properties);
+
+        // Clear.
+        description.SortDescriptions.Clear();
+        Assert.Empty(description.SortDescriptions);
+        Assert.Null(description.CustomSort);
+        Assert.Equal(3, callCount);
+        Assert.Equal(new[] { "CustomSort", "SortDescriptions", "SortDescriptions" }, properties);
+
+        // Remove handler.
+        ((INotifyPropertyChanged)description).PropertyChanged -= handler;
+        description.SortDescriptions.Add(description2);
+        Assert.Equal(new[] { description2 }, description.SortDescriptions.Cast<SortDescription>());
+        Assert.Null(description.CustomSort);
+        Assert.Equal(3, callCount);
+        Assert.Equal(new[] { "CustomSort", "SortDescriptions", "SortDescriptions" }, properties);
+    }
+
+    [Fact]
+    public void SortDescriptions_ShouldSerialize_ReturnsExpected()
+    {
+        var description = new SubGroupDescription();
+        PropertyDescriptor property = TypeDescriptor.GetProperties(typeof(GroupDescription))[nameof(GroupDescription.SortDescriptions)]!;
+        Assert.False(property.ShouldSerializeValue(description));
+
+        Assert.Empty(description.SortDescriptions);
+        Assert.False(property.ShouldSerializeValue(description));
+
+        description.SortDescriptions.Add(new SortDescription("Name", ListSortDirection.Ascending));
+        Assert.True(property.ShouldSerializeValue(description));
+
+        description.SortDescriptions.Clear();
+        Assert.False(property.ShouldSerializeValue(description));
+    }
+
+    [Fact]
+    public void PropertyChanged_INotifyPropertyChangedAddRemove_Success()
+    {
+        INotifyPropertyChanged description = new SubGroupDescription();
+
+        int callCount = 0;
+        PropertyChangedEventHandler handler = (s, e) => callCount++;
+        ((INotifyPropertyChanged)description).PropertyChanged += handler;
+        Assert.Equal(0, callCount);
+
+        ((INotifyPropertyChanged)description).PropertyChanged -= handler;
+        Assert.Equal(0, callCount);
+
+        // Remove non existent.
+        ((INotifyPropertyChanged)description).PropertyChanged -= handler;
+        Assert.Equal(0, callCount);
+
+        // Add null.
+        ((INotifyPropertyChanged)description).PropertyChanged += null;
+        Assert.Equal(0, callCount);
+
+        // Remove null.
+        ((INotifyPropertyChanged)description).PropertyChanged -= null;
+        Assert.Equal(0, callCount);
+    }
+
+    public static IEnumerable<object?[]> NamesMatch_TestData()
+    {
+        yield return new object?[] { null, null, true };
+
+        var obj = new object();
+        yield return new object?[] { obj, obj, true };
+        yield return new object?[] { obj, new object(), false };
+        yield return new object?[] { obj, null, false };
+        yield return new object?[] { null, null, true };
+        yield return new object?[] { null, new object(), false };
+    }
+
+    [Theory]
+    [MemberData(nameof(NamesMatch_TestData))]
+    public void NamesMatch_Invoke_ReturnsExpected(object? groupName1, object? groupName2, bool expected)
+    {
+        var description = new SubGroupDescription();
+        Assert.Equal(expected, description.NamesMatch(groupName1, groupName2));
+    }
+
+    public static IEnumerable<object?[]> OnPropertyChanged_TestData()
+    {
+        yield return new object?[] { new PropertyChangedEventArgs("Name") };
+        yield return new object?[] { null };
+    }
+
+    [Theory]
+    [MemberData(nameof(OnPropertyChanged_TestData))]
+    public void OnPropertyChanged_Invoke_CallsPropertyChangedEvent(PropertyChangedEventArgs eventArgs)
+    {
+        var description = new SubGroupDescription();
+        int callCount = 0;
+        PropertyChangedEventHandler handler = (sender, e) =>
+        {
+            Assert.Same(description, sender);
+            Assert.Same(eventArgs, e);
+            callCount++;
+        };
+
+        // Call with handler.
+        ((INotifyPropertyChanged)description).PropertyChanged += handler;
+        description.OnPropertyChanged(eventArgs);
+        Assert.Equal(1, callCount);
+
+        // Remove handler.
+        ((INotifyPropertyChanged)description).PropertyChanged -= handler;
+        description.OnPropertyChanged(eventArgs);
+        Assert.Equal(1, callCount);
+    }
+
+    [Fact]
+    public void ShouldSerializeGroupNames_Invoke_ReturnsExpected()
+    {
+        var description = new SubGroupDescription();
+        PropertyDescriptor property = TypeDescriptor.GetProperties(typeof(GroupDescription))[nameof(GroupDescription.GroupNames)]!;
+        Assert.False(description.ShouldSerializeGroupNames());
+
+        Assert.Empty(description.GroupNames);
+        Assert.False(description.ShouldSerializeGroupNames());
+
+        description.GroupNames.Add("Name");
+        Assert.True(description.ShouldSerializeGroupNames());
+
+        description.GroupNames.Clear();
+        Assert.False(description.ShouldSerializeGroupNames());
+    }
+
+    [Fact]
+    public void ShouldSerializeGroupNames_Invoke_DoesNotCallPropertyChanged()
+    {
+        var description = new SubGroupDescription();
+        int callCount = 0;
+        ((INotifyPropertyChanged)description).PropertyChanged += (sender, e) => callCount++;
+
+        Assert.False(description.ShouldSerializeGroupNames());
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void ShouldSerializeSortDescriptions_Invoke_ReturnsExpected()
+    {
+        var description = new SubGroupDescription();
+        Assert.False(description.ShouldSerializeSortDescriptions());
+
+        Assert.Empty(description.SortDescriptions);
+        Assert.False(description.ShouldSerializeSortDescriptions());
+
+        description.SortDescriptions.Add(new SortDescription("Name", ListSortDirection.Ascending));
+        Assert.True(description.ShouldSerializeSortDescriptions());
+
+        description.SortDescriptions.Clear();
+        Assert.False(description.ShouldSerializeSortDescriptions());
+    }
+
+    [Fact]
+    public void ShouldSerializeSortDescriptions_Invoke_DoesNotCallPropertyChanged()
+    {
+        var description = new SubGroupDescription();
+        int callCount = 0;
+        ((INotifyPropertyChanged)description).PropertyChanged += (sender, e) => callCount++;
+
+        Assert.False(description.ShouldSerializeSortDescriptions());
+        Assert.Equal(0, callCount);
+    }
+
+    private class SubGroupDescription : GroupDescription
+    {
+        public SubGroupDescription() : base()
+        {
+        }
+
+        public override object GroupNameFromItem(object item, int level, CultureInfo culture)
+            => throw new NotImplementedException();
+
+        public new void OnPropertyChanged(PropertyChangedEventArgs e) => base.OnPropertyChanged(e);
+    }
+}
\ No newline at end of file
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/ItemPropertyInfoTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/ItemPropertyInfoTests.cs
new file mode 100644
index 00000000000..74ae82ff1ba
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/ItemPropertyInfoTests.cs
@@ -0,0 +1,25 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.ComponentModel.Tests;
+
+public class ItemPropertyInfoTests
+{
+    public static IEnumerable<object?[]> Ctor_String_Type_Object_TestData()
+    {
+        yield return new object?[] { null, null, null };
+        yield return new object?[] { string.Empty, typeof(int), new object() };
+        yield return new object?[] { "name", typeof(object), 1 };
+    }
+
+    [Theory]
+    [MemberData(nameof(Ctor_String_Type_Object_TestData))]
+    public void Ctor_String_Type_Object(string name, Type type, object descriptor)
+    {
+        var propertyInfo = new ItemPropertyInfo(name, type, descriptor);
+        Assert.Equal(descriptor, propertyInfo.Descriptor);
+        Assert.Equal(name, propertyInfo.Name);
+        Assert.Equal(type, propertyInfo.PropertyType);
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/PropertyChangedEventManagerTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/PropertyChangedEventManagerTests.cs
new file mode 100644
index 00000000000..e7fbb20d533
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/PropertyChangedEventManagerTests.cs
@@ -0,0 +1,1274 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Windows;
+
+namespace System.ComponentModel.Tests;
+
+public class PropertyChangedEventManagerTests
+{
+    [Fact]
+    public void AddHandler_InvokeWithHandler_CallsErrorsChanged()
+    {
+        var source = new CustomNotifyPropertyChanged();
+        int callCount1 = 0;
+        var listener1 = new CustomWeakEventListener();
+        listener1.HandlerAction += (actualSender, actualE) =>
+        {
+            Assert.Same(source, actualSender);
+            callCount1++;
+        };
+        EventHandler<PropertyChangedEventArgs> handler1 = (EventHandler<PropertyChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<PropertyChangedEventArgs>), listener1, nameof(CustomWeakEventListener.Handler));
+        int callCount2 = 0;
+        var listener2 = new CustomWeakEventListener();
+        listener2.HandlerAction += (actualSender, actualE) =>
+        {
+            Assert.Same(source, actualSender);
+            callCount2++;
+        };
+        EventHandler<PropertyChangedEventArgs> handler2 = (EventHandler<PropertyChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<PropertyChangedEventArgs>), listener2, nameof(CustomWeakEventListener.Handler));
+
+        // Add.
+        PropertyChangedEventManager.AddHandler(source, handler1, "propertyName");
+
+        // Call.
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Call null property name.
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs(null));
+        Assert.Equal(2, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Call empty property name.
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs(string.Empty));
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Call invalid source.
+        source.OnPropertyChanged(listener1, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(3, callCount1);    
+        Assert.Equal(0, callCount2);
+        
+        source.OnPropertyChanged(new object(), new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+        
+        source.OnPropertyChanged(null!, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Add again.
+        PropertyChangedEventManager.AddHandler(source, handler1, "propertyName");
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(5, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Add another.
+        PropertyChangedEventManager.AddHandler(source, handler2, "propertyName");
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(7, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove second.
+        PropertyChangedEventManager.RemoveHandler(source, handler2, "propertyName");
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(9, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove first.
+        PropertyChangedEventManager.RemoveHandler(source, handler1, "propertyName");
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(10, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove again.
+        PropertyChangedEventManager.RemoveHandler(source, handler1, "propertyName");
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(10, callCount1);
+        Assert.Equal(1, callCount2);
+    }
+
+    [Theory]
+    [InlineData("propertyName")]
+    [InlineData("PROPERTYNAME")]
+    public void AddHandler_InvokeMultipleTimes_Success(string propertyName)
+    {
+        var source1 = new CustomNotifyPropertyChanged();
+        var source2 = new CustomNotifyPropertyChanged();
+        var target1 = new CustomWeakEventListener();
+        int callCount1 = 0;
+        target1.HandlerAction += (s, e) => callCount1++;
+        EventHandler<PropertyChangedEventArgs> handler1 = (EventHandler<PropertyChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<PropertyChangedEventArgs>), target1, nameof(CustomWeakEventListener.Handler));
+        var target2 = new CustomWeakEventListener();
+        int callCount2 = 0;
+        target2.HandlerAction += (s, e) => callCount2++;
+        EventHandler<PropertyChangedEventArgs> handler2 = (EventHandler<PropertyChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<PropertyChangedEventArgs>), target2, nameof(CustomWeakEventListener.Handler));
+        var target3 = new CustomWeakEventListener();
+        int callCount3 = 0;
+        target3.HandlerAction += (s, e) => callCount3++;
+        EventHandler<PropertyChangedEventArgs> handler3 = (EventHandler<PropertyChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<PropertyChangedEventArgs>), target3, nameof(CustomWeakEventListener.Handler));
+        var target4 = new CustomWeakEventListener();
+        int callCount4 = 0;
+        target4.HandlerAction += (s, e) => callCount4++;
+        EventHandler<PropertyChangedEventArgs> handler4 = (EventHandler<PropertyChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<PropertyChangedEventArgs>), target4, nameof(CustomWeakEventListener.Handler));
+        var target5 = new CustomWeakEventListener();
+        int callCount5 = 0;
+        target5.HandlerAction += (s, e) => callCount5++;
+        EventHandler<PropertyChangedEventArgs> handler5 = (EventHandler<PropertyChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<PropertyChangedEventArgs>), target5, nameof(CustomWeakEventListener.Handler));
+
+        // Add.
+        PropertyChangedEventManager.AddHandler(source1, handler1, "propertyName");
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(propertyName));
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs("propertyName2"));
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(string.Empty));
+        Assert.Equal(2, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(null));
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(propertyName));
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(string.Empty));
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(null));
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+
+        // Add again.
+        PropertyChangedEventManager.AddHandler(source1, handler1, "propertyName");
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(propertyName));
+        Assert.Equal(5, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs("propertyName2"));
+        Assert.Equal(5, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(string.Empty));
+        Assert.Equal(7, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(null));
+        Assert.Equal(9, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(propertyName));
+        Assert.Equal(9, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(string.Empty));
+        Assert.Equal(9, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(null));
+        Assert.Equal(9, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+
+        // Add another handler.
+        PropertyChangedEventManager.AddHandler(source1, handler2, "propertyName");
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(propertyName));
+        Assert.Equal(11, callCount1);
+        Assert.Equal(1, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs("propertyName2"));
+        Assert.Equal(11, callCount1);
+        Assert.Equal(1, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(string.Empty));
+        Assert.Equal(13, callCount1);
+        Assert.Equal(2, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(null));
+        Assert.Equal(15, callCount1);
+        Assert.Equal(3, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(propertyName));
+        Assert.Equal(15, callCount1);
+        Assert.Equal(3, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(string.Empty));
+        Assert.Equal(15, callCount1);
+        Assert.Equal(3, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(null));
+        Assert.Equal(15, callCount1);
+        Assert.Equal(3, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+
+        // Add another property name.
+        PropertyChangedEventManager.AddHandler(source1, handler3, "propertyName2");
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(propertyName));
+        Assert.Equal(17, callCount1);
+        Assert.Equal(4, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs("propertyName2"));
+        Assert.Equal(17, callCount1);
+        Assert.Equal(4, callCount2);
+        Assert.Equal(1, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(string.Empty));
+        Assert.Equal(19, callCount1);
+        Assert.Equal(5, callCount2);
+        Assert.Equal(2, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(null));
+        Assert.Equal(21, callCount1);
+        Assert.Equal(6, callCount2);
+        Assert.Equal(3, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(propertyName));
+        Assert.Equal(21, callCount1);
+        Assert.Equal(6, callCount2);
+        Assert.Equal(3, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(string.Empty));
+        Assert.Equal(21, callCount1);
+        Assert.Equal(6, callCount2);
+        Assert.Equal(3, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(null));
+        Assert.Equal(21, callCount1);
+        Assert.Equal(6, callCount2);
+        Assert.Equal(3, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+
+        // Add another source.
+        PropertyChangedEventManager.AddHandler(source2, handler4, "propertyName");
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(propertyName));
+        Assert.Equal(23, callCount1);
+        Assert.Equal(7, callCount2);
+        Assert.Equal(3, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs("propertyName2"));
+        Assert.Equal(23, callCount1);
+        Assert.Equal(7, callCount2);
+        Assert.Equal(4, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(string.Empty));
+        Assert.Equal(25, callCount1);
+        Assert.Equal(8, callCount2);
+        Assert.Equal(5, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(null));
+        Assert.Equal(27, callCount1);
+        Assert.Equal(9, callCount2);
+        Assert.Equal(6, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(propertyName));
+        Assert.Equal(27, callCount1);
+        Assert.Equal(9, callCount2);
+        Assert.Equal(6, callCount3);
+        Assert.Equal(1, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(string.Empty));
+        Assert.Equal(27, callCount1);
+        Assert.Equal(9, callCount2);
+        Assert.Equal(6, callCount3);
+        Assert.Equal(2, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(null));
+        Assert.Equal(27, callCount1);
+        Assert.Equal(9, callCount2);
+        Assert.Equal(6, callCount3);
+        Assert.Equal(3, callCount4);
+        Assert.Equal(0, callCount5);
+
+        // Add another source (empty).
+        PropertyChangedEventManager.AddHandler(source2, handler5, "");
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(propertyName));
+        Assert.Equal(29, callCount1);
+        Assert.Equal(10, callCount2);
+        Assert.Equal(6, callCount3);
+        Assert.Equal(3, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs("propertyName2"));
+        Assert.Equal(29, callCount1);
+        Assert.Equal(10, callCount2);
+        Assert.Equal(7, callCount3);
+        Assert.Equal(3, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(string.Empty));
+        Assert.Equal(31, callCount1);
+        Assert.Equal(11, callCount2);
+        Assert.Equal(8, callCount3);
+        Assert.Equal(3, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(null));
+        Assert.Equal(33, callCount1);
+        Assert.Equal(12, callCount2);
+        Assert.Equal(9, callCount3);
+        Assert.Equal(3, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(propertyName));
+        Assert.Equal(33, callCount1);
+        Assert.Equal(12, callCount2);
+        Assert.Equal(9, callCount3);
+        Assert.Equal(4, callCount4);
+        Assert.Equal(1, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(string.Empty));
+        Assert.Equal(33, callCount1);
+        Assert.Equal(12, callCount2);
+        Assert.Equal(9, callCount3);
+        Assert.Equal(5, callCount4);
+        Assert.Equal(2, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(null));
+        Assert.Equal(33, callCount1);
+        Assert.Equal(12, callCount2);
+        Assert.Equal(9, callCount3);
+        Assert.Equal(6, callCount4);
+        Assert.Equal(3, callCount5);
+    }
+
+    [Fact]
+    public void AddHandler_NullSource_ThrowsArgumentNullException()
+    {
+        var target = new CustomWeakEventListener();
+        EventHandler<PropertyChangedEventArgs> handler = (EventHandler<PropertyChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<PropertyChangedEventArgs>), target, nameof(CustomWeakEventListener.Handler));
+        // TODO: this should be NullReferenceException.
+        Assert.Throws<NullReferenceException>(() => PropertyChangedEventManager.AddHandler(null, handler, "propertyName"));
+    
+        // Add again.
+        Assert.Throws<NullReferenceException>(() => PropertyChangedEventManager.AddHandler(null, handler, "propertyName"));
+    }
+
+    [Fact]
+    public void AddHandler_NullHandler_ThrowsArgumentNullException()
+    {
+        var source = new CustomNotifyPropertyChanged();
+        Assert.Throws<ArgumentNullException>("handler", () => PropertyChangedEventManager.AddHandler(source, null, "propertyName"));
+    }
+
+    [Fact]
+    public void AddHandler_NullPropertyName_ThrowsArgumentNullException()
+    {
+        var source = new CustomNotifyPropertyChanged();
+        var target = new CustomWeakEventListener();
+        EventHandler<PropertyChangedEventArgs> handler = (EventHandler<PropertyChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<PropertyChangedEventArgs>), target, nameof(CustomWeakEventListener.Handler));
+        // TODO: incorrect paramName.
+        Assert.Throws<ArgumentNullException>("key", () => PropertyChangedEventManager.AddHandler(source, handler, null));
+    }
+    [Fact]
+    public void AddListener_InvokeWithHandler_CallsErrorsChanged()
+    {
+        var source = new CustomNotifyPropertyChanged();
+        int callCount1 = 0;
+        var listener1 = new CustomWeakEventListener();
+        listener1.ReceiveWeakEventAction += (actualManagerType, actualSender, actualE) =>
+        {
+            Assert.Equal(typeof(PropertyChangedEventManager), actualManagerType);
+            Assert.Same(source, actualSender);
+            callCount1++;
+            return true;
+        };
+        int callCount2 = 0;
+        var listener2 = new CustomWeakEventListener();
+        listener2.ReceiveWeakEventAction += (actualManagerType, actualSender, actualE) =>
+        {
+            Assert.Equal(typeof(PropertyChangedEventManager), actualManagerType);
+            Assert.Same(source, actualSender);
+            callCount2++;
+            return true;
+        };
+
+        // Add.
+        PropertyChangedEventManager.AddListener(source, listener1, "propertyName");
+
+        // Call.
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Call null property name.
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs(null));
+        Assert.Equal(2, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Call empty property name.
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs(string.Empty));
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Call invalid source.
+        source.OnPropertyChanged(listener1, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(3, callCount1);    
+        Assert.Equal(0, callCount2);
+        
+        source.OnPropertyChanged(new object(), new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+        
+        source.OnPropertyChanged(null!, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Add again.
+        PropertyChangedEventManager.AddListener(source, listener1, "propertyName");
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(5, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Add another.
+        PropertyChangedEventManager.AddListener(source, listener2, "propertyName");
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(7, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove second.
+        PropertyChangedEventManager.RemoveListener(source, listener2, "propertyName");
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(9, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove first.
+        PropertyChangedEventManager.RemoveListener(source, listener1, "propertyName");
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(10, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove again.
+        PropertyChangedEventManager.RemoveListener(source, listener1, "propertyName");
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(10, callCount1);
+        Assert.Equal(1, callCount2);
+    }
+
+    [Theory]
+    [InlineData("propertyName")]
+    [InlineData("PROPERTYNAME")]
+    public void AddListener_InvokeMultipleTimes_Success(string propertyName)
+    {
+        var source1 = new CustomNotifyPropertyChanged();
+        var source2 = new CustomNotifyPropertyChanged();
+        var listener1 = new CustomWeakEventListener();
+        int callCount1 = 0;
+        listener1.ReceiveWeakEventAction += (t, s, e) =>
+        {
+            callCount1++;
+            return true;
+        };
+        var listener2 = new CustomWeakEventListener();
+        int callCount2 = 0;
+        listener2.ReceiveWeakEventAction += (t, s, e) =>
+        {
+            callCount2++;
+            return true;
+        };
+        var listener3 = new CustomWeakEventListener();
+        int callCount3 = 0;
+        listener3.ReceiveWeakEventAction += (t, s, e) =>
+        {
+            callCount3++;
+            return true;
+        };
+        var listener4 = new CustomWeakEventListener();
+        int callCount4 = 0;
+        listener4.ReceiveWeakEventAction += (t, s, e) =>
+        {
+            callCount4++;
+            return true;
+        };
+        var listener5 = new CustomWeakEventListener();
+        int callCount5 = 0;
+        listener5.ReceiveWeakEventAction += (t, s, e) =>
+        {
+            callCount5++;
+            return true;
+        };
+
+        // Add.
+        PropertyChangedEventManager.AddListener(source1, listener1, "propertyName");
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(propertyName));
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs("propertyName2"));
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(string.Empty));
+        Assert.Equal(2, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(null));
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(propertyName));
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(string.Empty));
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(null));
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+
+        // Add again.
+        PropertyChangedEventManager.AddListener(source1, listener1, "propertyName");
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(propertyName));
+        Assert.Equal(5, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs("propertyName2"));
+        Assert.Equal(5, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(string.Empty));
+        Assert.Equal(7, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(null));
+        Assert.Equal(9, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(propertyName));
+        Assert.Equal(9, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(string.Empty));
+        Assert.Equal(9, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(null));
+        Assert.Equal(9, callCount1);
+        Assert.Equal(0, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+
+        // Add another listener.
+        PropertyChangedEventManager.AddListener(source1, listener2, "propertyName");
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(propertyName));
+        Assert.Equal(11, callCount1);
+        Assert.Equal(1, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs("propertyName2"));
+        Assert.Equal(11, callCount1);
+        Assert.Equal(1, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(string.Empty));
+        Assert.Equal(13, callCount1);
+        Assert.Equal(2, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(null));
+        Assert.Equal(15, callCount1);
+        Assert.Equal(3, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(propertyName));
+        Assert.Equal(15, callCount1);
+        Assert.Equal(3, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(string.Empty));
+        Assert.Equal(15, callCount1);
+        Assert.Equal(3, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(null));
+        Assert.Equal(15, callCount1);
+        Assert.Equal(3, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+
+        // Add another property name.
+        PropertyChangedEventManager.AddListener(source1, listener3, "propertyName2");
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(propertyName));
+        Assert.Equal(17, callCount1);
+        Assert.Equal(4, callCount2);
+        Assert.Equal(0, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs("propertyName2"));
+        Assert.Equal(17, callCount1);
+        Assert.Equal(4, callCount2);
+        Assert.Equal(1, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(string.Empty));
+        Assert.Equal(19, callCount1);
+        Assert.Equal(5, callCount2);
+        Assert.Equal(2, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(null));
+        Assert.Equal(21, callCount1);
+        Assert.Equal(6, callCount2);
+        Assert.Equal(3, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(propertyName));
+        Assert.Equal(21, callCount1);
+        Assert.Equal(6, callCount2);
+        Assert.Equal(3, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(string.Empty));
+        Assert.Equal(21, callCount1);
+        Assert.Equal(6, callCount2);
+        Assert.Equal(3, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(null));
+        Assert.Equal(21, callCount1);
+        Assert.Equal(6, callCount2);
+        Assert.Equal(3, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+
+        // Add another source.
+        PropertyChangedEventManager.AddListener(source2, listener4, "propertyName");
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(propertyName));
+        Assert.Equal(23, callCount1);
+        Assert.Equal(7, callCount2);
+        Assert.Equal(3, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs("propertyName2"));
+        Assert.Equal(23, callCount1);
+        Assert.Equal(7, callCount2);
+        Assert.Equal(4, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(string.Empty));
+        Assert.Equal(25, callCount1);
+        Assert.Equal(8, callCount2);
+        Assert.Equal(5, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(null));
+        Assert.Equal(27, callCount1);
+        Assert.Equal(9, callCount2);
+        Assert.Equal(6, callCount3);
+        Assert.Equal(0, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(propertyName));
+        Assert.Equal(27, callCount1);
+        Assert.Equal(9, callCount2);
+        Assert.Equal(6, callCount3);
+        Assert.Equal(1, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(string.Empty));
+        Assert.Equal(27, callCount1);
+        Assert.Equal(9, callCount2);
+        Assert.Equal(6, callCount3);
+        Assert.Equal(2, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(null));
+        Assert.Equal(27, callCount1);
+        Assert.Equal(9, callCount2);
+        Assert.Equal(6, callCount3);
+        Assert.Equal(3, callCount4);
+        Assert.Equal(0, callCount5);
+
+        // Add another source (empty).
+        PropertyChangedEventManager.AddListener(source2, listener5, "");
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(propertyName));
+        Assert.Equal(29, callCount1);
+        Assert.Equal(10, callCount2);
+        Assert.Equal(6, callCount3);
+        Assert.Equal(3, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs("propertyName2"));
+        Assert.Equal(29, callCount1);
+        Assert.Equal(10, callCount2);
+        Assert.Equal(7, callCount3);
+        Assert.Equal(3, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(string.Empty));
+        Assert.Equal(31, callCount1);
+        Assert.Equal(11, callCount2);
+        Assert.Equal(8, callCount3);
+        Assert.Equal(3, callCount4);
+        Assert.Equal(0, callCount5);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs(null));
+        Assert.Equal(33, callCount1);
+        Assert.Equal(12, callCount2);
+        Assert.Equal(9, callCount3);
+        Assert.Equal(3, callCount4);
+        Assert.Equal(0, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(propertyName));
+        Assert.Equal(33, callCount1);
+        Assert.Equal(12, callCount2);
+        Assert.Equal(9, callCount3);
+        Assert.Equal(4, callCount4);
+        Assert.Equal(1, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(string.Empty));
+        Assert.Equal(33, callCount1);
+        Assert.Equal(12, callCount2);
+        Assert.Equal(9, callCount3);
+        Assert.Equal(5, callCount4);
+        Assert.Equal(2, callCount5);
+        source2.OnPropertyChanged(source2, new PropertyChangedEventArgs(null));
+        Assert.Equal(33, callCount1);
+        Assert.Equal(12, callCount2);
+        Assert.Equal(9, callCount3);
+        Assert.Equal(6, callCount4);
+        Assert.Equal(3, callCount5);
+    }
+
+    [Fact]
+    public void AddListener_NullSource_ThrowsArgumentNullException()
+    {
+        var listener = new CustomWeakEventListener();
+        Assert.Throws<ArgumentNullException>("source", () => PropertyChangedEventManager.AddListener(null, listener, "propertyName"));
+    
+        // Add again.
+        Assert.Throws<ArgumentNullException>("source", () => PropertyChangedEventManager.AddListener(null, listener, "propertyName"));
+    }
+
+    [Fact]
+    public void AddListener_NullListener_ThrowsArgumentNullException()
+    {
+        var source = new CustomNotifyPropertyChanged();
+        Assert.Throws<ArgumentNullException>("listener", () => PropertyChangedEventManager.AddListener(source, null, "propertyName"));
+    }
+
+    [Fact]
+    public void AddListener_NullPropertyName_ThrowsArgumentNullException()
+    {
+        var source = new CustomNotifyPropertyChanged();
+        var listener = new CustomWeakEventListener();
+        // TODO: incorrect paramName.
+        Assert.Throws<ArgumentNullException>("key", () => PropertyChangedEventManager.AddListener(source, listener, null));
+    }
+
+    [Theory]
+    [InlineData("propertyName")]
+    [InlineData("PROPERTYNAME")]
+    public void RemoveHandler_Invoke_Success(string propertyName)
+    {
+        var source = new CustomNotifyPropertyChanged();
+        var target = new CustomWeakEventListener();
+        int callCount = 0;
+        target.HandlerAction += (s, e) => callCount++;
+        EventHandler<PropertyChangedEventArgs> handler = (EventHandler<PropertyChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<PropertyChangedEventArgs>), target, nameof(CustomWeakEventListener.Handler));
+        PropertyChangedEventManager.AddHandler(source, handler, "propertyName");
+
+        // Remove.
+        PropertyChangedEventManager.RemoveHandler(source, handler, propertyName);
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(0, callCount);
+
+        // Remove again.
+        PropertyChangedEventManager.RemoveHandler(source, handler, propertyName);
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void RemoveHandler_InvokeMultipleNames_Success()
+    {
+        var source = new CustomNotifyPropertyChanged();
+        var target1 = new CustomWeakEventListener();
+        int callCount1 = 0;
+        target1.HandlerAction += (s, e) => callCount1++;
+        EventHandler<PropertyChangedEventArgs> handler1 = (EventHandler<PropertyChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<PropertyChangedEventArgs>), target1, nameof(CustomWeakEventListener.Handler));
+        var target2 = new CustomWeakEventListener();
+        int callCount2 = 0;
+        target2.HandlerAction += (s, e) => callCount2++;
+        EventHandler<PropertyChangedEventArgs> handler2 = (EventHandler<PropertyChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<PropertyChangedEventArgs>), target2, nameof(CustomWeakEventListener.Handler));
+        var target3 = new CustomWeakEventListener();
+        int callCount3 = 0;
+        target3.HandlerAction += (s, e) => callCount3++;
+        EventHandler<PropertyChangedEventArgs> handler3 = (EventHandler<PropertyChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<PropertyChangedEventArgs>), target3, nameof(CustomWeakEventListener.Handler));
+        PropertyChangedEventManager.AddHandler(source, handler1, "propertyName1");
+        PropertyChangedEventManager.AddHandler(source, handler2, "propertyName2");
+        PropertyChangedEventManager.AddHandler(source, handler3, "");
+
+        // Remove.
+        PropertyChangedEventManager.RemoveHandler(source, handler1, "propertyName1");
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs(null));
+        Assert.Equal(0, callCount1);
+        Assert.Equal(1, callCount2);
+        Assert.Equal(1, callCount3);
+
+        // Remove again.
+        PropertyChangedEventManager.RemoveHandler(source, handler1, "propertyName1");
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs(null));
+        Assert.Equal(0, callCount1);
+        Assert.Equal(2, callCount2);
+        Assert.Equal(2, callCount3);
+
+        // Remove another.
+        PropertyChangedEventManager.RemoveHandler(source, handler3, "");
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs(null));
+        Assert.Equal(0, callCount1);
+        Assert.Equal(3, callCount2);
+        Assert.Equal(2, callCount3);
+
+        // Remove last.
+        PropertyChangedEventManager.RemoveHandler(source, handler2, "propertyName2");
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs(null));
+        Assert.Equal(0, callCount1);
+        Assert.Equal(3, callCount2);
+        Assert.Equal(2, callCount3);
+    }
+
+    [Fact]
+    public void RemoveHandler_InvokeNoSource_Success()
+    {
+        var target = new CustomWeakEventListener();
+        EventHandler<PropertyChangedEventArgs> handler = (EventHandler<PropertyChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<PropertyChangedEventArgs>), target, nameof(CustomWeakEventListener.Handler));
+
+        // Remove.
+        PropertyChangedEventManager.RemoveHandler(null, handler, "propertyName");
+
+        // Remove again.
+        PropertyChangedEventManager.RemoveHandler(null, handler, "propertyName");
+    }
+
+    [Theory]
+    [InlineData("propertyName")]
+    [InlineData("")]
+    [InlineData(null)]
+    public void RemoveHandler_InvokeNoSuchSource_Nop(string? propertyName)
+    {
+        var source1 = new CustomNotifyPropertyChanged();
+        var source2 = new CustomNotifyPropertyChanged();
+        var target = new CustomWeakEventListener();
+        int callCount = 0;
+        target.HandlerAction += (s, e) => callCount++;
+        EventHandler<PropertyChangedEventArgs> handler = (EventHandler<PropertyChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<PropertyChangedEventArgs>), target, nameof(CustomWeakEventListener.Handler));
+        PropertyChangedEventManager.AddHandler(source1, handler, "propertyName");
+
+        // Remove.
+        PropertyChangedEventManager.RemoveHandler(source2, handler, propertyName);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs("propertyName"));
+
+        // Remove again.
+        PropertyChangedEventManager.RemoveHandler(source2, handler, propertyName);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs("propertyName"));
+    }
+
+    [Fact]
+    public void RemoveHandler_InvokeNoSuchHandler_Nop()
+    {
+        var source = new CustomNotifyPropertyChanged();
+        var target1 = new CustomWeakEventListener();
+        int callCount1 = 0;
+        target1.HandlerAction += (s, e) => callCount1++;
+        EventHandler<PropertyChangedEventArgs> handler1 = (EventHandler<PropertyChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<PropertyChangedEventArgs>), target1, nameof(CustomWeakEventListener.Handler));
+        var target2 = new CustomWeakEventListener();
+        int callCount2 = 0;
+        target2.HandlerAction += (s, e) => callCount2++;
+        EventHandler<PropertyChangedEventArgs> handler2 = (EventHandler<PropertyChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<PropertyChangedEventArgs>), target2, nameof(CustomWeakEventListener.Handler));
+        PropertyChangedEventManager.AddHandler(source, handler1, "propertyName");
+
+        // Remove.
+        PropertyChangedEventManager.RemoveHandler(source, handler2, "propertyName");
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Remove again.
+        PropertyChangedEventManager.RemoveHandler(source, handler2, "propertyName");
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(2, callCount1);
+    }
+
+    [Theory]
+    [InlineData("propertyName2")]
+    [InlineData("")]
+    public void RemoveHandler_InvokeNoSuchPropertyName_Nop(string propertyName)
+    {
+        var source = new CustomNotifyPropertyChanged();
+        var target = new CustomWeakEventListener();
+        int callCount = 0;
+        target.HandlerAction += (s, e) => callCount++;
+        EventHandler<PropertyChangedEventArgs> handler = (EventHandler<PropertyChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<PropertyChangedEventArgs>), target, nameof(CustomWeakEventListener.Handler));
+        PropertyChangedEventManager.AddHandler(source, handler, "propertyName");
+
+        // Remove.
+        PropertyChangedEventManager.RemoveHandler(source, handler, propertyName);
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(1, callCount);
+
+        // Remove again.
+        PropertyChangedEventManager.RemoveHandler(source, handler, propertyName);
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void RemoveHandler_NullPropertyName_ThrowsArgumentNullException()
+    {
+        var source = new CustomNotifyPropertyChanged();
+        var target = new CustomWeakEventListener();
+        int callCount = 0;
+        target.HandlerAction += (s, e) => callCount++;
+        EventHandler<PropertyChangedEventArgs> handler = (EventHandler<PropertyChangedEventArgs>)Delegate.CreateDelegate(typeof(EventHandler<PropertyChangedEventArgs>), target, nameof(CustomWeakEventListener.Handler));
+        PropertyChangedEventManager.AddHandler(source, handler, "propertyName");
+
+        // Remove.
+        // TODO: incorrect paramName.
+        Assert.Throws<ArgumentNullException>("key", () => PropertyChangedEventManager.RemoveHandler(source, handler, null));
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(1, callCount);
+
+        // Remove again.
+        // TODO: incorrect paramName.
+        Assert.Throws<ArgumentNullException>("key", () => PropertyChangedEventManager.RemoveHandler(source, handler, null));
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void RemoveHandler_NullHandler_ThrowsArgumentNullException()
+    {
+        var source = new CustomNotifyPropertyChanged();
+        Assert.Throws<ArgumentNullException>("handler", () => PropertyChangedEventManager.RemoveHandler(source, null, "propertyName"));
+    }
+
+    [Theory]
+    [InlineData("propertyName")]
+    [InlineData("PROPERTYNAME")]
+    public void RemoveListener_Invoke_Success(string propertyName)
+    {
+        var source = new CustomNotifyPropertyChanged();
+        var listener = new CustomWeakEventListener();
+        int callCount = 0;
+        listener.ReceiveWeakEventAction += (t, s, e) =>
+        {
+            callCount++;
+            return true;
+        };
+        PropertyChangedEventManager.AddListener(source, listener, "propertyName");
+
+        // Remove.
+        PropertyChangedEventManager.RemoveListener(source, listener, propertyName);
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(0, callCount);
+
+        // Remove again.
+        PropertyChangedEventManager.RemoveListener(source, listener, propertyName);
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void RemoveListener_InvokeMultipleNames_Success()
+    {
+        var source = new CustomNotifyPropertyChanged();
+        var listener1 = new CustomWeakEventListener();
+        int callCount1 = 0;
+        listener1.ReceiveWeakEventAction += (t, s, e) =>
+        {
+            callCount1++;
+            return true;
+        };
+        var listener2 = new CustomWeakEventListener();
+        int callCount2 = 0;
+        listener2.ReceiveWeakEventAction += (t, s, e) =>
+        {
+            callCount2++;
+            return true;
+        };
+        var listener3 = new CustomWeakEventListener();
+        int callCount3 = 0;
+        listener3.ReceiveWeakEventAction += (t, s, e) =>
+        {
+            callCount3++;
+            return true;
+        };
+        PropertyChangedEventManager.AddListener(source, listener1, "propertyName1");
+        PropertyChangedEventManager.AddListener(source, listener2, "propertyName2");
+        PropertyChangedEventManager.AddListener(source, listener3, "");
+
+        // Remove.
+        PropertyChangedEventManager.RemoveListener(source, listener1, "propertyName1");
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs(null));
+        Assert.Equal(0, callCount1);
+        Assert.Equal(1, callCount2);
+        Assert.Equal(1, callCount3);
+
+        // Remove again.
+        PropertyChangedEventManager.RemoveListener(source, listener1, "propertyName1");
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs(null));
+        Assert.Equal(0, callCount1);
+        Assert.Equal(2, callCount2);
+        Assert.Equal(2, callCount3);
+
+        // Remove another.
+        PropertyChangedEventManager.RemoveListener(source, listener3, "");
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs(null));
+        Assert.Equal(0, callCount1);
+        Assert.Equal(3, callCount2);
+        Assert.Equal(2, callCount3);
+
+        // Remove last.
+        PropertyChangedEventManager.RemoveListener(source, listener2, "propertyName2");
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs(null));
+        Assert.Equal(0, callCount1);
+        Assert.Equal(3, callCount2);
+        Assert.Equal(2, callCount3);
+    }
+
+    [Fact]
+    public void RemoveListener_InvokeNoSource_Success()
+    {
+        var listener = new CustomWeakEventListener();
+
+        // Remove.
+        PropertyChangedEventManager.RemoveListener(null, listener, "propertyName");
+
+        // Remove again.
+        PropertyChangedEventManager.RemoveListener(null, listener, "propertyName");
+    }
+
+    [Theory]
+    [InlineData("propertyName")]
+    [InlineData("")]
+    [InlineData(null)]
+    public void RemoveListener_InvokeNoSuchSource_Nop(string? propertyName)
+    {
+        var source1 = new CustomNotifyPropertyChanged();
+        var source2 = new CustomNotifyPropertyChanged();
+        var listener = new CustomWeakEventListener();
+        int callCount = 0;
+        listener.ReceiveWeakEventAction += (t, s, e) =>
+        {
+            callCount++;
+            return true;
+        };
+        PropertyChangedEventManager.AddListener(source1, listener, "propertyName");
+
+        // Remove.
+        PropertyChangedEventManager.RemoveListener(source2, listener, propertyName);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs("propertyName"));
+
+        // Remove again.
+        PropertyChangedEventManager.RemoveListener(source2, listener, propertyName);
+        source1.OnPropertyChanged(source1, new PropertyChangedEventArgs("propertyName"));
+    }
+
+    [Fact]
+    public void RemoveListener_InvokeNoSuchListener_Nop()
+    {
+        var source = new CustomNotifyPropertyChanged();
+        var listener1 = new CustomWeakEventListener();
+        int callCount1 = 0;
+        listener1.ReceiveWeakEventAction += (t, s, e) =>
+        {
+            callCount1++;
+            return true;
+        };
+        var listener2 = new CustomWeakEventListener();
+        int callCount2 = 0;
+        listener2.ReceiveWeakEventAction += (t, s, e) =>
+        {
+            callCount2++;
+            return true;
+        };
+        PropertyChangedEventManager.AddListener(source, listener1, "propertyName");
+
+        // Remove.
+        PropertyChangedEventManager.RemoveListener(source, listener2, "propertyName");
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Remove again.
+        PropertyChangedEventManager.RemoveListener(source, listener2, "propertyName");
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(2, callCount1);
+    }
+
+    [Theory]
+    [InlineData("propertyName2")]
+    [InlineData("")]
+    public void RemoveListener_InvokeNoSuchPropertyName_Nop(string propertyName)
+    {
+        var source = new CustomNotifyPropertyChanged();
+        var listener = new CustomWeakEventListener();
+        int callCount = 0;
+        listener.ReceiveWeakEventAction += (t, s, e) =>
+        {
+            callCount++;
+            return true;
+        };
+        PropertyChangedEventManager.AddListener(source, listener, "propertyName");
+
+        // Remove.
+        PropertyChangedEventManager.RemoveListener(source, listener, propertyName);
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(1, callCount);
+
+        // Remove again.
+        PropertyChangedEventManager.RemoveListener(source, listener, propertyName);
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void RemoveListener_NullPropertyName_ThrowsArgumentNullException()
+    {
+        var source = new CustomNotifyPropertyChanged();
+        var listener = new CustomWeakEventListener();
+        int callCount = 0;
+        listener.ReceiveWeakEventAction += (t, s, e) =>
+        {
+            callCount++;
+            return true;
+        };
+        PropertyChangedEventManager.AddListener(source, listener, "propertyName");
+
+        // Remove.
+        // TODO: incorrect paramName.
+        Assert.Throws<ArgumentNullException>("key", () => PropertyChangedEventManager.RemoveListener(source, listener, null));
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(1, callCount);
+
+        // Remove again.
+        // TODO: incorrect paramName.
+        Assert.Throws<ArgumentNullException>("key", () => PropertyChangedEventManager.RemoveListener(source, listener, null));
+        source.OnPropertyChanged(source, new PropertyChangedEventArgs("propertyName"));
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void RemoveListener_NullListener_ThrowsArgumentNullException()
+    {
+        var source = new CustomNotifyPropertyChanged();
+        Assert.Throws<ArgumentNullException>("listener", () => PropertyChangedEventManager.RemoveListener(source, null, "propertyName"));
+    }
+
+    private class CustomNotifyPropertyChanged : INotifyPropertyChanged
+    {
+        public event PropertyChangedEventHandler? PropertyChanged;
+
+        public void OnPropertyChanged(object sender, PropertyChangedEventArgs e) => PropertyChanged?.Invoke(sender, e);
+    }
+
+    private class CustomWeakEventListener : IWeakEventListener
+    {
+        public Func<Type, object, EventArgs, bool>? ReceiveWeakEventAction { get; set; }
+
+        public bool ReceiveWeakEvent(Type managerType, object sender, EventArgs e)
+        {
+            if (ReceiveWeakEventAction is null)
+            {
+                return true;
+            }
+
+            return ReceiveWeakEventAction(managerType, sender, e);
+        }
+
+        public Action<object, PropertyChangedEventArgs>? HandlerAction { get; set; }
+
+        public void Handler(object sender, PropertyChangedEventArgs e)
+        {
+            HandlerAction?.Invoke(sender, e);
+        }
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/PropertyFilterAttributeTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/PropertyFilterAttributeTests.cs
new file mode 100644
index 00000000000..6fdc2a65e02
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/PropertyFilterAttributeTests.cs
@@ -0,0 +1,76 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.ComponentModel.Tests;
+
+public class PropertyFilterAttributeTests
+{
+    [Theory]
+    [InlineData(PropertyFilterOptions.All)]
+    [InlineData(PropertyFilterOptions.SetValues)]
+    [InlineData(PropertyFilterOptions.Invalid)]
+    [InlineData(PropertyFilterOptions.None)]
+    [InlineData(PropertyFilterOptions.None - 1)]
+    public void Ctor_PropertyFilterOptions(PropertyFilterOptions filter)
+    {
+        var attribute = new PropertyFilterAttribute(filter);
+        Assert.Equal(filter, attribute.Filter);
+    }
+
+    [Fact]
+    public void Default_Get_ReturnsExpected()
+    {
+        PropertyFilterAttribute attribute = PropertyFilterAttribute.Default;
+        Assert.Equal(PropertyFilterOptions.All, attribute.Filter);
+        Assert.Same(attribute, PropertyFilterAttribute.Default);
+    }
+
+    public static IEnumerable<object?[]> Equals_TestData()
+    {
+        yield return new object?[] { new PropertyFilterAttribute(PropertyFilterOptions.None), new PropertyFilterAttribute(PropertyFilterOptions.None), true };
+        yield return new object?[] { new PropertyFilterAttribute(PropertyFilterOptions.None), new PropertyFilterAttribute(PropertyFilterOptions.All), false };
+        yield return new object?[] { new PropertyFilterAttribute(PropertyFilterOptions.None), new PropertyFilterAttribute(PropertyFilterOptions.SetValues), false };
+        yield return new object?[] { new PropertyFilterAttribute(PropertyFilterOptions.SetValues), new PropertyFilterAttribute(PropertyFilterOptions.SetValues), true };
+        yield return new object?[] { new PropertyFilterAttribute(PropertyFilterOptions.SetValues), new PropertyFilterAttribute(PropertyFilterOptions.All), false };
+        yield return new object?[] { new PropertyFilterAttribute(PropertyFilterOptions.SetValues), new PropertyFilterAttribute(PropertyFilterOptions.None), false };
+        yield return new object?[] { new PropertyFilterAttribute(PropertyFilterOptions.All), new PropertyFilterAttribute(PropertyFilterOptions.All), true };
+        yield return new object?[] { new PropertyFilterAttribute(PropertyFilterOptions.All), new PropertyFilterAttribute(PropertyFilterOptions.None), false };
+        yield return new object?[] { new PropertyFilterAttribute(PropertyFilterOptions.All), new PropertyFilterAttribute(PropertyFilterOptions.SetValues), false };
+        yield return new object?[] { new PropertyFilterAttribute(PropertyFilterOptions.None), new object(), false };
+        yield return new object?[] { new PropertyFilterAttribute(PropertyFilterOptions.None), null, false };
+    }
+
+    [Theory]
+    [MemberData(nameof(Equals_TestData))]
+    public void Equals_Object_ReturnsExpected(PropertyFilterAttribute attribute, object other, bool expected)
+    {
+        Assert.Equal(expected, attribute.Equals(other));
+        if (other is PropertyFilterAttribute)
+        {
+            Assert.Equal(expected, attribute.GetHashCode().Equals(other.GetHashCode()));
+        }
+    }
+
+    public static IEnumerable<object?[]> Match_TestData()
+    {
+        yield return new object?[] { new PropertyFilterAttribute(PropertyFilterOptions.None), new PropertyFilterAttribute(PropertyFilterOptions.None), true };
+        yield return new object?[] { new PropertyFilterAttribute(PropertyFilterOptions.None), new PropertyFilterAttribute(PropertyFilterOptions.All), true };
+        yield return new object?[] { new PropertyFilterAttribute(PropertyFilterOptions.None), new PropertyFilterAttribute(PropertyFilterOptions.SetValues), true };
+        yield return new object?[] { new PropertyFilterAttribute(PropertyFilterOptions.All), new PropertyFilterAttribute(PropertyFilterOptions.All), true };
+        yield return new object?[] { new PropertyFilterAttribute(PropertyFilterOptions.All), new PropertyFilterAttribute(PropertyFilterOptions.None), false };
+        yield return new object?[] { new PropertyFilterAttribute(PropertyFilterOptions.All), new PropertyFilterAttribute(PropertyFilterOptions.SetValues), false };
+        yield return new object?[] { new PropertyFilterAttribute(PropertyFilterOptions.SetValues), new PropertyFilterAttribute(PropertyFilterOptions.SetValues), true };
+        yield return new object?[] { new PropertyFilterAttribute(PropertyFilterOptions.SetValues), new PropertyFilterAttribute(PropertyFilterOptions.All), true };
+        yield return new object?[] { new PropertyFilterAttribute(PropertyFilterOptions.SetValues), new PropertyFilterAttribute(PropertyFilterOptions.None), false };
+        yield return new object?[] { new PropertyFilterAttribute(PropertyFilterOptions.None), new object(), false };
+        yield return new object?[] { new PropertyFilterAttribute(PropertyFilterOptions.None), null, false };
+    }
+
+    [Theory]
+    [MemberData(nameof(Match_TestData))]
+    public void Match_Object_ReturnsExpected(PropertyFilterAttribute attribute, object value, bool expected)
+    {
+        Assert.Equal(expected, attribute.Match(value));
+    }
+}
\ No newline at end of file
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/SortDescriptionCollectionTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/SortDescriptionCollectionTests.cs
new file mode 100644
index 00000000000..ea9fdd6f4ff
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/SortDescriptionCollectionTests.cs
@@ -0,0 +1,807 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections;
+using System.Collections.Specialized;
+using System.Linq;
+
+namespace System.ComponentModel.Tests;
+
+public class SortDescriptionCollectionTests
+{
+    [Fact]
+    public void Ctor_Default()
+    {
+        var collection = new SortDescriptionCollection();
+        Assert.Empty(collection);
+        Assert.False(((IList)collection).IsFixedSize);
+        Assert.False(((IList)collection).IsReadOnly);
+        Assert.False(((IList)collection).IsSynchronized);
+    }
+
+    [Fact]
+    public void CollectionChanged_INotifyCollectionChangedAddRemove_Success()
+    {
+        INotifyCollectionChanged collection = new SortDescriptionCollection();
+
+        int callCount = 0;
+        NotifyCollectionChangedEventHandler handler = (s, e) => callCount++;
+        ((INotifyCollectionChanged)collection).CollectionChanged += handler;
+        Assert.Equal(0, callCount);
+
+        ((INotifyCollectionChanged)collection).CollectionChanged -= handler;
+        Assert.Equal(0, callCount);
+
+        // Remove non existent.
+        ((INotifyCollectionChanged)collection).CollectionChanged -= handler;
+        Assert.Equal(0, callCount);
+
+        // Add null.
+        ((INotifyCollectionChanged)collection).CollectionChanged += null;
+        Assert.Equal(0, callCount);
+
+        // Remove null.
+        ((INotifyCollectionChanged)collection).CollectionChanged -= null;
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void Item_Set_GetReturnsExpected()
+    {
+        var collection = new SortDescriptionCollection();
+        var description1 = new SortDescription("Name1", ListSortDirection.Ascending);
+        var description2 = new SortDescription("Name2", ListSortDirection.Descending);
+
+        collection.Add(description1);
+
+        // Set.
+        collection[0] = description2;
+        Assert.Single(collection);
+        Assert.Equal(description2, collection[0]);
+        Assert.True(collection[0].IsSealed);
+    }
+
+    [Fact]
+    public void Item_SetWithHandler_GetReturnsExpected()
+    {
+        var collection = new SortDescriptionCollection();
+        var description1 = new SortDescription("Name1", ListSortDirection.Ascending);
+        var description2 = new SortDescription("Name2", ListSortDirection.Descending);
+        var description3 = new SortDescription("Name3", ListSortDirection.Descending);
+
+        collection.Add(description1);
+
+        var events = new List<NotifyCollectionChangedEventArgs>(); 
+        int callCount = 0;
+        NotifyCollectionChangedEventHandler handler = (s, e) =>
+        {
+            Assert.Same(collection, s);
+            events.Add(e);
+            callCount++;
+        };
+        ((INotifyCollectionChanged)collection).CollectionChanged += handler;
+
+        // Set.
+        collection[0] = description2;
+        Assert.Single(collection);
+        Assert.Equal(description2, collection[0]);
+        Assert.True(collection[0].IsSealed);
+        Assert.Equal(2, callCount);
+        Assert.Equal(NotifyCollectionChangedAction.Remove, events[0].Action);
+        Assert.Null(events[0].NewItems);
+        Assert.Equal(new[] { description1 }, events[0].OldItems!.Cast<SortDescription>());
+        Assert.Equal(-1, events[0].NewStartingIndex);
+        Assert.Equal(0, events[0].OldStartingIndex);
+        Assert.Equal(NotifyCollectionChangedAction.Add, events[1].Action);
+        Assert.Equal(new[] { description2 }, events[1].NewItems!.Cast<SortDescription>());
+        Assert.Equal(0, events[1].NewStartingIndex);
+        Assert.Equal(-1, events[1].OldStartingIndex);
+
+        // Remove handler.
+        ((INotifyCollectionChanged)collection).CollectionChanged -= handler;
+        collection[0] = description3;
+        Assert.Single(collection);
+        Assert.Equal(description3, collection[0]);
+        Assert.True(collection[0].IsSealed);
+        Assert.Equal(2, callCount);
+    }
+
+    [Theory]
+    [InlineData(-1)]
+    [InlineData(0)]
+    [InlineData(1)]
+    public void Item_GetInvalidIndex_ThrowsArgumentOutOfRangeException(int index)
+    {
+        var collection = new SortDescriptionCollection();
+        Assert.Throws<ArgumentOutOfRangeException>("index", () => collection[index]);
+    }
+
+    [Theory]
+    [InlineData(-1)]
+    [InlineData(0)]
+    [InlineData(1)]
+    public void Item_SetInvalidIndex_ThrowsArgumentOutOfRangeException(int index)
+    {
+        var collection = new SortDescriptionCollection();
+        var description = new SortDescription("Name", ListSortDirection.Ascending);
+        Assert.Throws<ArgumentOutOfRangeException>("index", () => collection[index] = description);
+    }
+
+    [Fact]
+    public void Add_Invoke_Success()
+    {
+        var collection = new SortDescriptionCollection();
+        var description1 = new SortDescription("Name1", ListSortDirection.Ascending);
+        var description2 = new SortDescription("Name2", ListSortDirection.Descending);
+
+        // Add.
+        collection.Add(description1);
+        Assert.Single(collection);
+        Assert.Equal(description1, collection[0]);
+        Assert.True(collection[0].IsSealed);
+
+        // Add again.
+        collection.Add(description2);
+        Assert.Equal(2, collection.Count);
+        Assert.Equal(description1, collection[0]);
+        Assert.True(collection[0].IsSealed);
+        Assert.Equal(description2, collection[1]);
+        Assert.True(collection[1].IsSealed);
+    }
+
+    [Fact]
+    public void Add_InvokeWithHandler_CallsCollectionChanged()
+    {
+        var collection = new SortDescriptionCollection();
+        var description1 = new SortDescription("Name1", ListSortDirection.Ascending);
+        var description2 = new SortDescription("Name2", ListSortDirection.Descending);
+        var description3 = new SortDescription("Name3", ListSortDirection.Descending);
+
+        var events = new List<NotifyCollectionChangedEventArgs>(); 
+        int callCount = 0;
+        NotifyCollectionChangedEventHandler handler = (s, e) =>
+        {
+            Assert.Same(collection, s);
+            events.Add(e);
+            callCount++;
+        };
+        ((INotifyCollectionChanged)collection).CollectionChanged += handler;
+
+        // Add.
+        collection.Add(description1);
+        Assert.Single(collection);
+        Assert.Equal(description1, collection[0]);
+        Assert.True(collection[0].IsSealed);
+        Assert.Equal(1, callCount);
+        Assert.Equal(NotifyCollectionChangedAction.Add, events[0].Action);
+        Assert.Equal(new[] { description1 }, events[0].NewItems!.Cast<SortDescription>());
+        Assert.Null(events[0].OldItems);
+        Assert.Equal(0, events[0].NewStartingIndex);
+        Assert.Equal(-1, events[0].OldStartingIndex);
+
+        // Add again.
+        collection.Add(description2);
+        Assert.Equal(2, collection.Count);
+        Assert.Equal(description1, collection[0]);
+        Assert.True(collection[0].IsSealed);
+        Assert.Equal(description2, collection[1]);
+        Assert.True(collection[1].IsSealed);
+        Assert.Equal(2, callCount);
+        Assert.Equal(NotifyCollectionChangedAction.Add, events[1].Action);
+        Assert.Equal(new[] { description1 }, events[0].NewItems!.Cast<SortDescription>());
+        Assert.Null(events[1].OldItems);
+        Assert.Equal(1, events[1].NewStartingIndex);
+        Assert.Equal(-1, events[1].OldStartingIndex);
+
+        // Remove handler.
+        ((INotifyCollectionChanged)collection).CollectionChanged -= handler;
+        collection.Add(description3);
+        Assert.Equal(3, collection.Count);
+        Assert.Equal(description1, collection[0]);
+        Assert.True(collection[0].IsSealed);
+        Assert.Equal(description2, collection[1]);
+        Assert.True(collection[1].IsSealed);
+        Assert.Equal(description3, collection[2]);
+        Assert.True(collection[2].IsSealed);
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void Insert_Invoke_Success()
+    {
+        var collection = new SortDescriptionCollection();
+        var description1 = new SortDescription("Name1", ListSortDirection.Ascending);
+        var description2 = new SortDescription("Name2", ListSortDirection.Descending);
+
+        // Add.
+        collection.Insert(0, description1);
+        Assert.Single(collection);
+        Assert.Equal(description1, collection[0]);
+        Assert.True(collection[0].IsSealed);
+
+        // Add again.
+        collection.Insert(0, description2);
+        Assert.Equal(2, collection.Count);
+        Assert.Equal(description2, collection[0]);
+        Assert.True(collection[0].IsSealed);
+        Assert.Equal(description1, collection[1]);
+        Assert.True(collection[1].IsSealed);
+    }
+
+    [Fact]
+    public void Insert_InvokeWithHandler_CallsCollectionChanged()
+    {
+        var collection = new SortDescriptionCollection();
+        var description1 = new SortDescription("Name1", ListSortDirection.Ascending);
+        var description2 = new SortDescription("Name2", ListSortDirection.Descending);
+        var description3 = new SortDescription("Name3", ListSortDirection.Descending);
+
+        var events = new List<NotifyCollectionChangedEventArgs>(); 
+        int callCount = 0;
+        NotifyCollectionChangedEventHandler handler = (s, e) =>
+        {
+            Assert.Same(collection, s);
+            events.Add(e);
+            callCount++;
+        };
+        ((INotifyCollectionChanged)collection).CollectionChanged += handler;
+
+        // Add.
+        collection.Insert(0, description1);
+        Assert.Single(collection);
+        Assert.Equal(description1, collection[0]);
+        Assert.True(collection[0].IsSealed);
+        Assert.Equal(1, callCount);
+        Assert.Equal(NotifyCollectionChangedAction.Add, events[0].Action);
+        Assert.Equal(new[] { description1 }, events[0].NewItems!.Cast<SortDescription>());
+        Assert.Null(events[0].OldItems);
+        Assert.Equal(0, events[0].NewStartingIndex);
+        Assert.Equal(-1, events[0].OldStartingIndex);
+
+        // Add again.
+        collection.Insert(0, description2);
+        Assert.Equal(2, collection.Count);
+        Assert.Equal(description2, collection[0]);
+        Assert.True(collection[0].IsSealed);
+        Assert.Equal(description1, collection[1]);
+        Assert.True(collection[1].IsSealed);
+        Assert.Equal(2, callCount);
+        Assert.Equal(NotifyCollectionChangedAction.Add, events[1].Action);
+        Assert.Equal(new[] { description2 }, events[1].NewItems!.Cast<SortDescription>());
+        Assert.Null(events[1].OldItems);
+        Assert.Equal(0, events[1].NewStartingIndex);
+        Assert.Equal(-1, events[1].OldStartingIndex);
+
+        // Remove handler.
+        ((INotifyCollectionChanged)collection).CollectionChanged -= handler;
+        collection.Insert(2, description3);
+        Assert.Equal(3, collection.Count);
+        Assert.Equal(description2, collection[0]);
+        Assert.True(collection[0].IsSealed);
+        Assert.Equal(description1, collection[1]);
+        Assert.True(collection[1].IsSealed);
+        Assert.Equal(description3, collection[2]);
+        Assert.True(collection[2].IsSealed);
+        Assert.Equal(2, callCount);
+    }
+
+    [Theory]
+    [InlineData(-1)]
+    [InlineData(1)]
+    public void Insert_InvalidIndex_ThrowsArgumentOutOfRangeException(int index)
+    {
+        var collection = new SortDescriptionCollection();
+        var description = new SortDescription("Name", ListSortDirection.Ascending);
+        Assert.Throws<ArgumentOutOfRangeException>("index", () => collection.Insert(index, description));
+    }
+
+    [Fact]
+    public void InsertItem_Invoke_Success()
+    {
+        var collection = new SubSortDescriptionCollection();
+        var description1 = new SortDescription("Name1", ListSortDirection.Ascending);
+        var description2 = new SortDescription("Name2", ListSortDirection.Descending);
+
+        // Add.
+        collection.InsertItem(0, description1);
+        Assert.Single(collection);
+        Assert.Equal(description1, collection[0]);
+        Assert.True(collection[0].IsSealed);
+
+        // Add again.
+        collection.InsertItem(0, description2);
+        Assert.Equal(2, collection.Count);
+        Assert.Equal(description2, collection[0]);
+        Assert.True(collection[0].IsSealed);
+        Assert.Equal(description1, collection[1]);
+        Assert.True(collection[1].IsSealed);
+    }
+
+    [Fact]
+    public void InsertItem_InvokeWithHandler_CallsCollectionChanged()
+    {
+        var collection = new SubSortDescriptionCollection();
+        var description1 = new SortDescription("Name1", ListSortDirection.Ascending);
+        var description2 = new SortDescription("Name2", ListSortDirection.Descending);
+        var description3 = new SortDescription("Name3", ListSortDirection.Descending);
+
+        var events = new List<NotifyCollectionChangedEventArgs>(); 
+        int callCount = 0;
+        NotifyCollectionChangedEventHandler handler = (s, e) =>
+        {
+            Assert.Same(collection, s);
+            events.Add(e);
+            callCount++;
+        };
+        ((INotifyCollectionChanged)collection).CollectionChanged += handler;
+
+        // Add.
+        collection.InsertItem(0, description1);
+        Assert.Single(collection);
+        Assert.Equal(description1, collection[0]);
+        Assert.True(collection[0].IsSealed);
+        Assert.Equal(1, callCount);
+        Assert.Equal(NotifyCollectionChangedAction.Add, events[0].Action);
+        Assert.Equal(new[] { description1 }, events[0].NewItems!.Cast<SortDescription>());
+        Assert.Null(events[0].OldItems);
+        Assert.Equal(0, events[0].NewStartingIndex);
+        Assert.Equal(-1, events[0].OldStartingIndex);
+
+        // Add again.
+        collection.InsertItem(0, description2);
+        Assert.Equal(2, collection.Count);
+        Assert.Equal(description2, collection[0]);
+        Assert.True(collection[0].IsSealed);
+        Assert.Equal(description1, collection[1]);
+        Assert.True(collection[1].IsSealed);
+        Assert.Equal(2, callCount);
+        Assert.Equal(NotifyCollectionChangedAction.Add, events[1].Action);
+        Assert.Equal(new[] { description2 }, events[1].NewItems!.Cast<SortDescription>());
+        Assert.Null(events[1].OldItems);
+        Assert.Equal(0, events[1].NewStartingIndex);
+        Assert.Equal(-1, events[1].OldStartingIndex);
+
+        // Remove handler.
+        ((INotifyCollectionChanged)collection).CollectionChanged -= handler;
+        collection.InsertItem(2, description3);
+        Assert.Equal(3, collection.Count);
+        Assert.Equal(description2, collection[0]);
+        Assert.True(collection[0].IsSealed);
+        Assert.Equal(description1, collection[1]);
+        Assert.True(collection[1].IsSealed);
+        Assert.Equal(description3, collection[2]);
+        Assert.True(collection[2].IsSealed);
+        Assert.Equal(2, callCount);
+    }
+
+    [Theory]
+    [InlineData(-1)]
+    [InlineData(1)]
+    public void InsertItem_InvalidIndex_ThrowsArgumentOutOfRangeException(int index)
+    {
+        var collection = new SubSortDescriptionCollection();
+        var description = new SortDescription("Name", ListSortDirection.Ascending);
+        Assert.Throws<ArgumentOutOfRangeException>("index", () => collection.InsertItem(index, description));
+    }
+
+    [Fact]
+    public void Clear_Invoke_Success()
+    {
+        var collection = new SortDescriptionCollection();
+
+        // Clear empty.
+        collection.Clear();
+        Assert.Empty(collection);
+
+        collection.Add(new SortDescription("Name", ListSortDirection.Ascending));
+
+        // Clear.
+        collection.Clear();
+        Assert.Empty(collection);
+
+        // Clear again.
+        collection.Clear();
+    }
+
+    [Fact]
+    public void Clear_InvokeWithHandler_CallsCollectionChanged()
+    {
+        var collection = new SortDescriptionCollection();
+        var events = new List<NotifyCollectionChangedEventArgs>(); 
+        int callCount = 0;
+        NotifyCollectionChangedEventHandler handler = (s, e) =>
+        {
+            Assert.Same(collection, s);
+            events.Add(e);
+            callCount++;
+        };
+        ((INotifyCollectionChanged)collection).CollectionChanged += handler;
+
+        // Clear empty.
+        collection.Clear();
+        Assert.Empty(collection);
+        Assert.Equal(1, callCount);
+        Assert.Equal(NotifyCollectionChangedAction.Reset, events[0].Action);
+        Assert.Null(events[0].NewItems);
+        Assert.Null(events[0].OldItems);
+        Assert.Equal(-1, events[0].NewStartingIndex);
+        Assert.Equal(-1, events[0].OldStartingIndex);
+
+        collection.Add(new SortDescription("Name", ListSortDirection.Ascending));
+        Assert.Equal(2, callCount);
+
+        // Clear.
+        collection.Clear();
+        Assert.Empty(collection);
+        Assert.Equal(3, callCount);
+        Assert.Equal(NotifyCollectionChangedAction.Reset, events[2].Action);
+        Assert.Null(events[2].NewItems);
+        Assert.Null(events[2].OldItems);
+        Assert.Equal(-1, events[2].NewStartingIndex);
+        Assert.Equal(-1, events[2].OldStartingIndex);
+
+        // Clear again.
+        collection.Clear();
+        Assert.Empty(collection);
+        Assert.Equal(4, callCount);
+        Assert.Equal(NotifyCollectionChangedAction.Reset, events[3].Action);
+        Assert.Null(events[3].NewItems);
+        Assert.Null(events[3].OldItems);
+        Assert.Equal(-1, events[3].NewStartingIndex);
+        Assert.Equal(-1, events[3].OldStartingIndex);
+
+        // Remove handler.
+        ((INotifyCollectionChanged)collection).CollectionChanged -= handler;
+        collection.Clear();
+        Assert.Equal(4, callCount);
+    }
+
+    [Fact]
+    public void ClearItems_Invoke_Success()
+    {
+        var collection = new SubSortDescriptionCollection();
+
+        // Clear empty.
+        collection.ClearItems();
+        Assert.Empty(collection);
+
+        collection.Add(new SortDescription("Name", ListSortDirection.Ascending));
+
+        // Clear.
+        collection.ClearItems();
+        Assert.Empty(collection);
+
+        // Clear again.
+        collection.ClearItems();
+    }
+
+    [Fact]
+    public void ClearItems_InvokeWithHandler_CallsCollectionChanged()
+    {
+        var collection = new SubSortDescriptionCollection();
+        var events = new List<NotifyCollectionChangedEventArgs>(); 
+        int callCount = 0;
+        NotifyCollectionChangedEventHandler handler = (s, e) =>
+        {
+            Assert.Same(collection, s);
+            events.Add(e);
+            callCount++;
+        };
+        ((INotifyCollectionChanged)collection).CollectionChanged += handler;
+
+        // Clear empty.
+        collection.ClearItems();
+        Assert.Empty(collection);
+        Assert.Equal(1, callCount);
+        Assert.Equal(NotifyCollectionChangedAction.Reset, events[0].Action);
+        Assert.Null(events[0].NewItems);
+        Assert.Null(events[0].OldItems);
+        Assert.Equal(-1, events[0].NewStartingIndex);
+        Assert.Equal(-1, events[0].OldStartingIndex);
+
+        collection.Add(new SortDescription("Name", ListSortDirection.Ascending));
+        Assert.Equal(2, callCount);
+
+        // Clear.
+        collection.ClearItems();
+        Assert.Empty(collection);
+        Assert.Equal(3, callCount);
+        Assert.Equal(NotifyCollectionChangedAction.Reset, events[2].Action);
+        Assert.Null(events[2].NewItems);
+        Assert.Null(events[2].OldItems);
+        Assert.Equal(-1, events[2].NewStartingIndex);
+        Assert.Equal(-1, events[2].OldStartingIndex);
+
+        // Clear again.
+        collection.ClearItems();
+        Assert.Empty(collection);
+        Assert.Equal(4, callCount);
+        Assert.Equal(NotifyCollectionChangedAction.Reset, events[3].Action);
+        Assert.Null(events[3].NewItems);
+        Assert.Null(events[3].OldItems);
+        Assert.Equal(-1, events[3].NewStartingIndex);
+        Assert.Equal(-1, events[3].OldStartingIndex);
+
+        // Remove handler.
+        ((INotifyCollectionChanged)collection).CollectionChanged -= handler;
+        collection.ClearItems();
+        Assert.Equal(4, callCount);
+    }
+
+    [Fact]
+    public void RemoveAt_Invoke_Success()
+    {
+        var collection = new SubSortDescriptionCollection();
+        var description1 = new SortDescription("Name1", ListSortDirection.Ascending);
+        var description2 = new SortDescription("Name2", ListSortDirection.Descending);
+
+        collection.Add(description1);
+        collection.Add(description2);
+
+        // Remove last.
+        collection.RemoveAt(1);
+        Assert.Single(collection);
+        Assert.Equal(description1, collection[0]);
+        Assert.True(collection[0].IsSealed);
+
+        // Remove first.
+        collection.RemoveAt(0);
+        Assert.Empty(collection);
+    }
+
+    [Fact]
+    public void RemoveAt_InvokeWithHandler_CallsCollectionChanged()
+    {
+        var collection = new SubSortDescriptionCollection();
+        var description1 = new SortDescription("Name1", ListSortDirection.Ascending);
+        var description2 = new SortDescription("Name2", ListSortDirection.Descending);
+        var description3 = new SortDescription("Name3", ListSortDirection.Descending);
+
+        collection.Add(description1);
+        collection.Add(description2);
+        collection.Add(description3);
+
+        var events = new List<NotifyCollectionChangedEventArgs>(); 
+        int callCount = 0;
+        NotifyCollectionChangedEventHandler handler = (s, e) =>
+        {
+            Assert.Same(collection, s);
+            events.Add(e);
+            callCount++;
+        };
+        ((INotifyCollectionChanged)collection).CollectionChanged += handler;
+
+        // Remove middle.
+        collection.RemoveAt(1);
+        Assert.Equal(2, collection.Count);
+        Assert.Equal(description1, collection[0]);
+        Assert.True(collection[0].IsSealed);
+        Assert.Equal(description3, collection[1]);
+        Assert.True(collection[1].IsSealed);
+        Assert.Equal(1, callCount);
+        Assert.Equal(NotifyCollectionChangedAction.Remove, events[0].Action);
+        Assert.Null(events[0].NewItems);
+        Assert.Equal(new[] { description2 }, events[0].OldItems!.Cast<SortDescription>());
+        Assert.Equal(-1, events[0].NewStartingIndex);
+        Assert.Equal(1, events[0].OldStartingIndex);
+
+        // Remove last.
+        collection.RemoveAt(1);
+        Assert.Single(collection);
+        Assert.Equal(description1, collection[0]);
+        Assert.True(collection[0].IsSealed);
+        Assert.Equal(2, callCount);
+        Assert.Equal(NotifyCollectionChangedAction.Remove, events[1].Action);
+        Assert.Null(events[1].NewItems);
+        Assert.Equal(new[] { description3 }, events[1].OldItems!.Cast<SortDescription>());
+        Assert.Equal(-1, events[1].NewStartingIndex);
+        Assert.Equal(1, events[1].OldStartingIndex);
+
+        // Remove handler.
+        ((INotifyCollectionChanged)collection).CollectionChanged -= handler;
+        collection.RemoveAt(0);
+        Assert.Empty(collection);
+        Assert.Equal(2, callCount);
+    }
+
+    [Theory]
+    [InlineData(-1)]
+    [InlineData(0)]
+    [InlineData(1)]
+    public void RemoveAt_InvalidIndex_ThrowsArgumentOutOfRangeException(int index)
+    {
+        var collection = new SubSortDescriptionCollection();
+        Assert.Throws<ArgumentOutOfRangeException>("index", () => collection.RemoveAt(index));
+    }
+
+    [Fact]
+    public void RemoveItem_Invoke_Success()
+    {
+        var collection = new SubSortDescriptionCollection();
+        var description1 = new SortDescription("Name1", ListSortDirection.Ascending);
+        var description2 = new SortDescription("Name2", ListSortDirection.Descending);
+
+        collection.Add(description1);
+        collection.Add(description2);
+
+        // Remove last.
+        collection.RemoveItem(1);
+        Assert.Single(collection);
+        Assert.Equal(description1, collection[0]);
+        Assert.True(collection[0].IsSealed);
+
+        // Remove first.
+        collection.RemoveItem(0);
+        Assert.Empty(collection);
+    }
+
+    [Fact]
+    public void RemoveItem_InvokeWithHandler_CallsCollectionChanged()
+    {
+        var collection = new SubSortDescriptionCollection();
+        var description1 = new SortDescription("Name1", ListSortDirection.Ascending);
+        var description2 = new SortDescription("Name2", ListSortDirection.Descending);
+        var description3 = new SortDescription("Name3", ListSortDirection.Descending);
+
+        collection.Add(description1);
+        collection.Add(description2);
+        collection.Add(description3);
+
+        var events = new List<NotifyCollectionChangedEventArgs>(); 
+        int callCount = 0;
+        NotifyCollectionChangedEventHandler handler = (s, e) =>
+        {
+            Assert.Same(collection, s);
+            events.Add(e);
+            callCount++;
+        };
+        ((INotifyCollectionChanged)collection).CollectionChanged += handler;
+
+        // Remove middle.
+        collection.RemoveItem(1);
+        Assert.Equal(2, collection.Count);
+        Assert.Equal(description1, collection[0]);
+        Assert.True(collection[0].IsSealed);
+        Assert.Equal(description3, collection[1]);
+        Assert.True(collection[1].IsSealed);
+        Assert.Equal(1, callCount);
+        Assert.Equal(NotifyCollectionChangedAction.Remove, events[0].Action);
+        Assert.Null(events[0].NewItems);
+        Assert.Equal(new[] { description2 }, events[0].OldItems!.Cast<SortDescription>());
+        Assert.Equal(-1, events[0].NewStartingIndex);
+        Assert.Equal(1, events[0].OldStartingIndex);
+
+        // Remove last.
+        collection.RemoveItem(1);
+        Assert.Single(collection);
+        Assert.Equal(description1, collection[0]);
+        Assert.True(collection[0].IsSealed);
+        Assert.Equal(2, callCount);
+        Assert.Equal(NotifyCollectionChangedAction.Remove, events[1].Action);
+        Assert.Null(events[1].NewItems);
+        Assert.Equal(new[] { description3 }, events[1].OldItems!.Cast<SortDescription>());
+        Assert.Equal(-1, events[1].NewStartingIndex);
+        Assert.Equal(1, events[1].OldStartingIndex);
+
+        // Remove handler.
+        ((INotifyCollectionChanged)collection).CollectionChanged -= handler;
+        collection.RemoveItem(0);
+        Assert.Empty(collection);
+        Assert.Equal(2, callCount);
+    }
+
+    [Theory]
+    [InlineData(-1)]
+    [InlineData(0)]
+    [InlineData(1)]
+    public void RemoveItem_InvalidIndex_ThrowsArgumentOutOfRangeException(int index)
+    {
+        var collection = new SubSortDescriptionCollection();
+        Assert.Throws<ArgumentOutOfRangeException>("index", () => collection.RemoveItem(index));
+    }
+
+
+    [Fact]
+    public void SetItem_Invoke_GetReturnsExpected()
+    {
+        var collection = new SubSortDescriptionCollection();
+        var description1 = new SortDescription("Name1", ListSortDirection.Ascending);
+        var description2 = new SortDescription("Name2", ListSortDirection.Descending);
+
+        collection.Add(description1);
+
+        // Set.
+        collection.SetItem(0, description2);
+        Assert.Single(collection);
+        Assert.Equal(description2, collection[0]);
+        Assert.True(collection[0].IsSealed);
+    }
+
+    [Fact]
+    public void SetItem_WithHandler_GetReturnsExpected()
+    {
+        var collection = new SubSortDescriptionCollection();
+        var description1 = new SortDescription("Name1", ListSortDirection.Ascending);
+        var description2 = new SortDescription("Name2", ListSortDirection.Descending);
+        var description3 = new SortDescription("Name3", ListSortDirection.Descending);
+
+        collection.Add(description1);
+
+        var events = new List<NotifyCollectionChangedEventArgs>(); 
+        int callCount = 0;
+        NotifyCollectionChangedEventHandler handler = (s, e) =>
+        {
+            Assert.Same(collection, s);
+            events.Add(e);
+            callCount++;
+        };
+        ((INotifyCollectionChanged)collection).CollectionChanged += handler;
+
+        // Set.
+        collection.SetItem(0, description2);
+        Assert.Single(collection);
+        Assert.Equal(description2, collection[0]);
+        Assert.True(collection[0].IsSealed);
+        Assert.Equal(2, callCount);
+        Assert.Equal(NotifyCollectionChangedAction.Remove, events[0].Action);
+        Assert.Null(events[0].NewItems);
+        Assert.Equal(new[] { description1 }, events[0].OldItems!.Cast<SortDescription>());
+        Assert.Equal(-1, events[0].NewStartingIndex);
+        Assert.Equal(0, events[0].OldStartingIndex);
+        Assert.Equal(NotifyCollectionChangedAction.Add, events[1].Action);
+        Assert.Equal(new[] { description2 }, events[1].NewItems!.Cast<SortDescription>());
+        Assert.Equal(0, events[1].NewStartingIndex);
+        Assert.Equal(-1, events[1].OldStartingIndex);
+
+        // Remove handler.
+        ((INotifyCollectionChanged)collection).CollectionChanged -= handler;
+        collection.SetItem(0, description3);
+        Assert.Single(collection);
+        Assert.Equal(description3, collection[0]);
+        Assert.True(collection[0].IsSealed);
+        Assert.Equal(2, callCount);
+    }
+
+    [Theory]
+    [InlineData(-1)]
+    [InlineData(0)]
+    [InlineData(1)]
+    public void SetItem_InvalidIndex_ThrowsArgumentOutOfRangeException(int index)
+    {
+        var collection = new SubSortDescriptionCollection();
+        var description = new SortDescription("Name", ListSortDirection.Ascending);
+        Assert.Throws<ArgumentOutOfRangeException>("index", () => collection.SetItem(index, description));
+    }
+
+    [Fact]
+    public void Empty_Get_ReturnsExpected()
+    {
+        SortDescriptionCollection collection = SortDescriptionCollection.Empty;
+        Assert.Empty(collection);
+        Assert.Same(SortDescriptionCollection.Empty, collection);
+        Assert.True(((IList)collection).IsFixedSize);
+        Assert.True(((IList)collection).IsReadOnly);
+        Assert.False(((IList)collection).IsSynchronized);
+    }
+
+    [Fact]
+    public void Empty_Modify_ThrowsNotSupportedException()
+    {
+        SortDescriptionCollection collection = SortDescriptionCollection.Empty;
+        Assert.Throws<NotSupportedException>(() => collection.Add(new SortDescription("Name", ListSortDirection.Ascending)));
+        Assert.Throws<NotSupportedException>(() => collection.Insert(0, new SortDescription("Name", ListSortDirection.Ascending)));
+        Assert.Throws<NotSupportedException>(() => collection.Clear());
+    }
+
+    private class SubSortDescriptionCollection : SortDescriptionCollection
+    {
+        public new void ClearItems() => base.ClearItems();
+
+        public new void InsertItem(int index, SortDescription item) => base.InsertItem(index, item);
+
+        public new void RemoveItem(int index) => base.RemoveItem(index);
+
+        public new void SetItem(int index, SortDescription item) => base.SetItem(index, item);
+    }
+}
\ No newline at end of file
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/SortDescriptionTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/SortDescriptionTests.cs
new file mode 100644
index 00000000000..8bcd23879d3
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/ComponentModel/SortDescriptionTests.cs
@@ -0,0 +1,134 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.ComponentModel.Tests;
+
+public class SortDescriptionTests
+{
+    [Fact]
+    public void Ctor_Default()
+    {
+        var description = new SortDescription();
+        Assert.Null(description.PropertyName);
+        Assert.Equal(ListSortDirection.Ascending, description.Direction);
+        Assert.False(description.IsSealed);
+    }
+
+    [Theory]
+    [InlineData(null, ListSortDirection.Ascending)]
+    [InlineData("", ListSortDirection.Ascending)]
+    [InlineData("Name", ListSortDirection.Ascending)]
+    [InlineData("Name", ListSortDirection.Descending)]
+    public void Ctor_String_ListSortDirection(string? propertyName, ListSortDirection direction)
+    {
+        var description = new SortDescription(propertyName, direction);
+        Assert.Equal(direction, description.Direction);
+        Assert.Equal(propertyName, description.PropertyName);
+        Assert.False(description.IsSealed);
+    }
+
+    [Theory]
+    [InlineData(ListSortDirection.Ascending - 1)]
+    [InlineData(ListSortDirection.Descending + 1)]
+    public void Ctor_InvalidDirection_ThrowsInvalidEnumArgumentException(ListSortDirection direction)
+    {
+        Assert.Throws<InvalidEnumArgumentException>("direction", () => new SortDescription("Name", direction));
+    }
+
+    [Theory]
+    [InlineData(ListSortDirection.Ascending)]
+    [InlineData(ListSortDirection.Descending)]
+    public void Direction_Set_GetReturnsExpected(ListSortDirection value)
+    {
+        var description = new SortDescription
+        {
+            Direction = value
+        };
+        Assert.Equal(value, description.Direction);
+
+        // Set same.
+        description.Direction = value;
+        Assert.Equal(value, description.Direction);
+    }
+
+    [Theory]
+    [InlineData(ListSortDirection.Ascending - 1)]
+    [InlineData(ListSortDirection.Descending + 1)]
+    public void Direction_SetInvalid_ThrowsInvalidEnumArgumentException(ListSortDirection value)
+    {
+        var description = new SortDescription();
+        Assert.Throws<InvalidEnumArgumentException>("value", () => description.Direction = value);
+    }
+
+    [Theory]
+    [InlineData(ListSortDirection.Ascending - 1)]
+    [InlineData(ListSortDirection.Ascending)]
+    [InlineData(ListSortDirection.Descending)]
+    [InlineData(ListSortDirection.Descending + 1)]
+    public void Direction_SetSealed_ThrowsInvalidOperationException(ListSortDirection value)
+    {
+        var collection = new SortDescriptionCollection();
+        collection.Add(new SortDescription());
+
+        SortDescription description = collection[0];
+        Assert.Throws<InvalidOperationException>(() => description.Direction = value);
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("")]
+    [InlineData("Name")]
+    public void PropertyName_Set_GetReturnsExpected(string? value)
+    {
+        var description = new SortDescription
+        {
+            PropertyName = value
+        };
+        Assert.Equal(value, description.PropertyName);
+
+        // Set same.
+        description.PropertyName = value;
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("")]
+    [InlineData("Name")]
+    public void PropertyName_SetSealed_ThrowsInvalidOperationException(string? value)
+    {
+        var collection = new SortDescriptionCollection();
+        collection.Add(new SortDescription());
+
+        SortDescription description = collection[0];
+        Assert.Throws<InvalidOperationException>(() => description.PropertyName = value);
+    }
+
+    public static IEnumerable<object?[]> Equals_TestData()
+    {
+        yield return new object?[] { new SortDescription("Name", ListSortDirection.Ascending), new SortDescription("Name", ListSortDirection.Ascending), true };
+        yield return new object?[] { new SortDescription("Name", ListSortDirection.Ascending), new SortDescription(null, ListSortDirection.Ascending), false };
+        yield return new object?[] { new SortDescription("Name", ListSortDirection.Ascending), new SortDescription("", ListSortDirection.Ascending), false };
+        yield return new object?[] { new SortDescription("Name", ListSortDirection.Ascending), new SortDescription("Name2", ListSortDirection.Ascending), false };
+        yield return new object?[] { new SortDescription("Name", ListSortDirection.Ascending), new SortDescription("Name", ListSortDirection.Descending), false };
+        yield return new object?[] { new SortDescription(null, ListSortDirection.Descending), new SortDescription(null, ListSortDirection.Descending), true };
+        yield return new object?[] { new SortDescription(null, ListSortDirection.Descending), new SortDescription("", ListSortDirection.Descending), false };
+        yield return new object?[] { new SortDescription(null, ListSortDirection.Descending), new SortDescription("Name2", ListSortDirection.Descending), false };
+        yield return new object?[] { new SortDescription(null, ListSortDirection.Descending), new SortDescription(null, ListSortDirection.Ascending), false };
+        yield return new object?[] { new SortDescription("Name", ListSortDirection.Ascending), new object(), false };
+        yield return new object?[] { new SortDescription("Name", ListSortDirection.Ascending), null, false };
+    }
+
+    [Theory]
+    [MemberData(nameof(Equals_TestData))]
+    public void Equals_Object_ReturnsExpected(SortDescription description, object other, bool expected)
+    {
+        Assert.Equal(expected, description.Equals(other));
+        if (other is SortDescription otherDescription)
+        {
+            Assert.Equal(expected, description.GetHashCode().Equals(otherDescription.GetHashCode()));
+            Assert.Equal(expected, description == otherDescription);
+            Assert.Equal(!expected, description != otherDescription);
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Diagnostics/PresentationTraceSourcesTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Diagnostics/PresentationTraceSourcesTests.cs
new file mode 100644
index 00000000000..fae01cb07eb
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Diagnostics/PresentationTraceSourcesTests.cs
@@ -0,0 +1,178 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Windows;
+
+namespace System.Diagnostics.Tests;
+
+public class PresentationTraceSourcesTests
+{
+    [Fact]
+    public void TraceLevelProperty_Get_ReturnsExpected()
+    {
+        DependencyProperty property = PresentationTraceSources.TraceLevelProperty;
+        Assert.NotNull(property.DefaultMetadata);
+        Assert.Same(property.DefaultMetadata, property.DefaultMetadata);
+        Assert.Null(property.DefaultMetadata.CoerceValueCallback);
+        Assert.Equal(PresentationTraceLevel.None, property.DefaultMetadata.DefaultValue);
+        Assert.Null(property.DefaultMetadata.PropertyChangedCallback);
+        Assert.True(property.GlobalIndex >= 0);
+        Assert.Equal("TraceLevel", property.Name);
+        Assert.Equal(typeof(PresentationTraceSources), property.OwnerType);
+        Assert.Equal(typeof(PresentationTraceLevel), property.PropertyType);
+        Assert.False(property.ReadOnly);
+        Assert.Null(property.ValidateValueCallback);
+        Assert.Same(property, PresentationTraceSources.TraceLevelProperty);
+    }
+
+    public static IEnumerable<object?[]> Element_TestData()
+    {
+        yield return new object?[] { new object() };
+        yield return new object?[] { null };
+    }
+
+    [Theory]
+    [MemberData(nameof(Element_TestData))]
+    public void GetTraceLevel_Get_ReturnsExpected(object element)
+    {
+        PresentationTraceLevel value = PresentationTraceSources.GetTraceLevel(element);
+        Assert.True(Enum.IsDefined(value));
+        Assert.Equal(value, PresentationTraceSources.GetTraceLevel(element));
+    }
+
+    [Theory]
+    [MemberData(nameof(Element_TestData))]
+    public void Refresh_Invoke_Success(object element)
+    {
+        PresentationTraceLevel value = PresentationTraceSources.GetTraceLevel(element);
+        PresentationTraceSources.Refresh();
+        Assert.Equal(value, PresentationTraceSources.GetTraceLevel(element));
+    }
+
+    public static IEnumerable<object?[]> SetTraceLevel_TestData()
+    {
+        yield return new object?[] { null, PresentationTraceLevel.None, PresentationTraceLevel.None };
+        yield return new object?[] { new object(), PresentationTraceLevel.Low, PresentationTraceLevel.Low };
+        yield return new object?[] { new object(), PresentationTraceLevel.None - 1, PresentationTraceLevel.None };
+        yield return new object?[] { new object(), PresentationTraceLevel.High + 1, PresentationTraceLevel.High + 1 };
+    }
+
+    [Theory]
+    [MemberData(nameof(SetTraceLevel_TestData))]
+    public void SetTraceLevel_Invoke_GetReturnsExpected(object element, PresentationTraceLevel traceLevel, PresentationTraceLevel expected)
+    {
+        PresentationTraceSources.SetTraceLevel(element, traceLevel);
+        Assert.Equal(expected, PresentationTraceSources.GetTraceLevel(element));
+    }
+
+    [Fact]
+    public void AnimationSource_Get_ReturnsExpected()
+    {
+        TraceSource source = PresentationTraceSources.AnimationSource;
+        Assert.NotNull(source);
+        Assert.Same(source, PresentationTraceSources.AnimationSource);
+        Assert.Equal("System.Windows.Media.Animation", source.Name);
+        Assert.True(Enum.IsDefined(source.Switch.Level));
+    }
+
+    [Fact]
+    public void DataBindingSource_Get_ReturnsExpected()
+    {
+        TraceSource source = PresentationTraceSources.DataBindingSource;
+        Assert.NotNull(source);
+        Assert.Same(source, PresentationTraceSources.DataBindingSource);
+        Assert.Equal("System.Windows.Data", source.Name);
+        Assert.True(Enum.IsDefined(source.Switch.Level));
+    }
+
+    [Fact]
+    public void DependencyPropertySource_Get_ReturnsExpected()
+    {
+        TraceSource source = PresentationTraceSources.DependencyPropertySource;
+        Assert.NotNull(source);
+        Assert.Same(source, PresentationTraceSources.DependencyPropertySource);
+        Assert.Equal("System.Windows.DependencyProperty", source.Name);
+        Assert.True(Enum.IsDefined(source.Switch.Level));
+    }
+
+    [Fact]
+    public void DocumentsSource_Get_ReturnsExpected()
+    {
+        TraceSource source = PresentationTraceSources.DocumentsSource;
+        Assert.NotNull(source);
+        Assert.Same(source, PresentationTraceSources.DocumentsSource);
+        Assert.Equal("System.Windows.Documents", source.Name);
+        Assert.True(Enum.IsDefined(source.Switch.Level));
+    }
+
+    [Fact]
+    public void FreezableSource_Get_ReturnsExpected()
+    {
+        TraceSource source = PresentationTraceSources.FreezableSource;
+        Assert.NotNull(source);
+        Assert.Same(source, PresentationTraceSources.FreezableSource);
+        Assert.Equal("System.Windows.Freezable", source.Name);
+        Assert.True(Enum.IsDefined(source.Switch.Level));
+    }
+
+    [Fact]
+    public void HwndHostSource_Get_ReturnsExpected()
+    {
+        TraceSource source = PresentationTraceSources.HwndHostSource;
+        Assert.NotNull(source);
+        Assert.Same(source, PresentationTraceSources.HwndHostSource);
+        Assert.Equal("System.Windows.Interop.HwndHost", source.Name);
+        Assert.True(Enum.IsDefined(source.Switch.Level));
+    }
+
+    [Fact]
+    public void MarkupSource_Get_ReturnsExpected()
+    {
+        TraceSource source = PresentationTraceSources.MarkupSource;
+        Assert.NotNull(source);
+        Assert.Same(source, PresentationTraceSources.MarkupSource);
+        Assert.Equal("System.Windows.Markup", source.Name);
+        Assert.True(Enum.IsDefined(source.Switch.Level));
+    }
+
+    [Fact]
+    public void NameScopeSource_Get_ReturnsExpected()
+    {
+        TraceSource source = PresentationTraceSources.NameScopeSource;
+        Assert.NotNull(source);
+        Assert.Same(source, PresentationTraceSources.NameScopeSource);
+        Assert.Equal("System.Windows.NameScope", source.Name);
+        Assert.True(Enum.IsDefined(source.Switch.Level));
+    }
+
+    [Fact]
+    public void ResourceDictionarySource_Get_ReturnsExpected()
+    {
+        TraceSource source = PresentationTraceSources.ResourceDictionarySource;
+        Assert.NotNull(source);
+        Assert.Same(source, PresentationTraceSources.ResourceDictionarySource);
+        Assert.Equal("System.Windows.ResourceDictionary", source.Name);
+        Assert.True(Enum.IsDefined(source.Switch.Level));
+    }
+
+    [Fact]
+    public void RoutedEventSource_Get_ReturnsExpected()
+    {
+        TraceSource source = PresentationTraceSources.RoutedEventSource;
+        Assert.NotNull(source);
+        Assert.Same(source, PresentationTraceSources.RoutedEventSource);
+        Assert.Equal("System.Windows.RoutedEvent", source.Name);
+        Assert.True(Enum.IsDefined(source.Switch.Level));
+    }
+
+    [Fact]
+    public void ShellSource_Get_ReturnsExpected()
+    {
+        TraceSource source = PresentationTraceSources.ShellSource;
+        Assert.NotNull(source);
+        Assert.Same(source, PresentationTraceSources.ShellSource);
+        Assert.Equal("System.Windows.Shell", source.Name);
+        Assert.True(Enum.IsDefined(source.Switch.Level));
+    }
+}
\ No newline at end of file
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/IO/Packaging/EncryptedPackageEnvelopeTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/IO/Packaging/EncryptedPackageEnvelopeTests.cs
new file mode 100644
index 00000000000..3d52675718d
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/IO/Packaging/EncryptedPackageEnvelopeTests.cs
@@ -0,0 +1,64 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Security.RightsManagement;
+
+namespace System.IO.Packaging.Tests;
+
+public class EncryptedPackageEnvelopeTests
+{
+    [Fact]
+    public void Open_NullStream_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("envelopeStream", () => EncryptedPackageEnvelope.Open((Stream)null!));
+    }
+
+    [Fact]
+    public void Open_WriteOnlyStream_ThrowsArgumentException()
+    {
+        using var stream = new WriteOnlyStream();
+        Assert.Throws<ArgumentException>(() => EncryptedPackageEnvelope.Open(stream));
+    }
+
+    [Fact]
+    public void Open_InvalidStream_ThrowsIOException()
+    {
+        using var stream = new MemoryStream();
+        Assert.Throws<IOException>(() => EncryptedPackageEnvelope.Open(stream));
+    }
+    
+    [Fact]
+    public void Open_NullEnvelopeFileName_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("envelopeFileName", () => EncryptedPackageEnvelope.Open((string)null!));
+        Assert.Throws<ArgumentNullException>("envelopeFileName", () => EncryptedPackageEnvelope.Open(null!, FileAccess.Read));
+        Assert.Throws<ArgumentNullException>("envelopeFileName", () => EncryptedPackageEnvelope.Open(null!, FileAccess.Read, FileShare.Read));
+    }
+    
+    [Fact]
+    public void Open_DocumentDoesNotContainPackage_ThrowsFileFormatException()
+    {
+        string path = Helpers.GetResourcePath("test-ole-file.doc");
+        using var stream = File.OpenRead(path);
+        Assert.Throws<FileFormatException>(() => EncryptedPackageEnvelope.Open(stream));
+    }
+    
+    [Fact]
+    public void Open_DocumentDoesNotContainRightsManagementProtectedStream_ThrowsFileFormatException()
+    {
+        string path = Helpers.GetResourcePath("Invalid_1.xps");
+        using var stream = File.OpenRead(path);
+        Assert.Throws<FileFormatException>(() => EncryptedPackageEnvelope.Open(stream));
+    }
+
+    private class ReadOnlyStream : MemoryStream
+    {
+        public override bool CanWrite => false;
+    }
+
+    private class WriteOnlyStream : MemoryStream
+    {
+        public override bool CanRead => false;
+    }
+}
\ No newline at end of file
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/IO/Packaging/PackageDigitalSignatureManagerTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/IO/Packaging/PackageDigitalSignatureManagerTests.cs
new file mode 100644
index 00000000000..88cb5386141
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/IO/Packaging/PackageDigitalSignatureManagerTests.cs
@@ -0,0 +1,367 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Security.Cryptography.X509Certificates;
+
+namespace System.IO.Packaging.Tests;
+
+public class PackageDigitalSignatureManagerTests
+{
+    // TODO:
+    // Signatures - signed.
+    // SignatureOrigin - signed.
+    // Countersign - signed.
+    // GetSignature - signed.
+    // RemoveAllSignatures - signed.
+    // RemoveSignature - signed.
+    // Sign
+    // VerifySignatures - signed.
+
+    [Fact]
+    public void Ctor_Package()
+    {
+        var package = new CustomPackage(FileAccess.ReadWrite);
+        var manager = new PackageDigitalSignatureManager(package);
+        Assert.Equal(CertificateEmbeddingOption.InCertificatePart, manager.CertificateOption);
+        Assert.Equal("http://www.w3.org/2001/04/xmlenc#sha256", manager.HashAlgorithm);
+        Assert.False(manager.IsSigned);
+        Assert.Equal(IntPtr.Zero, manager.ParentWindow);
+        Assert.Equal(new Uri("/package/services/digital-signature/origin.psdsor", UriKind.Relative), manager.SignatureOrigin);
+        Assert.Empty(manager.Signatures);
+        Assert.Same(manager.Signatures, manager.Signatures);
+        Assert.Equal("YYYY-MM-DDThh:mm:ss.sTZD", manager.TimeFormat);
+        Assert.NotEmpty(manager.TransformMapping);
+        Assert.Same(manager.TransformMapping, manager.TransformMapping);
+        Assert.Equal(2, manager.TransformMapping.Count);
+        Assert.Equal("http://www.w3.org/TR/2001/REC-xml-c14n-20010315", manager.TransformMapping["application/vnd.openxmlformats-package.relationships+xml"]);
+        Assert.Equal("http://www.w3.org/TR/2001/REC-xml-c14n-20010315", manager.TransformMapping["application/vnd.openxmlformats-package.digital-signature-xmlsignature+xml"]);
+    }
+
+    [Fact]
+    public void Ctor_NullPackage_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("package", () => new PackageDigitalSignatureManager(null));
+    }
+
+    [Fact]
+    public void DefaultHashAlgorithm_Get_ReturnsExpected()
+    {
+        Assert.Equal("http://www.w3.org/2001/04/xmlenc#sha256", PackageDigitalSignatureManager.DefaultHashAlgorithm);
+    }
+
+    [Fact]
+    public void SignatureOriginRelationshipType_Get_ReturnsExpected()
+    {
+        Assert.Equal("http://schemas.openxmlformats.org/package/2006/relationships/digital-signature/origin", PackageDigitalSignatureManager.SignatureOriginRelationshipType);
+    }
+
+    [Fact]
+    public void VerifyCertificate_NullCertificate_ThrowsArgumentNullException()
+    {
+        var package = new CustomPackage(FileAccess.ReadWrite);
+        var manager = new PackageDigitalSignatureManager(package);
+        Assert.Throws<ArgumentNullException>("certificate", () => PackageDigitalSignatureManager.VerifyCertificate(null));
+    }
+
+    [Fact]
+    public void VerifyCertificate_InvokeDefaultCertificate_ThrowsArgumentException()
+    {
+#pragma warning disable SYSLIB0026
+        var c = new X509Certificate();
+#pragma warning restore 0618
+        Assert.Throws<ArgumentException>("handle", () => PackageDigitalSignatureManager.VerifyCertificate(c));
+    }
+
+    [Theory]
+    [InlineData(CertificateEmbeddingOption.InCertificatePart)]
+    [InlineData(CertificateEmbeddingOption.InSignaturePart)]
+    [InlineData(CertificateEmbeddingOption.NotEmbedded)]
+    public void CertificateOption_Set_GetReturnsExpected(CertificateEmbeddingOption value)
+    {
+        var package = new CustomPackage(FileAccess.ReadWrite);
+        var manager = new PackageDigitalSignatureManager(package);
+
+        // Set.
+        manager.CertificateOption = value;
+        Assert.Equal(value, manager.CertificateOption);
+
+        // Set same.
+        manager.CertificateOption = value;
+        Assert.Equal(value, manager.CertificateOption);
+    }
+
+    [Theory]
+    [InlineData(CertificateEmbeddingOption.InCertificatePart - 1)]
+    [InlineData(CertificateEmbeddingOption.NotEmbedded + 1)]
+    public void CertificateOption_SetInvalid_ThrowsArgumentOutOfRangeException(CertificateEmbeddingOption value)
+    {
+        var package = new CustomPackage(FileAccess.ReadWrite);
+        var manager = new PackageDigitalSignatureManager(package);
+        Assert.Throws<ArgumentOutOfRangeException>("value", () => manager.CertificateOption = value);
+    }
+
+    [Theory]
+    [InlineData("http://www.w3.org/2001/04/xmlenc#sha256")]
+    [InlineData("value")]
+    [InlineData("  ")]
+    public void HashAlgorithm_Set_GetReturnsExpected(string value)
+    {
+        var package = new CustomPackage(FileAccess.ReadWrite);
+        var manager = new PackageDigitalSignatureManager(package);
+
+        // Set.
+        manager.HashAlgorithm = value;
+        Assert.Equal(value, manager.HashAlgorithm);
+
+        // Set same.
+        manager.HashAlgorithm = value;
+        Assert.Equal(value, manager.HashAlgorithm);
+    }
+
+    [Fact]
+    public void HashAlgortithm_SetNull_ThrowsArgumentNullException()
+    {
+        var package = new CustomPackage(FileAccess.ReadWrite);
+        var manager = new PackageDigitalSignatureManager(package);
+        Assert.Throws<ArgumentNullException>("value", () => manager.HashAlgorithm = null);
+    }
+
+    [Fact]
+    public void HashAlgorithm_SetEmpty_ThrowsArgumentException()
+    {
+        var package = new CustomPackage(FileAccess.ReadWrite);
+        var manager = new PackageDigitalSignatureManager(package);
+        Assert.Throws<ArgumentException>("value", () => manager.HashAlgorithm = string.Empty);
+    }
+    
+    public static IEnumerable<object[]> ParentWindow_Set_TestData()
+    {
+        yield return new object[] { (IntPtr)(-1) };
+        yield return new object[] { IntPtr.Zero };
+        yield return new object[] { (IntPtr)1 };
+    }
+
+    [Theory]
+    [MemberData(nameof(ParentWindow_Set_TestData))]
+    public void ParentWindow_Set_GetReturnsExpected(IntPtr value)
+    {
+        var package = new CustomPackage(FileAccess.ReadWrite);
+        var manager = new PackageDigitalSignatureManager(package);
+
+        // Set.
+        manager.ParentWindow = value;
+        Assert.Equal(value, manager.ParentWindow);
+
+        // Set same.
+        manager.ParentWindow = value;
+        Assert.Equal(value, manager.ParentWindow);
+    }
+
+    [Theory]
+    [InlineData("YYYY-MM-DDThh:mm:ss.sTZD")]
+    [InlineData("YYYY-MM-DDThh:mm:ssTZD")]
+    [InlineData("YYYY-MM-DDThh:mmTZD")]
+    [InlineData("YYYY-MM-DD")]
+    [InlineData("YYYY-MM")]                 
+    [InlineData("YYYY")]
+    public void TimeFormat_Set_GetReturnsExpected(string value)
+    {
+        var package = new CustomPackage(FileAccess.ReadWrite);
+        var manager = new PackageDigitalSignatureManager(package);
+
+        // Set.
+        manager.TimeFormat = value;
+        Assert.Equal(value, manager.TimeFormat);
+
+        // Set same.
+        manager.TimeFormat = value;
+        Assert.Equal(value, manager.TimeFormat);
+    }
+
+    [Fact]
+    public void TimeFormat_SetNull_ThrowsArgumentNullException()
+    {
+        var package = new CustomPackage(FileAccess.ReadWrite);
+        var manager = new PackageDigitalSignatureManager(package);
+        Assert.Throws<ArgumentNullException>("value", () => manager.TimeFormat = null);
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData("  ")]
+    [InlineData("value")]
+    [InlineData("yyyy-MM-ddTHH:mm:ss.fzzz")]
+    [InlineData("yyyy-MM-ddTHH:mm:sszzz")] 
+    [InlineData("yyyy-MM-ddTHH:mmzzz")]   
+    [InlineData("yyyy-MM-dd")]
+    [InlineData("yyyy-MM")]
+    [InlineData("yyyy")] 
+    [InlineData("yyyy-MM-ddTHH:mm:ss.fZ")]
+    [InlineData("yyyy-MM-ddTHH:mm:ssZ")]
+    [InlineData("yyyy-MM-ddTHH:mmZ")]
+    [InlineData(" YYYY ")]
+    public void TimeFormat_SetInvalid_ThrowsFormatException(string value)
+    {
+        var package = new CustomPackage(FileAccess.ReadWrite);
+        var manager = new PackageDigitalSignatureManager(package);
+        Assert.Throws<FormatException>(() => manager.TimeFormat = value);
+    }
+
+    [Fact]
+    public void Countersign_NotSigned_ThrowsInvalidOperationException()
+    {
+        var package = new CustomPackage(FileAccess.ReadWrite);
+        var manager = new PackageDigitalSignatureManager(package);
+        Assert.Throws<InvalidOperationException>(() => manager.Countersign());
+
+#pragma warning disable SYSLIB0026
+        var c = new X509Certificate();
+#pragma warning restore 0618
+        Assert.Throws<InvalidOperationException>(() => manager.Countersign(c));
+        Assert.Throws<InvalidOperationException>(() => manager.Countersign(c, new Uri[0]));
+    }
+
+    [Fact]
+    public void Countersign_NullCertificate_ThrowsArgumentNullException()
+    {
+        var package = new CustomPackage(FileAccess.ReadWrite);
+        var manager = new PackageDigitalSignatureManager(package);
+        Assert.Throws<ArgumentNullException>("certificate", () => manager.Countersign(null));
+        Assert.Throws<ArgumentNullException>("certificate", () => manager.Countersign(null, new Uri[0]));
+    }
+
+    [Fact]
+    public void Countersign_NullSignatures_ThrowsArgumentNullException()
+    {
+        var package = new CustomPackage(FileAccess.ReadWrite);
+        var manager = new PackageDigitalSignatureManager(package);
+        
+#pragma warning disable SYSLIB0026
+        var c = new X509Certificate();
+#pragma warning restore 0618
+        Assert.Throws<ArgumentNullException>("signatures", () => manager.Countersign(c, null));
+    }
+
+    [Fact]
+    public void GetSignature_InvokeNotSigned_ReturnsNull()
+    {
+        var package = new CustomPackage(FileAccess.ReadWrite);
+        var manager = new PackageDigitalSignatureManager(package);
+        Assert.Null(manager.GetSignature(new Uri("http://microsoft.com")));
+    }
+
+    [Fact]
+    public void GetSignature_NullSignatureUri_ThrowsArgumentNullException()
+    {
+        var package = new CustomPackage(FileAccess.ReadWrite);
+        var manager = new PackageDigitalSignatureManager(package);
+        Assert.Throws<ArgumentNullException>("signatureUri", () => manager.GetSignature(null));
+    }
+
+    [Fact]
+    public void RemoveAllSignatures_InvokeNotSigned_Nop()
+    {
+        var package = new CustomPackage(FileAccess.ReadWrite);
+        var manager = new PackageDigitalSignatureManager(package);
+        int callCount = 0;
+        var parts = new List<Uri>();
+        package.DeletePartCoreAction = (uri) =>
+        {
+            parts.Add(uri);
+            callCount++;
+        };
+
+        // Remove.
+        manager.RemoveAllSignatures();
+        Assert.Equal(2, callCount);
+        Assert.Equal(new Uri[] { new Uri("/package/services/digital-signature/origin.psdsor", UriKind.Relative), new Uri("/package/services/digital-signature/_rels/origin.psdsor.rels", UriKind.Relative) }, parts);
+        Assert.Empty(manager.Signatures);
+        Assert.Same(manager.Signatures, manager.Signatures);
+
+        // Remove again.
+        manager.RemoveAllSignatures();
+        Assert.Equal(4, callCount);
+        Assert.Equal(new Uri[] { new Uri("/package/services/digital-signature/origin.psdsor", UriKind.Relative), new Uri("/package/services/digital-signature/_rels/origin.psdsor.rels", UriKind.Relative), new Uri("/package/services/digital-signature/origin.psdsor", UriKind.Relative), new Uri("/package/services/digital-signature/_rels/origin.psdsor.rels", UriKind.Relative) }, parts);
+        Assert.Empty(manager.Signatures);
+        Assert.Same(manager.Signatures, manager.Signatures);
+    }
+
+    [Fact]
+    public void RemoveSignature_InvokeNotSigned_Nop()
+    {
+        var package = new CustomPackage(FileAccess.ReadWrite);
+        var manager = new PackageDigitalSignatureManager(package);
+        int callCount = 0;
+        package.DeletePartCoreAction = (uri) => callCount++;
+
+        // Remove.
+        manager.RemoveSignature(new Uri("https://microsoft.com"));
+        Assert.Equal(0, callCount);
+        Assert.Empty(manager.Signatures);
+        Assert.Same(manager.Signatures, manager.Signatures);
+
+        // Remove again.
+        manager.RemoveSignature(new Uri("https://microsoft.com"));
+        Assert.Equal(0, callCount);
+        Assert.Empty(manager.Signatures);
+        Assert.Same(manager.Signatures, manager.Signatures);
+    }
+
+    [Fact]
+    public void RemoveSignature_NullSignatureUri_ThrowsArgumentNullException()
+    {
+        var package = new CustomPackage(FileAccess.ReadWrite);
+        var manager = new PackageDigitalSignatureManager(package);
+        Assert.Throws<ArgumentNullException>("signatureUri", () => manager.RemoveSignature(null));
+    }
+
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void VerifySignatures_InvokeNotSigned_ReturnsNotSigned(bool exitOnFailure)
+    {
+        var package = new CustomPackage(FileAccess.ReadWrite);
+        var manager = new PackageDigitalSignatureManager(package);
+        Assert.Equal(VerifyResult.NotSigned, manager.VerifySignatures(exitOnFailure));
+    }
+
+    private class CustomPackage : Package
+    {
+        public CustomPackage(FileAccess openFileAccess) : base(openFileAccess)
+        {
+        }
+
+        protected override PackagePart CreatePartCore(Uri partUri, string contentType, CompressionOption compressionOption)
+        {
+            throw new NotImplementedException();
+        }
+
+        public Action<Uri>? DeletePartCoreAction { get; set; }
+
+        protected override void DeletePartCore(Uri partUri)
+        {
+            if (DeletePartCoreAction is null)
+            {
+                throw new NotImplementedException();
+            }
+
+            DeletePartCoreAction(partUri);
+        }
+
+        protected override void FlushCore()
+        {
+            throw new NotImplementedException();
+        }
+
+        protected override PackagePart? GetPartCore(Uri partUri)
+        {
+            throw new NotImplementedException();
+        }
+
+        protected override PackagePart[] GetPartsCore()
+        {
+            throw new NotImplementedException();
+        }
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Security/RightsManagement/ContentGrantTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Security/RightsManagement/ContentGrantTests.cs
new file mode 100644
index 00000000000..1913000ce87
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Security/RightsManagement/ContentGrantTests.cs
@@ -0,0 +1,89 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Security.RightsManagement.Tests;
+ 
+public class ContentGrantTests
+{
+    public static IEnumerable<object[]> Ctor_ContentUser_ContentRight_TestData()
+    {
+        yield return new object[] { ContentUser.AnyoneUser, ContentRight.View };
+        yield return new object[] { ContentUser.OwnerUser, ContentRight.Edit };
+        yield return new object[] { new ContentUser("name", AuthenticationType.Windows), ContentRight.Print };
+        yield return new object[] { new ContentUser("name", AuthenticationType.Windows), ContentRight.Extract };
+        yield return new object[] { new ContentUser("name", AuthenticationType.Windows), ContentRight.ObjectModel };
+        yield return new object[] { new ContentUser("name", AuthenticationType.Windows), ContentRight.Owner };
+        yield return new object[] { new ContentUser("name", AuthenticationType.Windows), ContentRight.ViewRightsData };
+        yield return new object[] { new ContentUser("name", AuthenticationType.Windows), ContentRight.Forward };
+        yield return new object[] { new ContentUser("name", AuthenticationType.Windows), ContentRight.Reply };
+        yield return new object[] { new ContentUser("name", AuthenticationType.Windows), ContentRight.ReplyAll };
+        yield return new object[] { new ContentUser("name", AuthenticationType.Windows), ContentRight.Sign };
+        yield return new object[] { new ContentUser("name", AuthenticationType.Windows), ContentRight.DocumentEdit };
+        yield return new object[] { new ContentUser("name", AuthenticationType.Windows), ContentRight.Export };
+    }
+
+    [Theory]
+    [MemberData(nameof(Ctor_ContentUser_ContentRight_TestData))]
+    public void Ctor_ContentUser_ContentRight(ContentUser user, ContentRight right)
+    {
+        var grant = new ContentGrant(user, right);
+        Assert.Equal(user, grant.User);
+        Assert.Equal(right, grant.Right);
+        Assert.Equal(DateTime.MinValue, grant.ValidFrom);
+        Assert.Equal(DateTime.MaxValue, grant.ValidUntil);
+    }
+    public static IEnumerable<object[]> Ctor_ContentUser_ContentRight_DateTime_DateTime_TestData()
+    {
+        yield return new object[] { ContentUser.AnyoneUser, ContentRight.View, DateTime.MinValue, DateTime.MaxValue };
+        yield return new object[] { ContentUser.OwnerUser, ContentRight.Edit, DateTime.MinValue, DateTime.MaxValue };
+        yield return new object[] { new ContentUser("name", AuthenticationType.Windows), ContentRight.Print, DateTime.MinValue, DateTime.MaxValue };
+        yield return new object[] { new ContentUser("name", AuthenticationType.Windows), ContentRight.Extract, DateTime.MinValue, DateTime.MaxValue };
+        yield return new object[] { new ContentUser("name", AuthenticationType.Windows), ContentRight.ObjectModel, DateTime.MinValue, DateTime.MaxValue };
+        yield return new object[] { new ContentUser("name", AuthenticationType.Windows), ContentRight.Owner, DateTime.MinValue, DateTime.MaxValue };
+        yield return new object[] { new ContentUser("name", AuthenticationType.Windows), ContentRight.ViewRightsData, DateTime.MinValue, DateTime.MaxValue };
+        yield return new object[] { new ContentUser("name", AuthenticationType.Windows), ContentRight.Forward, DateTime.MinValue, DateTime.MaxValue };
+        yield return new object[] { new ContentUser("name", AuthenticationType.Windows), ContentRight.Reply, DateTime.MinValue, DateTime.MaxValue };
+        yield return new object[] { new ContentUser("name", AuthenticationType.Windows), ContentRight.ReplyAll, DateTime.MinValue, DateTime.MaxValue };
+        yield return new object[] { new ContentUser("name", AuthenticationType.Windows), ContentRight.Sign, DateTime.MinValue, DateTime.MaxValue };
+        yield return new object[] { new ContentUser("name", AuthenticationType.Windows), ContentRight.DocumentEdit, DateTime.MinValue, DateTime.MaxValue };
+        yield return new object[] { new ContentUser("name", AuthenticationType.Windows), ContentRight.Export, DateTime.MinValue, DateTime.MaxValue };
+        yield return new object[] { new ContentUser("name", AuthenticationType.Windows), ContentRight.Export, DateTime.MinValue, DateTime.MinValue };
+        yield return new object[] { new ContentUser("name", AuthenticationType.Windows), ContentRight.Export, DateTime.MaxValue, DateTime.MaxValue };
+        yield return new object[] { new ContentUser("name", AuthenticationType.Windows), ContentRight.Export, new DateTime(2023, 01, 01), new DateTime(2023, 01, 02) };
+    }
+
+    [Theory]
+    [MemberData(nameof(Ctor_ContentUser_ContentRight_DateTime_DateTime_TestData))]
+    public void Ctor_ContentUser_ContentRight_DateTime_DateTime(ContentUser user, ContentRight right, DateTime validFrom, DateTime validUntil)
+    {
+        var grant = new ContentGrant(user, right, validFrom, validUntil);
+        Assert.Equal(user, grant.User);
+        Assert.Equal(right, grant.Right);
+        Assert.Equal(validFrom, grant.ValidFrom);
+        Assert.Equal(validUntil, grant.ValidUntil);
+    }
+
+    [Fact]
+    public void Ctor_NullUser_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("user", () => new ContentGrant(null, ContentRight.View));
+        Assert.Throws<ArgumentNullException>("user", () => new ContentGrant(null, ContentRight.View, DateTime.MinValue, DateTime.MaxValue));
+    }
+
+    [Theory]
+    [InlineData(ContentRight.View - 1)]
+    [InlineData(ContentRight.Export + 1)]
+    public void Ctor_ContentUser_ContentRight_InvalidRight(ContentRight right)
+    {
+        var user = new ContentUser("name", AuthenticationType.Windows);
+        Assert.Throws<ArgumentOutOfRangeException>("right", () => new ContentGrant(user, right));
+    }
+
+    [Fact]
+    public void Ctor_InvalidValidFrom_ThrowsArgumentOutOfRangeException()
+    {
+        var user = new ContentUser("name", AuthenticationType.Windows);
+        Assert.Throws<ArgumentOutOfRangeException>("validFrom", () => new ContentGrant(user, ContentRight.View, new DateTime(2023, 01, 01), new DateTime(2023, 01, 01).AddTicks(-1)));
+    }
+}
\ No newline at end of file
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Security/RightsManagement/ContentUserTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Security/RightsManagement/ContentUserTests.cs
new file mode 100644
index 00000000000..c469084ef5e
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Security/RightsManagement/ContentUserTests.cs
@@ -0,0 +1,141 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Security.RightsManagement.Tests;
+
+public class ContentUserTests
+{
+    [Theory]
+    [InlineData("name", AuthenticationType.Windows)]
+    [InlineData("NaMe", AuthenticationType.Passport)]
+    [InlineData("name", AuthenticationType.WindowsPassport)]
+    [InlineData("  name  ", AuthenticationType.Windows)]
+    [InlineData("anyone", AuthenticationType.Windows)]
+    [InlineData("anyone", AuthenticationType.Passport)]
+    [InlineData("anyone", AuthenticationType.WindowsPassport)]
+    [InlineData("anyone", AuthenticationType.Internal)]
+    [InlineData("ANYONE", AuthenticationType.Internal)]
+    [InlineData("owner", AuthenticationType.Internal)]
+    [InlineData("OWNER", AuthenticationType.Internal)]
+    public void Ctor_String_AuthenticationType(string name, AuthenticationType authenticationType)
+    {
+        var user = new ContentUser(name, authenticationType);
+        Assert.Equal(name, user.Name);
+        Assert.Equal(authenticationType, user.AuthenticationType);
+    }
+
+    [Fact]
+    public void Ctor_NullName_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("name", () => new ContentUser(null!, AuthenticationType.Windows));
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData("  ")]
+    public void Ctor_InvalidName_ThrowsArgumentOutOfRangeException(string name)
+    {
+        Assert.Throws<ArgumentOutOfRangeException>("name", () => new ContentUser(name, AuthenticationType.Windows));
+    }
+
+    [Theory]
+    [InlineData(AuthenticationType.Windows - 1)]
+    [InlineData(AuthenticationType.Internal + 1)]
+    public void Ctor_InvalidAuthenticationType_ThrowsArgumentOutOfRangeException(AuthenticationType authenticationType)
+    {
+        Assert.Throws<ArgumentOutOfRangeException>("authenticationType", () => new ContentUser("name", authenticationType));
+    }
+
+    [Theory]
+    [InlineData("name")]
+    [InlineData(" anyone ")]
+    [InlineData(" owner ")]
+    public void Ctor_InvalidInternalName_ThrowsArgumentOutOfRangeException(string name)
+    {
+        Assert.Throws<ArgumentOutOfRangeException>("name", () => new ContentUser(name, AuthenticationType.Internal));
+    }
+
+    [Fact]
+    public void AnyoneUser_Get_ReturnsExpected()
+    {
+        ContentUser user = ContentUser.AnyoneUser;
+        Assert.Same(user, ContentUser.AnyoneUser);
+        Assert.Equal("Anyone", user.Name);
+        Assert.Equal(AuthenticationType.Internal, user.AuthenticationType);
+    }
+
+    [Fact]
+    public void OwnerUser_Get_ReturnsExpected()
+    {
+        ContentUser user = ContentUser.OwnerUser;
+        Assert.Same(user, ContentUser.OwnerUser);
+        Assert.Equal("Owner", user.Name);
+        Assert.Equal(AuthenticationType.Internal, user.AuthenticationType);
+    }
+
+    public static IEnumerable<object?[]> Equals_TestData()
+    {
+        yield return new object?[] { new ContentUser("name", AuthenticationType.Windows), new ContentUser("name", AuthenticationType.Windows), true };
+        yield return new object?[] { new ContentUser("name", AuthenticationType.Windows), new SubContentUser("name", AuthenticationType.Windows), false };
+        yield return new object?[] { new ContentUser("name", AuthenticationType.Windows), new ContentUser("NAME", AuthenticationType.Windows), true };
+        yield return new object?[] { new ContentUser("name", AuthenticationType.Windows), new ContentUser("nAME", AuthenticationType.Windows), true };
+        yield return new object?[] { new ContentUser("name", AuthenticationType.Windows), new ContentUser(" name ", AuthenticationType.Windows), false };
+        yield return new object?[] { new ContentUser("name", AuthenticationType.Windows), new ContentUser("name2", AuthenticationType.Windows), false };
+        yield return new object?[] { new ContentUser("name", AuthenticationType.Windows), new ContentUser("name", AuthenticationType.WindowsPassport), false };
+        yield return new object?[] { new ContentUser("name", AuthenticationType.Windows), new object(), false };
+        yield return new object?[] { new ContentUser("name", AuthenticationType.Windows), null, false };
+        
+        yield return new object?[] { new SubContentUser("name", AuthenticationType.Windows), new SubContentUser("name", AuthenticationType.Windows), true };
+        yield return new object?[] { new SubContentUser("name", AuthenticationType.Windows), new ContentUser("name", AuthenticationType.Windows), false };
+        yield return new object?[] { new ContentUser("name", AuthenticationType.Windows), new SubContentUser("name", AuthenticationType.Windows), false };
+    }
+
+    [Theory]
+    [MemberData(nameof(Equals_TestData))]
+    public void Equals_Object_ReturnsExpected(ContentUser user, object obj, bool expected)
+    {
+        Assert.Equal(expected, user.Equals(obj));
+        if (user?.GetType() == obj?.GetType())
+        {
+            Assert.Equal(expected, user!.GetHashCode().Equals(obj!.GetHashCode()));
+        }
+    }
+
+    [Fact]
+    public void IsAuthenticated_InvokeWindows_ReturnsFalse()
+    {
+        var user = new ContentUser("name", AuthenticationType.Windows);
+        Assert.False(user.IsAuthenticated());
+    }
+
+    [Fact]
+    public void IsAuthenticated_InvokePassport_ReturnsFalse()
+    {
+        var user = new ContentUser("name", AuthenticationType.Passport);
+        Assert.False(user.IsAuthenticated());
+    }
+
+    [Fact]
+    public void IsAuthenticated_InvokeWindowsPassport_ReturnsFalse()
+    {
+        var user = new ContentUser("name", AuthenticationType.WindowsPassport);
+        Assert.False(user.IsAuthenticated());
+    }
+
+    [Theory]
+    [InlineData("anyone")]
+    [InlineData("owner")]
+    public void IsAuthenticated_InvokeInternal_ReturnsFalse(string name)
+    {
+        var user = new ContentUser(name, AuthenticationType.Internal);
+        Assert.False(user.IsAuthenticated());
+    }
+
+    private class SubContentUser : ContentUser
+    {
+        public SubContentUser(string name, AuthenticationType authenticationType) : base(name, authenticationType)
+        {
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Security/RightsManagement/CryptoProviderTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Security/RightsManagement/CryptoProviderTests.cs
new file mode 100644
index 00000000000..c10c51d69a1
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Security/RightsManagement/CryptoProviderTests.cs
@@ -0,0 +1,9 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Security.RightsManagement;
+
+public class CryptoProviderTests
+{
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Security/RightsManagement/LocalizedNameDescriptionPairTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Security/RightsManagement/LocalizedNameDescriptionPairTests.cs
new file mode 100644
index 00000000000..8945aff35f4
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Security/RightsManagement/LocalizedNameDescriptionPairTests.cs
@@ -0,0 +1,63 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Security.RightsManagement.Tests;
+
+public class LocalizedNameDescriptionPairTests
+{
+    [Theory]
+    [InlineData("", "")]
+    [InlineData("  ", "  ")]
+    [InlineData("name", "description")]
+    public void Ctor_String_String(string name, string description)
+    {
+        var pair = new LocalizedNameDescriptionPair(name, description);
+        Assert.Equal(name, pair.Name);
+        Assert.Equal(description, pair.Description);
+    }
+
+    public static IEnumerable<object?[]> Equals_TestData()
+    {
+        var pair = new LocalizedNameDescriptionPair("name", "description");
+
+        yield return new object?[] { pair, pair, true, true };
+        yield return new object?[] { pair, new LocalizedNameDescriptionPair("name", "description"), true, true };
+        yield return new object?[] { pair, new LocalizedNameDescriptionPair("NAME", "description"), false, false };
+        yield return new object?[] { pair, new LocalizedNameDescriptionPair("name", "DESCRIPTION"), false, false };
+        yield return new object?[] { pair, new LocalizedNameDescriptionPair("name2", "description"), false, false };
+        yield return new object?[] { pair, new LocalizedNameDescriptionPair("name", "description2"), false, false };
+        yield return new object?[] { pair, new LocalizedNameDescriptionPair("", "description"), false, false };
+        yield return new object?[] { pair, new LocalizedNameDescriptionPair("name", ""), false, false };
+        yield return new object?[] { pair, new SubLocalizedNameDescriptionPair("name", "description"), false, true };
+        yield return new object?[] { pair, new object(), false, false };
+        yield return new object?[] { pair, null, false, false };
+    }
+
+    [Theory]
+    [MemberData(nameof(Equals_TestData))]
+    public void Equals_Object_ReturnsExpected(LocalizedNameDescriptionPair pair, object obj, bool expected, bool expectedHashCode)
+    {
+        Assert.Equal(expected, pair.Equals(obj));
+        if (obj is LocalizedNameDescriptionPair otherPair)
+        {
+            Assert.Equal(expected, otherPair.Equals(pair));
+            Assert.Equal(expectedHashCode, pair.GetHashCode().Equals(otherPair.GetHashCode()));
+        }
+    }
+
+    [Fact]
+    public void GetHashCode_Invoke_ReturnsEqual()
+    {
+        var pair = new LocalizedNameDescriptionPair("name", "description");
+        Assert.NotEqual(0, pair.GetHashCode());
+        Assert.Equal(pair.GetHashCode(), pair.GetHashCode());
+    }
+
+    private class SubLocalizedNameDescriptionPair : LocalizedNameDescriptionPair
+    {
+        public SubLocalizedNameDescriptionPair(string name, string description) : base(name, description)
+        {
+        }
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Security/RightsManagement/PublishLicenseTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Security/RightsManagement/PublishLicenseTests.cs
new file mode 100644
index 00000000000..13db90ab354
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Security/RightsManagement/PublishLicenseTests.cs
@@ -0,0 +1,350 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Security.RightsManagement.Tests;
+
+public class PublishLicenseTests
+{
+    // Taken from https://github.com/dotnet/dotnet-api-docs/blob/main/snippets/csharp/System.Security.RightsManagement/CryptoProvider/BlockSize/Content/Truffle.png.PublishLicense.xml.
+    private const string PublishLicenseTemplate = """
+<XrML version="1.2" xmlns="">
+  <BODY type="Microsoft Rights Label" version="3.0">
+    <ISSUEDTIME>2006-04-19T03:14</ISSUEDTIME>
+    <ISSUER>
+      <OBJECT type="Group-Identity">
+        <ID type="Windows">S-1-5-21-2127521184-1604012920-1887927527-1723404</ID>
+        <NAME>jack.davis@microsoft.com</NAME>
+      </OBJECT>
+      <PUBLICKEY>
+        <ALGORITHM>RSA</ALGORITHM>
+        <PARAMETER name="public-exponent">
+          <VALUE encoding="integer32">65537</VALUE>
+        </PARAMETER>
+        <PARAMETER name="modulus">
+          <VALUE encoding="base64" size="1024">r1rbEmgQhskJ29p8xpX00ZlROS13kHMzv0DrOQOn+4mijO3Eanelw1F+mYdSdrByU9MbamWHalUqku6wESZY2DCpRU2C3xw2lCvPtrYqtJkxSt835Ez4quDYVNQq+15DzA6qyl5gc07XuoQi1AC0Nfb5tMy0R85SocFE195VUq4=</VALUE>
+        </PARAMETER>
+      </PUBLICKEY>
+      <SECURITYLEVEL name="SDK" value="5.2.3790.134" />
+    </ISSUER>
+    <DISTRIBUTIONPOINT>
+      <OBJECT type="License-Acquisition-URL">
+        <ID type="MS-GUID">{0F45FD50-383B-43EE-90A4-ED013CD0CFE5}</ID>
+        <NAME>DRM Server Cluster</NAME>
+        <ADDRESS type="URL">http://ed-drm-red3/_wmcs/licensing</ADDRESS>
+      </OBJECT>
+    </DISTRIBUTIONPOINT>
+    <ISSUEDPRINCIPALS>
+      <PRINCIPAL internal-id="1">
+        <OBJECT type="MS-DRM-Server">
+          <ID type="MS-GUID">{1d59a4ae-e6ae-4151-b458-afc5251fe0c3}</ID>
+          <ADDRESS type="URL">http://ed-drm-red3/_wmcs</ADDRESS>
+        </OBJECT>
+        <PUBLICKEY>
+          <ALGORITHM>RSA</ALGORITHM>
+          <PARAMETER name="public-exponent">
+            <VALUE encoding="integer32">65537</VALUE>
+          </PARAMETER>
+          <PARAMETER name="modulus">
+            <VALUE encoding="base64" size="1024">43b8U8yG5ifu38tkAa8K/2DnMOZqgVdj8OZCY+V0332efhaocT7EGV8JE3Htolc2mqTDdLlHQQoJ9jrG36efYYqo4aivo7ddx5w9NlMo9O4mXb+s70LD1VPaM6TywWYYfho+6vTGI1SwPJVgmwS2Qgha/AXOJrK0t5gEX8CZPMo=</VALUE>
+          </PARAMETER>
+        </PUBLICKEY>
+        <SECURITYLEVEL name="Server-Version" value="5.2.3790.134" />
+        <SECURITYLEVEL name="Server-SKU" value="RMS 1.0" />
+        <ENABLINGBITS type="sealed-key">
+          <VALUE encoding="base64" size="1536">OmZReXce7iXuQZ+ySktmUyK0sApe4IxmBTIpzsPaIcYK/ll4SxzxwUO5BLUAV9SY41nPYX+zFMKKOkVC2GdKuKlERXYgR8LvyDIifKm8/OUL2q5XKsW4pRXMfm4ccGokq1lv0pCMS0qIreAmSURdK+FIVjWwPeFQu2N1iKwHigDjHKbva9ICtkxXfZtgEwgakypbFV/T7WqrpWxS8l4bBsIAKcYzuUbLgQOYCc/lJBUWDJqMMPsyV1J65ZHlO3Nd</VALUE>
+        </ENABLINGBITS>
+      </PRINCIPAL>
+    </ISSUEDPRINCIPALS>
+    <WORK>
+      <OBJECT>
+        <ID type="MS-GUID">{9257669d-2753-4f8f-94c6-028987c0434b}</ID>
+      </OBJECT>
+      <METADATA>
+        <OWNER>
+          <OBJECT>
+            <ID type="Windows" />
+            <NAME>jack.davis@microsoft.com</NAME>
+          </OBJECT>
+        </OWNER>
+      </METADATA>
+    </WORK>
+    <AUTHENTICATEDDATA id="Encrypted-Rights-Data">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</AUTHENTICATEDDATA>
+  </BODY>
+  <SIGNATURE>
+    <ALGORITHM>RSA PKCS#1-V1.5</ALGORITHM>
+    <DIGEST>
+      <ALGORITHM>SHA1</ALGORITHM>
+      <PARAMETER name="codingtype">
+        <VALUE encoding="string">surface-coding</VALUE>
+      </PARAMETER>
+      <VALUE encoding="base64" size="160">0zkJi3NJke+OehTek7lsFT675JU=</VALUE>
+    </DIGEST>
+    <VALUE encoding="base64" size="1024">VObVcSvMdfw4pE7S2Q1o/oeE3d72yhuu42hZz5vpcg8elVfRPFrpxECWR1f9cNxSX6j32JJ9W1+vD2YNOeykWg9iIcbq0e82d/WTvkOs5eIFIWtqjGidOvnG7UCUYBktBiKJ5IDeo68P6GfsEtby8o54MlIztvWXeB5T21nhz2I=</VALUE>
+  </SIGNATURE>
+</XrML>
+""";
+
+    [Fact]
+    public void Ctor_TruffleExample()
+    {
+        var license = new PublishLicense(PublishLicenseTemplate);
+        Assert.Equal(new Guid("9257669d-2753-4f8f-94c6-028987c0434b"), license.ContentId);
+        Assert.Null(license.ReferralInfoName);
+        Assert.Null(license.ReferralInfoUri);
+        Assert.Equal(new Uri("http://ed-drm-red3/_wmcs/licensing"), license.UseLicenseAcquisitionUrl);
+    }
+
+    [Fact]
+    public void Ctor_NullSignedPublishLicense_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("signedPublishLicense", () => new PublishLicense(null!));
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData(" ")]
+    [InlineData("<manifest></manifest>")]
+    public void Ctor_InvalidSignedPublishLicense_ThrowsRightsManagementException(string signedPublishLicense)
+    {
+        Assert.Throws<RightsManagementException>(() => new PublishLicense(signedPublishLicense));
+    }
+
+    [Fact]
+    public void Ctor_EmptyUseLicenseAcquisitionUrl_ThrowsArgumentNullException()
+    {
+        const string PublishLicenseTemplate = """
+<XrML version="1.2" xmlns="">
+</XrML>
+""";
+        Assert.Throws<ArgumentNullException>("uriString", () => new PublishLicense(PublishLicenseTemplate));
+    }
+
+    [Fact]
+    public void Ctor_InvalidUseLicenseAcquisitionUrl_ThrowsUriFormatException()
+    {
+        const string PublishLicenseTemplate = """
+<XrML version="1.2" xmlns="">
+    <BODY type="Microsoft Rights Label" version="3.0">
+        <DISTRIBUTIONPOINT>
+            <OBJECT type="License-Acquisition-URL">
+                <ID type="MS-GUID">{0F45FD50-383B-43EE-90A4-ED013CD0CFE5}</ID>
+                <NAME>DRM Server Cluster</NAME>
+                <ADDRESS type="URL">invalid</ADDRESS>
+            </OBJECT>
+        </DISTRIBUTIONPOINT>
+    </BODY>
+</XrML>
+""";
+        Assert.Throws<UriFormatException>(() => new PublishLicense(PublishLicenseTemplate));
+    }
+
+    [Fact]
+    public void Ctor_NoQueries_ThrowsRightsManagementException()
+    {
+        const string PublishLicenseTemplate = """
+<XrML version="1.2" xmlns="">
+    <BODY type="Microsoft Rights Label" version="3.0">
+        <DISTRIBUTIONPOINT>
+            <OBJECT type="License-Acquisition-URL">
+                <ID type="MS-GUID">{0F45FD50-383B-43EE-90A4-ED013CD0CFE5}</ID>
+                <NAME>DRM Server Cluster</NAME>
+                <ADDRESS type="URL">https://google.com</ADDRESS>
+            </OBJECT>
+        </DISTRIBUTIONPOINT>
+    </BODY>
+</XrML>
+""";
+        Assert.Throws<RightsManagementException>(() => new PublishLicense(PublishLicenseTemplate));
+    }
+
+    [Fact]
+    public void Ctor_InvalidContentId_ThrowsFormatException()
+    {
+        const string PublishLicenseTemplate = """
+<XrML version="1.2" xmlns="">
+  <BODY type="Microsoft Rights Label" version="3.0">
+    <ISSUEDTIME>2006-04-19T03:14</ISSUEDTIME>
+    <ISSUER>
+      <OBJECT type="Group-Identity">
+        <ID type="Windows">S-1-5-21-2127521184-1604012920-1887927527-1723404</ID>
+        <NAME>jack.davis@microsoft.com</NAME>
+      </OBJECT>
+      <PUBLICKEY>
+        <ALGORITHM>RSA</ALGORITHM>
+        <PARAMETER name="public-exponent">
+          <VALUE encoding="integer32">65537</VALUE>
+        </PARAMETER>
+        <PARAMETER name="modulus">
+          <VALUE encoding="base64" size="1024">r1rbEmgQhskJ29p8xpX00ZlROS13kHMzv0DrOQOn+4mijO3Eanelw1F+mYdSdrByU9MbamWHalUqku6wESZY2DCpRU2C3xw2lCvPtrYqtJkxSt835Ez4quDYVNQq+15DzA6qyl5gc07XuoQi1AC0Nfb5tMy0R85SocFE195VUq4=</VALUE>
+        </PARAMETER>
+      </PUBLICKEY>
+      <SECURITYLEVEL name="SDK" value="5.2.3790.134" />
+    </ISSUER>
+    <DISTRIBUTIONPOINT>
+      <OBJECT type="License-Acquisition-URL">
+        <ID type="MS-GUID">{0F45FD50-383B-43EE-90A4-ED013CD0CFE5}</ID>
+        <NAME>DRM Server Cluster</NAME>
+        <ADDRESS type="URL">http://ed-drm-red3/_wmcs/licensing</ADDRESS>
+      </OBJECT>
+    </DISTRIBUTIONPOINT>
+    <ISSUEDPRINCIPALS>
+      <PRINCIPAL internal-id="1">
+        <OBJECT type="MS-DRM-Server">
+          <ID type="MS-GUID">{1d59a4ae-e6ae-4151-b458-afc5251fe0c3}</ID>
+          <ADDRESS type="URL">http://ed-drm-red3/_wmcs</ADDRESS>
+        </OBJECT>
+        <PUBLICKEY>
+          <ALGORITHM>RSA</ALGORITHM>
+          <PARAMETER name="public-exponent">
+            <VALUE encoding="integer32">65537</VALUE>
+          </PARAMETER>
+          <PARAMETER name="modulus">
+            <VALUE encoding="base64" size="1024">43b8U8yG5ifu38tkAa8K/2DnMOZqgVdj8OZCY+V0332efhaocT7EGV8JE3Htolc2mqTDdLlHQQoJ9jrG36efYYqo4aivo7ddx5w9NlMo9O4mXb+s70LD1VPaM6TywWYYfho+6vTGI1SwPJVgmwS2Qgha/AXOJrK0t5gEX8CZPMo=</VALUE>
+          </PARAMETER>
+        </PUBLICKEY>
+        <SECURITYLEVEL name="Server-Version" value="5.2.3790.134" />
+        <SECURITYLEVEL name="Server-SKU" value="RMS 1.0" />
+        <ENABLINGBITS type="sealed-key">
+          <VALUE encoding="base64" size="1536">OmZReXce7iXuQZ+ySktmUyK0sApe4IxmBTIpzsPaIcYK/ll4SxzxwUO5BLUAV9SY41nPYX+zFMKKOkVC2GdKuKlERXYgR8LvyDIifKm8/OUL2q5XKsW4pRXMfm4ccGokq1lv0pCMS0qIreAmSURdK+FIVjWwPeFQu2N1iKwHigDjHKbva9ICtkxXfZtgEwgakypbFV/T7WqrpWxS8l4bBsIAKcYzuUbLgQOYCc/lJBUWDJqMMPsyV1J65ZHlO3Nd</VALUE>
+        </ENABLINGBITS>
+      </PRINCIPAL>
+    </ISSUEDPRINCIPALS>
+    <WORK>
+      <OBJECT>
+        <ID type="MS-GUID">invalid</ID>
+      </OBJECT>
+      <METADATA>
+        <OWNER>
+          <OBJECT>
+            <ID type="Windows" />
+            <NAME>jack.davis@microsoft.com</NAME>
+          </OBJECT>
+        </OWNER>
+      </METADATA>
+    </WORK>
+    <AUTHENTICATEDDATA id="Encrypted-Rights-Data">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</AUTHENTICATEDDATA>
+  </BODY>
+  <SIGNATURE>
+    <ALGORITHM>RSA PKCS#1-V1.5</ALGORITHM>
+    <DIGEST>
+      <ALGORITHM>SHA1</ALGORITHM>
+      <PARAMETER name="codingtype">
+        <VALUE encoding="string">surface-coding</VALUE>
+      </PARAMETER>
+      <VALUE encoding="base64" size="160">0zkJi3NJke+OehTek7lsFT675JU=</VALUE>
+    </DIGEST>
+    <VALUE encoding="base64" size="1024">VObVcSvMdfw4pE7S2Q1o/oeE3d72yhuu42hZz5vpcg8elVfRPFrpxECWR1f9cNxSX6j32JJ9W1+vD2YNOeykWg9iIcbq0e82d/WTvkOs5eIFIWtqjGidOvnG7UCUYBktBiKJ5IDeo68P6GfsEtby8o54MlIztvWXeB5T21nhz2I=</VALUE>
+  </SIGNATURE>
+</XrML>
+""";
+        Assert.Throws<FormatException>(() => new PublishLicense(PublishLicenseTemplate));
+    }
+
+    [Fact]
+    public void Ctor_NoContentId_ThrowsRightsManagementException()
+    {
+        const string PublishLicenseTemplate = """
+<XrML version="1.2" xmlns="">
+  <BODY type="Microsoft Rights Label" version="3.0">
+    <ISSUEDTIME>2006-04-19T03:14</ISSUEDTIME>
+    <ISSUER>
+      <OBJECT type="Group-Identity">
+        <ID type="Windows">S-1-5-21-2127521184-1604012920-1887927527-1723404</ID>
+        <NAME>jack.davis@microsoft.com</NAME>
+      </OBJECT>
+      <PUBLICKEY>
+        <ALGORITHM>RSA</ALGORITHM>
+        <PARAMETER name="public-exponent">
+          <VALUE encoding="integer32">65537</VALUE>
+        </PARAMETER>
+        <PARAMETER name="modulus">
+          <VALUE encoding="base64" size="1024">r1rbEmgQhskJ29p8xpX00ZlROS13kHMzv0DrOQOn+4mijO3Eanelw1F+mYdSdrByU9MbamWHalUqku6wESZY2DCpRU2C3xw2lCvPtrYqtJkxSt835Ez4quDYVNQq+15DzA6qyl5gc07XuoQi1AC0Nfb5tMy0R85SocFE195VUq4=</VALUE>
+        </PARAMETER>
+      </PUBLICKEY>
+      <SECURITYLEVEL name="SDK" value="5.2.3790.134" />
+    </ISSUER>
+    <DISTRIBUTIONPOINT>
+      <OBJECT type="License-Acquisition-URL">
+        <ID type="MS-GUID">{0F45FD50-383B-43EE-90A4-ED013CD0CFE5}</ID>
+        <NAME>DRM Server Cluster</NAME>
+        <ADDRESS type="URL">http://ed-drm-red3/_wmcs/licensing</ADDRESS>
+      </OBJECT>
+    </DISTRIBUTIONPOINT>
+    <ISSUEDPRINCIPALS>
+      <PRINCIPAL internal-id="1">
+        <OBJECT type="MS-DRM-Server">
+          <ID type="MS-GUID">{1d59a4ae-e6ae-4151-b458-afc5251fe0c3}</ID>
+          <ADDRESS type="URL">http://ed-drm-red3/_wmcs</ADDRESS>
+        </OBJECT>
+        <PUBLICKEY>
+          <ALGORITHM>RSA</ALGORITHM>
+          <PARAMETER name="public-exponent">
+            <VALUE encoding="integer32">65537</VALUE>
+          </PARAMETER>
+          <PARAMETER name="modulus">
+            <VALUE encoding="base64" size="1024">43b8U8yG5ifu38tkAa8K/2DnMOZqgVdj8OZCY+V0332efhaocT7EGV8JE3Htolc2mqTDdLlHQQoJ9jrG36efYYqo4aivo7ddx5w9NlMo9O4mXb+s70LD1VPaM6TywWYYfho+6vTGI1SwPJVgmwS2Qgha/AXOJrK0t5gEX8CZPMo=</VALUE>
+          </PARAMETER>
+        </PUBLICKEY>
+        <SECURITYLEVEL name="Server-Version" value="5.2.3790.134" />
+        <SECURITYLEVEL name="Server-SKU" value="RMS 1.0" />
+        <ENABLINGBITS type="sealed-key">
+          <VALUE encoding="base64" size="1536">OmZReXce7iXuQZ+ySktmUyK0sApe4IxmBTIpzsPaIcYK/ll4SxzxwUO5BLUAV9SY41nPYX+zFMKKOkVC2GdKuKlERXYgR8LvyDIifKm8/OUL2q5XKsW4pRXMfm4ccGokq1lv0pCMS0qIreAmSURdK+FIVjWwPeFQu2N1iKwHigDjHKbva9ICtkxXfZtgEwgakypbFV/T7WqrpWxS8l4bBsIAKcYzuUbLgQOYCc/lJBUWDJqMMPsyV1J65ZHlO3Nd</VALUE>
+        </ENABLINGBITS>
+      </PRINCIPAL>
+    </ISSUEDPRINCIPALS>
+    <WORK>
+      <METADATA>
+        <OWNER>
+          <OBJECT>
+            <ID type="Windows" />
+            <NAME>jack.davis@microsoft.com</NAME>
+          </OBJECT>
+        </OWNER>
+      </METADATA>
+    </WORK>
+    <AUTHENTICATEDDATA id="Encrypted-Rights-Data">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</AUTHENTICATEDDATA>
+  </BODY>
+  <SIGNATURE>
+    <ALGORITHM>RSA PKCS#1-V1.5</ALGORITHM>
+    <DIGEST>
+      <ALGORITHM>SHA1</ALGORITHM>
+      <PARAMETER name="codingtype">
+        <VALUE encoding="string">surface-coding</VALUE>
+      </PARAMETER>
+      <VALUE encoding="base64" size="160">0zkJi3NJke+OehTek7lsFT675JU=</VALUE>
+    </DIGEST>
+    <VALUE encoding="base64" size="1024">VObVcSvMdfw4pE7S2Q1o/oeE3d72yhuu42hZz5vpcg8elVfRPFrpxECWR1f9cNxSX6j32JJ9W1+vD2YNOeykWg9iIcbq0e82d/WTvkOs5eIFIWtqjGidOvnG7UCUYBktBiKJ5IDeo68P6GfsEtby8o54MlIztvWXeB5T21nhz2I=</VALUE>
+  </SIGNATURE>
+</XrML>
+""";
+        Assert.Throws<RightsManagementException>(() => new PublishLicense(PublishLicenseTemplate));
+    }
+
+    [Fact]
+    public void AcquireUseLicense_NullSecureEnvironment_ThrowsArgumentNullException()
+    {
+        var license = new PublishLicense(PublishLicenseTemplate);
+        Assert.Throws<ArgumentNullException>("secureEnvironment", () => license.AcquireUseLicense(null));
+    }
+
+    [Fact]
+    public void AcquireUseLicenseNoUI_NullSecureEnvironment_ThrowsArgumentNullException()
+    {
+        var license = new PublishLicense(PublishLicenseTemplate);
+        Assert.Throws<ArgumentNullException>("secureEnvironment", () => license.AcquireUseLicenseNoUI(null));
+    }
+
+    [Fact]
+    public void DecryptUnsignedPublishLicense_Invoke_Success()
+    {
+        var license = new PublishLicense(PublishLicenseTemplate);
+    }
+
+    [Fact]
+    public void DecryptUnsignedPublishLicense_NullCryptoProvider_ThrowsArgumentNullException()
+    {
+        var license = new PublishLicense(PublishLicenseTemplate);
+        Assert.Throws<ArgumentNullException>("cryptoProvider", () => license.DecryptUnsignedPublishLicense(null));
+    }
+}
\ No newline at end of file
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Security/RightsManagement/RightsManagementExceptionTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Security/RightsManagement/RightsManagementExceptionTests.cs
new file mode 100644
index 00000000000..f78730c9902
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Security/RightsManagement/RightsManagementExceptionTests.cs
@@ -0,0 +1,267 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System.Security.RightsManagement.Tests;
+
+public class RightsManagementExceptionTests
+{
+    [Fact]
+    public void Ctor_Default()
+    {
+        var exception = new RightsManagementException();
+        Assert.Equal(RightsManagementFailureCode.Success, exception.FailureCode);
+        Assert.Equal(-2146233088, exception.HResult);
+        Assert.Null(exception.InnerException);
+        Assert.NotEmpty(exception.Message);
+        Assert.Null(exception.Source);
+        Assert.Null(exception.TargetSite);
+    }
+
+    [Theory]
+    [InlineData(RightsManagementFailureCode.Success)]
+    [InlineData(RightsManagementFailureCode.ServerError)]
+    [InlineData(RightsManagementFailureCode.Success - 1)]
+    public void Ctor_RightsManagementFailureCode(RightsManagementFailureCode failureCode)
+    {
+        var exception = new RightsManagementException(failureCode);
+        Assert.Equal(failureCode, exception.FailureCode);
+        Assert.Equal(-2146233088, exception.HResult);
+        Assert.Null(exception.InnerException);
+        Assert.NotEmpty(exception.Message);
+        Assert.Null(exception.Source);
+        Assert.Null(exception.TargetSite);
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData("message")]
+    public void Ctor_String(string message)
+    {
+        var exception = new RightsManagementException(message);
+        Assert.Equal(RightsManagementFailureCode.Success, exception.FailureCode);
+        Assert.Equal(-2146233088, exception.HResult);
+        Assert.Null(exception.InnerException);
+        Assert.Equal(message, exception.Message);
+        Assert.Null(exception.Source);
+        Assert.Null(exception.TargetSite);
+    }
+
+    [Fact]
+    public void Ctor_String_Null()
+    {
+        var exception = new RightsManagementException(null!);
+        Assert.Equal(RightsManagementFailureCode.Success, exception.FailureCode);
+        Assert.Equal(-2146233088, exception.HResult);
+        Assert.Null(exception.InnerException);
+        Assert.NotEmpty(exception.Message);
+        Assert.Null(exception.Source);
+        Assert.Null(exception.TargetSite);
+    }
+
+    public static IEnumerable<object?[]> Ctor_RightsManagementFailureCode_Exception_TestData()
+    {
+        yield return new object?[] { RightsManagementFailureCode.Success, null };
+        yield return new object?[] { RightsManagementFailureCode.ServerError, new Exception() };
+        yield return new object?[] { RightsManagementFailureCode.Success - 1, new Exception() };
+    }
+
+    [Theory]
+    [MemberData(nameof(Ctor_RightsManagementFailureCode_Exception_TestData))]
+    public void Ctor_RightsManagementFailureCode_Exception(RightsManagementFailureCode failureCode, Exception innerException)
+    {
+        var exception = new RightsManagementException(failureCode, innerException);
+        Assert.Equal(failureCode, exception.FailureCode);
+        Assert.Equal(-2146233088, exception.HResult);
+        Assert.Same(innerException, exception.InnerException);
+        Assert.NotEmpty(exception.Message);
+        Assert.Null(exception.Source);
+        Assert.Null(exception.TargetSite);
+    }
+
+    [Theory]
+    [InlineData(RightsManagementFailureCode.Success, "")]
+    [InlineData(RightsManagementFailureCode.ServerError, "message")]
+    [InlineData(RightsManagementFailureCode.Success - 1, "message")]
+    public void Ctor_RightsManagementFailureCode_String(RightsManagementFailureCode failureCode, string message)
+    {
+        var exception = new RightsManagementException(failureCode, message);
+        Assert.Equal(failureCode, exception.FailureCode);
+        Assert.Equal(-2146233088, exception.HResult);
+        Assert.Null(exception.InnerException);
+        Assert.Equal(message, exception.Message);
+        Assert.Null(exception.Source);
+        Assert.Null(exception.TargetSite);
+    }
+
+    [Theory]
+    [InlineData(RightsManagementFailureCode.Success)]
+    [InlineData(RightsManagementFailureCode.ServerError)]
+    [InlineData(RightsManagementFailureCode.Success - 1)]
+    public void Ctor_RightsManagementFailureCode_String_Null(RightsManagementFailureCode failureCode)
+    {
+        var exception = new RightsManagementException(failureCode, (string)null!);
+        Assert.Equal(failureCode, exception.FailureCode);
+        Assert.Equal(-2146233088, exception.HResult);
+        Assert.Null(exception.InnerException);
+        Assert.NotEmpty(exception.Message);
+        Assert.Null(exception.Source);
+        Assert.Null(exception.TargetSite);
+    }
+
+    public static IEnumerable<object?[]> Ctor_String_Exception_TestData()
+    {
+        yield return new object?[] { "", null };
+        yield return new object?[] { "message", new Exception() };
+    }
+
+    [Theory]
+    [MemberData(nameof(Ctor_String_Exception_TestData))]
+    public void Ctor_String_Exception(string message, Exception innerException)
+    {
+        var exception = new RightsManagementException(message, innerException);
+        Assert.Equal(RightsManagementFailureCode.Success, exception.FailureCode);
+        Assert.Equal(-2146233088, exception.HResult);
+        Assert.Same(innerException, exception.InnerException);
+        Assert.Equal(message, exception.Message);
+        Assert.Null(exception.Source);
+        Assert.Null(exception.TargetSite);
+    }
+
+    public static IEnumerable<object?[]> Ctor_String_Exception_Null_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { new Exception() };
+    }
+
+    [Theory]
+    [MemberData(nameof(Ctor_String_Exception_Null_TestData))]
+    public void Ctor_String_Exception_Null(Exception innerException)
+    {
+        var exception = new RightsManagementException(null, innerException);
+        Assert.Equal(RightsManagementFailureCode.Success, exception.FailureCode);
+        Assert.Equal(-2146233088, exception.HResult);
+        Assert.Same(innerException, exception.InnerException);
+        Assert.NotEmpty(exception.Message);
+        Assert.Null(exception.Source);
+        Assert.Null(exception.TargetSite);
+    }
+
+    public static IEnumerable<object?[]> Ctor_RightsManagementFailureCode_String_Exception_TestData()
+    {
+        yield return new object?[] { RightsManagementFailureCode.Success, "", null };
+        yield return new object?[] { RightsManagementFailureCode.ServerError, "message", new Exception() };
+        yield return new object?[] { RightsManagementFailureCode.Success - 1, "message", new Exception() };
+    }
+
+    [Theory]
+    [MemberData(nameof(Ctor_RightsManagementFailureCode_String_Exception_TestData))]
+    public void Ctor_RightsManagementFailureCode_String_Exception(RightsManagementFailureCode failureCode, string message, Exception innerException)
+    {
+        var exception = new RightsManagementException(failureCode, message, innerException);
+        Assert.Equal(failureCode, exception.FailureCode);
+        Assert.Equal(-2146233088, exception.HResult);
+        Assert.Same(innerException, exception.InnerException);
+        Assert.Equal(message, exception.Message);
+        Assert.Null(exception.Source);
+        Assert.Null(exception.TargetSite);
+    }
+
+    public static IEnumerable<object?[]> Ctor_RightsManagementFailureCode_String_Exception_Null_TestData()
+    {
+        yield return new object?[] { RightsManagementFailureCode.Success, null };
+        yield return new object?[] { RightsManagementFailureCode.ServerError, new Exception() };
+        yield return new object?[] { RightsManagementFailureCode.Success - 1, new Exception() };
+    }
+
+    [Theory]
+    [MemberData(nameof(Ctor_RightsManagementFailureCode_String_Exception_Null_TestData))]
+    public void Ctor_RightsManagementFailureCode_String_Exception_Null(RightsManagementFailureCode failureCode, Exception innerException)
+    {
+        var exception = new RightsManagementException(failureCode, null, innerException);
+        Assert.Equal(failureCode, exception.FailureCode);
+        Assert.Equal(-2146233088, exception.HResult);
+        Assert.Same(innerException, exception.InnerException);
+        Assert.NotEmpty(exception.Message);
+        Assert.Null(exception.Source);
+        Assert.Null(exception.TargetSite);
+    }
+
+#pragma warning disable SYSLIB0050, SYSLIB0051
+    [Fact]
+    public void Ctor_SerializationInfo_StreamingContext()
+    {
+        var info = new SerializationInfo(typeof(RightsManagementException), new FormatterConverter());
+        info.AddValue("FailureCode", RightsManagementFailureCode.ServerError);
+        info.AddValue("Message", "message");
+        info.AddValue("InnerException", new DivideByZeroException());
+        info.AddValue("HelpURL", "HelpURL");
+        info.AddValue("StackTraceString", "StackTraceString");
+        info.AddValue("RemoteStackTraceString", "RemoteStackTraceString");
+        info.AddValue("HResult", -2146233088);
+        info.AddValue("Source", null);
+
+        var exception = new SubRightsManagementException(info, new StreamingContext());
+        Assert.Equal(RightsManagementFailureCode.ServerError, exception.FailureCode);
+        Assert.Equal(-2146233088, exception.HResult);
+        Assert.NotNull(exception.InnerException);
+        Assert.Equal("message", exception.Message);
+        Assert.Null(exception.Source);
+        Assert.Null(exception.TargetSite);
+    }
+
+    [Fact]
+    public void Ctor_NullInfo_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("info", () => new SubRightsManagementException((SerializationInfo)null!, default));
+    }
+
+    [Fact]
+    public void GetObjectData_Invoke_Success()
+    {
+        var exception = new RightsManagementException();
+        var info = new SerializationInfo(typeof(RightsManagementException), new FormatterConverter());
+        var context = new StreamingContext();
+
+        exception.GetObjectData(info, context);
+        Assert.Equal(0, info.GetValue("FailureCode", typeof(int)));
+        Assert.Equal(-2146233088, info.GetInt32("HResult"));
+        Assert.Null(exception.InnerException);
+        Assert.NotEmpty(exception.Message);
+        Assert.Null(exception.Source);
+        Assert.Null(exception.TargetSite);
+    }
+
+    [Fact]
+    public void GetObjectData_InvokeCustomFailureCode_Success()
+    {
+        var exception = new RightsManagementException(RightsManagementFailureCode.ManifestPolicyViolation);
+        var info = new SerializationInfo(typeof(RightsManagementException), new FormatterConverter());
+        var context = new StreamingContext();
+
+        exception.GetObjectData(info, context);
+        Assert.Equal(-2147183860, info.GetValue("FailureCode", typeof(int)));
+        Assert.Equal(-2146233088, info.GetInt32("HResult"));
+        Assert.Null(exception.InnerException);
+        Assert.NotEmpty(exception.Message);
+        Assert.Null(exception.Source);
+        Assert.Null(exception.TargetSite);
+    }
+
+    [Fact]
+    public void GetObjectData_NullInfo_ThrowsArgumentNullException()
+    {
+        var exception = new RightsManagementException();
+        Assert.Throws<ArgumentNullException>("info", () => exception.GetObjectData(null!, default));
+    }
+#pragma warning restore SYSLIB0050, SYSLIB0051
+
+    private class SubRightsManagementException : RightsManagementException
+    {
+        public SubRightsManagementException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Security/RightsManagement/SecureEnvironmentTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Security/RightsManagement/SecureEnvironmentTests.cs
new file mode 100644
index 00000000000..b791d6ed93b
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Security/RightsManagement/SecureEnvironmentTests.cs
@@ -0,0 +1,204 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+
+namespace System.Security.RightsManagement.Tests;
+
+public class SecureEnvironmentTests
+{
+#if false
+    [Fact]
+    public void Create()
+    {
+        const string Manifest =
+@"<?xml version=""1.0"" encoding=""UTF-8"" standalone=""yes""?>
+
+<assembly xmlns=""urn:schemas-microsoft-com:asm.v1"" manifestVersion=""1.0"">
+    <assemblyIdentity version=""1.0.0.0"" name=""YourAppName.app""/>
+    <trustInfo xmlns=""urn:schemas-microsoft-com:asm.v2"">
+        <security>
+            <requestedPrivileges xmlns=""urn:schemas-microsoft-com:asm.v3"">
+                <requestedExecutionLevel level=""asInvoker"" uiAccess=""false""/>
+            </requestedPrivileges>
+        </security>
+    </trustInfo>
+</assembly>";
+        SecureEnvironment environment = SecureEnvironment.Create(Manifest, AuthenticationType.Passport, UserActivationMode.Permanent);
+    }
+#endif
+
+    [Fact]
+    public void Create_NullApplicationManifest_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("applicationManifest", () => SecureEnvironment.Create(null!, AuthenticationType.Windows, UserActivationMode.Permanent));
+        Assert.Throws<ArgumentNullException>("applicationManifest", () => SecureEnvironment.Create(null!, new ContentUser("name", AuthenticationType.Windows)));
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData("  ")]
+    public void Create_EmptyApplicationManifest_ThrowsRightsManagementException(string applicationManifest)
+    {
+        Assert.Throws<DllNotFoundException>(() => SecureEnvironment.Create(applicationManifest, AuthenticationType.Windows, UserActivationMode.Permanent));
+        Assert.Throws<RightsManagementException>(() => SecureEnvironment.Create(applicationManifest, new ContentUser("name", AuthenticationType.Windows)));
+    }
+
+    [Theory]
+    [InlineData("applicationManifest")]
+    public void Create_InvokeInvalidApplicationManifest_ThrowsRightsManagementException(string applicationManifest)
+    {
+        Assert.Throws<DllNotFoundException>(() => SecureEnvironment.Create(applicationManifest, AuthenticationType.Windows, UserActivationMode.Permanent));
+        Assert.Throws<RightsManagementException>(() => SecureEnvironment.Create(applicationManifest, new ContentUser("name", AuthenticationType.Windows)));
+    }
+
+    [Theory]
+    [InlineData(AuthenticationType.Internal)]
+    [InlineData(AuthenticationType.WindowsPassport)]
+    [InlineData(AuthenticationType.Windows - 1)]
+    [InlineData(AuthenticationType.Internal + 1)]
+    public void Create_InvalidAuthenticationType_ThrowsArgumentOutOfRangeException(AuthenticationType authentication)
+    {
+        Assert.Throws<ArgumentOutOfRangeException>("authentication", () => SecureEnvironment.Create("manifest", authentication, UserActivationMode.Permanent));
+    }
+
+    [Theory]
+    [InlineData(UserActivationMode.Permanent - 1)]
+    [InlineData(UserActivationMode.Temporary + 1)]
+    public void Create_InvalidUserActivationMode_ThrowsArgumentOutOfRangeException(UserActivationMode userActivationMode)
+    {
+        Assert.Throws<ArgumentOutOfRangeException>("userActivationMode", () => SecureEnvironment.Create("manifest", AuthenticationType.Windows, userActivationMode));
+    }
+
+    [Fact]
+    public void Create_NullUser_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("user", () => SecureEnvironment.Create("manifest", null!));
+    }
+
+    [Fact]
+    public void Create_UserNotActivatedWindows_ThrowsRightsManagementException()
+    {
+        var user = new ContentUser("name", AuthenticationType.Windows);
+        Assert.Throws<RightsManagementException>(() => SecureEnvironment.Create("<manifest></manifest>", user));
+    }
+
+    [Fact]
+    public void Create_UserNotActivatedPassport_ThrowsRightsManagementException()
+    {
+        var user = new ContentUser("name", AuthenticationType.Passport);
+        Assert.Throws<RightsManagementException>(() => SecureEnvironment.Create("<manifest></manifest>", user));
+    }
+
+    [Fact]
+    public void Create_WindowsPassportUser_ThrowsArgumentOutOfRangeException()
+    {
+        var user = new ContentUser("name", AuthenticationType.WindowsPassport);
+        Assert.Throws<ArgumentOutOfRangeException>("user", () => SecureEnvironment.Create("manifest", user));
+    }
+
+    [Theory]
+    [InlineData("anyone")]
+    [InlineData("owner")]
+    public void Create_InternalUser_ThrowsArgumentOutOfRangeException(string name)
+    {
+        var user = new ContentUser(name, AuthenticationType.Internal);
+        Assert.Throws<ArgumentOutOfRangeException>("user", () => SecureEnvironment.Create("manifest", user));
+    }
+
+    [Fact]
+    public void Create_NotActivatedWindowsUser_ThrowsRightsManagementException()
+    {
+        var user = new ContentUser("name", AuthenticationType.Windows);
+        Assert.Throws<RightsManagementException>(() => SecureEnvironment.Create("manifest", user));
+    }
+
+    [Fact]
+    public void Create_NotActivatedPassportUser_ThrowsRightsManagementException()
+    {
+        var user = new ContentUser("name", AuthenticationType.Passport);
+        Assert.Throws<RightsManagementException>(() => SecureEnvironment.Create("manifest", user));
+    }
+
+    [Fact]
+    public void GetActivatedUsers_Invoke_ReturnsExpected()
+    {
+        var users = SecureEnvironment.GetActivatedUsers();
+        Assert.NotNull(users);
+    }
+
+    [Fact]
+    public void IsUserActivated_WindowsUser_ReturnsFalse()
+    {
+        var user = new ContentUser("name", AuthenticationType.Windows);
+        Assert.False(SecureEnvironment.IsUserActivated(user));
+    }
+    
+    [Fact]
+    public void IsUserActivated_PassportUser_ReturnsFalse()
+    {
+        var user = new ContentUser("name", AuthenticationType.Passport);
+        Assert.False(SecureEnvironment.IsUserActivated(user));
+    }
+
+    [Fact]
+    public void IsUserActivated_NullUser_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("user", () => SecureEnvironment.IsUserActivated(null!));
+    }
+
+    [Fact]
+    public void IsUserActivated_WindowsPassportUser_ThrowsArgumentOutOfRangeException()
+    {
+        var user = new ContentUser("name", AuthenticationType.WindowsPassport);
+        Assert.Throws<ArgumentOutOfRangeException>("user", () => SecureEnvironment.IsUserActivated(user));
+    }
+
+    [Theory]
+    [InlineData("anyone")]
+    [InlineData("owner")]
+    public void IsUserActivated_InternalUser_ThrowsArgumentOutOfRangeException(string name)
+    {
+        var user = new ContentUser(name, AuthenticationType.Internal);
+        Assert.Throws<ArgumentOutOfRangeException>("user", () => SecureEnvironment.IsUserActivated(user));
+    }
+
+    [Fact]
+    public void RemoveActivatedUser_WindowsUser_ReturnsFalse()
+    {
+        var user = new ContentUser("name", AuthenticationType.Windows);
+        SecureEnvironment.RemoveActivatedUser(user);
+        Assert.False(SecureEnvironment.IsUserActivated(user));
+    }
+    
+    [Fact]
+    public void RemoveActivatedUser_PassportUser_ReturnsFalse()
+    {
+        var user = new ContentUser("name", AuthenticationType.Passport);
+        SecureEnvironment.RemoveActivatedUser(user);
+        Assert.False(SecureEnvironment.IsUserActivated(user));
+    }
+
+    [Fact]
+    public void RemoveActivatedUser_NullUser_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("user", () => SecureEnvironment.RemoveActivatedUser(null!));
+    }
+
+    [Fact]
+    public void RemoveActivatedUser_WindowsPassportUser_ThrowsArgumentOutOfRangeException()
+    {
+        var user = new ContentUser("name", AuthenticationType.WindowsPassport);
+        Assert.Throws<ArgumentOutOfRangeException>("user", () => SecureEnvironment.RemoveActivatedUser(user));
+    }
+
+    [Theory]
+    [InlineData("anyone")]
+    [InlineData("owner")]
+    public void RemoveActivatedUser_InternalUser_ThrowsArgumentOutOfRangeException(string name)
+    {
+        var user = new ContentUser(name, AuthenticationType.Internal);
+        Assert.Throws<ArgumentOutOfRangeException>("user", () => SecureEnvironment.RemoveActivatedUser(user));
+    }
+}
\ No newline at end of file
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Security/RightsManagement/UnsignedPublishLicenseTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Security/RightsManagement/UnsignedPublishLicenseTests.cs
new file mode 100644
index 00000000000..207f8956133
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Security/RightsManagement/UnsignedPublishLicenseTests.cs
@@ -0,0 +1,138 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Security.RightsManagement.Tests;
+
+public class UnsignedPublishLicenseTests
+{
+    [Fact]
+    public void Ctor_Default()
+    {
+        var license = new UnsignedPublishLicense();
+        Assert.NotEqual(Guid.Empty, license.ContentId);
+        Assert.Empty(license.Grants);
+        Assert.Same(license.Grants, license.Grants);
+        Assert.Empty(license.LocalizedNameDescriptionDictionary);
+        Assert.Same(license.LocalizedNameDescriptionDictionary, license.LocalizedNameDescriptionDictionary);
+        Assert.Null(license.Owner);
+        Assert.Null(license.ReferralInfoName);
+        Assert.Null(license.ReferralInfoUri);
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData("  ")]
+    [InlineData("unsignedPublishLicense")]
+    [InlineData("<xml></xml>")]
+    public void Ctor_InvalidPublishLicenseTemplate_ThrowsRightsManagementException(string unsignedPublishLicense)
+    {
+        Assert.Throws<RightsManagementException>(() => new UnsignedPublishLicense(unsignedPublishLicense));
+    }
+
+    [Fact]
+    public void Ctor_NullPublishLicenseTemplate_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("publishLicenseTemplate", () => new UnsignedPublishLicense(null));
+    }
+
+    public static IEnumerable<object[]> ContentId_TestData()
+    {
+        yield return new object[] { Guid.Empty };
+        yield return new object[] { Guid.NewGuid() };
+    }
+
+    [Theory]
+    [MemberData(nameof(ContentId_TestData))]
+    public void ContentId_Set_GetReturnsExpected(Guid value)
+    {
+        var license = new UnsignedPublishLicense
+        {
+            ContentId = value
+        };
+        Assert.Equal(value, license.ContentId);
+
+        // Set same.
+        license.ContentId = value;
+        Assert.Equal(value, license.ContentId);
+    }
+
+    public static IEnumerable<object?[]> Owner_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { new ContentUser("name", AuthenticationType.Windows) };
+        yield return new object?[] { new ContentUser("name", AuthenticationType.Passport) };
+        yield return new object?[] { new ContentUser("name", AuthenticationType.WindowsPassport) };
+        yield return new object?[] { new ContentUser("anyone", AuthenticationType.Internal) };
+        yield return new object?[] { new ContentUser("owner", AuthenticationType.Internal) };
+    }
+
+    [Theory]
+    [MemberData(nameof(Owner_TestData))]
+    public void Owner_Set_GetReturnsExpected(ContentUser? value)
+    {
+        var license = new UnsignedPublishLicense
+        {
+            Owner = value
+        };
+        Assert.Equal(value, license.Owner);
+
+        // Set same.
+        license.Owner = value;
+        Assert.Equal(value, license.Owner);
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("")]
+    [InlineData("referralInfoName")]
+    public void ReferralInfoName_Set_GetReturnsExpected(string? value)
+    {
+        var license = new UnsignedPublishLicense
+        {
+            ReferralInfoName = value
+        };
+        Assert.Equal(value, license.ReferralInfoName);
+
+        // Set same.
+        license.ReferralInfoName = value;
+        Assert.Equal(value, license.ReferralInfoName);
+    }
+
+    public static IEnumerable<object?[]> ReferralInfoUri_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { new Uri("https://google.com") };
+    }
+
+    [Theory]
+    [MemberData(nameof(ReferralInfoUri_TestData))]
+    public void ReferralInfoUri_Set_GetReturnsExpected(Uri? value)
+    {
+        var license = new UnsignedPublishLicense
+        {
+            ReferralInfoUri = value
+        };
+        Assert.Equal(value, license.ReferralInfoUri);
+
+        // Set same.
+        license.ReferralInfoUri = value;
+        Assert.Equal(value, license.ReferralInfoUri);
+    }
+
+    [Fact]
+    public void Sign_NullSecureEnvironment_ThrowsArgumentNullException()
+    {
+        var license = new UnsignedPublishLicense();
+        UseLicense? useLicense = null;
+        Assert.Throws<ArgumentNullException>("secureEnvironment", () => license.Sign(null!, out useLicense));
+        Assert.Null(useLicense);
+    }
+
+    [Fact]
+    public void ToString_Default_ThrowsRightsManagementException()
+    {
+        var license = new UnsignedPublishLicense();
+        Assert.Throws<RightsManagementException>(() => license.ToString());
+    }
+}
\ No newline at end of file
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Security/RightsManagement/UseLicenseTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Security/RightsManagement/UseLicenseTests.cs
new file mode 100644
index 00000000000..bca0b07a54f
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Security/RightsManagement/UseLicenseTests.cs
@@ -0,0 +1,24 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Security.RightsManagement.Tests;
+
+public class UseLicenseTests
+{
+    [Fact]
+    public void Ctor_NullUseLicense_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("useLicense", () => new UseLicense(null!));
+    }
+    
+    [Theory]
+    [InlineData("")]
+    [InlineData("  ")]
+    [InlineData("name")]
+    [InlineData("<xml></xml>")]
+    public void Ctor_InvalidUseLicense_ThrowsRightsManagementException(string useLicense)
+    {
+        Assert.Throws<RightsManagementException>(() => new UseLicense(useLicense));
+    }
+}
\ No newline at end of file
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/AttachedPropertyBrowsableForTypeAttributeTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/AttachedPropertyBrowsableForTypeAttributeTests.cs
new file mode 100644
index 00000000000..f0371ea76d5
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/AttachedPropertyBrowsableForTypeAttributeTests.cs
@@ -0,0 +1,56 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Windows.Tests;
+
+public class AttachedPropertyBrowsableForTypeAttributeTests
+{
+    // TODO:
+    // - IsBrowsable
+    // - UnionResults
+    
+    [Fact]
+    public void Ctor_Type()
+    {
+        var attribute = new AttachedPropertyBrowsableForTypeAttribute(typeof(string));
+        Assert.Equal(typeof(string), attribute.TargetType);
+        Assert.Same(attribute, attribute.TypeId);
+    }
+
+    [Fact]
+    public void Ctor_NullTargetType_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("targetType", () => new AttachedPropertyBrowsableForTypeAttribute(null!));
+    }
+
+    public static IEnumerable<object?[]> Equals_TestData()
+    {
+        var attribute = new AttachedPropertyBrowsableForTypeAttribute(typeof(string));
+        yield return new object?[] { attribute, attribute, true };
+        yield return new object?[] { attribute, new AttachedPropertyBrowsableForTypeAttribute(typeof(string)), true };
+        yield return new object?[] { attribute, new AttachedPropertyBrowsableForTypeAttribute(typeof(int)), false };
+        yield return new object?[] { attribute, new object(), false };
+        yield return new object?[] { attribute, null, false };
+    }
+
+    [Theory]
+    [MemberData(nameof(Equals_TestData))]
+    public void Equals_Object_ReturnsExpected(AttachedPropertyBrowsableForTypeAttribute attribute, object obj, bool expected)
+    {
+        Assert.Equal(expected, attribute.Equals(obj));
+        if (obj is AttachedPropertyBrowsableForTypeAttribute otherAttribute)
+        {
+            Assert.Equal(expected, otherAttribute.Equals(attribute));
+            Assert.Equal(expected, attribute.GetHashCode().Equals(obj.GetHashCode()));
+        }
+    }
+
+    [Fact]
+    public void GetHashCode_Invoke_ReturnsEqual()
+    {
+        var attribute = new AttachedPropertyBrowsableForTypeAttribute(typeof(string));
+        Assert.NotEqual(0, attribute.GetHashCode());
+        Assert.Equal(attribute.GetHashCode(), attribute.GetHashCode());
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/AttachedPropertyBrowsableWhenAttributePresentAttributeTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/AttachedPropertyBrowsableWhenAttributePresentAttributeTests.cs
new file mode 100644
index 00000000000..3970ef8eba8
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/AttachedPropertyBrowsableWhenAttributePresentAttributeTests.cs
@@ -0,0 +1,55 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Windows.Tests;
+
+public class AttachedPropertyBrowsableWhenAttributePresentAttributeTests
+{
+    // TODO:
+    // - IsBrowsable
+    
+    [Fact]
+    public void Ctor_Type()
+    {
+        var attribute = new AttachedPropertyBrowsableWhenAttributePresentAttribute(typeof(string));
+        Assert.Equal(typeof(string), attribute.AttributeType);
+        Assert.Equal(typeof(AttachedPropertyBrowsableWhenAttributePresentAttribute), attribute.TypeId);
+    }
+
+    [Fact]
+    public void Ctor_NullAttributeType_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("attributeType", () => new AttachedPropertyBrowsableWhenAttributePresentAttribute(null!));
+    }
+
+    public static IEnumerable<object?[]> Equals_TestData()
+    {
+        var attribute = new AttachedPropertyBrowsableWhenAttributePresentAttribute(typeof(string));
+        yield return new object?[] { attribute, attribute, true };
+        yield return new object?[] { attribute, new AttachedPropertyBrowsableWhenAttributePresentAttribute(typeof(string)), true };
+        yield return new object?[] { attribute, new AttachedPropertyBrowsableWhenAttributePresentAttribute(typeof(int)), false };
+        yield return new object?[] { attribute, new object(), false };
+        yield return new object?[] { attribute, null, false };
+    }
+
+    [Theory]
+    [MemberData(nameof(Equals_TestData))]
+    public void Equals_Object_ReturnsExpected(AttachedPropertyBrowsableWhenAttributePresentAttribute attribute, object obj, bool expected)
+    {
+        Assert.Equal(expected, attribute.Equals(obj));
+        if (obj is AttachedPropertyBrowsableWhenAttributePresentAttribute otherAttribute)
+        {
+            Assert.Equal(expected, otherAttribute.Equals(attribute));
+            Assert.Equal(expected, attribute.GetHashCode().Equals(obj.GetHashCode()));
+        }
+    }
+
+    [Fact]
+    public void GetHashCode_Invoke_ReturnsEqual()
+    {
+        var attribute = new AttachedPropertyBrowsableWhenAttributePresentAttribute(typeof(string));
+        Assert.NotEqual(0, attribute.GetHashCode());
+        Assert.Equal(attribute.GetHashCode(), attribute.GetHashCode());
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/BaseCompatibilityPreferencesTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/BaseCompatibilityPreferencesTests.cs
new file mode 100644
index 00000000000..3555537190c
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/BaseCompatibilityPreferencesTests.cs
@@ -0,0 +1,37 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Windows.Tests;
+
+public class BaseCompatibilityPreferencesTests
+{
+    [Fact]
+    public void GetFlowDirectionFromLayoutRounding_Get_ReturnsExpected()
+    {
+        bool value = BaseCompatibilityPreferences.FlowDispatcherSynchronizationContextPriority;
+        Assert.Equal(value, BaseCompatibilityPreferences.FlowDispatcherSynchronizationContextPriority);
+    }
+    
+    [Fact]
+    public void HandleDispatcherRequestProcessingFailure_Get_ReturnsExpected()
+    {
+        BaseCompatibilityPreferences.HandleDispatcherRequestProcessingFailureOptions value = BaseCompatibilityPreferences.HandleDispatcherRequestProcessingFailure;
+        Assert.True(Enum.IsDefined(value));
+        Assert.Equal(value, BaseCompatibilityPreferences.HandleDispatcherRequestProcessingFailure);
+    }
+
+    [Fact]
+    public void InlineDispatcherSynchronizationContextSend_Get_ReturnsExpected()
+    {
+        bool value = BaseCompatibilityPreferences.InlineDispatcherSynchronizationContextSend;
+        Assert.Equal(value, BaseCompatibilityPreferences.InlineDispatcherSynchronizationContextSend);
+    }
+
+    [Fact]
+    public void ReuseDispatcherSynchronizationContextInstance_Get_ReturnsExpected()
+    {
+        bool value = BaseCompatibilityPreferences.ReuseDispatcherSynchronizationContextInstance;
+        Assert.Equal(value, BaseCompatibilityPreferences.ReuseDispatcherSynchronizationContextInstance);
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Converters/Int32RectValueSerializerTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Converters/Int32RectValueSerializerTests.cs
new file mode 100644
index 00000000000..985c4589337
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Converters/Int32RectValueSerializerTests.cs
@@ -0,0 +1,127 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.Windows.Markup;
+using System.Windows.Tests;
+
+namespace System.Windows.Converters.Tests;
+
+public class Int32RectValueSerializerTests
+{
+    public static IEnumerable<object?[]> CanConvertToString_TestData()
+    {
+        yield return new object?[] { null, false };
+        yield return new object?[] { string.Empty, false };
+        yield return new object?[] { "value", false };
+        yield return new object?[] { new object(), false };
+        
+        yield return new object?[] { new Int32Rect(), true };
+    }
+
+    [Theory]
+    [MemberData(nameof(CanConvertToString_TestData))]
+    public void CanConvertToString_Invoke_ReturnsExpected(object value, bool expected)
+    {
+        var serializer = new Int32RectValueSerializer();
+        Assert.Equal(expected, serializer.CanConvertToString(value, null));
+        Assert.Equal(expected, serializer.CanConvertToString(value, new CustomValueSerializerContext()));
+    }
+    
+    [Theory]
+    [MemberData(nameof(Int32RectTests.ToString_TestData), MemberType = typeof(Int32RectTests))]
+    public void ConvertToString_Invoke_ReturnsExpected(Int32Rect matrix, string expected)
+    {
+        var serializer = new Int32RectValueSerializer();
+        Assert.Equal(expected, serializer.ConvertToString(matrix, null));
+        Assert.Equal(expected, serializer.ConvertToString(matrix, new CustomValueSerializerContext()));
+    }
+
+    public static IEnumerable<object?[]> ConvertToString_CantConvert_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { string.Empty };
+        yield return new object?[] { "value" };
+        yield return new object?[] { new object() };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertToString_CantConvert_TestData))]
+    public void ConvertToString_CantConvert_ThrowsNotSupportedException(object value)
+    {
+        var serializer = new Int32RectValueSerializer();
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertToString(value, null));
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertToString(value, new CustomValueSerializerContext()));
+    }
+
+    public static IEnumerable<object?[]> CanConvertFromString_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { string.Empty };
+        yield return new object?[] { "value" };
+    }
+
+    [Theory]
+    [MemberData(nameof(CanConvertFromString_TestData))]
+    public void CanConvertFromString_Invoke_ReturnsTrue(string value)
+    {
+        var serializer = new Int32RectValueSerializer();
+        Assert.True(serializer.CanConvertFromString(value, null));
+        Assert.True(serializer.CanConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [MemberData(nameof(Int32RectTests.Parse_TestData), MemberType = typeof(Int32RectTests))]
+    public void ConvertFromString_Invoke_ReturnsExpected(string value, Int32Rect expected)
+    {
+        var serializer = new Int32RectValueSerializer();
+        Assert.Equal(expected, serializer.ConvertFromString(value, null));
+        Assert.Equal(expected, serializer.ConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    [Fact]
+    public void ConvertFromString_NullValue_ThrowsNotSupportedException()
+    {
+        var serializer = new Int32RectValueSerializer();
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertFromString(null, null));
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertFromString(null, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [MemberData(nameof(Int32RectTests.Parse_InvalidSource_TestData), MemberType = typeof(Int32RectTests))]
+    public void ConvertFromString_InvalidValue_ThrowsInvalidOperationException(string value)
+    {
+        var serializer = new Int32RectValueSerializer();
+        Assert.Throws<InvalidOperationException>(() => serializer.ConvertFromString(value, null));
+        Assert.Throws<InvalidOperationException>(() => serializer.ConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [MemberData(nameof(Int32RectTests.Parse_NotInt32_TestData), MemberType = typeof(Int32RectTests))]
+    public void ConvertFromString_NotInt_ThrowsFormatException(string value)
+    {
+        var serializer = new Int32RectValueSerializer();
+        Assert.Throws<FormatException>(() => serializer.ConvertFromString(value, null));
+        Assert.Throws<FormatException>(() => serializer.ConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    private class CustomValueSerializerContext : IValueSerializerContext
+    {
+        public IContainer Container => throw new NotImplementedException();
+
+        public object Instance => throw new NotImplementedException();
+
+        public PropertyDescriptor PropertyDescriptor => throw new NotImplementedException();
+
+        public object? GetService(Type serviceType) => throw new NotImplementedException();
+
+        public ValueSerializer GetValueSerializerFor(PropertyDescriptor descriptor) => throw new NotImplementedException();
+
+        public ValueSerializer GetValueSerializerFor(Type type) => throw new NotImplementedException();
+
+        public void OnComponentChanged() => throw new NotImplementedException();
+
+        public bool OnComponentChanging() => throw new NotImplementedException();
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Converters/PointValueSerializerTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Converters/PointValueSerializerTests.cs
new file mode 100644
index 00000000000..525352b473a
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Converters/PointValueSerializerTests.cs
@@ -0,0 +1,127 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.Windows.Markup;
+using System.Windows.Tests;
+
+namespace System.Windows.Converters.Tests;
+
+public class PointValueSerializerTests
+{
+    public static IEnumerable<object?[]> CanConvertToString_TestData()
+    {
+        yield return new object?[] { null, false };
+        yield return new object?[] { string.Empty, false };
+        yield return new object?[] { "value", false };
+        yield return new object?[] { new object(), false };
+        
+        yield return new object?[] { new Point(), true };
+    }
+
+    [Theory]
+    [MemberData(nameof(CanConvertToString_TestData))]
+    public void CanConvertToString_Invoke_ReturnsExpected(object value, bool expected)
+    {
+        var serializer = new PointValueSerializer();
+        Assert.Equal(expected, serializer.CanConvertToString(value, null));
+        Assert.Equal(expected, serializer.CanConvertToString(value, new CustomValueSerializerContext()));
+    }
+    
+    [Theory]
+    [MemberData(nameof(PointTests.ToString_TestData), MemberType = typeof(PointTests))]
+    public void ConvertToString_Invoke_ReturnsExpected(Point matrix, string expected)
+    {
+        var serializer = new PointValueSerializer();
+        Assert.Equal(expected, serializer.ConvertToString(matrix, null));
+        Assert.Equal(expected, serializer.ConvertToString(matrix, new CustomValueSerializerContext()));
+    }
+
+    public static IEnumerable<object?[]> ConvertToString_CantConvert_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { string.Empty };
+        yield return new object?[] { "value" };
+        yield return new object?[] { new object() };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertToString_CantConvert_TestData))]
+    public void ConvertToString_CantConvert_ThrowsNotSupportedException(object value)
+    {
+        var serializer = new PointValueSerializer();
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertToString(value, null));
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertToString(value, new CustomValueSerializerContext()));
+    }
+
+    public static IEnumerable<object?[]> CanConvertFromString_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { string.Empty };
+        yield return new object?[] { "value" };
+    }
+
+    [Theory]
+    [MemberData(nameof(CanConvertFromString_TestData))]
+    public void CanConvertFromString_Invoke_ReturnsTrue(string value)
+    {
+        var serializer = new PointValueSerializer();
+        Assert.True(serializer.CanConvertFromString(value, null));
+        Assert.True(serializer.CanConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [MemberData(nameof(PointTests.Parse_TestData), MemberType = typeof(PointTests))]
+    public void ConvertFromString_Invoke_ReturnsExpected(string value, Point expected)
+    {
+        var serializer = new PointValueSerializer();
+        Assert.Equal(expected, serializer.ConvertFromString(value, null));
+        Assert.Equal(expected, serializer.ConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    [Fact]
+    public void ConvertFromString_NullValue_ThrowsNotSupportedException()
+    {
+        var serializer = new PointValueSerializer();
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertFromString(null, null));
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertFromString(null, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [MemberData(nameof(PointTests.Parse_InvalidSource_TestData), MemberType = typeof(PointTests))]
+    public void ConvertFromString_InvalidValue_ThrowsInvalidOperationException(string value)
+    {
+        var serializer = new PointValueSerializer();
+        Assert.Throws<InvalidOperationException>(() => serializer.ConvertFromString(value, null));
+        Assert.Throws<InvalidOperationException>(() => serializer.ConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [MemberData(nameof(PointTests.Parse_NotDouble_TestData), MemberType = typeof(PointTests))]
+    public void ConvertFromString_NotDouble_ThrowsFormatException(string value)
+    {
+        var serializer = new PointValueSerializer();
+        Assert.Throws<FormatException>(() => serializer.ConvertFromString(value, null));
+        Assert.Throws<FormatException>(() => serializer.ConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    private class CustomValueSerializerContext : IValueSerializerContext
+    {
+        public IContainer Container => throw new NotImplementedException();
+
+        public object Instance => throw new NotImplementedException();
+
+        public PropertyDescriptor PropertyDescriptor => throw new NotImplementedException();
+
+        public object? GetService(Type serviceType) => throw new NotImplementedException();
+
+        public ValueSerializer GetValueSerializerFor(PropertyDescriptor descriptor) => throw new NotImplementedException();
+
+        public ValueSerializer GetValueSerializerFor(Type type) => throw new NotImplementedException();
+
+        public void OnComponentChanged() => throw new NotImplementedException();
+
+        public bool OnComponentChanging() => throw new NotImplementedException();
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Converters/RectValueSerializerTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Converters/RectValueSerializerTests.cs
new file mode 100644
index 00000000000..c1cfd9fc4aa
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Converters/RectValueSerializerTests.cs
@@ -0,0 +1,136 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.Windows.Markup;
+using System.Windows.Tests;
+
+namespace System.Windows.Converters.Tests;
+
+public class RectValueSerializerTests
+{
+    public static IEnumerable<object?[]> CanConvertToString_TestData()
+    {
+        yield return new object?[] { null, false };
+        yield return new object?[] { string.Empty, false };
+        yield return new object?[] { "value", false };
+        yield return new object?[] { new object(), false };
+        
+        yield return new object?[] { new Rect(), true };
+    }
+
+    [Theory]
+    [MemberData(nameof(CanConvertToString_TestData))]
+    public void CanConvertToString_Invoke_ReturnsExpected(object value, bool expected)
+    {
+        var serializer = new RectValueSerializer();
+        Assert.Equal(expected, serializer.CanConvertToString(value, null));
+        Assert.Equal(expected, serializer.CanConvertToString(value, new CustomValueSerializerContext()));
+    }
+    
+    [Theory]
+    [MemberData(nameof(RectTests.ToString_TestData), MemberType = typeof(RectTests))]
+    public void ConvertToString_Invoke_ReturnsExpected(Rect matrix, string expected)
+    {
+        var serializer = new RectValueSerializer();
+        Assert.Equal(expected, serializer.ConvertToString(matrix, null));
+        Assert.Equal(expected, serializer.ConvertToString(matrix, new CustomValueSerializerContext()));
+    }
+
+    public static IEnumerable<object?[]> ConvertToString_CantConvert_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { string.Empty };
+        yield return new object?[] { "value" };
+        yield return new object?[] { new object() };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertToString_CantConvert_TestData))]
+    public void ConvertToString_CantConvert_ThrowsNotSupportedException(object value)
+    {
+        var serializer = new RectValueSerializer();
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertToString(value, null));
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertToString(value, new CustomValueSerializerContext()));
+    }
+
+    public static IEnumerable<object?[]> CanConvertFromString_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { string.Empty };
+        yield return new object?[] { "value" };
+    }
+
+    [Theory]
+    [MemberData(nameof(CanConvertFromString_TestData))]
+    public void CanConvertFromString_Invoke_ReturnsTrue(string value)
+    {
+        var serializer = new RectValueSerializer();
+        Assert.True(serializer.CanConvertFromString(value, null));
+        Assert.True(serializer.CanConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [MemberData(nameof(RectTests.Parse_TestData), MemberType = typeof(RectTests))]
+    public void ConvertFromString_Invoke_ReturnsExpected(string value, Rect expected)
+    {
+        var serializer = new RectValueSerializer();
+        Assert.Equal(expected, serializer.ConvertFromString(value, null));
+        Assert.Equal(expected, serializer.ConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    [Fact]
+    public void ConvertFromString_NullValue_ThrowsNotSupportedException()
+    {
+        var serializer = new RectValueSerializer();
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertFromString(null, null));
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertFromString(null, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [MemberData(nameof(RectTests.Parse_InvalidSource_TestData), MemberType = typeof(RectTests))]
+    public void ConvertFromString_InvalidValue_ThrowsInvalidOperationException(string value)
+    {
+        var serializer = new RectValueSerializer();
+        Assert.Throws<InvalidOperationException>(() => serializer.ConvertFromString(value, null));
+        Assert.Throws<InvalidOperationException>(() => serializer.ConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [MemberData(nameof(RectTests.Parse_NotDouble_TestData), MemberType = typeof(RectTests))]
+    public void ConvertFromString_NotDouble_ThrowsFormatException(string value)
+    {
+        var serializer = new RectValueSerializer();
+        Assert.Throws<FormatException>(() => serializer.ConvertFromString(value, null));
+        Assert.Throws<FormatException>(() => serializer.ConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [MemberData(nameof(RectTests.Parse_Negative_TestData), MemberType = typeof(RectTests))]
+    public void ConvertFromString_Negative_ThrowsArgumentException(string value)
+    {
+        var serializer = new RectValueSerializer();
+        Assert.Throws<ArgumentException>(() => serializer.ConvertFromString(value, null));
+        Assert.Throws<ArgumentException>(() => serializer.ConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    private class CustomValueSerializerContext : IValueSerializerContext
+    {
+        public IContainer Container => throw new NotImplementedException();
+
+        public object Instance => throw new NotImplementedException();
+
+        public PropertyDescriptor PropertyDescriptor => throw new NotImplementedException();
+
+        public object? GetService(Type serviceType) => throw new NotImplementedException();
+
+        public ValueSerializer GetValueSerializerFor(PropertyDescriptor descriptor) => throw new NotImplementedException();
+
+        public ValueSerializer GetValueSerializerFor(Type type) => throw new NotImplementedException();
+
+        public void OnComponentChanged() => throw new NotImplementedException();
+
+        public bool OnComponentChanging() => throw new NotImplementedException();
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Converters/SizeValueSerializerTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Converters/SizeValueSerializerTests.cs
new file mode 100644
index 00000000000..b95482919aa
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Converters/SizeValueSerializerTests.cs
@@ -0,0 +1,136 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.Windows.Markup;
+using System.Windows.Tests;
+
+namespace System.Windows.Converters.Tests;
+
+public class SizeValueSerializerTests
+{
+    public static IEnumerable<object?[]> CanConvertToString_TestData()
+    {
+        yield return new object?[] { null, false };
+        yield return new object?[] { string.Empty, false };
+        yield return new object?[] { "value", false };
+        yield return new object?[] { new object(), false };
+        
+        yield return new object?[] { new Size(), true };
+    }
+
+    [Theory]
+    [MemberData(nameof(CanConvertToString_TestData))]
+    public void CanConvertToString_Invoke_ReturnsExpected(object value, bool expected)
+    {
+        var serializer = new SizeValueSerializer();
+        Assert.Equal(expected, serializer.CanConvertToString(value, null));
+        Assert.Equal(expected, serializer.CanConvertToString(value, new CustomValueSerializerContext()));
+    }
+    
+    [Theory]
+    [MemberData(nameof(SizeTests.ToString_TestData), MemberType = typeof(SizeTests))]
+    public void ConvertToString_Invoke_ReturnsExpected(Size matrix, string expected)
+    {
+        var serializer = new SizeValueSerializer();
+        Assert.Equal(expected, serializer.ConvertToString(matrix, null));
+        Assert.Equal(expected, serializer.ConvertToString(matrix, new CustomValueSerializerContext()));
+    }
+
+    public static IEnumerable<object?[]> ConvertToString_CantConvert_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { string.Empty };
+        yield return new object?[] { "value" };
+        yield return new object?[] { new object() };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertToString_CantConvert_TestData))]
+    public void ConvertToString_CantConvert_ThrowsNotSupportedException(object value)
+    {
+        var serializer = new SizeValueSerializer();
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertToString(value, null));
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertToString(value, new CustomValueSerializerContext()));
+    }
+
+    public static IEnumerable<object?[]> CanConvertFromString_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { string.Empty };
+        yield return new object?[] { "value" };
+    }
+
+    [Theory]
+    [MemberData(nameof(CanConvertFromString_TestData))]
+    public void CanConvertFromString_Invoke_ReturnsTrue(string value)
+    {
+        var serializer = new SizeValueSerializer();
+        Assert.True(serializer.CanConvertFromString(value, null));
+        Assert.True(serializer.CanConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [MemberData(nameof(SizeTests.Parse_TestData), MemberType = typeof(SizeTests))]
+    public void ConvertFromString_Invoke_ReturnsExpected(string value, Size expected)
+    {
+        var serializer = new SizeValueSerializer();
+        Assert.Equal(expected, serializer.ConvertFromString(value, null));
+        Assert.Equal(expected, serializer.ConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    [Fact]
+    public void ConvertFromString_NullValue_ThrowsNotSupportedException()
+    {
+        var serializer = new SizeValueSerializer();
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertFromString(null, null));
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertFromString(null, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [MemberData(nameof(SizeTests.Parse_InvalidSource_TestData), MemberType = typeof(SizeTests))]
+    public void ConvertFromString_InvalidValue_ThrowsInvalidOperationException(string value)
+    {
+        var serializer = new SizeValueSerializer();
+        Assert.Throws<InvalidOperationException>(() => serializer.ConvertFromString(value, null));
+        Assert.Throws<InvalidOperationException>(() => serializer.ConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [MemberData(nameof(SizeTests.Parse_NotDouble_TestData), MemberType = typeof(SizeTests))]
+    public void ConvertFromString_NotDouble_ThrowsFormatException(string value)
+    {
+        var serializer = new SizeValueSerializer();
+        Assert.Throws<FormatException>(() => serializer.ConvertFromString(value, null));
+        Assert.Throws<FormatException>(() => serializer.ConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [MemberData(nameof(SizeTests.Parse_Negative_TestData), MemberType = typeof(SizeTests))]
+    public void ConvertFromString_Negative_ThrowsArgumentException(string value)
+    {
+        var serializer = new SizeValueSerializer();
+        Assert.Throws<ArgumentException>(() => serializer.ConvertFromString(value, null));
+        Assert.Throws<ArgumentException>(() => serializer.ConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    private class CustomValueSerializerContext : IValueSerializerContext
+    {
+        public IContainer Container => throw new NotImplementedException();
+
+        public object Instance => throw new NotImplementedException();
+
+        public PropertyDescriptor PropertyDescriptor => throw new NotImplementedException();
+
+        public object? GetService(Type serviceType) => throw new NotImplementedException();
+
+        public ValueSerializer GetValueSerializerFor(PropertyDescriptor descriptor) => throw new NotImplementedException();
+
+        public ValueSerializer GetValueSerializerFor(Type type) => throw new NotImplementedException();
+
+        public void OnComponentChanged() => throw new NotImplementedException();
+
+        public bool OnComponentChanging() => throw new NotImplementedException();
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Converters/VectorValueSerializerTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Converters/VectorValueSerializerTests.cs
new file mode 100644
index 00000000000..2527d05ef73
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Converters/VectorValueSerializerTests.cs
@@ -0,0 +1,127 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.Windows.Markup;
+using System.Windows.Tests;
+
+namespace System.Windows.Converters.Tests;
+
+public class VectorValueSerializerTests
+{
+    public static IEnumerable<object?[]> CanConvertToString_TestData()
+    {
+        yield return new object?[] { null, false };
+        yield return new object?[] { string.Empty, false };
+        yield return new object?[] { "value", false };
+        yield return new object?[] { new object(), false };
+        
+        yield return new object?[] { new Vector(), true };
+    }
+
+    [Theory]
+    [MemberData(nameof(CanConvertToString_TestData))]
+    public void CanConvertToString_Invoke_ReturnsExpected(object value, bool expected)
+    {
+        var serializer = new VectorValueSerializer();
+        Assert.Equal(expected, serializer.CanConvertToString(value, null));
+        Assert.Equal(expected, serializer.CanConvertToString(value, new CustomValueSerializerContext()));
+    }
+    
+    [Theory]
+    [MemberData(nameof(VectorTests.ToString_TestData), MemberType = typeof(VectorTests))]
+    public void ConvertToString_Invoke_ReturnsExpected(Vector matrix, string expected)
+    {
+        var serializer = new VectorValueSerializer();
+        Assert.Equal(expected, serializer.ConvertToString(matrix, null));
+        Assert.Equal(expected, serializer.ConvertToString(matrix, new CustomValueSerializerContext()));
+    }
+
+    public static IEnumerable<object?[]> ConvertToString_CantConvert_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { string.Empty };
+        yield return new object?[] { "value" };
+        yield return new object?[] { new object() };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertToString_CantConvert_TestData))]
+    public void ConvertToString_CantConvert_ThrowsNotSupportedException(object value)
+    {
+        var serializer = new VectorValueSerializer();
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertToString(value, null));
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertToString(value, new CustomValueSerializerContext()));
+    }
+
+    public static IEnumerable<object?[]> CanConvertFromString_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { string.Empty };
+        yield return new object?[] { "value" };
+    }
+
+    [Theory]
+    [MemberData(nameof(CanConvertFromString_TestData))]
+    public void CanConvertFromString_Invoke_ReturnsTrue(string value)
+    {
+        var serializer = new VectorValueSerializer();
+        Assert.True(serializer.CanConvertFromString(value, null));
+        Assert.True(serializer.CanConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [MemberData(nameof(VectorTests.Parse_TestData), MemberType = typeof(VectorTests))]
+    public void ConvertFromString_Invoke_ReturnsExpected(string value, Vector expected)
+    {
+        var serializer = new VectorValueSerializer();
+        Assert.Equal(expected, serializer.ConvertFromString(value, null));
+        Assert.Equal(expected, serializer.ConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    [Fact]
+    public void ConvertFromString_NullValue_ThrowsNotSupportedException()
+    {
+        var serializer = new VectorValueSerializer();
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertFromString(null, null));
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertFromString(null, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [MemberData(nameof(VectorTests.Parse_InvalidSource_TestData), MemberType = typeof(VectorTests))]
+    public void ConvertFromString_InvalidValue_ThrowsInvalidOperationException(string value)
+    {
+        var serializer = new VectorValueSerializer();
+        Assert.Throws<InvalidOperationException>(() => serializer.ConvertFromString(value, null));
+        Assert.Throws<InvalidOperationException>(() => serializer.ConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [MemberData(nameof(VectorTests.Parse_NotDouble_TestData), MemberType = typeof(VectorTests))]
+    public void ConvertFromString_NotDouble_ThrowsFormatException(string value)
+    {
+        var serializer = new VectorValueSerializer();
+        Assert.Throws<FormatException>(() => serializer.ConvertFromString(value, null));
+        Assert.Throws<FormatException>(() => serializer.ConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    private class CustomValueSerializerContext : IValueSerializerContext
+    {
+        public IContainer Container => throw new NotImplementedException();
+
+        public object Instance => throw new NotImplementedException();
+
+        public PropertyDescriptor PropertyDescriptor => throw new NotImplementedException();
+
+        public object? GetService(Type serviceType) => throw new NotImplementedException();
+
+        public ValueSerializer GetValueSerializerFor(PropertyDescriptor descriptor) => throw new NotImplementedException();
+
+        public ValueSerializer GetValueSerializerFor(Type type) => throw new NotImplementedException();
+
+        public void OnComponentChanged() => throw new NotImplementedException();
+
+        public bool OnComponentChanging() => throw new NotImplementedException();
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Data/DataSourceProviderTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Data/DataSourceProviderTests.cs
new file mode 100644
index 00000000000..fccba18543b
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Data/DataSourceProviderTests.cs
@@ -0,0 +1,1953 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.Threading;
+using System.Windows.Threading;
+
+namespace System.Windows.Data.Tests;
+
+public class DataSourceProviderTests
+{
+    [Fact]
+    public void Ctor_Default()
+    {
+        var provider = new SubDataSourceProvider();
+        Assert.Null(provider.Data);
+        Assert.NotNull(provider.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, provider.Dispatcher);
+        Assert.Null(provider.Error);
+        Assert.True(provider.IsInitialLoadEnabled);
+        Assert.False(provider.IsRefreshDeferred);
+    }
+
+    [Fact]
+    public void DataChanged_AddRemove_Success()
+    {
+        var provider = new SubDataSourceProvider();
+
+        int callCount = 0;
+        EventHandler handler = (s, e) => callCount++;
+        provider.DataChanged += handler;
+        Assert.Equal(0, callCount);
+
+        provider.DataChanged -= handler;
+        Assert.Equal(0, callCount);
+
+        // Remove non existent.
+        provider.DataChanged -= handler;
+        Assert.Equal(0, callCount);
+
+        // Add null.
+        provider.DataChanged += null;
+        Assert.Equal(0, callCount);
+
+        // Remove null.
+        provider.DataChanged -= null;
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void PropertyChanged_INotifyPropertyChangedAddRemove_Success()
+    {
+        var provider = new SubDataSourceProvider();
+
+        int callCount = 0;
+        PropertyChangedEventHandler handler = (s, e) => callCount++;
+        ((INotifyPropertyChanged)provider).PropertyChanged += handler;
+        Assert.Equal(0, callCount);
+
+        ((INotifyPropertyChanged)provider).PropertyChanged -= handler;
+        Assert.Equal(0, callCount);
+
+        // Remove non existent.
+        ((INotifyPropertyChanged)provider).PropertyChanged -= handler;
+        Assert.Equal(0, callCount);
+
+        // Add null.
+        ((INotifyPropertyChanged)provider).PropertyChanged += null;
+        Assert.Equal(0, callCount);
+
+        // Remove null.
+        ((INotifyPropertyChanged)provider).PropertyChanged -= null;
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void PropertyChanged_AddRemove_Success()
+    {
+        var provider = new SubDataSourceProvider();
+
+        int callCount = 0;
+        PropertyChangedEventHandler handler = (s, e) => callCount++;
+        provider.PropertyChanged += handler;
+        Assert.Equal(0, callCount);
+
+        provider.PropertyChanged -= handler;
+        Assert.Equal(0, callCount);
+
+        // Remove non existent.
+        provider.PropertyChanged -= handler;
+        Assert.Equal(0, callCount);
+
+        // Add null.
+        provider.PropertyChanged += null;
+        Assert.Equal(0, callCount);
+
+        // Remove null.
+        provider.PropertyChanged -= null;
+        Assert.Equal(0, callCount);
+    }
+
+    public static IEnumerable<object?[]> Dispatcher_Set_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { Dispatcher.CurrentDispatcher };
+    }
+    
+    [Theory]
+    [MemberData(nameof(Dispatcher_Set_TestData))]
+    public void Dispatcher_Set_GetReturnsExpected(Dispatcher value)
+    {
+        var provider = new SubDataSourceProvider();
+        
+        // Set.
+        provider.Dispatcher = value;
+        Assert.Same(value, provider.Dispatcher);
+        
+        // Set same.
+        provider.Dispatcher = value;
+        Assert.Same(value, provider.Dispatcher);
+    }
+
+    [Fact]
+    public void Dispatcher_SetWithHandler_DoesNotCallPropertyChanged()
+    {
+        var provider = new SubDataSourceProvider();
+        int callCount = 0;
+        PropertyChangedEventHandler handler = (sender, e) => callCount++;
+        ((INotifyPropertyChanged)provider).PropertyChanged += handler;
+
+        // Set.
+        provider.Dispatcher = null;
+        Assert.Null(provider.Dispatcher);
+        Assert.Equal(0, callCount);
+
+        // Set same.
+        provider.Dispatcher = null;
+        Assert.Null(provider.Dispatcher);
+        Assert.Equal(0, callCount);
+
+        // Set different.
+        provider.Dispatcher = Dispatcher.CurrentDispatcher;
+        Assert.Same(Dispatcher.CurrentDispatcher, provider.Dispatcher);
+        Assert.Equal(0, callCount);
+
+        // Remove handler.
+        ((INotifyPropertyChanged)provider).PropertyChanged -= handler;
+        provider.Dispatcher = null;
+        Assert.Null(provider.Dispatcher);
+        Assert.Equal(0, callCount);
+    }
+
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void IsInitialLoadEnabled_Set_GetReturnsExpected(bool value)
+    {
+        var provider = new SubDataSourceProvider();
+
+        // Set.
+        provider.IsInitialLoadEnabled = value;
+        Assert.Equal(value, provider.IsInitialLoadEnabled);
+
+        // Set same.
+        provider.IsInitialLoadEnabled = value;
+        Assert.Equal(value, provider.IsInitialLoadEnabled);
+
+        // Set different.
+        provider.IsInitialLoadEnabled = !value;
+        Assert.Equal(!value, provider.IsInitialLoadEnabled);
+    }
+
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void IsInitialLoadEnabled_SetAlreadyLoaded_GetReturnsExpected(bool value)
+    {
+        var provider = new SubDataSourceProvider();
+        provider.InitialLoad();
+
+        // Set.
+        provider.IsInitialLoadEnabled = value;
+        Assert.Equal(value, provider.IsInitialLoadEnabled);
+
+        // Set same.
+        provider.IsInitialLoadEnabled = value;
+        Assert.Equal(value, provider.IsInitialLoadEnabled);
+
+        // Set different.
+        provider.IsInitialLoadEnabled = !value;
+        Assert.Equal(!value, provider.IsInitialLoadEnabled);
+    }
+
+    [Fact]
+    public void IsInitialLoadEnabled_SetWithHandler_CallsPropertyChanged()
+    {
+        var provider = new SubDataSourceProvider();
+        int callCount = 0;
+        PropertyChangedEventHandler handler = (sender, e) =>
+        {
+            Assert.Same(provider, sender);
+            Assert.Equal("IsInitialLoadEnabled", e.PropertyName);
+            callCount++;
+        };
+        ((INotifyPropertyChanged)provider).PropertyChanged += handler;
+
+        // Set.
+        provider.IsInitialLoadEnabled = false;
+        Assert.False(provider.IsInitialLoadEnabled);
+        Assert.Equal(1, callCount);
+
+        // Set same.
+        provider.IsInitialLoadEnabled = false;
+        Assert.False(provider.IsInitialLoadEnabled);
+        Assert.Equal(2, callCount);
+
+        // Set different.
+        provider.IsInitialLoadEnabled = true;
+        Assert.True(provider.IsInitialLoadEnabled);
+        Assert.Equal(3, callCount);
+
+        // Remove handler.
+        ((INotifyPropertyChanged)provider).PropertyChanged -= handler;
+        provider.IsInitialLoadEnabled = false;
+        Assert.False(provider.IsInitialLoadEnabled);
+        Assert.Equal(3, callCount);
+    }
+
+    [Fact]
+    public void BeginInit_Invoke_EndCallsBeginQuery()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction += () => callCount++;
+
+        // Begin.
+        provider.BeginInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+        
+        // End.
+        provider.EndInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+    }
+
+    [Fact]
+    public void BeginInit_InvokeInitialLoadDisabled_EndCallsBeginQuery()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider
+        {
+            IsInitialLoadEnabled = false
+        };
+        int callCount = 0;
+        provider.BeginQueryAction += () => callCount++;
+
+        // Begin.
+        provider.BeginInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+        
+        // End.
+        provider.EndInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+    }
+
+    [Fact]
+    public void BeginInit_InvokeInitialLoaded_EndCallsBeginQuery()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction += () => callCount++;
+
+        provider.InitialLoad();
+        Assert.Equal(1, callCount);
+
+        // Begin.
+        provider.BeginInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+        
+        // End.
+        provider.EndInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void BeginInit_InvokeRefreshed_EndCallsBeginQuery()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction += () => callCount++;
+
+        provider.Refresh();
+        Assert.Equal(1, callCount);
+
+        // Begin.
+        provider.BeginInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+        
+        // End.
+        provider.EndInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void BeginInit_InvokeRefreshDefer_EndCallsDoesNotCallBeginQuery()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider
+        {
+            IsInitialLoadEnabled = false
+        };
+        int callCount = 0;
+        provider.BeginQueryAction += () => callCount++;
+
+        IDisposable defer = provider.DeferRefresh();
+
+        // Begin.
+        provider.BeginInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+        
+        // End.
+        provider.EndInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // End defer.
+        defer.Dispose();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+    }
+
+    [Fact]
+    public void BeginInit_InvokeMultipleTimes_Success()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction += () => callCount++;
+
+        // Begin.
+        provider.BeginInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // Invoke again.
+        provider.BeginInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+        
+        // End.
+        provider.EndInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // End agian.
+        provider.EndInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+    }
+
+    [Fact]
+    public void BeginInit_InvokeMultipleTimesEnded_Success()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction += () => callCount++;
+
+        // End.
+        provider.EndInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // Begin.
+        provider.BeginInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // Invoke again.
+        provider.BeginInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // End agian.
+        provider.EndInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+    }
+
+    [Fact]
+    public void ISupportInitializeBeginInit_Invoke_EndCallsBeginQuery()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction += () => callCount++;
+
+        // Begin.
+        ((ISupportInitialize)provider).BeginInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+        
+        // End.
+        ((ISupportInitialize)provider).EndInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+    }
+
+    [Fact]
+    public void ISupportInitializeBeginInit_InvokeInitialLoadDisabled_EndCallsBeginQuery()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider
+        {
+            IsInitialLoadEnabled = false
+        };
+        int callCount = 0;
+        provider.BeginQueryAction += () => callCount++;
+
+        // Begin.
+        ((ISupportInitialize)provider).BeginInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+        
+        // End.
+        ((ISupportInitialize)provider).EndInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+    }
+
+    [Fact]
+    public void ISupportInitializeBeginInit_InvokeInitialLoaded_EndCallsBeginQuery()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction += () => callCount++;
+
+        provider.InitialLoad();
+        Assert.Equal(1, callCount);
+
+        // Begin.
+        ((ISupportInitialize)provider).BeginInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+        
+        // End.
+        ((ISupportInitialize)provider).EndInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void ISupportInitializeBeginInit_InvokeRefreshed_EndCallsBeginQuery()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction += () => callCount++;
+
+        provider.Refresh();
+        Assert.Equal(1, callCount);
+
+        // Begin.
+        ((ISupportInitialize)provider).BeginInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+        
+        // End.
+        ((ISupportInitialize)provider).EndInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void ISupportInitializeBeginInit_InvokeRefreshDefer_EndCallsDoesNotCallBeginQuery()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider
+        {
+            IsInitialLoadEnabled = false
+        };
+        int callCount = 0;
+        provider.BeginQueryAction += () => callCount++;
+
+        IDisposable defer = provider.DeferRefresh();
+
+        // Begin.
+        ((ISupportInitialize)provider).BeginInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+        
+        // End.
+        ((ISupportInitialize)provider).EndInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // End defer.
+        defer.Dispose();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+    }
+
+    [Fact]
+    public void ISupportInitializeBeginInit_InvokeMultipleTimes_Success()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction += () => callCount++;
+
+        // Begin.
+        ((ISupportInitialize)provider).BeginInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // Invoke again.
+        ((ISupportInitialize)provider).BeginInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+        
+        // End.
+        ((ISupportInitialize)provider).EndInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // End agian.
+        ((ISupportInitialize)provider).EndInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+    }
+
+    [Fact]
+    public void ISupportInitializeBeginInit_InvokeMultipleTimesEnded_Success()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction += () => callCount++;
+
+        // End.
+        ((ISupportInitialize)provider).EndInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // Begin.
+        ((ISupportInitialize)provider).BeginInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // Invoke again.
+        ((ISupportInitialize)provider).BeginInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // End agian.
+        ((ISupportInitialize)provider).EndInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+    }
+
+    [Fact]
+    public void ISupportInitializeBeginInit_Invoke_CallsBeginInit()
+    {
+        var provider = new CustomInitDataSourceProvider();
+        int callCount = 0;
+        provider.BeginInitAction += () => callCount++;
+
+        // Invoke.
+        ((ISupportInitialize)provider).BeginInit();
+        Assert.Equal(1, callCount);
+
+        // Invoke again.
+        ((ISupportInitialize)provider).BeginInit();
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void BeginQuery_Invoke_Nop()
+    {
+        var provider = new SubDataSourceProvider();
+
+        // Invoke.
+        provider.BeginQuery();
+        Assert.False(provider.IsRefreshDeferred);
+
+        // Invoke again.
+        provider.BeginQuery();
+        Assert.False(provider.IsRefreshDeferred);
+    }
+
+    [Fact]
+    public void DeferRefresh_Invoke_Success()
+    {
+        var provider = new SubDataSourceProvider();
+
+        IDisposable result1 = provider.DeferRefresh();
+        Assert.NotNull(result1);
+        Assert.True(provider.IsRefreshDeferred);
+
+        // Clear.
+        result1.Dispose();
+        Assert.False(provider.IsRefreshDeferred);
+        
+        // Clear again.
+        result1.Dispose();
+        Assert.False(provider.IsRefreshDeferred);
+    }
+
+    [Fact]
+    public void DeferRefresh_InvokeBeganInitialize_Success()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction += () => callCount++;
+
+        IDisposable result1 = provider.DeferRefresh();
+        Assert.NotNull(result1);
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // Begin.
+        provider.BeginInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // Clear.
+        result1.Dispose();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+        
+        // Clear again.
+        result1.Dispose();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // End init.
+        provider.EndInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+    }
+
+    [Fact]
+    public void DeferRefresh_InvokeEndedInitialize_Success()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction += () => callCount++;
+
+        IDisposable result1 = provider.DeferRefresh();
+        Assert.NotNull(result1);
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // Begin.
+        provider.BeginInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // End.
+        provider.EndInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // Clear.
+        result1.Dispose();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+        
+        // Clear again.
+        result1.Dispose();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+    }
+
+    [Fact]
+    public void DeferRefresh_InvokeMultipleTimes_Success()
+    {
+        var provider = new SubDataSourceProvider();
+
+        // Invoke.
+        IDisposable result1 = provider.DeferRefresh();
+        Assert.NotNull(result1);
+        Assert.True(provider.IsRefreshDeferred);
+
+        // Invoke again.
+        IDisposable result2 = provider.DeferRefresh();
+        Assert.NotNull(result2);
+        Assert.NotSame(result1, result2);
+        Assert.True(provider.IsRefreshDeferred);
+
+        // Clear first.
+        result1.Dispose();
+        Assert.True(provider.IsRefreshDeferred);
+
+        // Clear first again.
+        result1.Dispose();
+        Assert.True(provider.IsRefreshDeferred);
+
+        // Clear second.
+        result2.Dispose();
+        Assert.False(provider.IsRefreshDeferred);
+    }
+
+    [Fact]
+    public void EndInit_Invoke_Success()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction += () => callCount++;
+
+        // Begin.
+        provider.BeginInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // End.
+        provider.EndInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+    }
+
+    [Fact]
+    public void EndInit_InvokeMultipleTimes_Success()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction += () => callCount++;
+
+        // Begin.
+        provider.BeginInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // End.
+        provider.EndInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+
+        // End again. 
+        provider.EndInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+
+        // Begin.
+        provider.BeginInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+
+        // Begin again.
+        provider.BeginInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+    }
+
+    [Fact]
+    public void EndInit_InvokeNotBegan_Success()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction += () => callCount++;
+
+        // End.
+        provider.EndInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // Begin.
+        provider.BeginInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // End.
+        provider.EndInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void EndInit_InvokeInitialLoaded_Success()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction += () => callCount++;
+
+        // Begin.
+        provider.BeginInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // Load.
+        provider.InitialLoad();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+
+        // End.
+        provider.EndInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void EndInit_InvokeRefreshDeferred_Success()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction += () => callCount++;
+
+        // Begin.
+        provider.BeginInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // Defer.
+        IDisposable defer = provider.DeferRefresh();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // End.
+        provider.EndInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // End again.
+        provider.EndInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+    }
+
+    [Fact]
+    public void ISupportInitializeEndInit_Invoke_Success()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction += () => callCount++;
+
+        // Begin.
+        ((ISupportInitialize)provider).BeginInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // End.
+        ((ISupportInitialize)provider).EndInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+    }
+
+    [Fact]
+    public void ISupportInitializeEndInit_InvokeMultipleTimes_Success()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction += () => callCount++;
+
+        // Begin.
+        ((ISupportInitialize)provider).BeginInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // End.
+        ((ISupportInitialize)provider).EndInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+
+        // End again. 
+        ((ISupportInitialize)provider).EndInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+
+        // Begin.
+        ((ISupportInitialize)provider).BeginInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+
+        // Begin again.
+        ((ISupportInitialize)provider).BeginInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+    }
+
+    [Fact]
+    public void ISupportInitializeEndInit_InvokeNotBegan_Success()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction += () => callCount++;
+
+        // End.
+        ((ISupportInitialize)provider).EndInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // Begin.
+        ((ISupportInitialize)provider).BeginInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // End.
+        ((ISupportInitialize)provider).EndInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void ISupportInitializeEndInit_InvokeInitialLoaded_Success()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction += () => callCount++;
+
+        // Begin.
+        ((ISupportInitialize)provider).BeginInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // Load.
+        provider.InitialLoad();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+
+        // End.
+        ((ISupportInitialize)provider).EndInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void ISupportInitializeEndInit_InvokeRefreshDeferred_Success()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction += () => callCount++;
+
+        // Begin.
+        ((ISupportInitialize)provider).BeginInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // Defer.
+        IDisposable defer = provider.DeferRefresh();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // End.
+        ((ISupportInitialize)provider).EndInit();
+        Assert.True(provider.IsRefreshDeferred);
+        Assert.Equal(0, callCount);
+
+        // End again.
+        ((ISupportInitialize)provider).EndInit();
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+    }
+
+    [Fact]
+    public void ISupportInitializeEndInit_Invoke_CallsEndInit()
+    {
+        var provider = new CustomInitDataSourceProvider();
+        int callCount = 0;
+        provider.EndInitAction += () => callCount++;
+
+        // Invoke.
+        ((ISupportInitialize)provider).EndInit();
+        Assert.Equal(1, callCount);
+
+        // Invoke again.
+        ((ISupportInitialize)provider).EndInit();
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void InitialLoad_Invoke_CallsBeginQuery()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction = () => callCount++;
+        
+        // Invoke.
+        provider.InitialLoad();
+        Assert.Equal(1, callCount);
+        Assert.False(provider.IsRefreshDeferred);
+
+        // Invoke again.
+        provider.InitialLoad();
+        Assert.Equal(1, callCount);
+        Assert.False(provider.IsRefreshDeferred);
+    }
+
+    [Fact]
+    public void InitialLoad_InvokeInitialLoadNotEnabled_DoesNotCallBeginQuery()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider
+        {
+            IsInitialLoadEnabled = false
+        };
+        int callCount = 0;
+        provider.BeginQueryAction = () => callCount++;
+        
+        // Invoke.
+        provider.InitialLoad();
+        Assert.Equal(0, callCount);
+        Assert.True(provider.IsRefreshDeferred);
+
+        // Invoke again.
+        provider.InitialLoad();
+        Assert.Equal(0, callCount);
+        Assert.True(provider.IsRefreshDeferred);
+    }
+
+    [Fact]
+    public void InitialLoad_InvokeBeganInitialize_CallsBeginQuery()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction = () => callCount++;
+
+        provider.BeginInit();
+        Assert.Equal(0, callCount);
+        Assert.True(provider.IsRefreshDeferred);
+        
+        // Invoke.
+        provider.InitialLoad();
+        Assert.Equal(1, callCount);
+        Assert.True(provider.IsRefreshDeferred);
+
+        // Invoke again.
+        provider.InitialLoad();
+        Assert.Equal(1, callCount);
+        Assert.True(provider.IsRefreshDeferred);
+    }
+
+    [Fact]
+    public void InitialLoad_InvokeEndedInitialize_DoesNotCallBeginQuery()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction = () => callCount++;
+
+        provider.BeginInit();
+        Assert.Equal(0, callCount);
+        Assert.True(provider.IsRefreshDeferred);
+        
+        provider.EndInit();
+        Assert.Equal(1, callCount);
+        Assert.False(provider.IsRefreshDeferred);
+        
+        // Invoke.
+        provider.InitialLoad();
+        Assert.Equal(1, callCount);
+        Assert.False(provider.IsRefreshDeferred);
+
+        // Invoke again.
+        provider.InitialLoad();
+        Assert.Equal(1, callCount);
+        Assert.False(provider.IsRefreshDeferred);
+    }
+
+    [Fact]
+    public void InitialLoad_InvokeRefreshed_DoesNotCallBeginQuery()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction = () => callCount++;
+
+        provider.Refresh();
+        Assert.Equal(1, callCount);
+        Assert.False(provider.IsRefreshDeferred);
+        
+        // Invoke.
+        provider.InitialLoad();
+        Assert.Equal(1, callCount);
+        Assert.False(provider.IsRefreshDeferred);
+
+        // Invoke again.
+        provider.InitialLoad();
+        Assert.Equal(1, callCount);
+        Assert.False(provider.IsRefreshDeferred);
+    }
+
+    [Fact]
+    public void Refresh_Invoke_CallsBeginQuery()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction = () => callCount++;
+        
+        // Refresh.
+        provider.Refresh();
+        Assert.Equal(1, callCount);
+        Assert.False(provider.IsRefreshDeferred);
+
+        // Refresh again.
+        provider.Refresh();
+        Assert.Equal(2, callCount);
+        Assert.False(provider.IsRefreshDeferred);
+    }
+
+    [Fact]
+    public void Refresh_InvokeInitialLoaded_CallsBeginQuery()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction = () => callCount++;
+        
+        provider.InitialLoad();
+        Assert.Equal(1, callCount);
+        Assert.False(provider.IsRefreshDeferred);
+        
+        // Refresh.
+        provider.Refresh();
+        Assert.Equal(2, callCount);
+        Assert.False(provider.IsRefreshDeferred);
+
+        // Refresh again.
+        provider.Refresh();
+        Assert.Equal(3, callCount);
+        Assert.False(provider.IsRefreshDeferred);
+    }
+
+    [Fact]
+    public void Refresh_InvokeRefreshDeferred_CallsBeginQuery()
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction = () => callCount++;
+
+        provider.DeferRefresh();
+        Assert.Equal(0, callCount);
+        Assert.True(provider.IsRefreshDeferred);
+
+        // Refresh.
+        provider.Refresh();
+        Assert.Equal(1, callCount);
+        Assert.True(provider.IsRefreshDeferred);
+
+        // Refresh again.
+        provider.Refresh();
+        Assert.Equal(2, callCount);
+        Assert.True(provider.IsRefreshDeferred);
+    }
+
+    public static IEnumerable<object?[]> OnPropertyChanged_TestData()
+    {
+        yield return new object?[] { new PropertyChangedEventArgs("Name") };
+        yield return new object?[] { null };
+    }
+
+    [Theory]
+    [MemberData(nameof(OnPropertyChanged_TestData))]
+    public void OnPropertyChanged_Invoke_CallsPropertyChangedEvent(PropertyChangedEventArgs eventArgs)
+    {
+        var provider = new SubDataSourceProvider();
+        int callCount = 0;
+        PropertyChangedEventHandler handler = (sender, e) =>
+        {
+            Assert.Same(provider, sender);
+            Assert.Same(eventArgs, e);
+            callCount++;
+        };
+
+        // Call with handler.
+        ((INotifyPropertyChanged)provider).PropertyChanged += handler;
+        provider.OnPropertyChanged(eventArgs);
+        Assert.Equal(1, callCount);
+
+        // Remove handler.
+        ((INotifyPropertyChanged)provider).PropertyChanged -= handler;
+        provider.OnPropertyChanged(eventArgs);
+        Assert.Equal(1, callCount);
+    }
+
+    [Fact]
+    public void OnQueryFinished_InvokeSimple_Success()
+    {
+        var provider = new SubDataSourceProvider();
+        var newData = new object();
+        
+        // Invoke.
+        provider.OnQueryFinished(newData);
+        Assert.Same(newData, provider.Data);
+        Assert.NotNull(provider.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, provider.Dispatcher);
+        Assert.Null(provider.Error);
+        Assert.True(provider.IsInitialLoadEnabled);
+        Assert.False(provider.IsRefreshDeferred);
+        
+        // Invoke again.
+        provider.OnQueryFinished(newData);
+        Assert.Same(newData, provider.Data);
+        Assert.NotNull(provider.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, provider.Dispatcher);
+        Assert.Null(provider.Error);
+        Assert.True(provider.IsInitialLoadEnabled);
+        Assert.False(provider.IsRefreshDeferred);
+        
+        // Invoke null.
+        provider.OnQueryFinished(null!);
+        Assert.Null(provider.Data);
+        Assert.NotNull(provider.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, provider.Dispatcher);
+        Assert.Null(provider.Error);
+        Assert.True(provider.IsInitialLoadEnabled);
+        Assert.False(provider.IsRefreshDeferred);
+    }
+
+    [Theory]
+    [InlineData(1)]
+    [InlineData(null)]
+    public void OnQueryFinished_InvokeSimpleInitialLoaded_DoesNotResetInitialLoad(object? newData)
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction = () => callCount++;
+
+        provider.InitialLoad();
+        Assert.Equal(1, callCount);
+
+        // Invoke.
+        provider.OnQueryFinished(newData!);
+        Assert.Equal(newData, provider.Data);
+        Assert.NotNull(provider.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, provider.Dispatcher);
+        Assert.Null(provider.Error);
+        Assert.True(provider.IsInitialLoadEnabled);
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+        
+        // Load again.
+        provider.InitialLoad();
+        Assert.Equal(1, callCount);
+    }
+
+    [Theory]
+    [InlineData(1)]
+    [InlineData(null)]
+    public void OnQueryFinished_InvokeSimpleWithError_Success(object? newData)
+    {
+        var provider = new SubDataSourceProvider();
+        provider.OnQueryFinished(new object(), new Exception(), e => e, new object());
+
+        // Invoke.
+        provider.OnQueryFinished(newData!);
+        Assert.Equal(newData, provider.Data);
+        Assert.NotNull(provider.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, provider.Dispatcher);
+        Assert.Null(provider.Error);
+        Assert.True(provider.IsInitialLoadEnabled);
+        Assert.False(provider.IsRefreshDeferred);
+    }
+
+    [Fact]
+    public void OnQueryFinished_InvokeSimpleWithPropertyChangedHandler_CallsPropertyChanged()
+    {
+        var provider = new SubDataSourceProvider();
+        int callCount = 0;
+        object? newData = null;
+        PropertyChangedEventHandler handler = (sender, e) =>
+        {
+            Assert.Same(provider, sender);
+            Assert.Equal("Data", e.PropertyName);
+            Assert.Same(newData, provider.Data);
+            callCount++;
+        };
+        ((INotifyPropertyChanged)provider).PropertyChanged += handler;
+
+        // Call.
+        newData = new object();
+        provider.OnQueryFinished(newData);
+        Assert.Equal(1, callCount);
+
+        // Call again.
+        provider.OnQueryFinished(newData);
+        Assert.Equal(2, callCount);
+
+        // Call different.
+        newData = null;
+        provider.OnQueryFinished(null!);
+        Assert.Equal(3, callCount);
+
+        // Remove handler.
+        ((INotifyPropertyChanged)provider).PropertyChanged -= handler;
+        newData = new object();
+        provider.OnQueryFinished(newData);
+        Assert.Equal(3, callCount);
+    }
+
+    [Fact]
+    public void OnQueryFinished_InvokeSimpleWithDataChangedHandler_CallsDataChanged()
+    {
+        var provider = new SubDataSourceProvider();
+        int callCount = 0;
+        object? newData = null;
+        EventHandler handler = (sender, e) =>
+        {
+            Assert.Same(provider, sender);
+            Assert.Same(EventArgs.Empty, e);
+            Assert.Same(newData, provider.Data);
+            callCount++;
+        };
+        provider.DataChanged += handler;
+
+        // Call.
+        newData = new object();
+        provider.OnQueryFinished(newData);
+        Assert.Equal(1, callCount);
+
+        // Call again.
+        provider.OnQueryFinished(newData);
+        Assert.Equal(2, callCount);
+
+        // Call different.
+        newData = null;
+        provider.OnQueryFinished(newData!);
+        Assert.Equal(3, callCount);
+
+        // Remove handler.
+        provider.DataChanged -= handler;
+        newData = new object();
+        provider.OnQueryFinished(newData);
+        Assert.Equal(3, callCount);
+    }
+
+    [Fact]
+    public void OnQueryFinished_InvokeSimpleWithPropertyChangedAndDataChangedHandler_CallsPropertyChangedAndDataChanged()
+    {
+        var provider = new SubDataSourceProvider();
+        int propertyChangedCallCount = 0;
+        int dataChangedCallCount = 0;
+        object? newData = null;
+        PropertyChangedEventHandler propertyChangedHandler = (sender, e) =>
+        {
+            Assert.Equal(dataChangedCallCount, propertyChangedCallCount);
+            Assert.Same(provider, sender);
+            Assert.Equal("Data", e.PropertyName);
+            propertyChangedCallCount++;
+        };
+        ((INotifyPropertyChanged)provider).PropertyChanged += propertyChangedHandler;
+        EventHandler dataChangedHandler = (sender, e) =>
+        {
+            Assert.True(propertyChangedCallCount > dataChangedCallCount);
+            Assert.Same(provider, sender);
+            Assert.Same(EventArgs.Empty, e);
+            dataChangedCallCount++;
+        };
+        provider.DataChanged += dataChangedHandler;
+
+        // Call.
+        newData = new object();
+        provider.OnQueryFinished(newData);
+        Assert.Equal(1, propertyChangedCallCount);
+        Assert.Equal(1, dataChangedCallCount);
+
+        // Call again.
+        provider.OnQueryFinished(newData);
+        Assert.Equal(2, propertyChangedCallCount);
+        Assert.Equal(2, dataChangedCallCount);
+
+        // Call different.
+        newData = null;
+        provider.OnQueryFinished(newData!);
+        Assert.Equal(3, propertyChangedCallCount);
+        Assert.Equal(3, dataChangedCallCount);
+
+        // Remove handler.
+        ((INotifyPropertyChanged)provider).PropertyChanged -= propertyChangedHandler;
+        provider.DataChanged -= dataChangedHandler;
+        newData = new object();
+        provider.OnQueryFinished(newData);
+        Assert.Equal(3, propertyChangedCallCount);
+        Assert.Equal(3, dataChangedCallCount);
+    }
+
+    [Fact]
+    public void OnQueryFinished_InvokeSimpleOnDifferentThread_Success()
+    {
+        var provider = new SubDataSourceProvider();
+
+        bool? success = false;
+        var thread = new Thread(() =>
+        {
+            try
+            { 
+                provider.OnQueryFinished(new object());
+                success = true;
+            }
+            catch
+            {
+                success = false;
+            }
+        });
+        thread.Start();
+        thread.Join();
+        Assert.True(success);
+    }
+    
+    [Theory]
+    [InlineData(1)]
+    [InlineData(null)]
+    public void OnQueryFinished_InvokeSimple_CallsComplex(object? newData)
+    {
+        var provider = new CustomOnQueryFinishedDataSourceProvider();
+
+        int callCount = 0;
+        provider.OnQueryFinishedAction = (data, error, completionWork, callbackArguments) =>
+        {
+            Assert.Equal(newData, data);
+            Assert.Null(error);
+            Assert.Null(completionWork);
+            Assert.Null(callbackArguments);
+            callCount++;
+        };
+
+        // Call.
+        provider.OnQueryFinished(newData!);
+        Assert.Equal(1, callCount);
+
+        // Call again.
+        provider.OnQueryFinished(newData!);
+        Assert.Equal(2, callCount);
+    }
+
+    [Theory]
+    [InlineData(1)]
+    [InlineData(null)]
+    public void OnQueryFinished_InvokeComplex_Success(object? newData)
+    {
+        var provider = new SubDataSourceProvider();
+
+        // Invoke.
+        provider.OnQueryFinished(newData!, null!, null!, null!);
+        Assert.Equal(newData, provider.Data);
+        Assert.NotNull(provider.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, provider.Dispatcher);
+        Assert.Null(provider.Error);
+        Assert.True(provider.IsInitialLoadEnabled);
+        Assert.False(provider.IsRefreshDeferred);
+        
+        // Invoke again.
+        provider.OnQueryFinished(newData!, null!, null!, null!);
+        Assert.Equal(newData, provider.Data);
+        Assert.NotNull(provider.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, provider.Dispatcher);
+        Assert.Null(provider.Error);
+        Assert.True(provider.IsInitialLoadEnabled);
+        Assert.False(provider.IsRefreshDeferred);
+    }
+
+    [Theory]
+    [InlineData(1)]
+    [InlineData(null)]
+    public void OnQueryFinished_InvokeComplexWithError_Success(object? newData)
+    {
+        var provider = new SubDataSourceProvider();
+        var error = new Exception();
+
+        // Invoke.
+        provider.OnQueryFinished(newData!, error, null!, null!);
+        Assert.Null(provider.Data);
+        Assert.NotNull(provider.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, provider.Dispatcher);
+        Assert.Same(error, provider.Error);
+        Assert.True(provider.IsInitialLoadEnabled);
+        Assert.False(provider.IsRefreshDeferred);
+        
+        // Invoke again.
+        provider.OnQueryFinished(newData!, error, null!, null!);
+        Assert.Null(provider.Data);
+        Assert.NotNull(provider.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, provider.Dispatcher);
+        Assert.Same(error, provider.Error);
+        Assert.True(provider.IsInitialLoadEnabled);
+        Assert.False(provider.IsRefreshDeferred);
+        
+        // Clear error.
+        provider.OnQueryFinished(newData!, null!, null!, null!);
+        Assert.Equal(newData, provider.Data);
+        Assert.NotNull(provider.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, provider.Dispatcher);
+        Assert.Null(provider.Error);
+        Assert.True(provider.IsInitialLoadEnabled);
+        Assert.False(provider.IsRefreshDeferred);
+    }
+
+    [Theory]
+    [InlineData(1, 2)]
+    [InlineData(1, null)]
+    [InlineData(null, 2)]
+    [InlineData(null, null)]
+    public void OnQueryFinished_InvokeComplexWithCallback_CallsCallback(object? newData, object? callbackArg)
+    {
+        var provider = new SubDataSourceProvider();
+        int callbackCallCount = 0;
+        DispatcherOperationCallback callback = arg =>
+        {
+            Assert.Same(callbackArg, arg);
+            Assert.Equal(newData, provider.Data);
+            callbackCallCount++;
+            return null!;
+        };
+
+        // Invoke.
+        provider.OnQueryFinished(newData!, null!, callback, callbackArg!);
+        Assert.Equal(1, callbackCallCount);
+        Assert.Equal(newData, provider.Data);
+        Assert.NotNull(provider.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, provider.Dispatcher);
+        Assert.Null(provider.Error);
+        Assert.True(provider.IsInitialLoadEnabled);
+        Assert.False(provider.IsRefreshDeferred);
+        
+        // Invoke again.
+        provider.OnQueryFinished(newData!, null!, callback, callbackArg!);
+        Assert.Equal(2, callbackCallCount);
+        Assert.Equal(newData, provider.Data);
+        Assert.NotNull(provider.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, provider.Dispatcher);
+        Assert.Null(provider.Error);
+        Assert.True(provider.IsInitialLoadEnabled);
+        Assert.False(provider.IsRefreshDeferred);
+    }
+
+    [Theory]
+    [InlineData(1)]
+    [InlineData(null)]
+    public void OnQueryFinished_InvokeComplexInitialLoadedWithError_ResetsInitialLoad(object? newData)
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction = () => callCount++;
+        var error = new Exception();
+
+        provider.InitialLoad();
+        Assert.Equal(1, callCount);
+
+        // Invoke.
+        provider.OnQueryFinished(newData!, error, null!, null!);
+        Assert.Null(provider.Data);
+        Assert.NotNull(provider.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, provider.Dispatcher);
+        Assert.Same(error, provider.Error);
+        Assert.True(provider.IsInitialLoadEnabled);
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+        
+        // Load again.
+        provider.InitialLoad();
+        Assert.Equal(2, callCount);
+
+        // Invoke again.
+        provider.OnQueryFinished(newData!, error, null!, null!);
+        Assert.Null(provider.Data);
+        Assert.NotNull(provider.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, provider.Dispatcher);
+        Assert.Same(error, provider.Error);
+        Assert.True(provider.IsInitialLoadEnabled);
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(2, callCount);
+        
+        // Load again.
+        provider.InitialLoad();
+        Assert.Equal(3, callCount);
+    }
+
+    [Theory]
+    [InlineData(1)]
+    [InlineData(null)]
+    public void OnQueryFinished_InvokeComplexInitialLoadedWithoutError_DoesNotResetInitialLoad(object? newData)
+    {
+        var provider = new CustomBeginQueryDataSourceProvider();
+        int callCount = 0;
+        provider.BeginQueryAction = () => callCount++;
+
+        provider.InitialLoad();
+        Assert.Equal(1, callCount);
+
+        // Invoke.
+        provider.OnQueryFinished(newData!, null!, null!, null!);
+        Assert.Equal(newData, provider.Data);
+        Assert.NotNull(provider.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, provider.Dispatcher);
+        Assert.Null(provider.Error);
+        Assert.True(provider.IsInitialLoadEnabled);
+        Assert.False(provider.IsRefreshDeferred);
+        Assert.Equal(1, callCount);
+        
+        // Load again.
+        provider.InitialLoad();
+        Assert.Equal(1, callCount);
+    }
+
+    [Fact]
+    public void OnQueryFinished_InvokeComplexWithPropertyChangedHandler_CallsPropertyChanged()
+    {
+        var provider = new SubDataSourceProvider();
+        int callCount = 0;
+        int callbackCallCount = 0;
+        object? newData = null;
+        var callbackArguments = new object();
+        PropertyChangedEventHandler handler = (sender, e) =>
+        {
+            Assert.True(callbackCallCount > callCount);
+            Assert.Same(provider, sender);
+            Assert.Equal("Data", e.PropertyName);
+            Assert.Same(newData, provider.Data);
+            callCount++;
+        };
+        ((INotifyPropertyChanged)provider).PropertyChanged += handler;
+        DispatcherOperationCallback callback = (arg) =>
+        {
+            Assert.Equal(callbackCallCount, callCount);
+            Assert.Same(callbackArguments, arg);
+            Assert.Same(newData, provider.Data);
+            callbackCallCount++;
+            return null;
+        };
+
+        // Call.
+        newData = new object();
+        provider.OnQueryFinished(newData, null!, callback, callbackArguments);
+        Assert.Equal(1, callCount);
+        Assert.Equal(1, callbackCallCount);
+
+        // Call again.
+        provider.OnQueryFinished(newData, null!, callback, callbackArguments);
+        Assert.Equal(2, callCount);
+        Assert.Equal(2, callbackCallCount);
+
+        // Call different.
+        newData = null;
+        provider.OnQueryFinished(null!, null!, callback, callbackArguments);
+        Assert.Equal(3, callCount);
+        Assert.Equal(3, callbackCallCount);
+
+        // Remove handler.
+        ((INotifyPropertyChanged)provider).PropertyChanged -= handler;
+        newData = new object();
+        provider.OnQueryFinished(newData, null!, callback, callbackArguments);
+        Assert.Equal(3, callCount);
+        Assert.Equal(4, callbackCallCount);
+    }
+
+    [Fact]
+    public void OnQueryFinished_InvokeComplexWithErrorWithPropertyChangedHandler_CallsPropertyChanged()
+    {
+        var provider = new SubDataSourceProvider();
+        int callCount = 0;
+        object? newData = null;
+        var callbackArguments = new object();
+        var propertyNames = new List<string>();
+        PropertyChangedEventHandler handler = (sender, e) =>
+        {
+            Assert.Same(provider, sender);
+            propertyNames.Add(e.PropertyName!);
+            callCount++;
+        };
+        ((INotifyPropertyChanged)provider).PropertyChanged += handler;
+
+        var error1 = new Exception();
+        var error2 = new Exception();
+
+        // Call.
+        newData = new object();
+        provider.OnQueryFinished(newData, error1, null!, null!);
+        Assert.Equal(2, callCount);
+        Assert.Equal(new[] { "Data", "Error" }, propertyNames);
+        Assert.Same(error1, provider.Error);
+
+        // Call again.
+        provider.OnQueryFinished(newData, error1, null!, null!);
+        Assert.Equal(3, callCount);
+        Assert.Equal(new[] { "Data", "Error", "Data" }, propertyNames);
+        Assert.Same(error1, provider.Error);
+
+        // Call different.
+        newData = null;
+        provider.OnQueryFinished(null!, error2, null!, null!);
+        Assert.Equal(5, callCount);
+        Assert.Equal(new[] { "Data", "Error", "Data", "Data", "Error" }, propertyNames);
+        Assert.Same(error2, provider.Error);
+
+        // Call different.
+        provider.OnQueryFinished(null!, null!, null!, null!);
+        Assert.Equal(7, callCount);
+        Assert.Equal(new[] { "Data", "Error", "Data", "Data", "Error", "Data", "Error" }, propertyNames);
+        Assert.Null(provider.Error);
+
+        // Remove handler.
+        ((INotifyPropertyChanged)provider).PropertyChanged -= handler;
+        newData = new object();
+        provider.OnQueryFinished(newData, error1, null!, null!);
+        Assert.Equal(7, callCount);
+        Assert.Equal(new[] { "Data", "Error", "Data", "Data", "Error", "Data", "Error" }, propertyNames);
+        Assert.Same(error1, provider.Error);
+    }
+
+    [Fact]
+    public void OnQueryFinished_InvokeComplexWithDataChangedHandler_CallsDataChanged()
+    {
+        var provider = new SubDataSourceProvider();
+        int callCount = 0;
+        int callbackCallCount = 0;
+        var callbackArguments = new object();
+        object? newData = null;
+        EventHandler handler = (sender, e) =>
+        {
+            Assert.Same(provider, sender);
+            Assert.Same(EventArgs.Empty, e);
+            Assert.Same(newData, provider.Data);
+            callCount++;
+        };
+        provider.DataChanged += handler;
+        DispatcherOperationCallback callback = (arg) =>
+        {
+            Assert.Equal(callbackCallCount, callCount);
+            Assert.Same(callbackArguments, arg);
+            Assert.Same(newData, provider.Data);
+            callbackCallCount++;
+            return null;
+        };
+
+        // Call.
+        newData = new object();
+        provider.OnQueryFinished(newData, null!, callback, callbackArguments);
+        Assert.Equal(1, callCount);
+        Assert.Equal(1, callbackCallCount);
+
+        // Call again.
+        provider.OnQueryFinished(newData, null!, callback, callbackArguments);
+        Assert.Equal(2, callCount);
+        Assert.Equal(2, callbackCallCount);
+
+        // Call different.
+        newData = null;
+        provider.OnQueryFinished(newData!, null!, callback, callbackArguments);
+        Assert.Equal(3, callCount);
+        Assert.Equal(3, callbackCallCount);
+
+        // Remove handler.
+        provider.DataChanged -= handler;
+        newData = new object();
+        provider.OnQueryFinished(newData, null!, callback, callbackArguments);
+        Assert.Equal(3, callCount);
+        Assert.Equal(4, callbackCallCount);
+    }
+
+    [Fact]
+    public void OnQueryFinished_InvokeComplexWithPropertyChangedAndDataChangedHandler_CallsPropertyChangedAndDataChanged()
+    {
+        var provider = new SubDataSourceProvider();
+        int propertyChangedCallCount = 0;
+        int dataChangedCallCount = 0;
+        int callbackCallCount = 0;
+        var callbackArguments = new object();
+        object? newData = null;
+        PropertyChangedEventHandler propertyChangedHandler = (sender, e) =>
+        {
+            Assert.True(callbackCallCount > propertyChangedCallCount);
+            Assert.Equal(dataChangedCallCount, propertyChangedCallCount);
+            Assert.Same(provider, sender);
+            Assert.Equal("Data", e.PropertyName);
+            propertyChangedCallCount++;
+        };
+        ((INotifyPropertyChanged)provider).PropertyChanged += propertyChangedHandler;
+        EventHandler dataChangedHandler = (sender, e) =>
+        {
+            Assert.True(propertyChangedCallCount > dataChangedCallCount);
+            Assert.True(callbackCallCount > dataChangedCallCount);
+            Assert.Same(provider, sender);
+            Assert.Same(EventArgs.Empty, e);
+            dataChangedCallCount++;
+        };
+        provider.DataChanged += dataChangedHandler;
+        DispatcherOperationCallback callback = (arg) =>
+        {
+            Assert.Equal(callbackCallCount, propertyChangedCallCount);
+            Assert.Equal(callbackCallCount, dataChangedCallCount);
+            Assert.Same(callbackArguments, arg);
+            Assert.Same(newData, provider.Data);
+            callbackCallCount++;
+            return null;
+        };
+
+        // Call.
+        newData = new object();
+        provider.OnQueryFinished(newData, null!, callback, callbackArguments);
+        Assert.Equal(1, propertyChangedCallCount);
+        Assert.Equal(1, dataChangedCallCount);
+        Assert.Equal(1, callbackCallCount);
+
+        // Call again.
+        provider.OnQueryFinished(newData, null!, callback, callbackArguments);
+        Assert.Equal(2, propertyChangedCallCount);
+        Assert.Equal(2, dataChangedCallCount);
+        Assert.Equal(2, callbackCallCount);
+
+        // Call different.
+        newData = null;
+        provider.OnQueryFinished(newData!, null!, callback, callbackArguments);
+        Assert.Equal(3, propertyChangedCallCount);
+        Assert.Equal(3, dataChangedCallCount);
+        Assert.Equal(3, callbackCallCount);
+
+        // Remove handler.
+        ((INotifyPropertyChanged)provider).PropertyChanged -= propertyChangedHandler;
+        provider.DataChanged -= dataChangedHandler;
+        newData = new object();
+        provider.OnQueryFinished(newData, null!, callback, callbackArguments);
+        Assert.Equal(3, propertyChangedCallCount);
+        Assert.Equal(3, dataChangedCallCount);
+        Assert.Equal(4, callbackCallCount);
+    }
+
+    [Fact]
+    public void OnQueryFinished_InvokeComplexOnDifferentThread_Success()
+    {
+        var provider = new SubDataSourceProvider();
+
+        bool? success = false;
+        var thread = new Thread(() =>
+        {
+            try
+            { 
+                provider.OnQueryFinished(new object(), new Exception(), e => e, new object());
+                success = true;
+            }
+            catch
+            {
+                success = false;
+            }
+        });
+        thread.Start();
+        thread.Join();
+        Assert.True(success);
+    }
+
+    // TODO: this causes a crash.
+#if false
+    [Fact]
+    public void OnQueryFinished_NullDispatcher_ThrowsNullReferenceException()
+    {
+        var provider = new SubDataSourceProvider();
+        provider.Dispatcher = null;
+        Assert.Throws<NullReferenceException>(() => provider.OnQueryFinished(new object()));
+        Assert.Throws<NullReferenceException>(() => provider.OnQueryFinished(new object(), new Exception(), e => e, new object()));
+    }
+#endif
+
+    private class CustomBeginQueryDataSourceProvider : DataSourceProvider
+    {
+        public new Dispatcher? Dispatcher
+        {
+            get => base.Dispatcher;
+            set => base.Dispatcher = value;
+        }
+
+        public new bool IsRefreshDeferred => base.IsRefreshDeferred;
+
+        public new void BeginInit() => base.BeginInit();
+
+        public Action? BeginQueryAction { get; set; }
+
+        protected override void BeginQuery()
+        {
+            if (BeginQueryAction is null)
+            {
+                throw new NotImplementedException();
+            }
+
+            BeginQueryAction();
+        }
+
+        public new void EndInit() => base.EndInit();
+
+        public new void OnQueryFinished(object newData) => base.OnQueryFinished(newData);
+
+        public new void OnQueryFinished(object newData, Exception error, DispatcherOperationCallback completionWork, object callbackArguments) => base.OnQueryFinished(newData, error, completionWork, callbackArguments);
+    }
+
+    private class CustomInitDataSourceProvider : DataSourceProvider
+    {
+        public Action? BeginInitAction { get; set; }
+
+        protected override void BeginInit()
+        {
+            if (BeginInitAction is null)
+            {
+                throw new NotImplementedException();
+            }
+
+            BeginInitAction();
+        }
+
+        public Action? EndInitAction { get; set; }
+
+        protected override void EndInit()
+        {
+            if (EndInitAction is null)
+            {
+                throw new NotImplementedException();
+            }
+
+            EndInitAction();
+        }
+    }
+
+    private class CustomOnQueryFinishedDataSourceProvider : DataSourceProvider
+    {
+        public new void OnQueryFinished(object newData) => base.OnQueryFinished(newData);
+
+        public Action<object, Exception, DispatcherOperationCallback, object>? OnQueryFinishedAction { get; set; }
+
+        protected override void OnQueryFinished(object newData, Exception error, DispatcherOperationCallback completionWork, object callbackArguments)
+        {
+            if (OnQueryFinishedAction is null)
+            {
+                throw new NotImplementedException();
+            }
+
+            OnQueryFinishedAction(newData, error, completionWork, callbackArguments);
+        }
+    }
+
+    private class SubDataSourceProvider : DataSourceProvider
+    {
+        public SubDataSourceProvider() : base()
+        {
+        }
+
+        public new event PropertyChangedEventHandler PropertyChanged
+        {
+            add => base.PropertyChanged += value;
+            remove => base.PropertyChanged -= value;
+        }
+
+        public new Dispatcher? Dispatcher
+        {
+            get => base.Dispatcher;
+            set => base.Dispatcher = value;
+        }
+
+        public new bool IsRefreshDeferred => base.IsRefreshDeferred;
+
+        public new void BeginInit() => base.BeginInit();
+
+        public new void BeginQuery() => base.BeginQuery();
+
+        public new void EndInit() => base.EndInit();
+
+        public new void OnPropertyChanged(PropertyChangedEventArgs e) => base.OnPropertyChanged(e);
+
+        public new void OnQueryFinished(object newData) => base.OnQueryFinished(newData);
+
+        public new void OnQueryFinished(object newData, Exception error, DispatcherOperationCallback completionWork, object callbackArguments) => base.OnQueryFinished(newData, error, completionWork, callbackArguments);
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/DependencyObjectTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/DependencyObjectTests.cs
new file mode 100644
index 00000000000..c22e2ae48e5
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/DependencyObjectTests.cs
@@ -0,0 +1,3018 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections;
+using System.ComponentModel;
+using System.Reflection;
+using System.Windows.Threading;
+
+namespace System.Windows.Tests;
+
+public class DependencyObjectTests
+{
+    [Fact]
+    public void Ctor_Default()
+    {
+        var obj = new DependencyObject();
+        Assert.NotNull(obj.DependencyObjectType);
+        Assert.Same(obj.DependencyObjectType, obj.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(DependencyObject)), obj.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, obj.Dispatcher);
+        Assert.False(obj.IsSealed);
+    }
+
+    [Fact]
+    public void DependencyObjectType_Get_ReturnsExpected()
+    {
+        var obj = new DependencyObject();
+        Assert.NotNull(obj.DependencyObjectType);
+        Assert.Same(obj.DependencyObjectType, obj.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(DependencyObject)), obj.DependencyObjectType);
+    }
+
+    [Fact]
+    public void DependencyObjectType_GetOnDifferentThread_ReturnsExpected()
+    {
+        var obj = new DependencyObject();
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.NotNull(obj.DependencyObjectType);
+            Assert.Same(obj.DependencyObjectType, obj.DependencyObjectType);
+            Assert.Same(DependencyObjectType.FromSystemType(typeof(DependencyObject)), obj.DependencyObjectType);
+        });
+    }
+    
+    [Fact]
+    public void Dispatcher_Get_ReturnsExpected()
+    {
+        var obj = new DependencyObject();
+        Assert.Same(Dispatcher.CurrentDispatcher, obj.Dispatcher);
+    }
+
+    [Fact]
+    public void Dispatcher_GetOnDifferentThread_ReturnsExpected()
+    {
+        var obj = new DependencyObject();
+        Dispatcher expected = Dispatcher.CurrentDispatcher;
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Same(expected, obj.Dispatcher);
+        });
+    }
+
+    [Fact]
+    public void IsSealed_Get_ReturnsFalse()
+    {
+        var obj = new DependencyObject();
+        Assert.False(obj.IsSealed);
+    }
+
+    [Fact]
+    public void IsSealed_GetOnDifferentThread_ReturnsFalse()
+    {
+        var obj = new DependencyObject();
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.False(obj.IsSealed);
+        });
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyValueType_GetValueReturnsExpected()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject));
+        var obj = new DependencyObject();
+
+        // Clear default.
+        obj.ClearValue(property);
+        Assert.False((bool)obj.GetValue(property));
+
+        // Set custom.
+        obj.SetValue(property, true);
+        Assert.True((bool)obj.GetValue(property));
+
+        // Clear custom.
+        obj.ClearValue(property);
+        Assert.False((bool)obj.GetValue(property));
+
+        // Clear again.
+        obj.ClearValue(property);
+        Assert.False((bool)obj.GetValue(property));
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyNullable_GetValueReturnsExpected()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool?), typeof(DependencyObject));
+        var obj = new DependencyObject();
+
+        // Clear default.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+
+        // Set custom.
+        obj.SetValue(property, true);
+        Assert.True((bool)obj.GetValue(property));
+
+        // Clear custom.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+
+        // Clear again.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyReferenceType_GetValueReturnsExpected()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+
+        // Clear default.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+
+        // Set custom.
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Clear custom.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+
+        // Clear again.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyObject_GetValueReturnsExpected()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(DependencyObject));
+        var obj = new DependencyObject();
+
+        // Clear default.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+
+        // Set custom.
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Clear custom.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+
+        // Clear again.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyCustomDefaultValue_GetValueReturnsExpected()
+    {
+        var obj = new DependencyObject();
+        var typeMetadata = new PropertyMetadata("default");
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+
+        // Clear default.
+        obj.ClearValue(property);
+        Assert.Equal("default", obj.GetValue(property));
+
+        // Set custom.
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Clear custom.
+        obj.ClearValue(property);
+        Assert.Equal("default", obj.GetValue(property));
+
+        // Clear again.
+        obj.ClearValue(property);
+        Assert.Equal("default", obj.GetValue(property));
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyCustomPropertyChangedCallback_Success()
+    {
+        var obj = new DependencyObject();
+
+        int changedCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedOldValue = null;
+        object? expectedNewValue = null;
+        var typeMetadata = new PropertyMetadata(null, (d, e) =>
+        {
+            Assert.Same(obj, d);
+            Assert.Same(expectedProperty, e.Property);
+            Assert.Same(expectedOldValue, e.OldValue);
+            Assert.Same(expectedNewValue, e.NewValue);
+            Assert.Equal(expectedNewValue, obj.GetValue(e.Property));
+            changedCallCount++;
+        });
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        expectedProperty = property;
+
+        // Clear default.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(0, changedCallCount);
+
+        // Set custom.
+        expectedNewValue = "value";
+        expectedOldValue = null;
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+
+        // Clear custom.
+        expectedNewValue = null;
+        expectedOldValue = "value";
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+
+        // Clear again.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyCustomCoerceValueCallback_Success()
+    {
+        var obj = new DependencyObject();
+
+        int coerceValueCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedNewValue = null;
+        var typeMetadata = new PropertyMetadata(
+            null,
+            null,
+            (d, baseValue) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedNewValue, baseValue);
+                coerceValueCallCount++;
+                return baseValue;
+            });
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        expectedProperty = property;
+
+        // Clear default.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(0, coerceValueCallCount);
+
+        // Set custom.
+        expectedNewValue = "value";
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Clear custom.
+        expectedNewValue = null;
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Clear again.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallCount);
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyCustomPropertyChangedAndCoerceValueCallback_Success()
+    {
+        var obj = new DependencyObject();
+
+        int coerceValueCallCount = 0;
+        int changedCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedOldValue = null;
+        object? expectedNewValue = null;
+        var typeMetadata = new PropertyMetadata(
+            null,
+            (d, e) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedProperty, e.Property);
+                Assert.Same(expectedOldValue, e.OldValue);
+                Assert.Same(expectedNewValue, e.NewValue);
+                Assert.Equal(expectedNewValue, obj.GetValue(e.Property));
+                changedCallCount++;
+            },
+            (d, baseValue) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedNewValue, baseValue);
+                coerceValueCallCount++;
+                return baseValue;
+            });
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        expectedProperty = property;
+
+        // Clear default.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(0, changedCallCount);
+        Assert.Equal(0, coerceValueCallCount);
+
+        // Set custom.
+        expectedNewValue = "value";
+        expectedOldValue = null;
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Clear custom.
+        expectedNewValue = null;
+        expectedOldValue = "value";
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Clear again.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+        Assert.Equal(1, coerceValueCallCount);
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyCustomOnPropertyChanged_CallsOnPropertyChanged()
+    {
+        var obj = new CustomDependencyObject();
+
+        int onPropertyChangedCallCount = 0;
+        int changedCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedOldValue = null;
+        object? expectedNewValue = null;
+        obj.OnPropertyChangedAction = (e) =>
+        {
+            Assert.True(changedCallCount > onPropertyChangedCallCount);
+            Assert.Same(expectedProperty, e.Property);
+            Assert.Same(expectedOldValue, e.OldValue);
+            Assert.Same(expectedNewValue, e.NewValue);
+            Assert.Equal(expectedNewValue, obj.GetValue(e.Property));
+            onPropertyChangedCallCount++;
+        };
+        var typeMetadata = new PropertyMetadata(null, (d, e) =>
+        {
+            Assert.Equal(changedCallCount, onPropertyChangedCallCount);
+            Assert.Same(obj, d);
+            Assert.Same(expectedProperty, e.Property);
+            Assert.Same(expectedOldValue, e.OldValue);
+            Assert.Same(expectedNewValue, e.NewValue);
+            Assert.Equal(expectedNewValue, obj.GetValue(e.Property));
+            changedCallCount++;
+        });
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        expectedProperty = property;
+
+        // Clear default.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(0, changedCallCount);
+        Assert.Equal(0, onPropertyChangedCallCount);
+
+        // Set custom.
+        expectedNewValue = "value";
+        expectedOldValue = null;
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+        Assert.Equal(1, onPropertyChangedCallCount);
+
+        // Clear custom.
+        expectedNewValue = null;
+        expectedOldValue = "value";
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+        Assert.Equal(2, onPropertyChangedCallCount);
+
+        // Clear again.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+        Assert.Equal(2, onPropertyChangedCallCount);
+    }
+
+    [Fact]
+    public void ClearValue_DependencyPropertyNullDp_ThrowsArgumentNullException()
+    {
+        var obj = new DependencyObject();
+        Assert.Throws<ArgumentNullException>("dp", () => obj.ClearValue((DependencyProperty)null!));
+    }
+
+    [Fact]
+    public void ClearValue_DependencyPropertyReadOnly_ThrowsInvalidOperationException()
+    {
+        var obj = new DependencyObject();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+        Assert.Throws<InvalidOperationException>(() => obj.ClearValue(property));
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyOnDifferentThread_ThrowsInvalidOperationException()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject));
+        var obj = new DependencyObject();
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => obj.ClearValue(property));
+        });
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyKeyValueType_GetValueReturnsExpected()
+    {
+        var obj = new DependencyObject();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+
+        // Clear default.
+        obj.ClearValue(key);
+        Assert.False((bool)obj.GetValue(property));
+
+        // Set custom.
+        obj.SetValue(key, true);
+        Assert.True((bool)obj.GetValue(property));
+
+        // Clear custom.
+        obj.ClearValue(key);
+        Assert.False((bool)obj.GetValue(property));
+
+        // Clear again.
+        obj.ClearValue(key);
+        Assert.False((bool)obj.GetValue(property));
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyKeyNullable_GetValueReturnsExpected()
+    {
+        var obj = new DependencyObject();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool?), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+
+        // Clear default.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+
+        // Set custom.
+        obj.SetValue(key, true);
+        Assert.True((bool)obj.GetValue(property));
+
+        // Clear custom.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+
+        // Clear again.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyKeyReferenceType_GetValueReturnsExpected()
+    {
+        var obj = new DependencyObject();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+
+        // Clear default.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+
+        // Set custom.
+        obj.SetValue(key, "value");
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Clear custom.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+
+        // Clear again.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyKeyObject_GetValueReturnsExpected()
+    {
+        var obj = new DependencyObject();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+
+        // Clear default.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+
+        // Set custom.
+        obj.SetValue(key, "value");
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Clear custom.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+
+        // Clear again.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyKeyCustomDefaultValue_GetValueReturnsExpected()
+    {
+        var obj = new DependencyObject();
+        var typeMetadata = new PropertyMetadata("default");
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        DependencyProperty property = key.DependencyProperty;
+
+        // Clear default.
+        obj.ClearValue(key);
+        Assert.Equal("default", obj.GetValue(property));
+
+        // Set custom.
+        obj.SetValue(key, "value");
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Clear custom.
+        obj.ClearValue(key);
+        Assert.Equal("default", obj.GetValue(property));
+
+        // Clear again.
+        obj.ClearValue(key);
+        Assert.Equal("default", obj.GetValue(property));
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyKeyCustomPropertyChangedCallback_Success()
+    {
+        var obj = new DependencyObject();
+
+        int changedCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedOldValue = null;
+        object? expectedNewValue = null;
+        var typeMetadata = new PropertyMetadata(null, (d, e) =>
+        {
+            Assert.Same(obj, d);
+            Assert.Same(expectedProperty, e.Property);
+            Assert.Same(expectedOldValue, e.OldValue);
+            Assert.Same(expectedNewValue, e.NewValue);
+            Assert.Equal(expectedNewValue, obj.GetValue(e.Property));
+            changedCallCount++;
+        });
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        DependencyProperty property = key.DependencyProperty;
+        expectedProperty = property;
+
+        // Clear default.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(0, changedCallCount);
+
+        // Set custom.
+        expectedNewValue = "value";
+        expectedOldValue = null;
+        obj.SetValue(key, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+
+        // Clear custom.
+        expectedNewValue = null;
+        expectedOldValue = "value";
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+
+        // Clear again.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyKeyCustomCoerceValueCallback_Success()
+    {
+        var obj = new DependencyObject();
+
+        int coerceValueCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedNewValue = null;
+        var typeMetadata = new PropertyMetadata(
+            null,
+            null,
+            (d, baseValue) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedNewValue, baseValue);
+                coerceValueCallCount++;
+                return baseValue;
+            });
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        DependencyProperty property = key.DependencyProperty;
+        expectedProperty = property;
+
+        // Clear default.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(0, coerceValueCallCount);
+
+        // Set custom.
+        expectedNewValue = "value";
+        obj.SetValue(key, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Clear custom.
+        expectedNewValue = null;
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Clear again.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallCount);
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyKeyCustomPropertyChangedAndCoerceValueCallback_Success()
+    {
+        var obj = new DependencyObject();
+
+        int coerceValueCallCount = 0;
+        int changedCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedOldValue = null;
+        object? expectedNewValue = null;
+        var typeMetadata = new PropertyMetadata(
+            null,
+            (d, e) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedProperty, e.Property);
+                Assert.Same(expectedOldValue, e.OldValue);
+                Assert.Same(expectedNewValue, e.NewValue);
+                Assert.Equal(expectedNewValue, obj.GetValue(e.Property));
+                changedCallCount++;
+            },
+            (d, baseValue) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedNewValue, baseValue);
+                coerceValueCallCount++;
+                return baseValue;
+            });
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        DependencyProperty property = key.DependencyProperty;
+        expectedProperty = property;
+
+        // Clear default.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(0, changedCallCount);
+        Assert.Equal(0, coerceValueCallCount);
+
+        // Set custom.
+        expectedNewValue = "value";
+        expectedOldValue = null;
+        obj.SetValue(key, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Clear custom.
+        expectedNewValue = null;
+        expectedOldValue = "value";
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Clear again.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+        Assert.Equal(1, coerceValueCallCount);
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyKeyCustomOnPropertyChanged_CallsOnPropertyChanged()
+    {
+        var obj = new CustomDependencyObject();
+
+        int onPropertyChangedCallCount = 0;
+        int changedCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedOldValue = null;
+        object? expectedNewValue = null;
+        obj.OnPropertyChangedAction = (e) =>
+        {
+            Assert.True(changedCallCount > onPropertyChangedCallCount);
+            Assert.Same(expectedProperty, e.Property);
+            Assert.Same(expectedOldValue, e.OldValue);
+            Assert.Same(expectedNewValue, e.NewValue);
+            Assert.Equal(expectedNewValue, obj.GetValue(e.Property));
+            onPropertyChangedCallCount++;
+        };
+        var typeMetadata = new PropertyMetadata(null, (d, e) =>
+        {
+            Assert.Equal(changedCallCount, onPropertyChangedCallCount);
+            Assert.Same(obj, d);
+            Assert.Same(expectedProperty, e.Property);
+            Assert.Same(expectedOldValue, e.OldValue);
+            Assert.Same(expectedNewValue, e.NewValue);
+            Assert.Equal(expectedNewValue, obj.GetValue(e.Property));
+            changedCallCount++;
+        });
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        DependencyProperty property = key.DependencyProperty;
+        expectedProperty = property;
+
+        // Clear default.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(0, changedCallCount);
+        Assert.Equal(0, onPropertyChangedCallCount);
+
+        // Set custom.
+        expectedNewValue = "value";
+        expectedOldValue = null;
+        obj.SetValue(key, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+        Assert.Equal(1, onPropertyChangedCallCount);
+
+        // Clear custom.
+        expectedNewValue = null;
+        expectedOldValue = "value";
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+        Assert.Equal(2, onPropertyChangedCallCount);
+
+        // Clear again.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+        Assert.Equal(2, onPropertyChangedCallCount);
+    }
+
+    [Fact]
+    public void ClearValue_DependencyPropertyNullKey_ThrowsArgumentNullException()
+    {
+        var obj = new DependencyObject();
+        Assert.Throws<ArgumentNullException>("key", () => obj.ClearValue((DependencyPropertyKey)null!));
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyKeyOnDifferentThread_ThrowsInvalidOperationException()
+    {
+        var obj = new DependencyObject();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => obj.ClearValue(key));
+        });
+    }
+
+    [Fact]
+    public void CoerceValue_InvokeValueType_GetValueReturnsExpected()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject));
+        var obj = new DependencyObject();
+
+        // Coerce default.
+        obj.CoerceValue(property);
+        Assert.False((bool)obj.GetValue(property));
+
+        // Set true.
+        obj.SetValue(property, true);
+        Assert.True((bool)obj.GetValue(property));
+
+        // Coerce true.
+        obj.CoerceValue(property);
+        Assert.True((bool)obj.GetValue(property));
+
+        // Coerce again.
+        obj.CoerceValue(property);
+        Assert.True((bool)obj.GetValue(property));
+    }
+
+    [Fact]
+    public void CoerceValue_InvokeNullable_GetValueReturnsExpected()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool?), typeof(DependencyObject));
+        var obj = new DependencyObject();
+
+        // Coerce default.
+        obj.CoerceValue(property);
+        Assert.Null(obj.GetValue(property));
+
+        // Set custom.
+        obj.SetValue(property, true);
+        Assert.True((bool)obj.GetValue(property));
+
+        // Coerce custom.
+        obj.CoerceValue(property);
+        Assert.True((bool)obj.GetValue(property));
+
+        // Coerce again.
+        obj.CoerceValue(property);
+        Assert.True((bool)obj.GetValue(property));
+    }
+
+    [Fact]
+    public void CoerceValue_InvokeReferenceType_GetValueReturnsExpected()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+
+        // Coerce default.
+        obj.CoerceValue(property);
+        Assert.Null(obj.GetValue(property));
+
+        // Set custom.
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Coerce custom.
+        obj.CoerceValue(property);
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Coerce again.
+        obj.CoerceValue(property);
+        Assert.Equal("value", obj.GetValue(property));
+    }
+
+    [Fact]
+    public void CoerceValue_InvokeObject_GetValueReturnsExpected()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(DependencyObject));
+        var obj = new DependencyObject();
+
+        // Coerce default.
+        obj.CoerceValue(property);
+        Assert.Null(obj.GetValue(property));
+
+        // Set custom.
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Coerce custom.
+        obj.CoerceValue(property);
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Coerce again.
+        obj.CoerceValue(property);
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Set different.
+        obj.SetValue(property, 1);
+        Assert.Equal(1, obj.GetValue(property));
+
+        // Coerce custom.
+        obj.CoerceValue(property);
+        Assert.Equal(1, obj.GetValue(property));
+
+        // Coerce again.
+        obj.CoerceValue(property);
+        Assert.Equal(1, obj.GetValue(property));
+
+        // Set null.
+        obj.SetValue(property, null);
+        Assert.Null(obj.GetValue(property));
+
+        // Coerce custom.
+        obj.CoerceValue(property);
+        Assert.Null(obj.GetValue(property));
+
+        // Coerce again.
+        obj.CoerceValue(property);
+        Assert.Null(obj.GetValue(property));
+    }
+
+    [Fact]
+    public void CoerceValue_InvokeCustomPropertyChangeCallback_Success()
+    {
+        var obj = new DependencyObject();
+
+        int changedCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedOldValue = null;
+        object? expectedNewValue = null;
+        var typeMetadata = new PropertyMetadata(
+            null,
+            (d, e) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedProperty, e.Property);
+                Assert.Same(expectedOldValue, e.OldValue);
+                Assert.Same(expectedNewValue, e.NewValue);
+                Assert.Equal(expectedNewValue, obj.GetValue(e.Property));
+                changedCallCount++;
+            });
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        expectedProperty = property;
+
+        // Coerce default.
+        obj.CoerceValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(0, changedCallCount);
+
+        // Set custom.
+        expectedNewValue = "value";
+        expectedOldValue = null;
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+
+        // Coerce custom.
+        obj.CoerceValue(property);
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+
+        // Coerce again.
+        obj.CoerceValue(property);
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+    }
+
+    [Fact]
+    public void CoerceValue_InvokeCustomCoerceValueCallback_Success()
+    {
+        var obj = new DependencyObject();
+
+        int coerceValueCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedNewValue = null;
+        var typeMetadata = new PropertyMetadata(
+            null,
+            null,
+            (d, baseValue) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedNewValue, baseValue);
+                coerceValueCallCount++;
+                return baseValue;
+            }
+        );
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        expectedProperty = property;
+
+        // Coerce default.
+        obj.CoerceValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Set custom.
+        expectedNewValue = "value";
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(2, coerceValueCallCount);
+
+        // Coerce custom.
+        obj.CoerceValue(property);
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(3, coerceValueCallCount);
+
+        // Coerce again.
+        obj.CoerceValue(property);
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(4, coerceValueCallCount);
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("customCoercedValue")]
+    public void CoerceValue_InvokeCustomCoerceValueCallbackReturnsCustom_Success(object? customCoercedValue)
+    {
+        var obj = new DependencyObject();
+
+        int coerceValueCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedNewValue = null;
+        object? newBaseValue = "coercedValue";
+        var typeMetadata = new PropertyMetadata(
+            null,
+            null,
+            (d, baseValue) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedNewValue, baseValue);
+                coerceValueCallCount++;
+                return newBaseValue;
+            }
+        );
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name + customCoercedValue?.GetType().Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        expectedProperty = property;
+
+        // Coerce default.
+        obj.CoerceValue(property);
+        Assert.Equal("coercedValue", obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Set custom.
+        expectedNewValue = "value";
+        obj.SetValue(property, "value");
+        Assert.Equal("coercedValue", obj.GetValue(property));
+        Assert.Equal(2, coerceValueCallCount);
+
+        // Coerce custom.
+        newBaseValue = customCoercedValue;
+        obj.CoerceValue(property);
+        Assert.Equal(customCoercedValue, obj.GetValue(property));
+        Assert.Equal(3, coerceValueCallCount);
+
+        // Coerce again.
+        obj.CoerceValue(property);
+        Assert.Equal(customCoercedValue, obj.GetValue(property));
+        Assert.Equal(4, coerceValueCallCount);
+    }
+
+    [Fact]
+    public void CoerceValue_InvokeCustomCoerceValueCallbackReturnsUnset_Success()
+    {
+        var obj = new DependencyObject();
+
+        int coerceValueCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedBaseValue = null;
+        object? newBaseValue = null;
+        var typeMetadata = new PropertyMetadata(
+            null,
+            null,
+            (d, baseValue) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedBaseValue, baseValue);
+                coerceValueCallCount++;
+                return newBaseValue;
+            }
+        );
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        expectedProperty = property;
+
+        // Set custom.
+        expectedBaseValue = "value";
+        newBaseValue = "coercedValue";
+        obj.SetValue(property, "value");
+        Assert.Equal("coercedValue", obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Coerce.
+        expectedBaseValue = "value";
+        newBaseValue = DependencyProperty.UnsetValue;
+        obj.CoerceValue(property);
+        Assert.Equal("coercedValue", obj.GetValue(property));
+        Assert.Equal(2, coerceValueCallCount);
+    }
+
+    [Fact]
+    public void CoerceValue_InvokeChangeAndCoerceValueCallback_Success()
+    {
+        var obj = new DependencyObject();
+
+        int changedCallCount = 0;
+        int coerceValueCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedOldValue = null;
+        object? expectedNewValue = null;
+        var typeMetadata = new PropertyMetadata(
+            null,
+            (d, e) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedProperty, e.Property);
+                Assert.Same(expectedOldValue, e.OldValue);
+                Assert.Same(expectedNewValue, e.NewValue);
+                Assert.Equal(expectedNewValue, obj.GetValue(e.Property));
+                changedCallCount++;
+            },
+            (d, baseValue) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedNewValue, baseValue);
+                coerceValueCallCount++;
+                return baseValue;
+            }
+        );
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        expectedProperty = property;
+
+        // Coerce default.
+        obj.CoerceValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(0, changedCallCount);
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Set custom.
+        expectedNewValue = "value";
+        expectedOldValue = null;
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+        Assert.Equal(2, coerceValueCallCount);
+
+        // Coerce custom.
+        obj.CoerceValue(property);
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+        Assert.Equal(3, coerceValueCallCount);
+
+        // Coerce again.
+        obj.CoerceValue(property);
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+        Assert.Equal(4, coerceValueCallCount);
+    }
+
+    [Fact]
+    public void CoerceValue_InvokeReadOnly_GetValueReturnsExpected()
+    {
+        var obj = new DependencyObject();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+
+        // Coerce default.
+        obj.CoerceValue(property);
+        Assert.False((bool)obj.GetValue(property));
+
+        // Coerce again.
+        obj.CoerceValue(property);
+        Assert.False((bool)obj.GetValue(property));
+    }
+
+    [Fact]
+    public void CoerceValue_DependencyPropertyNullDp_ThrowsArgumentNullException()
+    {
+        var obj = new DependencyObject();
+        // TODO: this should throw ArgumentNullException
+        //Assert.Throws<ArgumentNullException>("dp", () => obj.CoerceValue(null!));
+        Assert.Throws<NullReferenceException>(() => obj.CoerceValue(null!));
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("value")]
+    public void CoerceValue_InvalidResultDefault_ThrowsArgumentException(object? invalidValue)
+    {
+        var obj = new DependencyObject();
+
+        int coerceValueCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedNewValue = null;
+        var typeMetadata = new PropertyMetadata(
+            0,
+            null,
+            (d, baseValue) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Equal(expectedNewValue, baseValue);
+                coerceValueCallCount++;
+                return invalidValue;
+            }
+        );
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name + invalidValue?.GetType().Name, typeof(int), typeof(DependencyObject), typeMetadata);
+        expectedProperty = property;
+
+        // Coerce default.
+        expectedNewValue = 0;
+        Assert.Throws<ArgumentException>(() => obj.CoerceValue(property));
+        Assert.Equal(0, obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallCount);
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("value")]
+    public void CoerceValue_InvalidResultCustom_ThrowsArgumentException(object? invalidValue)
+    {
+        var obj = new DependencyObject();
+
+        int coerceValueCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedNewValue = null;
+        object? newBaseValue = 1;
+        var typeMetadata = new PropertyMetadata(
+            0,
+            null,
+            (d, baseValue) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Equal(expectedNewValue, baseValue);
+                coerceValueCallCount++;
+                return newBaseValue;
+            }
+        );
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name + invalidValue?.GetType().Name, typeof(int), typeof(DependencyObject), typeMetadata);
+        expectedProperty = property;
+
+        // Set custom.
+        expectedNewValue = 2;
+        newBaseValue = 2;
+        obj.SetValue(property, 2);
+        Assert.Equal(2, obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Coerce custom.
+        newBaseValue = invalidValue;
+        Assert.Throws<ArgumentException>(() => obj.CoerceValue(property));
+        Assert.Equal(2, coerceValueCallCount);
+    }
+
+    [Fact]
+    public void CoerceValue_InvokeOnDifferentThread_ThrowsInvalidOperationException()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => obj.CoerceValue(property));
+        });
+    }
+
+    [Fact]
+    public void Equals_Invoke_ReturnsExpected()
+    {
+        var obj = new DependencyObject();
+        Assert.True(obj.Equals(obj));
+        Assert.False(obj.Equals(new DependencyObject()));
+        Assert.False(obj.Equals(null));
+    }
+
+    [Fact]
+    public void GetHashCode_Invoke_ReturnsEqual()
+    {
+        var obj = new DependencyObject();
+        Assert.NotEqual(0, obj.GetHashCode());
+        Assert.Equal(obj.GetHashCode(), obj.GetHashCode());
+    }
+
+    [Fact]
+    public void GetLocalValueEnumerator_InvokeNoProperties_ReturnsExpected()
+    {
+        var obj = new DependencyObject();
+        LocalValueEnumerator enumerator = obj.GetLocalValueEnumerator();
+        for (int i = 0; i < 2; i++)
+        {
+            Assert.Throws<InvalidOperationException>(() => enumerator.Current);
+            Assert.Throws<InvalidOperationException>(() => ((IEnumerator)enumerator).Current);
+
+            // Move.
+            Assert.False(enumerator.MoveNext());
+            Assert.Throws<InvalidOperationException>(() => enumerator.Current);
+            Assert.Throws<InvalidOperationException>(() => ((IEnumerator)enumerator).Current);
+
+            // Move end.
+            Assert.False(enumerator.MoveNext());
+            Assert.Throws<InvalidOperationException>(() => enumerator.Current);
+            Assert.Throws<InvalidOperationException>(() => ((IEnumerator)enumerator).Current);
+
+            // Move again.
+            Assert.False(enumerator.MoveNext());
+            Assert.Throws<InvalidOperationException>(() => enumerator.Current);
+            Assert.Throws<InvalidOperationException>(() => ((IEnumerator)enumerator).Current);
+
+            // Reset.
+            enumerator.Reset();
+        }
+    }
+
+    [Fact]
+    public void GetLocalValueEnumerator_InvokeWithProperties_ReturnsExpected()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+        obj.SetValue(property, "value");
+
+        LocalValueEnumerator enumerator = obj.GetLocalValueEnumerator();
+        for (int i = 0; i < 2; i++)
+        {
+            Assert.Throws<InvalidOperationException>(() => enumerator.Current);
+            Assert.Throws<InvalidOperationException>(() => ((IEnumerator)enumerator).Current);
+
+            // Move.
+            Assert.True(enumerator.MoveNext());
+            LocalValueEntry entry = enumerator.Current;
+            Assert.Same(property, entry.Property);
+            Assert.Equal("value", entry.Value);
+            
+            entry = Assert.IsType<LocalValueEntry>(((IEnumerator)enumerator).Current);
+            Assert.Same(property, entry.Property);
+            Assert.Equal("value", entry.Value);
+
+            // Move end.
+            Assert.False(enumerator.MoveNext());
+            Assert.Throws<InvalidOperationException>(() => enumerator.Current);
+            Assert.Throws<InvalidOperationException>(() => ((IEnumerator)enumerator).Current);
+
+            // Move again.
+            Assert.False(enumerator.MoveNext());
+            Assert.Throws<InvalidOperationException>(() => enumerator.Current);
+            Assert.Throws<InvalidOperationException>(() => ((IEnumerator)enumerator).Current);
+
+            // Reset.
+            enumerator.Reset();
+        }
+    }
+    
+
+    [Fact]
+    public void GetLocalValueEnumerator_InvokeWithPropertiesCoerced_ReturnsExpected()
+    {
+        var metadata = new PropertyMetadata(
+            null,
+            null,
+            (d, baseValue) => "coercedValue");
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+        obj.SetValue(property, "value");
+
+        LocalValueEnumerator enumerator = obj.GetLocalValueEnumerator();
+        for (int i = 0; i < 2; i++)
+        {
+            Assert.Throws<InvalidOperationException>(() => enumerator.Current);
+            Assert.Throws<InvalidOperationException>(() => ((IEnumerator)enumerator).Current);
+
+            // Move.
+            Assert.True(enumerator.MoveNext());
+            LocalValueEntry entry = enumerator.Current;
+            Assert.Same(property, entry.Property);
+            Assert.Equal("value", entry.Value);
+            
+            entry = Assert.IsType<LocalValueEntry>(((IEnumerator)enumerator).Current);
+            Assert.Same(property, entry.Property);
+            Assert.Equal("value", entry.Value);
+
+            // Move end.
+            Assert.False(enumerator.MoveNext());
+            Assert.Throws<InvalidOperationException>(() => enumerator.Current);
+            Assert.Throws<InvalidOperationException>(() => ((IEnumerator)enumerator).Current);
+
+            // Move again.
+            Assert.False(enumerator.MoveNext());
+            Assert.Throws<InvalidOperationException>(() => enumerator.Current);
+            Assert.Throws<InvalidOperationException>(() => ((IEnumerator)enumerator).Current);
+
+            // Reset.
+            enumerator.Reset();
+        }
+    }
+
+    [Fact]
+    public void GetLocalValueEnumerator_InvokeOnDifferentThread_ThrowsInvalidOperationException()
+    {
+        var obj = new DependencyObject();
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => obj.GetLocalValueEnumerator());
+        });
+    }
+
+    [Fact]
+    public void GetValue_InvokeValueType_ReturnsExpected()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject));
+        var obj = new DependencyObject();
+
+        Assert.False((bool)obj.GetValue(property));
+
+        // Call again to test caching.
+        Assert.False((bool)obj.GetValue(property));
+    }
+
+    [Fact]
+    public void GetValue_InvokeNullableType_ReturnsExpected()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool?), typeof(DependencyObject));
+        var obj = new DependencyObject();
+
+        Assert.Null(obj.GetValue(property));
+
+        // Call again to test caching.
+        Assert.Null(obj.GetValue(property));
+    }
+
+    [Fact]
+    public void GetValue_InvokeReferenceType_ReturnsExpected()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+
+        Assert.Null(obj.GetValue(property));
+
+        // Call again to test caching.
+        Assert.Null(obj.GetValue(property));
+    }
+
+    [Fact]
+    public void GetValue_InvokeObjectType_ReturnsExpected()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(DependencyObject));
+        var obj = new DependencyObject();
+
+        Assert.Null(obj.GetValue(property));
+
+        // Call again to test caching.
+        Assert.Null(obj.GetValue(property));
+    }
+
+    [Fact]
+    public void GetValue_InvokeDefaultValue_ReturnsExpected()
+    {
+        var metadata = new PropertyMetadata("value");
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), metadata);
+        var obj = new DependencyObject();
+
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Call again to test caching.
+        Assert.Equal("value", obj.GetValue(property));
+    }
+
+    [Fact]
+    public void GetValue_InvokeSetValue_ReturnsExpected()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+        obj.SetValue(property, "value");
+
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Call again to test caching.
+        Assert.Equal("value", obj.GetValue(property));
+    }
+
+    [Fact]
+    public void GetValue_InvokeSetValueCoerced_ReturnsExpected()
+    {
+        object coerceResult = "coercedValue";
+        int coerceValueCallbackCallCount = 0;
+        var metadata = new PropertyMetadata(
+            null,
+            null,
+            (d, baseValue) =>
+            {
+                coerceValueCallbackCallCount++;
+                return coerceResult;
+            });
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), metadata);
+        var obj = new DependencyObject();
+        obj.SetValue(property, "value");
+        Assert.Equal(1, coerceValueCallbackCallCount);
+
+        Assert.Equal("coercedValue", obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallbackCallCount);
+
+        // Call again to test caching.
+        Assert.Equal("coercedValue", obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallbackCallCount);
+
+        // Change coerce result.
+        coerceResult = "coercedValue2";
+        Assert.Equal("coercedValue", obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallbackCallCount);
+
+        // Set to unset.
+        coerceResult = DependencyProperty.UnsetValue;
+        obj.SetValue(property, "value2");
+        Assert.Equal("coercedValue", obj.GetValue(property));
+        Assert.Equal(2, coerceValueCallbackCallCount);
+    }
+
+    [Fact]
+    public void GetValue_InvokeClearedValue_ReturnsExpected()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+        obj.SetValue(property, "value");
+        obj.ClearValue(property);
+
+        Assert.Null(obj.GetValue(property));
+
+        // Call again to test caching.
+        Assert.Null(obj.GetValue(property));
+    }
+
+    [Fact]
+    public void GetValue_InvokeCustomDefaultValue_ReturnsExpected()
+    {
+        var obj = new DependencyObject();
+        var typeMetadata = new PropertyMetadata("value");
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Call again to test caching.
+        Assert.Equal("value", obj.GetValue(property));
+    }
+
+    [Fact]
+    public void GetValue_InvokeReadOnlyProperty_ReturnsExpected()
+    {
+        var obj = new DependencyObject();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+
+        Assert.False((bool)obj.GetValue(property));
+
+        // Call again to test caching.
+        Assert.False((bool)obj.GetValue(property));
+    }
+
+    [Fact]
+    public void GetValue_InvokeReadOnlyPropertySet_ReturnsExpected()
+    {
+        var obj = new DependencyObject();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+        obj.SetValue(key, "value");
+
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Call again to test caching.
+        Assert.Equal("value", obj.GetValue(property));
+    }
+
+    [Fact]
+    public void GetValue_InvokeReadOnlyPropertyUIElementIsVisible_ReturnsExpected()
+    {
+        // This has a special internal getter - GetReadOnlyValueCallback.
+        var obj = new DependencyObject();
+        DependencyProperty property = UIElement.IsVisibleProperty;
+
+        Assert.False((bool)obj.GetValue(property));
+
+        // Call again to test caching.
+        Assert.False((bool)obj.GetValue(property));
+    }
+
+    [Fact]
+    public void GetValue_InvokeReadOnlyPropertyUIElement3DIsVisible_ReturnsExpected()
+    {
+        // This has a special internal getter - GetReadOnlyValueCallback.
+        var obj = new DependencyObject();
+        DependencyProperty property = UIElement3D.IsVisibleProperty;
+
+        Assert.False((bool)obj.GetValue(property));
+
+        // Call again to test caching.
+        Assert.False((bool)obj.GetValue(property));
+    }
+
+    [Fact]
+    public void GetValue_InvokeReadOnlyPropertyFrameworkElementActualWidth_ReturnsExpected()
+    {
+        // This has a special internal getter - GetReadOnlyValueCallback.
+        var obj = new DependencyObject();
+        DependencyProperty property = FrameworkElement.ActualWidthProperty;
+
+        Assert.Equal(0.0, obj.GetValue(property));
+
+        // Call again to test caching.
+        Assert.Equal(0.0, obj.GetValue(property));
+    }
+
+    [Fact]
+    public void GetValue_InvokeReadOnlyPropertyFrameworkElementActualHeight_ReturnsExpected()
+    {
+        // This has a special internal getter - GetReadOnlyValueCallback.
+        var obj = new DependencyObject();
+        DependencyProperty property = FrameworkElement.ActualHeightProperty;
+
+        Assert.Equal(0.0, obj.GetValue(property));
+
+        // Call again to test caching.
+        Assert.Equal(0.0, obj.GetValue(property));
+    }
+
+    [Fact]
+    public void GetValue_NullProperty_ThrowsArgumentNullException()
+    {
+        var obj = new DependencyObject();
+        Assert.Throws<ArgumentNullException>("dp", () => obj.GetValue(null!));
+    }
+
+    [Fact]
+    public void GetValue_InvokeOnDifferentThread_ThrowsInvalidOperationException()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => obj.GetValue(property));
+        });
+    }
+
+    [Fact]
+    public void InvalidateProperty_InvokeNoSuchProperty_Success()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+
+        // Invalidate.
+        obj.InvalidateProperty(property);
+        Assert.Null(obj.GetValue(property));
+
+        // Invalidate again.
+        obj.InvalidateProperty(property);
+        Assert.Null(obj.GetValue(property));
+    }
+
+    [Fact]
+    public void InvalidateProperty_InvokeSetProperty_Success()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+        obj.SetValue(property, "value");
+
+        // Invalidate.
+        obj.InvalidateProperty(property);
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Invalidate again.
+        obj.InvalidateProperty(property);
+        Assert.Equal("value", obj.GetValue(property));
+    }
+
+    [Fact]
+    public void InvalidateProperty_InvokeClearedProperty_Success()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+        obj.SetValue(property, "value");
+        obj.ClearValue(property);
+
+        // Invalidate.
+        obj.InvalidateProperty(property);
+        Assert.Null(obj.GetValue(property));
+
+        // Invalidate again.
+        obj.InvalidateProperty(property);
+        Assert.Null(obj.GetValue(property));
+    }
+
+    [Fact]
+    public void InvalidateProperty_InvokeCoercedProperty_Success()
+    {
+        object coerceResult = "baseValue";
+        int coerceValueCallbackCallCount = 0;
+        var metadata = new PropertyMetadata(
+            null,
+            null,
+            (d, baseValue) =>
+            {
+                coerceValueCallbackCallCount++;
+                return coerceResult;
+            }
+        );
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), metadata);
+        var obj = new DependencyObject();
+        obj.SetValue(property, "value");
+        Assert.Equal(coerceResult, obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallbackCallCount);
+
+        // Change coerce result.
+        coerceResult = "other";
+        Assert.Equal("baseValue", obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallbackCallCount);
+
+        // Invalidate.
+        obj.InvalidateProperty(property);
+        Assert.Equal("other", obj.GetValue(property));
+        Assert.Equal(2, coerceValueCallbackCallCount);
+
+        // Invalidate again.
+        obj.InvalidateProperty(property);
+        Assert.Equal("other", obj.GetValue(property));
+        Assert.Equal(3, coerceValueCallbackCallCount);
+
+        // Set to unset.
+        coerceResult = DependencyProperty.UnsetValue;
+        obj.InvalidateProperty(property);
+        Assert.Equal("other", obj.GetValue(property));
+        Assert.Equal(4, coerceValueCallbackCallCount);
+    }
+
+    [Fact]
+    public void InvalidateProperty_NullDp_ThrowsArgumentNullException()
+    {
+        var obj = new DependencyObject();
+        Assert.Throws<ArgumentNullException>("dp", () => obj.InvalidateProperty(null!));
+    }
+
+    [Fact]
+    public void InvalidateProperty_InvokeOnDifferentThread_ThrowsInvalidOperationException()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => obj.InvalidateProperty(property));
+        });
+    }
+
+    [Fact]
+    public void InvalidateProperty_InvokeCoercedPropertyInvalid_ThrowsArgumentException()
+    {
+        object coerceResult = "baseValue";
+        int coerceValueCallbackCallCount = 0;
+        var metadata = new PropertyMetadata(
+            null,
+            null,
+            (d, baseValue) =>
+            {
+                coerceValueCallbackCallCount++;
+                return coerceResult;
+            }
+        );
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), metadata);
+        var obj = new DependencyObject();
+        obj.SetValue(property, "value");
+        Assert.Equal(coerceResult, obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallbackCallCount);
+
+        // Change coerce result.
+        coerceResult = new object();
+        Assert.Equal("baseValue", obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallbackCallCount);
+
+        // Invalidate.
+        coerceResult = new object();
+        Assert.Throws<ArgumentException>(() => obj.InvalidateProperty(property));
+        Assert.Equal("baseValue", obj.GetValue(property));
+        Assert.Equal(2, coerceValueCallbackCallCount);
+
+        // Invalidate again.
+        Assert.Throws<ArgumentException>(() => obj.InvalidateProperty(property));
+        Assert.Equal("baseValue", obj.GetValue(property));
+        Assert.Equal(3, coerceValueCallbackCallCount);
+    }
+
+    [Fact]
+    public void ReadLocalValue_InvokeValueType_ReturnsExpected()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject));
+        var obj = new DependencyObject();
+
+        Assert.Same(DependencyProperty.UnsetValue, obj.ReadLocalValue(property));
+
+        // Call again to test caching.
+        Assert.Same(DependencyProperty.UnsetValue, obj.ReadLocalValue(property));
+    }
+
+    [Fact]
+    public void ReadLocalValue_InvokeNullableType_ReturnsExpected()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool?), typeof(DependencyObject));
+        var obj = new DependencyObject();
+
+        Assert.Same(DependencyProperty.UnsetValue, obj.ReadLocalValue(property));
+
+        // Call again to test caching.
+        Assert.Same(DependencyProperty.UnsetValue, obj.ReadLocalValue(property));
+    }
+
+    [Fact]
+    public void ReadLocalValue_InvokeReferenceType_ReturnsExpected()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+
+        Assert.Same(DependencyProperty.UnsetValue, obj.ReadLocalValue(property));
+
+        // Call again to test caching.
+        Assert.Same(DependencyProperty.UnsetValue, obj.ReadLocalValue(property));
+    }
+
+    [Fact]
+    public void ReadLocalValue_InvokeObjectType_ReturnsExpected()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(DependencyObject));
+        var obj = new DependencyObject();
+
+        Assert.Same(DependencyProperty.UnsetValue, obj.ReadLocalValue(property));
+
+        // Call again to test caching.
+        Assert.Same(DependencyProperty.UnsetValue, obj.ReadLocalValue(property));
+    }
+
+    [Fact]
+    public void ReadLocalValue_InvokeDefaultValue_ReturnsExpected()
+    {
+        var metadata = new PropertyMetadata("value");
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), metadata);
+        var obj = new DependencyObject();
+
+        Assert.Same(DependencyProperty.UnsetValue, obj.ReadLocalValue(property));
+
+        // Call again to test caching.
+        Assert.Same(DependencyProperty.UnsetValue, obj.ReadLocalValue(property));
+    }
+
+    [Fact]
+    public void ReadLocalValue_InvokeSetValue_ReturnsExpected()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+        obj.SetValue(property, "value");
+
+        Assert.Equal("value", obj.ReadLocalValue(property));
+
+        // Call again to test caching.
+        Assert.Equal("value", obj.ReadLocalValue(property));
+    }
+
+    [Fact]
+    public void ReadLocalValue_InvokeSetValueCoerced_ReturnsExpected()
+    {
+        string coerceResult = "coercedValue";
+        int coerceValueCallbackCallCount = 0;
+        var metadata = new PropertyMetadata(
+            null,
+            null,
+            (d, baseValue) =>
+            {
+                coerceValueCallbackCallCount++;
+                return coerceResult;
+            });
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), metadata);
+        var obj = new DependencyObject();
+        obj.SetValue(property, "value");
+        Assert.Equal(1, coerceValueCallbackCallCount);
+
+        Assert.Equal("value", obj.ReadLocalValue(property));
+        Assert.Equal(1, coerceValueCallbackCallCount);
+
+        // Call again to test caching.
+        Assert.Equal("value", obj.ReadLocalValue(property));
+        Assert.Equal(1, coerceValueCallbackCallCount);
+
+        // Change coerce result.
+        coerceResult = "value";
+        Assert.Equal("value", obj.ReadLocalValue(property));
+        Assert.Equal(1, coerceValueCallbackCallCount);
+    }
+
+    [Fact]
+    public void ReadLocalValue_InvokeSetValueCoercedUnset_ReturnsExpected()
+    {
+        object coerceResult = "coercedValue";
+        int coerceValueCallbackCallCount = 0;
+        var metadata = new PropertyMetadata(
+            null,
+            null,
+            (d, baseValue) =>
+            {
+                coerceValueCallbackCallCount++;
+                return coerceResult;
+            });
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), metadata);
+        var obj = new DependencyObject();
+        obj.SetValue(property, "value");
+        Assert.Equal(1, coerceValueCallbackCallCount);
+
+        Assert.Equal("value", obj.ReadLocalValue(property));
+        Assert.Equal(1, coerceValueCallbackCallCount);
+
+        // Call again to test caching.
+        Assert.Equal("value", obj.ReadLocalValue(property));
+        Assert.Equal(1, coerceValueCallbackCallCount);
+
+        // Change coerce result.
+        coerceResult = "value";
+        Assert.Equal("value", obj.ReadLocalValue(property));
+        Assert.Equal(1, coerceValueCallbackCallCount);
+
+        // Set to unset.
+        coerceResult = DependencyProperty.UnsetValue;
+        obj.SetValue(property, "value2");
+        Assert.Equal("value2", obj.ReadLocalValue(property));
+        Assert.Equal(2, coerceValueCallbackCallCount);
+    }
+
+    [Fact]
+    public void ReadLocalValue_InvokeClearedValue_ReturnsExpected()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+        obj.SetValue(property, "value");
+        obj.ClearValue(property);
+
+        Assert.Same(DependencyProperty.UnsetValue, obj.ReadLocalValue(property));
+
+        // Call again to test caching.
+        Assert.Same(DependencyProperty.UnsetValue, obj.ReadLocalValue(property));
+    }
+
+    [Fact]
+    public void ReadLocalValue_InvokeCustomDefaultValue_ReturnsExpected()
+    {
+        var obj = new DependencyObject();
+        var typeMetadata = new PropertyMetadata("value");
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+
+        Assert.Same(DependencyProperty.UnsetValue, obj.ReadLocalValue(property));
+
+        // Call again to test caching.
+        Assert.Same(DependencyProperty.UnsetValue, obj.ReadLocalValue(property));
+    }
+
+    [Fact]
+    public void ReadLocalValue_InvokeReadOnlyProperty_ReturnsExpected()
+    {
+        var obj = new DependencyObject();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+
+        Assert.Same(DependencyProperty.UnsetValue, obj.ReadLocalValue(property));
+
+        // Call again to test caching.
+        Assert.Same(DependencyProperty.UnsetValue, obj.ReadLocalValue(property));
+    }
+
+    [Fact]
+    public void ReadLocalValue_InvokeReadOnlyPropertySet_ReturnsExpected()
+    {
+        var obj = new DependencyObject();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+        obj.SetValue(key, "value");
+
+        Assert.Equal("value", obj.ReadLocalValue(property));
+
+        // Call again to test caching.
+        Assert.Equal("value", obj.ReadLocalValue(property));
+    }
+
+    [Fact]
+    public void ReadLocalValue_InvokeReadOnlyPropertyUIElementIsVisible_ReturnsExpected()
+    {
+        // This has a special internal getter - GetReadOnlyValueCallback.
+        var obj = new DependencyObject();
+        DependencyProperty property = UIElement.IsVisibleProperty;
+
+        Assert.Same(DependencyProperty.UnsetValue, obj.ReadLocalValue(property));
+
+        // Call again to test caching.
+        Assert.Same(DependencyProperty.UnsetValue, obj.ReadLocalValue(property));
+    }
+
+    [Fact]
+    public void ReadLocalValue_InvokeReadOnlyPropertyUIElement3DIsVisible_ReturnsExpected()
+    {
+        // This has a special internal getter - GetReadOnlyValueCallback.
+        var obj = new DependencyObject();
+        DependencyProperty property = UIElement3D.IsVisibleProperty;
+
+        Assert.Same(DependencyProperty.UnsetValue, obj.ReadLocalValue(property));
+
+        // Call again to test caching.
+        Assert.Same(DependencyProperty.UnsetValue, obj.ReadLocalValue(property));
+    }
+
+    [Fact]
+    public void ReadLocalValue_InvokeReadOnlyPropertyFrameworkElementActualWidth_ReturnsExpected()
+    {
+        // This has a special internal getter - GetReadOnlyValueCallback.
+        var obj = new DependencyObject();
+        DependencyProperty property = FrameworkElement.ActualWidthProperty;
+
+        Assert.Same(DependencyProperty.UnsetValue, obj.ReadLocalValue(property));
+
+        // Call again to test caching.
+        Assert.Same(DependencyProperty.UnsetValue, obj.ReadLocalValue(property));
+    }
+
+    [Fact]
+    public void ReadLocalValue_InvokeReadOnlyPropertyFrameworkElementActualHeight_ReturnsExpected()
+    {
+        // This has a special internal getter - GetReadOnlyValueCallback.
+        var obj = new DependencyObject();
+        DependencyProperty property = FrameworkElement.ActualHeightProperty;
+
+        Assert.Same(DependencyProperty.UnsetValue, obj.ReadLocalValue(property));
+
+        // Call again to test caching.
+        Assert.Same(DependencyProperty.UnsetValue, obj.ReadLocalValue(property));
+    }
+
+    [Fact]
+    public void ReadLocalValue_NullProperty_ThrowsArgumentNullException()
+    {
+        var obj = new DependencyObject();
+        Assert.Throws<ArgumentNullException>("dp", () => obj.ReadLocalValue(null!));
+    }
+
+    [Fact]
+    public void ReadLocalValue_InvokeOnDifferentThread_ThrowsInvalidOperationException()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => obj.ReadLocalValue(property));
+        });
+    }
+
+    [Fact]
+    public void SetValue_InvokeDependencyPropertyValueType_GetValueReturnsExpected()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject));
+        var obj = new DependencyObject();
+
+        // Set true.
+        obj.SetValue(property, true);
+        Assert.True((bool)obj.GetValue(property));
+
+        // Set same.
+        obj.SetValue(property, true);
+        Assert.True((bool)obj.GetValue(property));
+
+        // Set false.
+        obj.SetValue(property, false);
+        Assert.False((bool)obj.GetValue(property));
+    }
+
+    [Fact]
+    public void SetValue_InvokeDependencyPropertyNullable_GetValueReturnsExpected()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool?), typeof(DependencyObject));
+        var obj = new DependencyObject();
+
+        // Set custom.
+        obj.SetValue(property, true);
+        Assert.True((bool)obj.GetValue(property));
+
+        // Set same.
+        obj.SetValue(property, true);
+        Assert.True((bool)obj.GetValue(property));
+
+        // Set null.
+        obj.SetValue(property, null);
+        Assert.Null(obj.GetValue(property));
+
+        // Set false.
+        obj.SetValue(property, false);
+        Assert.False((bool)obj.GetValue(property));
+    }
+
+    [Fact]
+    public void SetValue_InvokeDependencyPropertyReferenceType_GetValueReturnsExpected()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+
+        // Set value.
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Set same.
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Set different.
+        obj.SetValue(property, "other");
+        Assert.Equal("other", obj.GetValue(property));
+
+        // Set null.
+        obj.SetValue(property, null);
+        Assert.Null(obj.GetValue(property));
+    }
+
+    [Fact]
+    public void SetValue_InvokeDependencyPropertyObject_GetValueReturnsExpected()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(DependencyObject));
+        var obj = new DependencyObject();
+
+        // Set value.
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Set same.
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Set different.
+        obj.SetValue(property, 1);
+        Assert.Equal(1, obj.GetValue(property));
+
+        // Set null.
+        obj.SetValue(property, null);
+        Assert.Null(obj.GetValue(property));
+    }
+
+    [Fact]
+    public void SetValue_InvokeDependencyPropertyWithPropertyChangeCallback_Success()
+    {
+        var obj = new DependencyObject();
+
+        int changedCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedOldValue = null;
+        object? expectedNewValue = null;
+        var typeMetadata = new PropertyMetadata(
+            null,
+            (d, e) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedProperty, e.Property);
+                Assert.Same(expectedOldValue, e.OldValue);
+                Assert.Same(expectedNewValue, e.NewValue);
+                Assert.Equal(expectedNewValue, obj.GetValue(e.Property));
+                changedCallCount++;
+            });
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        expectedProperty = property;
+
+        // Set custom.
+        expectedNewValue = "value";
+        expectedOldValue = null;
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+
+        // Set same.
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+
+        // Set different.
+        expectedNewValue = "other";
+        expectedOldValue = "value";
+        obj.SetValue(property, "other");
+        Assert.Equal("other", obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+
+        // Set null.
+        expectedNewValue = null;
+        expectedOldValue = "other";
+        obj.SetValue(property, null);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(3, changedCallCount);
+    }
+
+    [Fact]
+    public void SetValue_InvokeDependencyPropertyWithCoerceCallback_Success()
+    {
+        var obj = new DependencyObject();
+
+        int coerceValueCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedNewValue = null;
+        var typeMetadata = new PropertyMetadata(
+            null,
+            null,
+            (d, baseValue) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedNewValue, baseValue);
+                coerceValueCallCount++;
+                return baseValue;
+            }
+        );
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        expectedProperty = property;
+
+        // Set custom.
+        expectedNewValue = "value";
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Set same.
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(2, coerceValueCallCount);
+
+        // Set different.
+        expectedNewValue = "other";
+        obj.SetValue(property, "other");
+        Assert.Equal("other", obj.GetValue(property));
+        Assert.Equal(3, coerceValueCallCount);
+
+        // Set null.
+        expectedNewValue = null;
+        obj.SetValue(property, null);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(4, coerceValueCallCount);
+    }
+
+    [Fact]
+    public void SetValue_InvokeDependencyPropertyWithCoerceCallbackCustom_Success()
+    {
+        var obj = new DependencyObject();
+
+        int coerceValueCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedNewValue = null;
+        var typeMetadata = new PropertyMetadata(
+            null,
+            null,
+            (d, baseValue) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedNewValue, baseValue);
+                coerceValueCallCount++;
+                return "coercedValue";
+            }
+        );
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        expectedProperty = property;
+
+        // Set custom.
+        expectedNewValue = "value";
+        obj.SetValue(property, "value");
+        Assert.Equal("coercedValue", obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Set same.
+        obj.SetValue(property, "value");
+        Assert.Equal("coercedValue", obj.GetValue(property));
+        Assert.Equal(2, coerceValueCallCount);
+
+        // Set different.
+        expectedNewValue = "other";
+        obj.SetValue(property, "other");
+        Assert.Equal("coercedValue", obj.GetValue(property));
+        Assert.Equal(3, coerceValueCallCount);
+
+        // Set null.
+        expectedNewValue = null;
+        obj.SetValue(property, null);
+        Assert.Equal("coercedValue", obj.GetValue(property));
+        Assert.Equal(4, coerceValueCallCount);
+    }
+
+    [Fact]
+    public void SetValue_InvokeDependencyPropertyWithPropertyChangeAndCoerceCallback_Success()
+    {
+        var obj = new DependencyObject();
+
+        int changedCallCount = 0;
+        int coerceValueCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedOldValue = null;
+        object? expectedNewValue = null;
+        var typeMetadata = new PropertyMetadata(
+            null,
+            (d, e) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedProperty, e.Property);
+                Assert.Same(expectedOldValue, e.OldValue);
+                Assert.Same(expectedNewValue, e.NewValue);
+                Assert.Equal(expectedNewValue, obj.GetValue(e.Property));
+                changedCallCount++;
+            },
+            (d, baseValue) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedNewValue, baseValue);
+                coerceValueCallCount++;
+                return baseValue;
+            }
+        );
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        expectedProperty = property;
+
+        // Set custom.
+        expectedNewValue = "value";
+        expectedOldValue = null;
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Set same.
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+        Assert.Equal(2, coerceValueCallCount);
+
+        // Set different.
+        expectedNewValue = "other";
+        expectedOldValue = "value";
+        obj.SetValue(property, "other");
+        Assert.Equal("other", obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+        Assert.Equal(3, coerceValueCallCount);
+
+        // Set null.
+        expectedNewValue = null;
+        expectedOldValue = "other";
+        obj.SetValue(property, null);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(3, changedCallCount);
+        Assert.Equal(4, coerceValueCallCount);
+    }
+
+    [Fact]
+    public void SetValue_InvokeDependencyPropertyCustomOnPropertyChanged_CallsOnPropertyChanged()
+    {
+        var obj = new CustomDependencyObject();
+
+        int onPropertyChangedCallCount = 0;
+        int changedCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedOldValue = null;
+        object? expectedNewValue = null;
+        obj.OnPropertyChangedAction = (e) =>
+        {
+            Assert.True(changedCallCount > onPropertyChangedCallCount);
+            Assert.Same(expectedProperty, e.Property);
+            Assert.Same(expectedOldValue, e.OldValue);
+            Assert.Same(expectedNewValue, e.NewValue);
+            Assert.Equal(expectedNewValue, obj.GetValue(e.Property));
+            onPropertyChangedCallCount++;
+        };
+        var typeMetadata = new PropertyMetadata(
+            null,
+            (d, e) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedProperty, e.Property);
+                Assert.Same(expectedOldValue, e.OldValue);
+                Assert.Same(expectedNewValue, e.NewValue);
+                Assert.Equal(expectedNewValue, obj.GetValue(e.Property));
+                changedCallCount++;
+            });
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        expectedProperty = property;
+
+        // Set custom.
+        expectedNewValue = "value";
+        expectedOldValue = null;
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+
+        // Set same.
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+
+        // Set different.
+        expectedNewValue = "other";
+        expectedOldValue = "value";
+        obj.SetValue(property, "other");
+        Assert.Equal("other", obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+
+        // Set null.
+        expectedNewValue = null;
+        expectedOldValue = "other";
+        obj.SetValue(property, null);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(3, changedCallCount);
+    }
+
+    [Fact]
+    public void SetValue_DependencyPropertyNullDp_ThrowsArgumentNullException()
+    {
+        var obj = new DependencyObject();
+        Assert.Throws<ArgumentNullException>("dp", () => obj.SetValue((DependencyProperty)null!, true));
+    }
+
+    [Fact]
+    public void SetValue_DependencyPropertyReadOnly_ThrowsInvalidOperationException()
+    {
+        var obj = new DependencyObject();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+        Assert.Throws<InvalidOperationException>(() => obj.SetValue(property, "value"));
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("value")]
+    [InlineData(1)]
+    public void SetValue_DependencyPropertyInvalidValueValueType_ThrowsArgumentException(object? value)
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name + value?.GetType().Name, typeof(bool), typeof(DependencyObject));
+        var obj = new DependencyObject();
+        // TODO: add paramName
+        Assert.Throws<ArgumentException>(() => obj.SetValue(property, value));
+    }
+
+    [Theory]
+    [InlineData("value")]
+    [InlineData(1)]
+    public void SetValue_DependencyPropertyInvalidValueNullable_ThrowsArgumentException(object value)
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name + value?.GetType().Name, typeof(bool?), typeof(DependencyObject));
+        var obj = new DependencyObject();
+        // TODO: add paramName
+        Assert.Throws<ArgumentException>(() => obj.SetValue(property, value));
+    }
+
+    public static IEnumerable<object[]> SetValue_DependencyPropertyInvalidValueReferenceType_TestData()
+    {
+        yield return new object[] { new object() };
+        yield return new object[] { 1 };
+    }
+
+    [Theory]
+    [MemberData(nameof(SetValue_DependencyPropertyInvalidValueReferenceType_TestData))]
+    public void SetValue_DependencyPropertyInvalidValueReferenceType_ThrowsArgumentException(object value)
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name + value?.GetType().Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+        // TODO: add paramName
+        Assert.Throws<ArgumentException>(() => obj.SetValue(property, value));
+    }
+
+    [Fact]
+    public void SetValue_InvokeDependencyPropertyOnDifferentThread_ThrowsInvalidOperationException()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => obj.SetValue(property, "value"));
+        });
+    }
+
+    [Fact]
+    public void SetValue_InvokeDependencyPropertyKeyValueType_GetValueReturnsExpected()
+    {
+        var obj = new DependencyObject();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+
+        // Set true.
+        obj.SetValue(key, true);
+        Assert.True((bool)obj.GetValue(property));
+
+        // Set same.
+        obj.SetValue(key, true);
+        Assert.True((bool)obj.GetValue(property));
+
+        // Set false.
+        obj.SetValue(key, false);
+        Assert.False((bool)obj.GetValue(property));
+    }
+
+    [Fact]
+    public void SetValue_InvokeDependencyPropertyKeyNullable_GetValueReturnsExpected()
+    {
+        var obj = new DependencyObject();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool?), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+
+        // Set true.
+        obj.SetValue(key, true);
+        Assert.True((bool)obj.GetValue(property));
+
+        // Set same.
+        obj.SetValue(key, true);
+        Assert.True((bool)obj.GetValue(property));
+
+        // Set null.
+        obj.SetValue(key, null);
+        Assert.Null(obj.GetValue(property));
+
+        // Set false.
+        obj.SetValue(key, false);
+        Assert.False((bool)obj.GetValue(property));
+    }
+
+    [Fact]
+    public void SetValue_InvokeDependencyPropertyKeyReferenceType_GetValueReturnsExpected()
+    {
+        var obj = new DependencyObject();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+
+        // Set value.
+        obj.SetValue(key, "value");
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Set same.
+        obj.SetValue(key, "value");
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Set different.
+        obj.SetValue(key, "other");
+        Assert.Equal("other", obj.GetValue(property));
+
+        // Set null.
+        obj.SetValue(key, null);
+        Assert.Null(obj.GetValue(property));
+    }
+
+    [Fact]
+    public void SetValue_InvokeDependencyPropertyKeyObject_GetValueReturnsExpected()
+    {
+        var obj = new DependencyObject();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+
+        // Set value.
+        obj.SetValue(key, "value");
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Set same.
+        obj.SetValue(key, "value");
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Set different.
+        obj.SetValue(key, 1);
+        Assert.Equal(1, obj.GetValue(property));
+
+        // Set null.
+        obj.SetValue(key, null);
+        Assert.Null(obj.GetValue(property));
+    }
+
+    [Fact]
+    public void SetValue_InvokeDependencyPropertyKeyWithPropertyChangeCallback_Success()
+    {
+        var obj = new DependencyObject();
+
+        int changedCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedOldValue = null;
+        object? expectedNewValue = null;
+        var typeMetadata = new PropertyMetadata(
+            null,
+            (d, e) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedProperty, e.Property);
+                Assert.Same(expectedOldValue, e.OldValue);
+                Assert.Same(expectedNewValue, e.NewValue);
+                Assert.Equal(expectedNewValue, obj.GetValue(e.Property));
+                changedCallCount++;
+            });
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        DependencyProperty property = key.DependencyProperty;
+        expectedProperty = property;
+
+        // Set custom.
+        expectedNewValue = "value";
+        expectedOldValue = null;
+        obj.SetValue(key, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+
+        // Set same.
+        obj.SetValue(key, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+
+        // Set different.
+        expectedNewValue = "other";
+        expectedOldValue = "value";
+        obj.SetValue(key, "other");
+        Assert.Equal("other", obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+
+        // Set null.
+        expectedNewValue = null;
+        expectedOldValue = "other";
+        obj.SetValue(key, null);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(3, changedCallCount);
+    }
+
+    [Fact]
+    public void SetValue_InvokeDependencyPropertyKeyWithCoerceCallback_Success()
+    {
+        var obj = new DependencyObject();
+
+        int coerceValueCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedNewValue = null;
+        var typeMetadata = new PropertyMetadata(
+            null,
+            null,
+            (d, baseValue) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedNewValue, baseValue);
+                coerceValueCallCount++;
+                return baseValue;
+            }
+        );
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        DependencyProperty property = key.DependencyProperty;
+        expectedProperty = property;
+
+        // Set custom.
+        expectedNewValue = "value";
+        obj.SetValue(key, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Set same.
+        obj.SetValue(key, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(2, coerceValueCallCount);
+
+        // Set different.
+        expectedNewValue = "other";
+        obj.SetValue(key, "other");
+        Assert.Equal("other", obj.GetValue(property));
+        Assert.Equal(3, coerceValueCallCount);
+
+        // Set null.
+        expectedNewValue = null;
+        obj.SetValue(key, null);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(4, coerceValueCallCount);
+    }
+
+    [Fact]
+    public void SetValue_InvokeDependencyPropertyKeyWithCoerceCallbackCustom_Success()
+    {
+        var obj = new DependencyObject();
+
+        int coerceValueCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedNewValue = null;
+        var typeMetadata = new PropertyMetadata(
+            null,
+            null,
+            (d, baseValue) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedNewValue, baseValue);
+                coerceValueCallCount++;
+                return "coercedValue";
+            }
+        );
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        DependencyProperty property = key.DependencyProperty;
+        expectedProperty = property;
+
+        // Set custom.
+        expectedNewValue = "value";
+        obj.SetValue(key, "value");
+        Assert.Equal("coercedValue", obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Set same.
+        obj.SetValue(key, "value");
+        Assert.Equal("coercedValue", obj.GetValue(property));
+        Assert.Equal(2, coerceValueCallCount);
+
+        // Set different.
+        expectedNewValue = "other";
+        obj.SetValue(key, "other");
+        Assert.Equal("coercedValue", obj.GetValue(property));
+        Assert.Equal(3, coerceValueCallCount);
+
+        // Set null.
+        expectedNewValue = null;
+        obj.SetValue(key, null);
+        Assert.Equal("coercedValue", obj.GetValue(property));
+        Assert.Equal(4, coerceValueCallCount);
+    }
+
+    [Fact]
+    public void SetValue_InvokeDependencyPropertyKeyWithPropertyChangeAndCoerceCallback_Success()
+    {
+        var obj = new DependencyObject();
+
+        int changedCallCount = 0;
+        int coerceValueCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedOldValue = null;
+        object? expectedNewValue = null;
+        var typeMetadata = new PropertyMetadata(
+            null,
+            (d, e) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedProperty, e.Property);
+                Assert.Same(expectedOldValue, e.OldValue);
+                Assert.Same(expectedNewValue, e.NewValue);
+                Assert.Equal(expectedNewValue, obj.GetValue(e.Property));
+                changedCallCount++;
+            },
+            (d, baseValue) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedNewValue, baseValue);
+                coerceValueCallCount++;
+                return baseValue;
+            }
+        );
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        DependencyProperty property = key.DependencyProperty;
+        expectedProperty = property;
+
+        // Set custom.
+        expectedNewValue = "value";
+        expectedOldValue = null;
+        obj.SetValue(key, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Set same.
+        obj.SetValue(key, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+        Assert.Equal(2, coerceValueCallCount);
+
+        // Set different.
+        expectedNewValue = "other";
+        expectedOldValue = "value";
+        obj.SetValue(key, "other");
+        Assert.Equal("other", obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+        Assert.Equal(3, coerceValueCallCount);
+
+        // Set null.
+        expectedNewValue = null;
+        expectedOldValue = "other";
+        obj.SetValue(key, null);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(3, changedCallCount);
+        Assert.Equal(4, coerceValueCallCount);
+    }
+
+    [Fact]
+    public void SetValue_InvokeDependencyPropertyKeyCustomOnPropertyChanged_CallsOnPropertyChanged()
+    {
+        var obj = new CustomDependencyObject();
+
+        int onPropertyChangedCallCount = 0;
+        int changedCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedOldValue = null;
+        object? expectedNewValue = null;
+        obj.OnPropertyChangedAction = (e) =>
+        {
+            Assert.True(changedCallCount > onPropertyChangedCallCount);
+            Assert.Same(expectedProperty, e.Property);
+            Assert.Same(expectedOldValue, e.OldValue);
+            Assert.Same(expectedNewValue, e.NewValue);
+            Assert.Equal(expectedNewValue, obj.GetValue(e.Property));
+            onPropertyChangedCallCount++;
+        };
+        var typeMetadata = new PropertyMetadata(
+            null,
+            (d, e) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedProperty, e.Property);
+                Assert.Same(expectedOldValue, e.OldValue);
+                Assert.Same(expectedNewValue, e.NewValue);
+                Assert.Equal(expectedNewValue, obj.GetValue(e.Property));
+                changedCallCount++;
+            });
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        DependencyProperty property = key.DependencyProperty;
+        expectedProperty = property;
+
+        // Set custom.
+        expectedNewValue = "value";
+        expectedOldValue = null;
+        obj.SetValue(key, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+        Assert.Equal(1, onPropertyChangedCallCount);
+
+        // Set same.
+        obj.SetValue(key, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+        Assert.Equal(1, onPropertyChangedCallCount);
+
+        // Set different.
+        expectedNewValue = "other";
+        expectedOldValue = "value";
+        obj.SetValue(key, "other");
+        Assert.Equal("other", obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+        Assert.Equal(2, onPropertyChangedCallCount);
+
+        // Set null.
+        expectedNewValue = null;
+        expectedOldValue = "other";
+        obj.SetValue(key, null);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(3, changedCallCount);
+        Assert.Equal(3, onPropertyChangedCallCount);
+    }
+
+    [Fact]
+    public void SetValue_NullPropertyKey_ThrowsArgumentNullException()
+    {
+        var obj = new DependencyObject();
+        Assert.Throws<ArgumentNullException>("key", () => obj.SetValue((DependencyPropertyKey)null!, true));
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("value")]
+    [InlineData(1)]
+    public void SetValue_DependencyPropertyKeyInvalidValueValueType_ThrowsArgumentException(object? value)
+    {
+        var obj = new DependencyObject();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name + value?.GetType().Name, typeof(bool), typeof(DependencyObject), new PropertyMetadata());
+        // TODO: add paramName
+        Assert.Throws<ArgumentException>(() => obj.SetValue(key, value));
+    }
+
+    [Theory]
+    [InlineData("value")]
+    [InlineData(1)]
+    public void SetValue_DependencyPropertyKeyInvalidValueNullable_ThrowsArgumentException(object value)
+    {
+        var obj = new DependencyObject();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name + value?.GetType().Name, typeof(bool?), typeof(DependencyObject), new PropertyMetadata());
+        // TODO: add paramName
+        Assert.Throws<ArgumentException>(() => obj.SetValue(key, value));
+    }
+
+    public static IEnumerable<object[]> SetValue_DependencyPropertyKeyInvalidValueReferenceType_TestData()
+    {
+        yield return new object[] { new object() };
+        yield return new object[] { 1 };
+    }
+
+    [Theory]
+    [MemberData(nameof(SetValue_DependencyPropertyKeyInvalidValueReferenceType_TestData))]
+    public void SetValue_DependencyPropertyKeyInvalidValueReferenceType_ThrowsArgumentException(object value)
+    {
+        var obj = new DependencyObject();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name + value?.GetType().Name, typeof(string), typeof(DependencyObject), new PropertyMetadata());
+        // TODO: add paramName
+        Assert.Throws<ArgumentException>(() => obj.SetValue(key, value));
+    }
+
+    [Fact]
+    public void SetValue_InvokeDependencyPropertyKeyOnDifferentThread_ThrowsInvalidOperationException()
+    {
+        var obj = new DependencyObject();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), new PropertyMetadata());
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => obj.SetValue(key, "value"));
+        });
+    }
+
+    [Fact]
+    public void OnPropertyChanged_InvokeNoMetadata_Nop()
+    {
+        var obj = new SubDependencyObject();
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        obj.OnPropertyChanged(new DependencyPropertyChangedEventArgs(property, new object(), new object()));
+    }
+
+    [Fact]
+    public void OnPropertyChanged_InvokeEmptyMetadata_Nop()
+    {
+        var obj = new SubDependencyObject();
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), new PropertyMetadata());
+        obj.OnPropertyChanged(new DependencyPropertyChangedEventArgs(property, new object(), new object()));
+    }
+
+    [Fact]
+    public void OnPropertyChanged_InvokeMetadataHasPropertyChangedCallback_Nop()
+    {
+        var obj = new SubDependencyObject();
+        int callCount = 0;
+        var metadata = new PropertyMetadata(null, (d, actualE) => callCount++);
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), metadata);
+        var e = new DependencyPropertyChangedEventArgs(property, new object(), new object());
+        obj.OnPropertyChanged(e);
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void OnPropertyChanged_InvokeOnDifferentThread_Nop()
+    {
+        var obj = new SubDependencyObject();
+        int callCount = 0;
+        var metadata = new PropertyMetadata(null, (d, actualE) => callCount++);
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), metadata);
+        var e = new DependencyPropertyChangedEventArgs(property, new object(), new object());
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            obj.OnPropertyChanged(e);
+            Assert.Equal(0, callCount);
+        });
+    }
+
+    [Fact]
+    public void OnPropertyChanged_NullEProperty_ThrowsArgumentException()
+    {
+        var obj = new SubDependencyObject();
+        DependencyPropertyChangedEventArgs e = default;
+        Assert.Throws<ArgumentException>("e", () => obj.OnPropertyChanged(e));
+    }
+
+    [Fact]
+    public void ShouldSerializeProperty_InvokeSetProperty_ReturnsTrue()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new SubDependencyObject();
+
+        obj.SetValue(property, "value");
+        Assert.True(obj.ShouldSerializeProperty(property));
+
+        // Call again to test caching.
+        Assert.True(obj.ShouldSerializeProperty(property));
+    }
+
+    [Fact]
+    public void ShouldSerializeProperty_InvokeSetPropertyReadOnly_ReturnsTrue()
+    {
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+        var obj = new SubDependencyObject();
+
+        obj.SetValue(key, "value");
+        Assert.True(obj.ShouldSerializeProperty(property));
+
+        // Call again to test caching.
+        Assert.True(obj.ShouldSerializeProperty(property));
+    }
+
+    [Fact]
+    public void ShouldSerializeProperty_InvokeNoSuchProperty_ReturnsFalse()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new SubDependencyObject();
+        Assert.False(obj.ShouldSerializeProperty(property));
+
+        // Call again to test caching.
+        Assert.False(obj.ShouldSerializeProperty(property));
+    }
+
+    [Fact]
+    public void ShouldSerializeProperty_InvokeNoSuchPropertyReadOnly_ReturnsFalse()
+    {
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+        var obj = new SubDependencyObject();
+        Assert.False(obj.ShouldSerializeProperty(property));
+
+        // Call again to test caching.
+        Assert.False(obj.ShouldSerializeProperty(property));
+    }
+
+    [Fact]
+    public void ShouldSerializeProperty_InvokeClearedProperty_ReturnsFalse()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new SubDependencyObject();
+        obj.SetValue(property, "value");
+        obj.ClearValue(property);
+        Assert.False(obj.ShouldSerializeProperty(property));
+
+        // Call again to test caching.
+        Assert.False(obj.ShouldSerializeProperty(property));
+    }
+
+    [Fact]
+    public void ShouldSerializeProperty_InvokeClearedPropertyReadOnly_ReturnsFalse()
+    {
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(DependencyObjectTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+        var obj = new SubDependencyObject();
+        obj.SetValue(key, "value");
+        obj.ClearValue(key);
+        Assert.False(obj.ShouldSerializeProperty(property));
+
+        // Call again to test caching.
+        Assert.False(obj.ShouldSerializeProperty(property));
+    }
+
+    private class CustomDependencyObject : DependencyObject
+    {
+        public Action<DependencyPropertyChangedEventArgs>? OnPropertyChangedAction { get; set; }
+
+        protected override void OnPropertyChanged(DependencyPropertyChangedEventArgs e)
+        {
+            base.OnPropertyChanged(e);
+            OnPropertyChangedAction?.Invoke(e);
+        }
+    }
+
+    private class SubDependencyObject : DependencyObject
+    {
+        public new void OnPropertyChanged(DependencyPropertyChangedEventArgs e) => base.OnPropertyChanged(e);
+
+        public new bool ShouldSerializeProperty(DependencyProperty dp) => base.ShouldSerializeProperty(dp);
+    }
+}
\ No newline at end of file
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/DependencyObjectTypeTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/DependencyObjectTypeTests.cs
new file mode 100644
index 00000000000..64236353253
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/DependencyObjectTypeTests.cs
@@ -0,0 +1,122 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Windows.Tests;
+
+public class DependencyObjectTypeTests
+{
+    [Fact]
+    public void FromSystemType_DependencyObject_Success()
+    {
+        DependencyObjectType type = DependencyObjectType.FromSystemType(typeof(DependencyObject));
+        Assert.NotNull(type);
+        Assert.Same(type, DependencyObjectType.FromSystemType(typeof(DependencyObject)));
+        Assert.Null(type.BaseType);
+        Assert.Equal(nameof(DependencyObject), type.Name);
+        Assert.True(type.Id >= 0);
+        Assert.Equal(typeof(DependencyObject), type.SystemType);
+    }
+    
+    [Fact]
+    public void FromSystemType_SubDependencyObject_Success()
+    {
+        DependencyObjectType type = DependencyObjectType.FromSystemType(typeof(SubDependencyObject));
+        Assert.NotNull(type);
+        Assert.Same(type, DependencyObjectType.FromSystemType(typeof(SubDependencyObject)));
+        Assert.NotNull(type.BaseType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(DependencyObject)), type.BaseType);
+        Assert.Equal(nameof(SubDependencyObject), type.Name);
+        Assert.True(type.Id >= 0);
+        Assert.Equal(typeof(SubDependencyObject), type.SystemType);
+    }
+
+    [Fact]
+    public void FromSystemType_MultipleTypes_IdDifferent()
+    {
+        DependencyObjectType type1 = DependencyObjectType.FromSystemType(typeof(DependencyObject));
+        DependencyObjectType type2 = DependencyObjectType.FromSystemType(typeof(SubDependencyObject));
+        Assert.NotEqual(type1.Id, type2.Id);
+    }
+
+    [Fact]
+    public void FromSystemType_NullSystemType_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("systemType", () => DependencyObjectType.FromSystemType(null!));
+    }
+
+    [Theory]
+    [InlineData(typeof(int))]
+    public void FromSystemType_InvalidSystemType_ThrowsArgumentException(Type systemType)
+    {
+        // TODO: add paramName to code.
+        Assert.Throws<ArgumentException>(() => DependencyObjectType.FromSystemType(systemType));
+    }
+
+    [Fact]
+    public void GetHashCode_Invoke_ReturnsExpected()
+    {
+        DependencyObjectType type = DependencyObjectType.FromSystemType(typeof(DependencyObject));
+        Assert.Equal(type.Id, type.GetHashCode());
+    }
+
+    public static IEnumerable<object?[]> IsInstanceOfType_TestData()
+    {
+        yield return new object?[] { typeof(DependencyObject), new DependencyObject(), true };
+        yield return new object?[] { typeof(DependencyObject), new SubDependencyObject(), true };
+        yield return new object?[] { typeof(DependencyObject), new OtherDependencyObject(), true };
+        yield return new object?[] { typeof(DependencyObject), null, false };
+        yield return new object?[] { typeof(SubDependencyObject), new DependencyObject(), false };
+        yield return new object?[] { typeof(SubDependencyObject), new SubDependencyObject(), true };
+        yield return new object?[] { typeof(SubDependencyObject), new OtherDependencyObject(), false };
+        yield return new object?[] { typeof(SubDependencyObject), new SubSubDependencyObject(), true };
+        yield return new object?[] { typeof(SubDependencyObject), null, false };
+        yield return new object?[] { typeof(SubSubDependencyObject), new DependencyObject(), false };
+        yield return new object?[] { typeof(SubSubDependencyObject), new OtherDependencyObject(), false };
+        yield return new object?[] { typeof(SubSubDependencyObject), new SubDependencyObject(), false };
+        yield return new object?[] { typeof(SubSubDependencyObject), new SubSubDependencyObject(), true };
+        yield return new object?[] { typeof(SubSubDependencyObject), null, false };
+    }
+
+    [Theory]
+    [MemberData(nameof(IsInstanceOfType_TestData))]
+    public void IsInstanceOfType_Invoke_ReturnsExpected(Type systemType, DependencyObject dependencyObject, bool expected)
+    {
+        DependencyObjectType type = DependencyObjectType.FromSystemType(systemType);
+        Assert.Equal(expected, type.IsInstanceOfType(dependencyObject));
+    }
+
+    [Theory]
+    [InlineData(typeof(DependencyObject), typeof(DependencyObject), false)]
+    [InlineData(typeof(DependencyObject), typeof(SubDependencyObject), false)]
+    [InlineData(typeof(DependencyObject), typeof(OtherDependencyObject), false)]
+    [InlineData(typeof(DependencyObject), null, false)]
+    [InlineData(typeof(SubDependencyObject), typeof(DependencyObject), true)]
+    [InlineData(typeof(SubDependencyObject), typeof(SubDependencyObject), false)]
+    [InlineData(typeof(SubDependencyObject), typeof(OtherDependencyObject), false)]
+    [InlineData(typeof(SubDependencyObject), typeof(SubSubDependencyObject), false)]
+    [InlineData(typeof(SubDependencyObject), null, false)]
+    [InlineData(typeof(SubSubDependencyObject), typeof(DependencyObject), true)]
+    [InlineData(typeof(SubSubDependencyObject), typeof(SubDependencyObject), true)]
+    [InlineData(typeof(SubSubDependencyObject), typeof(OtherDependencyObject), false)]
+    [InlineData(typeof(SubSubDependencyObject), typeof(SubSubDependencyObject), false)]
+    [InlineData(typeof(SubSubDependencyObject), null, false)]
+    public void IsSubclassOf_Invoke_ReturnsExpected(Type systemType, Type? dependencyObjectType, bool expected)
+    {
+        DependencyObjectType type = DependencyObjectType.FromSystemType(systemType);
+        DependencyObjectType? dependencyType = dependencyObjectType != null ? DependencyObjectType.FromSystemType(dependencyObjectType) : null;
+        Assert.Equal(expected, type.IsSubclassOf(dependencyType));
+    }
+
+    private class SubDependencyObject : DependencyObject
+    {
+    }
+
+    private class OtherDependencyObject : DependencyObject
+    {
+    }
+
+    private class SubSubDependencyObject : SubDependencyObject
+    {
+    }
+}
\ No newline at end of file
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/DependencyPropertyChangedEventArgsTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/DependencyPropertyChangedEventArgsTests.cs
new file mode 100644
index 00000000000..926d98451f8
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/DependencyPropertyChangedEventArgsTests.cs
@@ -0,0 +1,99 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.Reflection;
+
+namespace System.Windows.Tests;
+
+public class DependencyPropertyChangedEventArgsTests
+{
+    public static IEnumerable<object?[]> Ctor_DependencyProperty_Object_Object_TestData()
+    {
+        yield return new object?[] { null, null };
+        yield return new object?[] { "", "" };
+        yield return new object?[] { "oldValue", "newValue" };
+    }
+
+    [Theory]
+    [MemberData(nameof(Ctor_DependencyProperty_Object_Object_TestData))]
+    public void Ctor_DependencyProperty_Object_Object(object oldValue, object newValue)
+    {
+        DependencyProperty property = DependencyProperty.Register(MethodBase.GetCurrentMethod()!.Name + (oldValue?.ToString() ?? "null") + (newValue?.ToString() ?? "null"), typeof(string), typeof(DependencyObject));
+        var args = new DependencyPropertyChangedEventArgs(property, oldValue, newValue);
+        Assert.Equal(newValue, args.NewValue);
+        Assert.Equal(oldValue, args.OldValue);
+        Assert.Same(property, args.Property);
+    }
+
+    [Fact]
+    public void Ctor_NullProperty_ThrowsNullReferenceException()
+    {
+        // TODO: this should throw ANE.
+        Assert.Throws<NullReferenceException>(() => new DependencyPropertyChangedEventArgs(null, "oldValue", "newValue"));
+    }
+
+    private static DependencyProperty s_property = DependencyProperty.Register(nameof(DependencyPropertyChangedEventArgsTests), typeof(string), typeof(DependencyObject));
+
+    public static IEnumerable<object?[]> Equals_Object_TestData()
+    {
+        yield return new object?[] { new DependencyPropertyChangedEventArgs(s_property, "oldValue", "newValue"), new DependencyPropertyChangedEventArgs(s_property, "oldValue", "newValue"), true };
+        yield return new object?[] { new DependencyPropertyChangedEventArgs(s_property, "oldValue", "newValue"), new DependencyPropertyChangedEventArgs(ContentElement.IsMouseOverProperty, "oldValue", "newValue"), false };
+        yield return new object?[] { new DependencyPropertyChangedEventArgs(s_property, "oldValue", "newValue"), new DependencyPropertyChangedEventArgs(s_property, "oldValue2", "newValue"), false };
+        yield return new object?[] { new DependencyPropertyChangedEventArgs(s_property, "oldValue", "newValue"), new DependencyPropertyChangedEventArgs(s_property, null, "newValue"), false };
+        yield return new object?[] { new DependencyPropertyChangedEventArgs(s_property, "oldValue", "newValue"), new DependencyPropertyChangedEventArgs(s_property, "oldValue", "newValue2"), false };
+        yield return new object?[] { new DependencyPropertyChangedEventArgs(s_property, "oldValue", "newValue"), new DependencyPropertyChangedEventArgs(s_property, "oldValue", null), false };
+
+        yield return new object?[] { new DependencyPropertyChangedEventArgs(s_property, null, "newValue"), new DependencyPropertyChangedEventArgs(s_property, null, "newValue"), true };
+        yield return new object?[] { new DependencyPropertyChangedEventArgs(s_property, null, "newValue"), new DependencyPropertyChangedEventArgs(s_property, "other", "newValue"), false };
+        yield return new object?[] { new DependencyPropertyChangedEventArgs(s_property, "oldValue", null), new DependencyPropertyChangedEventArgs(s_property, "oldValue", null), true };
+        yield return new object?[] { new DependencyPropertyChangedEventArgs(s_property, "oldValue", null), new DependencyPropertyChangedEventArgs(s_property, "oldValue", "other"), false };
+        yield return new object?[] { new DependencyPropertyChangedEventArgs(s_property, null, null), new DependencyPropertyChangedEventArgs(s_property, null, null), true };
+        yield return new object?[] { new DependencyPropertyChangedEventArgs(s_property, null, null), new DependencyPropertyChangedEventArgs(s_property, "other", null), false };
+        yield return new object?[] { new DependencyPropertyChangedEventArgs(s_property, null, null), new DependencyPropertyChangedEventArgs(s_property, null, "other"), false };
+        yield return new object?[] { new DependencyPropertyChangedEventArgs(s_property, null, null), new DependencyPropertyChangedEventArgs(s_property, "other", "other"), false };
+
+        // TODO: these should not throw.
+        //yield return new object?[] { new DependencyPropertyChangedEventArgs(s_property, "oldValue", "newValue"), new object(), false };
+        //yield return new object?[] { new DependencyPropertyChangedEventArgs(s_property, "oldValue", "newValue"), null, false };
+    }
+
+    [Theory]
+    [MemberData(nameof(Equals_Object_TestData))]
+    public void Equals_Object_ReturnsExpected(DependencyPropertyChangedEventArgs args, object other, bool expected)
+    {
+        Assert.Equal(expected, args.Equals(other));
+        if (other is DependencyPropertyChangedEventArgs otherArgs)
+        {
+            Assert.Equal(expected, args.Equals(otherArgs));
+            Assert.Equal(expected, args == otherArgs);
+            Assert.Equal(!expected, args != otherArgs);
+        }
+    }
+
+    [Fact]
+    public void Equals_NullObjectOther_ThrowsNullReferenceException()
+    {
+        DependencyProperty property = DependencyProperty.Register(MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var args = new DependencyPropertyChangedEventArgs(property, "oldValue", "newValue");
+        Assert.Throws<NullReferenceException>(() => args.Equals(null));
+    }
+
+    [Fact]
+    public void Equals_OtherNotDependencyPropertyChangedEventArgs_ThrowsInvalidCastException()
+    {
+        DependencyProperty property = DependencyProperty.Register(MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var args = new DependencyPropertyChangedEventArgs(property, "oldValue", "newValue");
+        Assert.Throws<InvalidCastException>(() => args.Equals(new object()));
+    }
+
+    [Fact]
+    public void GetHashCode_Invoke_ReturnsEqual()
+    {
+        DependencyProperty property = DependencyProperty.Register(MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var args = new DependencyPropertyChangedEventArgs(property, "oldValue", "newValue");
+        Assert.NotEqual(0, args.GetHashCode());
+        Assert.Equal(args.GetHashCode(), args.GetHashCode());
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/DependencyPropertyKeyTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/DependencyPropertyKeyTests.cs
new file mode 100644
index 00000000000..4f6f8a1629f
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/DependencyPropertyKeyTests.cs
@@ -0,0 +1,77 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Reflection;
+using System.Windows.Threading;
+
+namespace System.Windows.Tests;
+
+public class DependencyPropertyKeyTests
+{
+    [Fact]
+    public void OverrideMetadata_InvokeSuper_Success()
+    {
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(SubDependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+        var typeMetadata = new PropertyMetadata();
+
+        key.OverrideMetadata(typeof(DependencyObject), typeMetadata);
+    }
+
+    [Fact]
+    public void OverrideMetadata_InvokeSub_Success()
+    {
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(SubDependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+        var typeMetadata = new PropertyMetadata();
+
+        key.OverrideMetadata(typeof(SubSubDependencyObject), typeMetadata);
+    }
+
+    [Fact]
+    public void OverrideMetadata_NullForType_ThrowsArgumentNullException()
+    {
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(DependencyObject), new PropertyMetadata());
+        Assert.Throws<ArgumentNullException>("forType", () => key.OverrideMetadata(null!, new PropertyMetadata()));
+    }
+    
+    [Theory]
+    [InlineData(typeof(int))]
+    [InlineData(typeof(object))]
+    public void OverrideMetadata_ForTypeNotDependencyObject_ThrowsArgumentException(Type forType)
+    {
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(MethodBase.GetCurrentMethod()!.Name + forType.Name, typeof(object), typeof(DependencyObject), new PropertyMetadata());
+        Assert.Throws<ArgumentException>(() => key.OverrideMetadata(forType, new PropertyMetadata()));
+    }
+
+    [Fact]
+    public void OverrideMetadata_NullTypeMetadata_Th1rowsArgumentNullException()
+    {
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(DependencyObject), new PropertyMetadata());
+        Assert.Throws<ArgumentNullException>("typeMetadata", () => key.OverrideMetadata(typeof(int), null));
+    }
+    
+    [Fact]
+    public void OverrideMetadata_SealedTypeMetadata_Th1rowsArgumentNullException()
+    {
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+        Assert.Throws<ArgumentException>(() => key.OverrideMetadata(typeof(int), property.DefaultMetadata));
+    }
+
+    [Fact]
+    public void OverrideMetadata_AlreadyRegistered_ThrowsArgumentException()
+    {
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(DependencyObject), new PropertyMetadata());
+        Assert.Throws<ArgumentException>(() => key.OverrideMetadata(typeof(DependencyObject), new PropertyMetadata()));
+    }
+
+    private class SubDependencyObject : DependencyObject
+    {
+    }
+
+    private class SubSubDependencyObject : SubDependencyObject
+    {
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/DependencyPropertyTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/DependencyPropertyTests.cs
new file mode 100644
index 00000000000..815576f19a3
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/DependencyPropertyTests.cs
@@ -0,0 +1,1224 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Reflection;
+using System.Windows.Threading;
+
+namespace System.Windows.Tests;
+
+public class DependencyPropertyTests
+{
+    public static IEnumerable<object?[]> Register_String_Type_Type_TestData()
+    {
+        yield return new object?[] { "Register_String_Type_Type_TestData1", typeof(string), typeof(DependencyObjectTests), null };
+        yield return new object?[] { "Register_String_Type_Type_TestData2", typeof(int), typeof(DependencyObjectTests), 0 };
+        yield return new object?[] { "Register_String_Type_Type_TestData3", typeof(int?), typeof(DependencyObjectTests), null };
+        yield return new object?[] { "Register_String_Type_Type_TestData4", typeof(List<int>), typeof(DependencyObjectTests), null };
+        yield return new object?[] { "Register_String_Type_Type_TestData5", typeof(Dictionary<string, int>), typeof(DependencyObjectTests), null };
+        yield return new object?[] { "Register_String_Type_Type_TestData6", typeof(object), typeof(DependencyObjectTests), null };
+        yield return new object?[] { " ", typeof(int), typeof(DependencyObjectTests), 0 };
+        yield return new object?[] { " Register_String_Type_Type_TestData7 ", typeof(int), typeof(DependencyObjectTests), 0 };
+    }
+
+    [Theory]
+    [MemberData(nameof(Register_String_Type_Type_TestData))]
+    public void Register_InvokeStringTypeType_Success(string name, Type propertyType, Type ownerType, object? expectedDefaultValue)
+    {
+        DependencyProperty property = DependencyProperty.Register(name, propertyType, ownerType);
+        Assert.NotNull(property.DefaultMetadata);
+        Assert.Same(property.DefaultMetadata, property.DefaultMetadata);
+        Assert.Null(property.DefaultMetadata.CoerceValueCallback);
+        Assert.Equal(expectedDefaultValue, property.DefaultMetadata.DefaultValue);
+        Assert.Null(property.DefaultMetadata.PropertyChangedCallback);
+        Assert.True(property.GlobalIndex >= 0);
+        Assert.Equal(name, property.Name);
+        Assert.Equal(propertyType, property.PropertyType);
+        Assert.Equal(ownerType, property.OwnerType);
+        Assert.False(property.ReadOnly);
+        Assert.Null(property.ValidateValueCallback);
+    }
+    
+    public static IEnumerable<object?[]> Register_String_Type_Type_PropertyMetadata_TestData()
+    {
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_TestData1", typeof(string), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_TestData2", typeof(string), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_TestData3", typeof(string), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_TestData4", typeof(string), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = "value" }, "value" };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_TestData5", typeof(string), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_TestData6", typeof(int), typeof(DependencyObjectTests), null, 0 };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_TestData7", typeof(int), typeof(DependencyObject), new PropertyMetadata(), 0 };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_TestData8", typeof(int), typeof(SubDependencyObject), new PropertyMetadata(), 0 };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_TestData9", typeof(int), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_TestData10", typeof(int?), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_TestData11", typeof(int?), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_TestData12", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_TestData13", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_TestData14", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_TestData15", typeof(List<int>), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_TestData16", typeof(List<int>), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_TestData17", typeof(List<int>), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_TestData18", typeof(List<int>), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = new List<int>() }, new List<int>() };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_TestData19", typeof(Dictionary<string, int>), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_TestData20", typeof(Dictionary<string, int>), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_TestData21", typeof(Dictionary<string, int>), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_TestData22", typeof(Dictionary<string, int>), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = new Dictionary<string, int>() }, new Dictionary<string, int>() };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_TestData23", typeof(object), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_TestData24", typeof(object), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_TestData25", typeof(object), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_TestData26", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = "value" }, "value" };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_TestData27", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_TestData28", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null };
+        yield return new object?[] { "  ", typeof(int), typeof(DependencyObjectTests), null, 0 };
+        yield return new object?[] { " Register_String_Type_Type_PropertyMetadata_TestData29 ", typeof(int), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+    }
+
+    [Theory]
+    [MemberData(nameof(Register_String_Type_Type_PropertyMetadata_TestData))]
+    public void Register_InvokeStringTypeTypePropertyMetadata_Success(string name, Type propertyType, Type ownerType, PropertyMetadata typeMetadata, object? expectedDefaultValue)
+    {
+        DependencyProperty property = DependencyProperty.Register(name, propertyType, ownerType, typeMetadata);
+        Assert.NotNull(property.DefaultMetadata);
+        Assert.Same(property.DefaultMetadata, property.DefaultMetadata);
+        Assert.Null(property.DefaultMetadata.CoerceValueCallback);
+        Assert.Equal(expectedDefaultValue, property.DefaultMetadata.DefaultValue);
+        Assert.Null(property.DefaultMetadata.PropertyChangedCallback);
+        Assert.True(property.GlobalIndex >= 0);
+        Assert.Equal(name, property.Name);
+        Assert.Equal(propertyType, property.PropertyType);
+        Assert.Equal(ownerType, property.OwnerType);
+        Assert.False(property.ReadOnly);
+        Assert.Null(property.ValidateValueCallback);
+    }
+
+    public static IEnumerable<object?[]> Register_String_Type_Type_Validate_TestData()
+    {
+        yield return new object?[] { "Register_String_Type_Type_Validate_TestData1", typeof(string), typeof(DependencyObjectTests), null, null, 1 };
+        yield return new object?[] { "Register_String_Type_Type_Validate_TestData2", typeof(string), typeof(DependencyObject), new PropertyMetadata(), null, 1 };
+        yield return new object?[] { "Register_String_Type_Type_Validate_TestData3", typeof(string), typeof(SubDependencyObject), new PropertyMetadata(), null, 1 };
+        yield return new object?[] { "Register_String_Type_Type_Validate_TestData4", typeof(string), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = "value" }, "value", 2 };
+        yield return new object?[] { "Register_String_Type_Type_Validate_TestData5", typeof(string), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null, 2 };
+        yield return new object?[] { "Register_String_Type_Type_Validate_TestData6", typeof(int), typeof(DependencyObjectTests), null, 0, 1 };
+        yield return new object?[] { "Register_String_Type_Type_Validate_TestData7", typeof(int), typeof(DependencyObject), new PropertyMetadata(), 0, 1 };
+        yield return new object?[] { "Register_String_Type_Type_Validate_TestData8", typeof(int), typeof(SubDependencyObject), new PropertyMetadata(), 0, 1 };
+        yield return new object?[] { "Register_String_Type_Type_Validate_TestData9", typeof(int), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1, 2 };
+        yield return new object?[] { "Register_String_Type_Type_Validate_TestData10", typeof(int?), typeof(DependencyObjectTests), null, null, 1 };
+        yield return new object?[] { "Register_String_Type_Type_Validate_TestData11", typeof(int?), typeof(DependencyObject), new PropertyMetadata(), null, 1 };
+        yield return new object?[] { "Register_String_Type_Type_Validate_TestData12", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata(), null, 1 };
+        yield return new object?[] { "Register_String_Type_Type_Validate_TestData13", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1, 2 };
+        yield return new object?[] { "Register_String_Type_Type_Validate_TestData14", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null, 2 };
+        yield return new object?[] { "Register_String_Type_Type_Validate_TestData15", typeof(List<int>), typeof(DependencyObjectTests), null, null, 1 };
+        yield return new object?[] { "Register_String_Type_Type_Validate_TestData16", typeof(List<int>), typeof(DependencyObject), new PropertyMetadata(), null, 1 };
+        yield return new object?[] { "Register_String_Type_Type_Validate_TestData17", typeof(List<int>), typeof(SubDependencyObject), new PropertyMetadata(), null, 1 };
+        yield return new object?[] { "Register_String_Type_Type_Validate_TestData18", typeof(List<int>), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = new List<int>() }, new List<int>(), 2 };
+        yield return new object?[] { "Register_String_Type_Type_Validate_TestData19", typeof(Dictionary<string, int>), typeof(DependencyObjectTests), null, null, 1 };
+        yield return new object?[] { "Register_String_Type_Type_Validate_TestData20", typeof(Dictionary<string, int>), typeof(DependencyObject), new PropertyMetadata(), null, 1 };
+        yield return new object?[] { "Register_String_Type_Type_Validate_TestData21", typeof(Dictionary<string, int>), typeof(SubDependencyObject), new PropertyMetadata(), null, 1 };
+        yield return new object?[] { "Register_String_Type_Type_Validate_TestData22", typeof(Dictionary<string, int>), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = new Dictionary<string, int>() }, new Dictionary<string, int>(), 2 };
+        yield return new object?[] { "Register_String_Type_Type_Validate_TestData23", typeof(object), typeof(DependencyObjectTests), null, null, 1 };
+        yield return new object?[] { "Register_String_Type_Type_Validate_TestData24", typeof(object), typeof(DependencyObject), new PropertyMetadata(), null, 1 };
+        yield return new object?[] { "Register_String_Type_Type_Validate_TestData25", typeof(object), typeof(SubDependencyObject), new PropertyMetadata(), null, 1 };
+        yield return new object?[] { "Register_String_Type_Type_Validate_TestData26", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = "value" }, "value", 2 };
+        yield return new object?[] { "Register_String_Type_Type_Validate_TestData27", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1, 2 };
+        yield return new object?[] { "Register_String_Type_Type_Validate_TestData28", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null, 2 };
+        yield return new object?[] { "   ", typeof(int), typeof(DependencyObjectTests), null, 0, 1 };
+        yield return new object?[] { " Register_String_Type_Type_Validate_TestData29 ", typeof(int), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1, 2 };
+    }
+
+    [Theory]
+    [MemberData(nameof(Register_String_Type_Type_Validate_TestData))]
+    public void Register_InvokeStringTypeTypePropertyMetadataValidate_Success(string name, Type propertyType, Type ownerType, PropertyMetadata typeMetadata, object? expectedDefaultValue, int expectedValidateValueCallbackCallCount)
+    {
+        int callCount = 0;
+        ValidateValueCallback validateValueCallback = value =>
+        {
+            Assert.Equal(expectedDefaultValue, value);
+            callCount++;
+            return true;
+        };
+        DependencyProperty property = DependencyProperty.Register(name, propertyType, ownerType, typeMetadata, validateValueCallback);
+        Assert.NotNull(property.DefaultMetadata);
+        Assert.Same(property.DefaultMetadata, property.DefaultMetadata);
+        Assert.Null(property.DefaultMetadata.CoerceValueCallback);
+        Assert.Equal(expectedDefaultValue, property.DefaultMetadata.DefaultValue);
+        Assert.Null(property.DefaultMetadata.PropertyChangedCallback);
+        Assert.True(property.GlobalIndex >= 0);
+        Assert.Equal(name, property.Name);
+        Assert.Equal(propertyType, property.PropertyType);
+        Assert.Equal(ownerType, property.OwnerType);
+        Assert.False(property.ReadOnly);
+        Assert.Same(validateValueCallback, property.ValidateValueCallback);
+        Assert.Equal(expectedValidateValueCallbackCallCount, callCount);
+    }
+
+    public static IEnumerable<object?[]> Register_String_Type_Type_PropertyMetadata_NullValidate_TestData()
+    {
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_NullValidate_TestData1", typeof(string), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_NullValidate_TestData2", typeof(string), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_NullValidate_TestData3", typeof(string), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_NullValidate_TestData4", typeof(string), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = "value" }, "value" };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_NullValidate_TestData5", typeof(string), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_NullValidate_TestData6", typeof(int), typeof(DependencyObjectTests), null, 0 };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_NullValidate_TestData7", typeof(int), typeof(DependencyObject), new PropertyMetadata(), 0 };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_NullValidate_TestData8", typeof(int), typeof(SubDependencyObject), new PropertyMetadata(), 0 };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_NullValidate_TestData9", typeof(int), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_NullValidate_TestData10", typeof(int?), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_NullValidate_TestData11", typeof(int?), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_NullValidate_TestData12", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_NullValidate_TestData13", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_NullValidate_TestData14", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_NullValidate_TestData15", typeof(List<int>), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_NullValidate_TestData16", typeof(List<int>), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_NullValidate_TestData17", typeof(List<int>), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_NullValidate_TestData18", typeof(List<int>), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = new List<int>() }, new List<int>() };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_NullValidate_TestData19", typeof(Dictionary<string, int>), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_NullValidate_TestData20", typeof(Dictionary<string, int>), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_NullValidate_TestData21", typeof(Dictionary<string, int>), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_NullValidate_TestData22", typeof(Dictionary<string, int>), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = new Dictionary<string, int>() }, new Dictionary<string, int>() };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_NullValidate_TestData23", typeof(object), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_NullValidate_TestData24", typeof(object), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_NullValidate_TestData25", typeof(object), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_NullValidate_TestData26", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = "value" }, "value" };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_NullValidate_TestData27", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "Register_String_Type_Type_PropertyMetadata_NullValidate_TestData28", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null };
+        yield return new object?[] { "    ", typeof(int), typeof(DependencyObjectTests), null, 0 };
+        yield return new object?[] { " Register_String_Type_Type_PropertyMetadata_NullValidate_TestData8 ", typeof(int), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+    }
+
+    [Theory]
+    [MemberData(nameof(Register_String_Type_Type_PropertyMetadata_NullValidate_TestData))]
+    public void Register_InvokeStringTypeTypePropertyMetadataNullValidate_Success(string name, Type propertyType, Type ownerType, PropertyMetadata typeMetadata, object? expectedDefaultValue)
+    {
+        DependencyProperty property = DependencyProperty.Register(name, propertyType, ownerType, typeMetadata, null);
+        Assert.NotNull(property.DefaultMetadata);
+        Assert.Same(property.DefaultMetadata, property.DefaultMetadata);
+        Assert.Null(property.DefaultMetadata.CoerceValueCallback);
+        Assert.Equal(expectedDefaultValue, property.DefaultMetadata.DefaultValue);
+        Assert.Null(property.DefaultMetadata.PropertyChangedCallback);
+        Assert.True(property.GlobalIndex >= 0);
+        Assert.Equal(name, property.Name);
+        Assert.Equal(propertyType, property.PropertyType);
+        Assert.Equal(ownerType, property.OwnerType);
+        Assert.False(property.ReadOnly);
+        Assert.Null(property.ValidateValueCallback);
+    }
+
+    [Fact]
+    public void Register_Multiple_GlobalIndexDifferent()
+    {
+        DependencyProperty property1 = DependencyProperty.Register(MethodBase.GetCurrentMethod()!.Name + "1", typeof(int), typeof(DependencyObjectTests));
+        DependencyProperty property2 = DependencyProperty.Register(MethodBase.GetCurrentMethod()!.Name + "2", typeof(int), typeof(DependencyObjectTests));
+        Assert.NotEqual(property1.GlobalIndex, property2.GlobalIndex);
+    }
+
+    [Fact]
+    public void Register_NullName_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("name", () => DependencyProperty.Register(null, typeof(int), typeof(DependencyPropertyTests)));
+    }
+
+    [Fact]
+    public void Register_EmptyName_ThrowsArgumentException()
+    {
+        Assert.Throws<ArgumentException>("name", () => DependencyProperty.Register(string.Empty, typeof(int), typeof(DependencyPropertyTests)));
+    }
+
+    [Fact]
+    public void Register_NullPropertyType_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("propertyType", () => DependencyProperty.Register(MethodBase.GetCurrentMethod()!.Name, null!, typeof(DependencyPropertyTests)));
+        Assert.Throws<ArgumentNullException>("propertyType", () => DependencyProperty.Register(MethodBase.GetCurrentMethod()!.Name, null!, typeof(DependencyPropertyTests), new PropertyMetadata()));
+        Assert.Throws<ArgumentNullException>("propertyType", () => DependencyProperty.Register(MethodBase.GetCurrentMethod()!.Name, null!, typeof(DependencyPropertyTests), new PropertyMetadata(), value => true));
+    }
+
+    [Fact]
+    public void Register_InvalidPropertyType_ThrowsNotSupportedException()
+    {
+        Assert.Throws<NotSupportedException>(() => DependencyProperty.Register(MethodBase.GetCurrentMethod()!.Name, typeof(void), typeof(DependencyPropertyTests)));
+        Assert.Throws<NotSupportedException>(() => DependencyProperty.Register(MethodBase.GetCurrentMethod()!.Name, typeof(void), typeof(DependencyPropertyTests), new PropertyMetadata()));
+        Assert.Throws<NotSupportedException>(() => DependencyProperty.Register(MethodBase.GetCurrentMethod()!.Name, typeof(void), typeof(DependencyPropertyTests), new PropertyMetadata(), value => true));
+    }
+
+    [Theory]
+    [InlineData(typeof(void), "DefaultValue")]
+    [InlineData(typeof(int), "DefaultValue")]
+    [InlineData(typeof(string), 1)]
+    [InlineData(typeof(int), null)]
+    public void Register_PropertyTypeDoesntMatchMetadata_ThrowsArgumentException(Type propertyType, object? defaultValue)
+    {
+        var metadata = new PropertyMetadata(defaultValue);
+        Assert.Throws<ArgumentException>(() => DependencyProperty.Register(MethodBase.GetCurrentMethod()!.Name, propertyType, typeof(DependencyPropertyTests), metadata));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.Register(MethodBase.GetCurrentMethod()!.Name, propertyType, typeof(DependencyPropertyTests), metadata, value => true));
+    }
+
+    [Fact]
+    public void Register_NullOwnerType_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("ownerType", () => DependencyProperty.Register(MethodBase.GetCurrentMethod()!.Name, typeof(int), null!));
+        Assert.Throws<ArgumentNullException>("ownerType", () => DependencyProperty.Register(MethodBase.GetCurrentMethod()!.Name, typeof(int), null!, new PropertyMetadata()));
+        Assert.Throws<ArgumentNullException>("ownerType", () => DependencyProperty.Register(MethodBase.GetCurrentMethod()!.Name, typeof(int), null!, new PropertyMetadata(), value => true));
+    }
+
+    [Theory]
+    [InlineData(typeof(int))]
+    [InlineData(typeof(DependencyPropertyTests))]
+    public void Register_OwnerTypeNotDependencyObjectWithMetadata_ThrowsArgumentException(Type ownerType)
+    {
+        Assert.Throws<ArgumentException>(() => DependencyProperty.Register(MethodBase.GetCurrentMethod()!.Name, typeof(int), ownerType, new PropertyMetadata()));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.Register(MethodBase.GetCurrentMethod()!.Name, typeof(int), ownerType, new PropertyMetadata { DefaultValue = 1 }));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.Register(MethodBase.GetCurrentMethod()!.Name, typeof(int), ownerType, new PropertyMetadata(), value => true));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.Register(MethodBase.GetCurrentMethod()!.Name, typeof(int), ownerType, new PropertyMetadata { DefaultValue = 1 }, value => true));
+    }
+
+    [Fact]
+    public void Register_ExpressionDefaultValue_ThrowsArgumentException()
+    {
+        var metadata = new PropertyMetadata(Activator.CreateInstance(typeof(Expression), nonPublic: true));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.Register(MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(SubDependencyObject), metadata));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.Register(MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(SubDependencyObject), metadata, value => true));
+    }
+
+    [Fact]
+    public void Register_DispatcherObjectDefaultValue_ThrowsArgumentException()
+    {
+        var metadata = new PropertyMetadata(new SubDispatcherObject());
+        Assert.Throws<ArgumentException>(() => DependencyProperty.Register(MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(SubDependencyObject), metadata));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.Register(MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(SubDependencyObject), metadata, value => true));
+    }
+
+    [Fact]
+    public void Register_AlreadyRegistered_ThrowsArgumentException()
+    {
+        DependencyProperty property = DependencyProperty.Register(MethodBase.GetCurrentMethod()!.Name, typeof(int), typeof(DependencyPropertyTests));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.Register(property.Name, typeof(int), typeof(DependencyPropertyTests)));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.Register(property.Name, typeof(int), typeof(DependencyPropertyTests), new PropertyMetadata()));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.Register(property.Name, typeof(int), typeof(DependencyPropertyTests), new PropertyMetadata(), value => true));
+    }
+
+    public static IEnumerable<object?[]> Register_String_Type_Type_ValidateFail_TestData()
+    {
+        yield return new object?[] { " ", typeof(int), typeof(DependencyObjectTests), null, 0 };
+        yield return new object?[] { " ", typeof(int), typeof(DependencyObject), new PropertyMetadata(), 0 };
+        yield return new object?[] { "Register_String_Type_Type_ValidateFail_TestData1", typeof(string), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "Register_String_Type_Type_ValidateFail_TestData2", typeof(string), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { " Register_String_Type_Type_ValidateFail_TestData3 ", typeof(int), typeof(DependencyObjectTests), null, 0 };
+        yield return new object?[] { " Register_String_Type_Type_ValidateFail_TestData4 ", typeof(int), typeof(DependencyObject), new PropertyMetadata(), 0 };
+    }
+
+    [Theory]
+    [MemberData(nameof(Register_String_Type_Type_ValidateFail_TestData))]
+    public void Register_InvokeStringTypeTypeValidateFail_Throws(string name, Type propertyType, Type ownerType, PropertyMetadata typeMetadata, object? expectedDefaultValue)
+    {
+        int callCount = 0;
+        ValidateValueCallback validateValueCallback = value =>
+        {
+            Assert.Equal(expectedDefaultValue, value);
+            callCount++;
+            return false;
+        };
+        Assert.Throws<ArgumentException>(() => DependencyProperty.Register(name, propertyType, ownerType, typeMetadata, validateValueCallback));
+        Assert.Equal(1, callCount);
+    }
+
+    public static IEnumerable<object?[]> RegisterAttached_String_Type_Type_TestData()
+    {
+        yield return new object?[] { "RegisterAttached_String_Type_Type_TestData1", typeof(string), typeof(DependencyObjectTests), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_TestData2", typeof(int), typeof(DependencyObjectTests), 0 };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_TestData3", typeof(int?), typeof(DependencyObjectTests), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_TestData4", typeof(List<int>), typeof(DependencyObjectTests), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_TestData5", typeof(Dictionary<string, int>), typeof(DependencyObjectTests), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_TestData6", typeof(object), typeof(DependencyObjectTests), null };
+        yield return new object?[] { "     ", typeof(int), typeof(DependencyObjectTests), 0 };
+        yield return new object?[] { " RegisterAttached_String_Type_Type_TestData7 ", typeof(int), typeof(DependencyObjectTests), 0 };
+    }
+
+    [Theory]
+    [MemberData(nameof(RegisterAttached_String_Type_Type_TestData))]
+    public void RegisterAttached_InvokeStringTypeType_Success(string name, Type propertyType, Type ownerType, object? expectedDefaultValue)
+    {
+        DependencyProperty property = DependencyProperty.RegisterAttached(name, propertyType, ownerType);
+        Assert.NotNull(property.DefaultMetadata);
+        Assert.Same(property.DefaultMetadata, property.DefaultMetadata);
+        Assert.Null(property.DefaultMetadata.CoerceValueCallback);
+        Assert.Equal(expectedDefaultValue, property.DefaultMetadata.DefaultValue);
+        Assert.Null(property.DefaultMetadata.PropertyChangedCallback);
+        Assert.True(property.GlobalIndex >= 0);
+        Assert.Equal(name, property.Name);
+        Assert.Equal(propertyType, property.PropertyType);
+        Assert.Equal(ownerType, property.OwnerType);
+        Assert.False(property.ReadOnly);
+        Assert.Null(property.ValidateValueCallback);
+    }
+    
+    public static IEnumerable<object?[]> RegisterAttached_String_Type_Type_PropertyMetadata_TestData()
+    {
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData1", typeof(string), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData2", typeof(string), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData3", typeof(string), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData4", typeof(string), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = "value" }, "value" };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData5", typeof(string), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData6", typeof(int), typeof(DependencyObjectTests), null, 0 };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData7", typeof(int), typeof(DependencyObject), new PropertyMetadata(), 0 };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData8", typeof(int), typeof(SubDependencyObject), new PropertyMetadata(), 0 };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData9", typeof(int), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData10", typeof(int?), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData11", typeof(int?), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData12", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData13", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData14", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData15", typeof(List<int>), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData16", typeof(List<int>), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData17", typeof(List<int>), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData18", typeof(List<int>), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = new List<int>() }, new List<int>() };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData19", typeof(Dictionary<string, int>), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData20", typeof(Dictionary<string, int>), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData21", typeof(Dictionary<string, int>), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData22", typeof(Dictionary<string, int>), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = new Dictionary<string, int>() }, new Dictionary<string, int>() };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData23", typeof(object), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData24", typeof(object), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData25", typeof(object), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData26", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = "value" }, "value" };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData27", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData28", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null };
+        yield return new object?[] { "      ", typeof(int), typeof(DependencyObjectTests), null, 0 };
+        yield return new object?[] { " RegisterAttached_String_Type_Type_PropertyMetadata_TestData29 ", typeof(int), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData30", typeof(int), typeof(int), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_TestData31", typeof(int), typeof(DependencyPropertyTests), new PropertyMetadata { DefaultValue = 1 }, 1 };
+    }
+
+    [Theory]
+    [MemberData(nameof(RegisterAttached_String_Type_Type_PropertyMetadata_TestData))]
+    public void RegisterAttached_InvokeStringTypeTypePropertyMetadata_Success(string name, Type propertyType, Type ownerType, PropertyMetadata typeMetadata, object? expectedDefaultValue)
+    {
+        DependencyProperty property = DependencyProperty.RegisterAttached(name, propertyType, ownerType, typeMetadata);
+        Assert.NotNull(property.DefaultMetadata);
+        Assert.Same(property.DefaultMetadata, property.DefaultMetadata);
+        Assert.Null(property.DefaultMetadata.CoerceValueCallback);
+        Assert.Equal(expectedDefaultValue, property.DefaultMetadata.DefaultValue);
+        Assert.Null(property.DefaultMetadata.PropertyChangedCallback);
+        Assert.True(property.GlobalIndex >= 0);
+        Assert.Equal(name, property.Name);
+        Assert.Equal(propertyType, property.PropertyType);
+        Assert.Equal(ownerType, property.OwnerType);
+        Assert.False(property.ReadOnly);
+        Assert.Null(property.ValidateValueCallback);
+    }
+
+    public static IEnumerable<object?[]> RegisterAttached_String_Type_Type_Validate_TestData()
+    {
+        yield return new object?[] { "RegisterAttached_String_Type_Type_Validate_TestData1", typeof(string), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_Validate_TestData2", typeof(string), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_Validate_TestData3", typeof(string), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_Validate_TestData4", typeof(string), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = "value" }, "value" };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_Validate_TestData5", typeof(string), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_Validate_TestData6", typeof(int), typeof(DependencyObjectTests), null, 0 };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_Validate_TestData7", typeof(int), typeof(DependencyObject), new PropertyMetadata(), 0 };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_Validate_TestData8", typeof(int), typeof(SubDependencyObject), new PropertyMetadata(), 0 };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_Validate_TestData9", typeof(int), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_Validate_TestData10", typeof(int?), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_Validate_TestData11", typeof(int?), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_Validate_TestData12", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_Validate_TestData13", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_Validate_TestData14", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_Validate_TestData15", typeof(List<int>), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_Validate_TestData16", typeof(List<int>), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_Validate_TestData17", typeof(List<int>), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_Validate_TestData18", typeof(List<int>), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = new List<int>() }, new List<int>() };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_Validate_TestData19", typeof(Dictionary<string, int>), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_Validate_TestData20", typeof(Dictionary<string, int>), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_Validate_TestData21", typeof(Dictionary<string, int>), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_Validate_TestData22", typeof(Dictionary<string, int>), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = new Dictionary<string, int>() }, new Dictionary<string, int>() };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_Validate_TestData23", typeof(object), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_Validate_TestData24", typeof(object), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_Validate_TestData25", typeof(object), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_Validate_TestData26", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = "value" }, "value" };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_Validate_TestData27", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_Validate_TestData28", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null };
+        yield return new object?[] { "       ", typeof(int), typeof(DependencyObjectTests), null, 0 };
+        yield return new object?[] { " RegisterAttached_String_Type_Type_Validate_TestData29 ", typeof(int), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+    }
+
+    [Theory]
+    [MemberData(nameof(RegisterAttached_String_Type_Type_Validate_TestData))]
+    public void RegisterAttached_InvokeStringTypeTypePropertyMetadataValidate_Success(string name, Type propertyType, Type ownerType, PropertyMetadata typeMetadata, object? expectedDefaultValue)
+    {
+        int callCount = 0;
+        ValidateValueCallback validateValueCallback = value =>
+        {
+            Assert.Equal(expectedDefaultValue, value);
+            callCount++;
+            return true;
+        };
+        DependencyProperty property = DependencyProperty.RegisterAttached(name, propertyType, ownerType, typeMetadata, validateValueCallback);
+        Assert.NotNull(property.DefaultMetadata);
+        Assert.Same(property.DefaultMetadata, property.DefaultMetadata);
+        Assert.Null(property.DefaultMetadata.CoerceValueCallback);
+        Assert.Equal(expectedDefaultValue, property.DefaultMetadata.DefaultValue);
+        Assert.Null(property.DefaultMetadata.PropertyChangedCallback);
+        Assert.True(property.GlobalIndex >= 0);
+        Assert.Equal(name, property.Name);
+        Assert.Equal(propertyType, property.PropertyType);
+        Assert.Equal(ownerType, property.OwnerType);
+        Assert.False(property.ReadOnly);
+        Assert.Same(validateValueCallback, property.ValidateValueCallback);
+        Assert.Equal(1, callCount);
+    }
+
+    public static IEnumerable<object?[]> RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData()
+    {
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData1", typeof(string), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData2", typeof(string), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData3", typeof(string), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData4", typeof(string), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = "value" }, "value" };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData5", typeof(string), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData6", typeof(int), typeof(DependencyObjectTests), null, 0 };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData7", typeof(int), typeof(DependencyObject), new PropertyMetadata(), 0 };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData8", typeof(int), typeof(SubDependencyObject), new PropertyMetadata(), 0 };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData9", typeof(int), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData10", typeof(int?), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData11", typeof(int?), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData12", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData13", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData14", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData15", typeof(List<int>), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData16", typeof(List<int>), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData17", typeof(List<int>), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData18", typeof(List<int>), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = new List<int>() }, new List<int>() };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData19", typeof(Dictionary<string, int>), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData20", typeof(Dictionary<string, int>), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData21", typeof(Dictionary<string, int>), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData22", typeof(Dictionary<string, int>), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = new Dictionary<string, int>() }, new Dictionary<string, int>() };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData23", typeof(object), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData24", typeof(object), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData25", typeof(object), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData26", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = "value" }, "value" };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData27", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData28", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null };
+        yield return new object?[] { "        ", typeof(int), typeof(DependencyObjectTests), null, 0 };
+        yield return new object?[] { " RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData8 ", typeof(int), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+    }
+
+    [Theory]
+    [MemberData(nameof(RegisterAttached_String_Type_Type_PropertyMetadata_NullValidate_TestData))]
+    public void RegisterAttached_InvokeStringTypeTypePropertyMetadataNullValidate_Success(string name, Type propertyType, Type ownerType, PropertyMetadata typeMetadata, object? expectedDefaultValue)
+    {
+        DependencyProperty property = DependencyProperty.RegisterAttached(name, propertyType, ownerType, typeMetadata, null);
+        Assert.NotNull(property.DefaultMetadata);
+        Assert.Same(property.DefaultMetadata, property.DefaultMetadata);
+        Assert.Null(property.DefaultMetadata.CoerceValueCallback);
+        Assert.Equal(expectedDefaultValue, property.DefaultMetadata.DefaultValue);
+        Assert.Null(property.DefaultMetadata.PropertyChangedCallback);
+        Assert.True(property.GlobalIndex >= 0);
+        Assert.Equal(name, property.Name);
+        Assert.Equal(propertyType, property.PropertyType);
+        Assert.Equal(ownerType, property.OwnerType);
+        Assert.False(property.ReadOnly);
+        Assert.Null(property.ValidateValueCallback);
+    }
+
+    [Fact]
+    public void RegisterAttached_Multiple_GlobalIndexDifferent()
+    {
+        DependencyProperty property1 = DependencyProperty.RegisterAttached(MethodBase.GetCurrentMethod()!.Name + "1", typeof(int), typeof(DependencyObjectTests));
+        DependencyProperty property2 = DependencyProperty.RegisterAttached(MethodBase.GetCurrentMethod()!.Name + "2", typeof(int), typeof(DependencyObjectTests));
+        Assert.NotEqual(property1.GlobalIndex, property2.GlobalIndex);
+    }
+
+    [Fact]
+    public void RegisterAttached_NullName_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("name", () => DependencyProperty.RegisterAttached(null, typeof(int), typeof(DependencyPropertyTests)));
+        Assert.Throws<ArgumentNullException>("name", () => DependencyProperty.RegisterAttached(null, typeof(int), typeof(DependencyPropertyTests), new PropertyMetadata()));
+        Assert.Throws<ArgumentNullException>("name", () => DependencyProperty.RegisterAttached(null, typeof(int), typeof(DependencyPropertyTests), new PropertyMetadata(), value => true));
+    }
+
+    [Fact]
+    public void RegisterAttached_EmptyName_ThrowsArgumentException()
+    {
+        Assert.Throws<ArgumentException>("name", () => DependencyProperty.RegisterAttached(string.Empty, typeof(int), typeof(DependencyPropertyTests)));
+        Assert.Throws<ArgumentException>("name", () => DependencyProperty.RegisterAttached(string.Empty, typeof(int), typeof(DependencyPropertyTests), new PropertyMetadata()));
+        Assert.Throws<ArgumentException>("name", () => DependencyProperty.RegisterAttached(string.Empty, typeof(int), typeof(DependencyPropertyTests), new PropertyMetadata(), value => true));
+    }
+
+    [Fact]
+    public void RegisterAttached_NullPropertyType_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("propertyType", () => DependencyProperty.RegisterAttached(MethodBase.GetCurrentMethod()!.Name, null!, typeof(DependencyPropertyTests)));
+        Assert.Throws<ArgumentNullException>("propertyType", () => DependencyProperty.RegisterAttached(MethodBase.GetCurrentMethod()!.Name, null!, typeof(DependencyPropertyTests), new PropertyMetadata()));
+        Assert.Throws<ArgumentNullException>("propertyType", () => DependencyProperty.RegisterAttached(MethodBase.GetCurrentMethod()!.Name, null!, typeof(DependencyPropertyTests), new PropertyMetadata(), value => true));
+    }
+
+    [Fact]
+    public void RegisterAttached_InvalidPropertyType_ThrowsNotSupportedException()
+    {
+        Assert.Throws<NotSupportedException>(() => DependencyProperty.RegisterAttached(MethodBase.GetCurrentMethod()!.Name, typeof(void), typeof(DependencyPropertyTests)));
+        Assert.Throws<NotSupportedException>(() => DependencyProperty.RegisterAttached(MethodBase.GetCurrentMethod()!.Name, typeof(void), typeof(DependencyPropertyTests), new PropertyMetadata()));
+        Assert.Throws<NotSupportedException>(() => DependencyProperty.RegisterAttached(MethodBase.GetCurrentMethod()!.Name, typeof(void), typeof(DependencyPropertyTests), new PropertyMetadata(), value => true));
+    }
+
+    [Theory]
+    [InlineData(typeof(void), "DefaultValue")]
+    [InlineData(typeof(int), "DefaultValue")]
+    [InlineData(typeof(string), 1)]
+    [InlineData(typeof(int), null)]
+    public void RegisterAttached_PropertyTypeDoesntMatchMetadata_ThrowsArgumentException(Type propertyType, object? defaultValue)
+    {
+        var metadata = new PropertyMetadata(defaultValue);
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterAttached(MethodBase.GetCurrentMethod()!.Name, propertyType, typeof(DependencyPropertyTests), metadata));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterAttached(MethodBase.GetCurrentMethod()!.Name, propertyType, typeof(DependencyPropertyTests), metadata, value => true));
+    }
+
+    [Fact]
+    public void RegisterAttached_NullOwnerType_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("ownerType", () => DependencyProperty.RegisterAttached(MethodBase.GetCurrentMethod()!.Name, typeof(int), null!));
+        Assert.Throws<ArgumentNullException>("ownerType", () => DependencyProperty.RegisterAttached(MethodBase.GetCurrentMethod()!.Name, typeof(int), null!, new PropertyMetadata()));
+        Assert.Throws<ArgumentNullException>("ownerType", () => DependencyProperty.RegisterAttached(MethodBase.GetCurrentMethod()!.Name, typeof(int), null!, new PropertyMetadata(), value => true));
+    }
+
+    [Fact]
+    public void RegisterAttached_ExpressionDefaultValue_ThrowsArgumentException()
+    {
+        var metadata = new PropertyMetadata(Activator.CreateInstance(typeof(Expression), nonPublic: true));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterAttached(MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(SubDependencyObject), metadata));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterAttached(MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(SubDependencyObject), metadata, value => true));
+    }
+
+    [Fact]
+    public void RegisterAttached_DispatcherObjectDefaultValue_ThrowsArgumentException()
+    {
+        var metadata = new PropertyMetadata(new SubDispatcherObject());
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterAttached(MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(SubDependencyObject), metadata));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterAttached(MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(SubDependencyObject), metadata, value => true));
+    }
+
+    [Fact]
+    public void RegisterAttached_AlreadyRegisterAttacheded_ThrowsArgumentException()
+    {
+        DependencyProperty property = DependencyProperty.RegisterAttached(MethodBase.GetCurrentMethod()!.Name, typeof(int), typeof(DependencyPropertyTests));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterAttached(property.Name, typeof(int), typeof(DependencyPropertyTests)));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterAttached(property.Name, typeof(int), typeof(DependencyPropertyTests), new PropertyMetadata()));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterAttached(property.Name, typeof(int), typeof(DependencyPropertyTests), new PropertyMetadata(), value => true));
+    }
+
+    public static IEnumerable<object?[]> RegisterAttached_String_Type_Type_ValidateFail_TestData()
+    {
+        yield return new object?[] { "         ", typeof(int), typeof(DependencyObjectTests), null, 0 };
+        yield return new object?[] { "          ", typeof(int), typeof(DependencyObject), new PropertyMetadata(), 0 };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_ValidateFail_TestData1", typeof(string), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "RegisterAttached_String_Type_Type_ValidateFail_TestData2", typeof(string), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { " RegisterAttached_String_Type_Type_ValidateFail_TestData3 ", typeof(int), typeof(DependencyObjectTests), null, 0 };
+        yield return new object?[] { " RegisterAttached_String_Type_Type_ValidateFail_TestData4 ", typeof(int), typeof(DependencyObject), new PropertyMetadata(), 0 };
+    }
+
+    [Theory]
+    [MemberData(nameof(RegisterAttached_String_Type_Type_ValidateFail_TestData))]
+    public void RegisterAttached_InvokeStringTypeTypeValidateFail_Throws(string name, Type propertyType, Type ownerType, PropertyMetadata typeMetadata, object? expectedDefaultValue)
+    {
+        int callCount = 0;
+        ValidateValueCallback validateValueCallback = value =>
+        {
+            Assert.Equal(expectedDefaultValue, value);
+            callCount++;
+            return false;
+        };
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterAttached(name, propertyType, ownerType, typeMetadata, validateValueCallback));
+        Assert.Equal(1, callCount);
+    }
+    
+    public static IEnumerable<object?[]> RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData()
+    {
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData1", typeof(string), typeof(DependencyObject), null, null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData2", typeof(string), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData3", typeof(string), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData4", typeof(string), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = "value" }, "value" };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData5", typeof(string), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData6", typeof(int), typeof(DependencyObject), null, 0 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData7", typeof(int), typeof(DependencyObject), new PropertyMetadata(), 0 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData8", typeof(int), typeof(SubDependencyObject), new PropertyMetadata(), 0 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData9", typeof(int), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData10", typeof(int?), typeof(DependencyObject), null, null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData11", typeof(int?), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData12", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData13", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData14", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData15", typeof(List<int>), typeof(DependencyObject), null, null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData16", typeof(List<int>), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData17", typeof(List<int>), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData18", typeof(List<int>), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = new List<int>() }, new List<int>() };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData19", typeof(Dictionary<string, int>), typeof(DependencyObject), null, null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData20", typeof(Dictionary<string, int>), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData21", typeof(Dictionary<string, int>), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData22", typeof(Dictionary<string, int>), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = new Dictionary<string, int>() }, new Dictionary<string, int>() };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData23", typeof(object), typeof(DependencyObject), null, null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData24", typeof(object), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData25", typeof(object), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData26", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = "value" }, "value" };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData27", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData28", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null };
+        yield return new object?[] { "           ", typeof(int), typeof(DependencyObject), null, 0 };
+        yield return new object?[] { " RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData29 ", typeof(int), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+    }
+
+    [Theory]
+    [MemberData(nameof(RegisterReadOnly_String_Type_Type_PropertyMetadata_TestData))]
+    public void RegisterReadOnly_InvokeStringTypeTypePropertyMetadata_Success(string name, Type propertyType, Type ownerType, PropertyMetadata typeMetadata, object? expectedDefaultValue)
+    {
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(name, propertyType, ownerType, typeMetadata);
+        Assert.NotNull(key.DependencyProperty);
+        Assert.Same(key.DependencyProperty, key.DependencyProperty);
+
+        DependencyProperty property = key.DependencyProperty;
+        Assert.NotNull(property.DefaultMetadata);
+        Assert.Same(property.DefaultMetadata, property.DefaultMetadata);
+        Assert.Null(property.DefaultMetadata.CoerceValueCallback);
+        Assert.Equal(expectedDefaultValue, property.DefaultMetadata.DefaultValue);
+        Assert.Null(property.DefaultMetadata.PropertyChangedCallback);
+        Assert.True(property.GlobalIndex >= 0);
+        Assert.Equal(name, property.Name);
+        Assert.Equal(propertyType, property.PropertyType);
+        Assert.Equal(ownerType, property.OwnerType);
+        Assert.True(property.ReadOnly);
+        Assert.Null(property.ValidateValueCallback);
+    }
+
+    public static IEnumerable<object?[]> RegisterReadOnly_String_Type_Type_Validate_TestData()
+    {
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_Validate_TestData1", typeof(string), typeof(DependencyObject), null, null, 4 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_Validate_TestData2", typeof(string), typeof(DependencyObject), new PropertyMetadata(), null, 2 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_Validate_TestData3", typeof(string), typeof(SubDependencyObject), new PropertyMetadata(), null, 2 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_Validate_TestData4", typeof(string), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = "value" }, "value", 2 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_Validate_TestData5", typeof(string), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null, 2 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_Validate_TestData6", typeof(int), typeof(DependencyObject), null, 0, 4 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_Validate_TestData7", typeof(int), typeof(DependencyObject), new PropertyMetadata(), 0, 2 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_Validate_TestData8", typeof(int), typeof(SubDependencyObject), new PropertyMetadata(), 0, 2 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_Validate_TestData9", typeof(int), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1, 2 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_Validate_TestData10", typeof(int?), typeof(DependencyObject), null, null, 4 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_Validate_TestData11", typeof(int?), typeof(DependencyObject), new PropertyMetadata(), null, 2 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_Validate_TestData12", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata(), null, 2 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_Validate_TestData13", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1, 2 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_Validate_TestData14", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null, 2 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_Validate_TestData15", typeof(List<int>), typeof(DependencyObject), null, null, 4 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_Validate_TestData16", typeof(List<int>), typeof(DependencyObject), new PropertyMetadata(), null, 2 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_Validate_TestData17", typeof(List<int>), typeof(SubDependencyObject), new PropertyMetadata(), null, 2 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_Validate_TestData18", typeof(List<int>), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = new List<int>() }, new List<int>(), 2 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_Validate_TestData19", typeof(Dictionary<string, int>), typeof(DependencyObject), null, null, 4 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_Validate_TestData20", typeof(Dictionary<string, int>), typeof(DependencyObject), new PropertyMetadata(), null, 2 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_Validate_TestData21", typeof(Dictionary<string, int>), typeof(SubDependencyObject), new PropertyMetadata(), null, 2 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_Validate_TestData22", typeof(Dictionary<string, int>), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = new Dictionary<string, int>() }, new Dictionary<string, int>(), 2 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_Validate_TestData23", typeof(object), typeof(DependencyObject), null, null, 4 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_Validate_TestData24", typeof(object), typeof(DependencyObject), new PropertyMetadata(), null, 2 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_Validate_TestData25", typeof(object), typeof(SubDependencyObject), new PropertyMetadata(), null, 2 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_Validate_TestData26", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = "value" }, "value", 2 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_Validate_TestData27", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1, 2 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_Validate_TestData28", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null, 2 };
+        yield return new object?[] { "            ", typeof(int), typeof(DependencyObject), null, 0, 4 };
+        yield return new object?[] { " RegisterReadOnly_String_Type_Type_Validate_TestData29 ", typeof(int), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1, 2 };
+    }
+
+    [Theory]
+    [MemberData(nameof(RegisterReadOnly_String_Type_Type_Validate_TestData))]
+    public void RegisterReadOnly_InvokeStringTypeTypePropertyMetadataValidate_Success(string name, Type propertyType, Type ownerType, PropertyMetadata typeMetadata, object? expectedDefaultValue, int expectedValidateValueCallbackCallCount)
+    {
+        int callCount = 0;
+        ValidateValueCallback validateValueCallback = value =>
+        {
+            Assert.Equal(expectedDefaultValue, value);
+            callCount++;
+            return true;
+        };
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(name, propertyType, ownerType, typeMetadata, validateValueCallback);
+        Assert.NotNull(key.DependencyProperty);
+        Assert.Same(key.DependencyProperty, key.DependencyProperty);
+
+        DependencyProperty property = key.DependencyProperty;
+        Assert.NotNull(property.DefaultMetadata);
+        Assert.Same(property.DefaultMetadata, property.DefaultMetadata);
+        Assert.Null(property.DefaultMetadata.CoerceValueCallback);
+        Assert.Equal(expectedDefaultValue, property.DefaultMetadata.DefaultValue);
+        Assert.Null(property.DefaultMetadata.PropertyChangedCallback);
+        Assert.True(property.GlobalIndex >= 0);
+        Assert.Equal(name, property.Name);
+        Assert.Equal(propertyType, property.PropertyType);
+        Assert.Equal(ownerType, property.OwnerType);
+        Assert.True(property.ReadOnly);
+        Assert.Same(validateValueCallback, property.ValidateValueCallback);
+        Assert.Equal(expectedValidateValueCallbackCallCount, callCount);
+    }
+
+    public static IEnumerable<object?[]> RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData()
+    {
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData1", typeof(string), typeof(DependencyObject), null, null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData2", typeof(string), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData3", typeof(string), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData4", typeof(string), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = "value" }, "value" };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData5", typeof(string), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData6", typeof(int), typeof(DependencyObject), null, 0 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData7", typeof(int), typeof(DependencyObject), new PropertyMetadata(), 0 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData8", typeof(int), typeof(SubDependencyObject), new PropertyMetadata(), 0 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData9", typeof(int), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData10", typeof(int?), typeof(DependencyObject), null, null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData11", typeof(int?), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData12", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData13", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData14", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData15", typeof(List<int>), typeof(DependencyObject), null, null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData16", typeof(List<int>), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData17", typeof(List<int>), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData18", typeof(List<int>), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = new List<int>() }, new List<int>() };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData19", typeof(Dictionary<string, int>), typeof(DependencyObject), null, null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData20", typeof(Dictionary<string, int>), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData21", typeof(Dictionary<string, int>), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData22", typeof(Dictionary<string, int>), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = new Dictionary<string, int>() }, new Dictionary<string, int>() };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData23", typeof(object), typeof(DependencyObject), null, null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData24", typeof(object), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData25", typeof(object), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData26", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = "value" }, "value" };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData27", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData28", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null };
+        yield return new object?[] { "             ", typeof(int), typeof(DependencyObject), null, 0 };
+        yield return new object?[] { " RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData8 ", typeof(int), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+    }
+
+    [Theory]
+    [MemberData(nameof(RegisterReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData))]
+    public void RegisterReadOnly_InvokeStringTypeTypePropertyMetadataNullValidate_Success(string name, Type propertyType, Type ownerType, PropertyMetadata typeMetadata, object? expectedDefaultValue)
+    {
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(name, propertyType, ownerType, typeMetadata, null);
+        Assert.NotNull(key.DependencyProperty);
+        Assert.Same(key.DependencyProperty, key.DependencyProperty);
+
+        DependencyProperty property = key.DependencyProperty;
+        Assert.NotNull(property.DefaultMetadata);
+        Assert.Same(property.DefaultMetadata, property.DefaultMetadata);
+        Assert.Null(property.DefaultMetadata.CoerceValueCallback);
+        Assert.Equal(expectedDefaultValue, property.DefaultMetadata.DefaultValue);
+        Assert.Null(property.DefaultMetadata.PropertyChangedCallback);
+        Assert.True(property.GlobalIndex >= 0);
+        Assert.Equal(name, property.Name);
+        Assert.Equal(propertyType, property.PropertyType);
+        Assert.Equal(ownerType, property.OwnerType);
+        Assert.True(property.ReadOnly);
+        Assert.Null(property.ValidateValueCallback);
+    }
+
+    [Fact]
+    public void RegisterReadOnly_Multiple_GlobalIndexDifferent()
+    {
+        DependencyProperty property1 = DependencyProperty.RegisterReadOnly(MethodBase.GetCurrentMethod()!.Name + "1", typeof(int), typeof(DependencyObject), new PropertyMetadata()).DependencyProperty;
+        DependencyProperty property2 = DependencyProperty.RegisterReadOnly(MethodBase.GetCurrentMethod()!.Name + "2", typeof(int), typeof(DependencyObject), new PropertyMetadata()).DependencyProperty;
+        Assert.NotEqual(property1.GlobalIndex, property2.GlobalIndex);
+    }
+
+    [Fact]
+    public void RegisterReadOnly_NullName_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("name", () => DependencyProperty.RegisterReadOnly(null, typeof(int), typeof(DependencyObject), new PropertyMetadata()));
+        Assert.Throws<ArgumentNullException>("name", () => DependencyProperty.RegisterReadOnly(null, typeof(int), typeof(DependencyObject), new PropertyMetadata(), value => true));
+    }
+
+    [Fact]
+    public void RegisterReadOnly_EmptyName_ThrowsArgumentException()
+    {
+        Assert.Throws<ArgumentException>("name", () => DependencyProperty.RegisterReadOnly(string.Empty, typeof(int), typeof(DependencyObject), new PropertyMetadata()));
+        Assert.Throws<ArgumentException>("name", () => DependencyProperty.RegisterReadOnly(string.Empty, typeof(int), typeof(DependencyObject), new PropertyMetadata(), value => true));
+    }
+
+    [Fact]
+    public void RegisterReadOnly_NullPropertyType_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("propertyType", () => DependencyProperty.RegisterReadOnly(MethodBase.GetCurrentMethod()!.Name, null!, typeof(DependencyProperty), new PropertyMetadata()));
+        Assert.Throws<ArgumentNullException>("propertyType", () => DependencyProperty.RegisterReadOnly(MethodBase.GetCurrentMethod()!.Name, null!, typeof(DependencyProperty), new PropertyMetadata(), value => true));
+    }
+
+    [Fact]
+    public void RegisterReadOnly_InvalidPropertyType_ThrowsNotSupportedException()
+    {
+        Assert.Throws<NotSupportedException>(() => DependencyProperty.RegisterReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(void), typeof(DependencyObject), new PropertyMetadata()));
+        Assert.Throws<NotSupportedException>(() => DependencyProperty.RegisterReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(void), typeof(DependencyObject), new PropertyMetadata(), value => true));
+    }
+
+    [Theory]
+    [InlineData(typeof(void), "DefaultValue")]
+    [InlineData(typeof(int), "DefaultValue")]
+    [InlineData(typeof(string), 1)]
+    [InlineData(typeof(int), null)]
+    public void RegisterReadOnly_PropertyTypeDoesntMatchMetadata_ThrowsArgumentException(Type propertyType, object? defaultValue)
+    {
+        var metadata = new PropertyMetadata(defaultValue);
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterReadOnly(MethodBase.GetCurrentMethod()!.Name, propertyType, typeof(DependencyProperty), metadata));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterReadOnly(MethodBase.GetCurrentMethod()!.Name, propertyType, typeof(DependencyProperty), metadata, value => true));
+    }
+
+    [Fact]
+    public void RegisterReadOnly_NullOwnerType_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("ownerType", () => DependencyProperty.RegisterReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(int), null!, new PropertyMetadata()));
+        Assert.Throws<ArgumentNullException>("ownerType", () => DependencyProperty.RegisterReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(int), null!, new PropertyMetadata(), value => true));
+    }
+
+    [Theory]
+    [InlineData(typeof(int))]
+    [InlineData(typeof(DependencyPropertyTests))]
+    public void RegisterReadOnly_OwnerTypeNotDependencyObjectWithMetadata_ThrowsArgumentException(Type ownerType)
+    {
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(int), ownerType, null));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(int), ownerType, new PropertyMetadata()));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(int), ownerType, new PropertyMetadata { DefaultValue = 1 }));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(int), ownerType, null, value => true));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(int), ownerType, new PropertyMetadata(), value => true));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(int), ownerType, new PropertyMetadata { DefaultValue = 1 }, value => true));
+    }
+
+    [Fact]
+    public void RegisterReadOnly_ExpressionDefaultValue_ThrowsArgumentException()
+    {
+        var metadata = new PropertyMetadata(Activator.CreateInstance(typeof(Expression), nonPublic: true));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(SubDependencyObject), metadata));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(SubDependencyObject), metadata, value => true));
+    }
+
+    [Fact]
+    public void RegisterReadOnly_DispatcherObjectDefaultValue_ThrowsArgumentException()
+    {
+        var metadata = new PropertyMetadata(new SubDispatcherObject());
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(SubDependencyObject), metadata));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(SubDependencyObject), metadata, value => true));
+    }
+
+    [Fact]
+    public void RegisterReadOnly_AlreadyRegistered_ThrowsArgumentException()
+    {
+        DependencyProperty property = DependencyProperty.RegisterReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(int), typeof(DependencyObject), new PropertyMetadata()).DependencyProperty;
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterReadOnly(property.Name, typeof(int), typeof(DependencyObject), new PropertyMetadata()));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterReadOnly(property.Name, typeof(int), typeof(DependencyObject), new PropertyMetadata(), value => true));
+    }
+
+    public static IEnumerable<object?[]> RegisterReadOnly_String_Type_Type_ValidateFail_TestData()
+    {
+        yield return new object?[] { " ", typeof(int), typeof(DependencyObject), null, 0 };
+        yield return new object?[] { " ", typeof(int), typeof(DependencyObject), new PropertyMetadata(), 0 };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_ValidateFail_TestData1", typeof(string), typeof(DependencyObject), null, null };
+        yield return new object?[] { "RegisterReadOnly_String_Type_Type_ValidateFail_TestData2", typeof(string), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { " RegisterReadOnly_String_Type_Type_ValidateFail_TestData3 ", typeof(int), typeof(DependencyObject), null, 0 };
+        yield return new object?[] { " RegisterReadOnly_String_Type_Type_ValidateFail_TestData4 ", typeof(int), typeof(DependencyObject), new PropertyMetadata(), 0 };
+    }
+
+    [Theory]
+    [MemberData(nameof(RegisterReadOnly_String_Type_Type_ValidateFail_TestData))]
+    public void RegisterReadOnly_InvokeStringTypeTypeValidateFail_Throws(string name, Type propertyType, Type ownerType, PropertyMetadata typeMetadata, object? expectedDefaultValue)
+    {
+        int callCount = 0;
+        ValidateValueCallback validateValueCallback = value =>
+        {
+            Assert.Equal(expectedDefaultValue, value);
+            callCount++;
+            return false;
+        };
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterReadOnly(name, propertyType, ownerType, typeMetadata, validateValueCallback));
+        Assert.Equal(1, callCount);
+    }
+
+    public static IEnumerable<object?[]> RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData()
+    {
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData1", typeof(string), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData2", typeof(string), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData3", typeof(string), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData4", typeof(string), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = "value" }, "value" };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData5", typeof(string), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData6", typeof(int), typeof(DependencyObjectTests), null, 0 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData7", typeof(int), typeof(DependencyObject), new PropertyMetadata(), 0 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData8", typeof(int), typeof(SubDependencyObject), new PropertyMetadata(), 0 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData9", typeof(int), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData10", typeof(int?), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData11", typeof(int?), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData12", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData13", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData14", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData15", typeof(List<int>), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData16", typeof(List<int>), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData17", typeof(List<int>), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData18", typeof(List<int>), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = new List<int>() }, new List<int>() };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData19", typeof(Dictionary<string, int>), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData20", typeof(Dictionary<string, int>), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData21", typeof(Dictionary<string, int>), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData22", typeof(Dictionary<string, int>), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = new Dictionary<string, int>() }, new Dictionary<string, int>() };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData23", typeof(object), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData24", typeof(object), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData25", typeof(object), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData26", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = "value" }, "value" };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData27", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData28", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null };
+        yield return new object?[] { "              ", typeof(int), typeof(DependencyObjectTests), null, 0 };
+        yield return new object?[] { " RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData29 ", typeof(int), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData30", typeof(int), typeof(int), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData31", typeof(int), typeof(DependencyPropertyTests), new PropertyMetadata { DefaultValue = 1 }, 1 };
+    }
+
+    [Theory]
+    [MemberData(nameof(RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_TestData))]
+    public void RegisterAttachedReadOnly_InvokeStringTypeTypePropertyMetadata_Success(string name, Type propertyType, Type ownerType, PropertyMetadata typeMetadata, object? expectedDefaultValue)
+    {
+        DependencyPropertyKey key = DependencyProperty.RegisterAttachedReadOnly(name, propertyType, ownerType, typeMetadata);
+        Assert.NotNull(key.DependencyProperty);
+        Assert.Same(key.DependencyProperty, key.DependencyProperty);
+
+        DependencyProperty property = key.DependencyProperty;
+        Assert.NotNull(property.DefaultMetadata);
+        Assert.Same(property.DefaultMetadata, property.DefaultMetadata);
+        Assert.Null(property.DefaultMetadata.CoerceValueCallback);
+        Assert.Equal(expectedDefaultValue, property.DefaultMetadata.DefaultValue);
+        Assert.Null(property.DefaultMetadata.PropertyChangedCallback);
+        Assert.True(property.GlobalIndex >= 0);
+        Assert.Equal(name, property.Name);
+        Assert.Equal(propertyType, property.PropertyType);
+        Assert.Equal(ownerType, property.OwnerType);
+        Assert.True(property.ReadOnly);
+        Assert.Null(property.ValidateValueCallback);
+    }
+
+    public static IEnumerable<object?[]> RegisterAttachedReadOnly_String_Type_Type_Validate_TestData()
+    {
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_Validate_TestData1", typeof(string), typeof(DependencyObjectTests), null, null, 2 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_Validate_TestData2", typeof(string), typeof(DependencyObject), new PropertyMetadata(), null, 1 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_Validate_TestData3", typeof(string), typeof(SubDependencyObject), new PropertyMetadata(), null, 1 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_Validate_TestData4", typeof(string), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = "value" }, "value", 1 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_Validate_TestData5", typeof(string), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null, 1 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_Validate_TestData6", typeof(int), typeof(DependencyObjectTests), null, 0, 2 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_Validate_TestData7", typeof(int), typeof(DependencyObject), new PropertyMetadata(), 0, 1 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_Validate_TestData8", typeof(int), typeof(SubDependencyObject), new PropertyMetadata(), 0, 1 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_Validate_TestData9", typeof(int), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1, 1 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_Validate_TestData10", typeof(int?), typeof(DependencyObjectTests), null, null, 2 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_Validate_TestData11", typeof(int?), typeof(DependencyObject), new PropertyMetadata(), null, 1 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_Validate_TestData12", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata(), null, 1 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_Validate_TestData13", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1, 1 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_Validate_TestData14", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null, 1 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_Validate_TestData15", typeof(List<int>), typeof(DependencyObjectTests), null, null, 2 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_Validate_TestData16", typeof(List<int>), typeof(DependencyObject), new PropertyMetadata(), null, 1 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_Validate_TestData17", typeof(List<int>), typeof(SubDependencyObject), new PropertyMetadata(), null, 1 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_Validate_TestData18", typeof(List<int>), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = new List<int>() }, new List<int>(), 1 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_Validate_TestData19", typeof(Dictionary<string, int>), typeof(DependencyObjectTests), null, null, 2 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_Validate_TestData20", typeof(Dictionary<string, int>), typeof(DependencyObject), new PropertyMetadata(), null, 1 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_Validate_TestData21", typeof(Dictionary<string, int>), typeof(SubDependencyObject), new PropertyMetadata(), null, 1 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_Validate_TestData22", typeof(Dictionary<string, int>), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = new Dictionary<string, int>() }, new Dictionary<string, int>(), 1 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_Validate_TestData23", typeof(object), typeof(DependencyObjectTests), null, null, 2 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_Validate_TestData24", typeof(object), typeof(DependencyObject), new PropertyMetadata(), null, 1 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_Validate_TestData25", typeof(object), typeof(SubDependencyObject), new PropertyMetadata(), null, 1 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_Validate_TestData26", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = "value" }, "value", 1 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_Validate_TestData27", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1, 1 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_Validate_TestData28", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null, 1 };
+        yield return new object?[] { "               ", typeof(int), typeof(DependencyObjectTests), null, 0, 2 };
+        yield return new object?[] { " RegisterAttachedReadOnly_String_Type_Type_Validate_TestData29 ", typeof(int), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1, 1 };
+    }
+
+    [Theory]
+    [MemberData(nameof(RegisterAttachedReadOnly_String_Type_Type_Validate_TestData))]
+    public void RegisterAttachedReadOnly_InvokeStringTypeTypePropertyMetadataValidate_Success(string name, Type propertyType, Type ownerType, PropertyMetadata typeMetadata, object? expectedDefaultValue, int expectedValidateValueCallbackCallCount)
+    {
+        int callCount = 0;
+        ValidateValueCallback validateValueCallback = value =>
+        {
+            Assert.Equal(expectedDefaultValue, value);
+            callCount++;
+            return true;
+        };
+        DependencyPropertyKey key = DependencyProperty.RegisterAttachedReadOnly(name, propertyType, ownerType, typeMetadata, validateValueCallback);
+        Assert.NotNull(key.DependencyProperty);
+        Assert.Same(key.DependencyProperty, key.DependencyProperty);
+
+        DependencyProperty property = key.DependencyProperty;
+        Assert.NotNull(property.DefaultMetadata);
+        Assert.Same(property.DefaultMetadata, property.DefaultMetadata);
+        Assert.Null(property.DefaultMetadata.CoerceValueCallback);
+        Assert.Equal(expectedDefaultValue, property.DefaultMetadata.DefaultValue);
+        Assert.Null(property.DefaultMetadata.PropertyChangedCallback);
+        Assert.True(property.GlobalIndex >= 0);
+        Assert.Equal(name, property.Name);
+        Assert.Equal(propertyType, property.PropertyType);
+        Assert.Equal(ownerType, property.OwnerType);
+        Assert.True(property.ReadOnly);
+        Assert.Same(validateValueCallback, property.ValidateValueCallback);
+        Assert.Equal(expectedValidateValueCallbackCallCount, callCount);
+    }
+
+    public static IEnumerable<object?[]> RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData()
+    {
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData1", typeof(string), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData2", typeof(string), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData3", typeof(string), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData4", typeof(string), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = "value" }, "value" };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData5", typeof(string), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData6", typeof(int), typeof(DependencyObjectTests), null, 0 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData7", typeof(int), typeof(DependencyObject), new PropertyMetadata(), 0 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData8", typeof(int), typeof(SubDependencyObject), new PropertyMetadata(), 0 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData9", typeof(int), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData10", typeof(int?), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData11", typeof(int?), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData12", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData13", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData14", typeof(int?), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData15", typeof(List<int>), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData16", typeof(List<int>), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData17", typeof(List<int>), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData18", typeof(List<int>), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = new List<int>() }, new List<int>() };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData19", typeof(Dictionary<string, int>), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData20", typeof(Dictionary<string, int>), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData21", typeof(Dictionary<string, int>), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData22", typeof(Dictionary<string, int>), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = new Dictionary<string, int>() }, new Dictionary<string, int>() };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData23", typeof(object), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData24", typeof(object), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData25", typeof(object), typeof(SubDependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData26", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = "value" }, "value" };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData27", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData28", typeof(object), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = null }, null };
+        yield return new object?[] { "                ", typeof(int), typeof(DependencyObjectTests), null, 0 };
+        yield return new object?[] { " RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData8 ", typeof(int), typeof(SubDependencyObject), new PropertyMetadata { DefaultValue = 1 }, 1 };
+    }
+
+    [Theory]
+    [MemberData(nameof(RegisterAttachedReadOnly_String_Type_Type_PropertyMetadata_NullValidate_TestData))]
+    public void RegisterAttachedReadOnly_InvokeStringTypeTypePropertyMetadataNullValidate_Success(string name, Type propertyType, Type ownerType, PropertyMetadata typeMetadata, object? expectedDefaultValue)
+    {
+        DependencyPropertyKey key = DependencyProperty.RegisterAttachedReadOnly(name, propertyType, ownerType, typeMetadata, null);
+        Assert.NotNull(key.DependencyProperty);
+        Assert.Same(key.DependencyProperty, key.DependencyProperty);
+
+        DependencyProperty property = key.DependencyProperty;        Assert.NotNull(property.DefaultMetadata);
+        Assert.Same(property.DefaultMetadata, property.DefaultMetadata);
+        Assert.Null(property.DefaultMetadata.CoerceValueCallback);
+        Assert.Equal(expectedDefaultValue, property.DefaultMetadata.DefaultValue);
+        Assert.Null(property.DefaultMetadata.PropertyChangedCallback);
+        Assert.True(property.GlobalIndex >= 0);
+        Assert.Equal(name, property.Name);
+        Assert.Equal(propertyType, property.PropertyType);
+        Assert.Equal(ownerType, property.OwnerType);
+        Assert.True(property.ReadOnly);
+        Assert.Null(property.ValidateValueCallback);
+    }
+
+    [Fact]
+    public void RegisterAttachedReadOnly_Multiple_GlobalIndexDifferent()
+    {
+        DependencyProperty property1 = DependencyProperty.RegisterAttachedReadOnly(MethodBase.GetCurrentMethod()!.Name + "1", typeof(int), typeof(DependencyObjectTests), new PropertyMetadata()).DependencyProperty;
+        DependencyProperty property2 = DependencyProperty.RegisterAttachedReadOnly(MethodBase.GetCurrentMethod()!.Name + "2", typeof(int), typeof(DependencyObjectTests), new PropertyMetadata()).DependencyProperty;
+        Assert.NotEqual(property1.GlobalIndex, property2.GlobalIndex);
+    }
+
+    [Fact]
+    public void RegisterAttachedReadOnly_NullName_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("name", () => DependencyProperty.RegisterAttachedReadOnly(null, typeof(int), typeof(DependencyPropertyTests), new PropertyMetadata()));
+        Assert.Throws<ArgumentNullException>("name", () => DependencyProperty.RegisterAttachedReadOnly(null, typeof(int), typeof(DependencyPropertyTests), new PropertyMetadata(), value => true));
+    }
+
+    [Fact]
+    public void RegisterAttachedReadOnly_EmptyName_ThrowsArgumentException()
+    {
+        Assert.Throws<ArgumentException>("name", () => DependencyProperty.RegisterAttachedReadOnly(string.Empty, typeof(int), typeof(DependencyPropertyTests), new PropertyMetadata()));
+        Assert.Throws<ArgumentException>("name", () => DependencyProperty.RegisterAttachedReadOnly(string.Empty, typeof(int), typeof(DependencyPropertyTests), new PropertyMetadata(), value => true));
+    }
+
+    [Fact]
+    public void RegisterAttachedReadOnly_NullPropertyType_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("propertyType", () => DependencyProperty.RegisterAttachedReadOnly(MethodBase.GetCurrentMethod()!.Name, null!, typeof(DependencyPropertyTests), new PropertyMetadata()));
+        Assert.Throws<ArgumentNullException>("propertyType", () => DependencyProperty.RegisterAttachedReadOnly(MethodBase.GetCurrentMethod()!.Name, null!, typeof(DependencyPropertyTests), new PropertyMetadata(), value => true));
+    }
+
+    [Fact]
+    public void RegisterAttachedReadOnly_InvalidPropertyType_ThrowsNotSupportedException()
+    {
+        Assert.Throws<NotSupportedException>(() => DependencyProperty.RegisterAttachedReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(void), typeof(DependencyPropertyTests), new PropertyMetadata()));
+        Assert.Throws<NotSupportedException>(() => DependencyProperty.RegisterAttachedReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(void), typeof(DependencyPropertyTests), new PropertyMetadata(), value => true));
+    }
+
+    [Theory]
+    [InlineData(typeof(void), "DefaultValue")]
+    [InlineData(typeof(int), "DefaultValue")]
+    [InlineData(typeof(string), 1)]
+    [InlineData(typeof(int), null)]
+    public void RegisterAttachedReadOnly_PropertyTypeDoesntMatchMetadata_ThrowsArgumentException(Type propertyType, object? defaultValue)
+    {
+        var metadata = new PropertyMetadata(defaultValue);
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterAttachedReadOnly(MethodBase.GetCurrentMethod()!.Name, propertyType, typeof(DependencyPropertyTests), metadata));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterAttachedReadOnly(MethodBase.GetCurrentMethod()!.Name, propertyType, typeof(DependencyPropertyTests), metadata, value => true));
+    }
+
+    [Fact]
+    public void RegisterAttachedReadOnly_NullOwnerType_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("ownerType", () => DependencyProperty.RegisterAttachedReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(int), null!, new PropertyMetadata()));
+        Assert.Throws<ArgumentNullException>("ownerType", () => DependencyProperty.RegisterAttachedReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(int), null!, new PropertyMetadata(), value => true));
+    }
+
+    [Fact]
+    public void RegisterAttachedReadOnly_ExpressionDefaultValue_ThrowsArgumentException()
+    {
+        var metadata = new PropertyMetadata(Activator.CreateInstance(typeof(Expression), nonPublic: true));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterAttachedReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(SubDependencyObject), metadata));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterAttachedReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(SubDependencyObject), metadata, value => true));
+    }
+
+    [Fact]
+    public void RegisterAttachedReadOnly_DispatcherObjectDefaultValue_ThrowsArgumentException()
+    {
+        var metadata = new PropertyMetadata(new SubDispatcherObject());
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterAttachedReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(SubDependencyObject), metadata));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterAttachedReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(SubDependencyObject), metadata, value => true));
+    }
+
+    [Fact]
+    public void RegisterAttachedReadOnly_AlreadyRegisterAttacheded_ThrowsArgumentException()
+    {
+        DependencyProperty property = DependencyProperty.RegisterAttachedReadOnly(MethodBase.GetCurrentMethod()!.Name, typeof(int), typeof(DependencyPropertyTests), new PropertyMetadata()).DependencyProperty;
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterAttachedReadOnly(property.Name, typeof(int), typeof(DependencyPropertyTests), new PropertyMetadata()));
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterAttachedReadOnly(property.Name, typeof(int), typeof(DependencyPropertyTests), new PropertyMetadata(), value => true));
+    }
+
+    public static IEnumerable<object?[]> RegisterAttachedReadOnly_String_Type_Type_ValidateFail_TestData()
+    {
+        yield return new object?[] { "         ", typeof(int), typeof(DependencyObjectTests), null, 0 };
+        yield return new object?[] { "          ", typeof(int), typeof(DependencyObject), new PropertyMetadata(), 0 };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_ValidateFail_TestData1", typeof(string), typeof(DependencyObjectTests), null, null };
+        yield return new object?[] { "RegisterAttachedReadOnly_String_Type_Type_ValidateFail_TestData2", typeof(string), typeof(DependencyObject), new PropertyMetadata(), null };
+        yield return new object?[] { " RegisterAttachedReadOnly_String_Type_Type_ValidateFail_TestData3 ", typeof(int), typeof(DependencyObjectTests), null, 0 };
+        yield return new object?[] { " RegisterAttachedReadOnly_String_Type_Type_ValidateFail_TestData4 ", typeof(int), typeof(DependencyObject), new PropertyMetadata(), 0 };
+    }
+
+    [Theory]
+    [MemberData(nameof(RegisterAttachedReadOnly_String_Type_Type_ValidateFail_TestData))]
+    public void RegisterAttachedReadOnly_InvokeStringTypeTypeValidateFail_Throws(string name, Type propertyType, Type ownerType, PropertyMetadata typeMetadata, object? expectedDefaultValue)
+    {
+        int callCount = 0;
+        ValidateValueCallback validateValueCallback = value =>
+        {
+            Assert.Equal(expectedDefaultValue, value);
+            callCount++;
+            return false;
+        };
+        Assert.Throws<ArgumentException>(() => DependencyProperty.RegisterAttachedReadOnly(name, propertyType, ownerType, typeMetadata, validateValueCallback));
+        Assert.Equal(1, callCount);
+    }
+
+    [Fact]
+    public void GetHashCode_Invoke_ReturnsGlobalIndex()
+    {
+        DependencyProperty property = DependencyProperty.Register(MethodBase.GetCurrentMethod()!.Name, typeof(int), typeof(DependencyPropertyTests));
+        Assert.Equal(property.GlobalIndex, property.GetHashCode());
+    }
+
+    [Fact]
+    public void ToString_Invoke_ReturnsName()
+    {
+        DependencyProperty property = DependencyProperty.Register(MethodBase.GetCurrentMethod()!.Name, typeof(int), typeof(DependencyPropertyTests));
+        Assert.Equal(property.Name, property.ToString());
+    }
+
+    private class SubDependencyObject : DependencyObject
+    {
+    }
+
+    private class SubDispatcherObject : DispatcherObject
+    {
+    }
+}
\ No newline at end of file
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/DesignerSerializationOptionsAttributeTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/DesignerSerializationOptionsAttributeTests.cs
new file mode 100644
index 00000000000..2dbf3f65fa5
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/DesignerSerializationOptionsAttributeTests.cs
@@ -0,0 +1,28 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.Windows.Markup;
+
+namespace System.Windows.Tests;
+
+public class DesignerSerializationOptionsAttributeTests
+{
+    [Theory]
+    [InlineData(DesignerSerializationOptions.SerializeAsAttribute)]
+    public void Ctor_DesignerSerializationOptions(DesignerSerializationOptions options)
+    {
+        var attribute = new DesignerSerializationOptionsAttribute(options);
+        Assert.Equal(options, attribute.DesignerSerializationOptions);
+    }
+
+    [Theory]
+    [InlineData((DesignerSerializationOptions)0)]
+    [InlineData(DesignerSerializationOptions.SerializeAsAttribute + 1)]
+    public void Ctor_InvalidOptions_ThrowsInvalidEnumArgumentException(DesignerSerializationOptions options)
+    {
+        // TODO: add paramName.
+        Assert.Throws<InvalidEnumArgumentException>(() => new DesignerSerializationOptionsAttribute(options));
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/ExpressionConverterTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/ExpressionConverterTests.cs
new file mode 100644
index 00000000000..d30fffad396
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/ExpressionConverterTests.cs
@@ -0,0 +1,123 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.ComponentModel.Design.Serialization;
+using System.Globalization;
+
+namespace System.Windows.Tests;
+
+public class ExpressionConverterTests
+{
+    [Theory]
+    [InlineData(null)]
+    [InlineData(typeof(object))]
+    [InlineData(typeof(string))]
+    [InlineData(typeof(InstanceDescriptor))]
+    [InlineData(typeof(Expression))]
+    public void CanConvertTo_Invoke_ReturnsFalse(Type? destinationType)
+    {
+        var converter = new ExpressionConverter();
+        Assert.False(converter.CanConvertTo(null, destinationType));
+        Assert.False(converter.CanConvertTo(new CustomTypeDescriptorContext(), destinationType));
+    }
+
+    public static IEnumerable<object?[]> ConvertTo_TestData()
+    {
+        // TODO: this should not throw NullReferenceException
+        //yield return new object?[] { null, null };
+        //yield return new object?[] { string.Empty, null };
+        //yield return new object?[] { "value", null };
+        //yield return new object?[] { new object(), null };
+        
+        yield return new object?[] { null, typeof(object) };
+        yield return new object?[] { string.Empty, typeof(object) };
+        yield return new object?[] { "value", typeof(object) };
+        yield return new object?[] { new object(), typeof(object) };
+        
+        yield return new object?[] { null, typeof(string) };
+        yield return new object?[] { string.Empty, typeof(string) };
+        yield return new object?[] { "value", typeof(string) };
+        yield return new object?[] { new object(), typeof(string) };
+        
+        yield return new object?[] { null, typeof(Expression) };
+        yield return new object?[] { string.Empty, typeof(Expression) };
+        yield return new object?[] { "value", typeof(Expression) };
+        yield return new object?[] { new object(), typeof(Expression) };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertTo_TestData))]
+    public void ConvertTo_Invoke_ThrowsNotSupportedException(object value, Type destinationType)
+    {
+        var converter = new ExpressionConverter();
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(value, destinationType));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(null, null, value, destinationType));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value, destinationType));
+    }
+
+    public static IEnumerable<object?[]> ConvertTo_NullDestinationType_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { string.Empty };
+        yield return new object?[] { "value" };
+        yield return new object?[] { new object() };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertTo_NullDestinationType_TestData))]
+    public void ConvertTo_NullDestinationType_ThrowsNullReferenceException(object value)
+    {
+        // TODO: this should not throw NullReferenceException
+        var converter = new ExpressionConverter();
+        Assert.Throws<NullReferenceException>(() => converter.ConvertTo(value, null!));
+        Assert.Throws<NullReferenceException>(() => converter.ConvertTo(null, null, value, null!));
+        Assert.Throws<NullReferenceException>(() => converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value, null!));
+    }
+    
+    [Theory]
+    [InlineData(null)]
+    [InlineData(typeof(object))]
+    [InlineData(typeof(string))]
+    [InlineData(typeof(InstanceDescriptor))]
+    [InlineData(typeof(Expression))]
+    public void CanConvertFrom_Invoke_ReturnsFalse(Type? sourceType)
+    {
+        var converter = new ExpressionConverter();
+        Assert.False(converter.CanConvertFrom(sourceType!));
+        Assert.False(converter.CanConvertFrom(null, sourceType));
+        Assert.False(converter.CanConvertFrom(new CustomTypeDescriptorContext(), sourceType));
+    }
+
+    public static IEnumerable<object?[]> ConvertFrom_CantConvert_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { new object() };
+    }
+    
+    [Theory]
+    [MemberData(nameof(ConvertFrom_CantConvert_TestData))]
+    public void ConvertFrom_CantConvert_ThrowsNotSupportedException(object value)
+    {
+        var converter = new ExpressionConverter();
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(value));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(null, null, value));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    private class CustomTypeDescriptorContext : ITypeDescriptorContext
+    {
+        public IContainer Container => throw new NotImplementedException();
+
+        public object Instance => throw new NotImplementedException();
+
+        public PropertyDescriptor PropertyDescriptor => throw new NotImplementedException();
+
+        public object? GetService(Type serviceType) => throw new NotImplementedException();
+
+        public void OnComponentChanged() => throw new NotImplementedException();
+
+        public bool OnComponentChanging() => throw new NotImplementedException();
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/ExpressionTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/ExpressionTests.cs
new file mode 100644
index 00000000000..9b137f04c86
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/ExpressionTests.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+
+namespace System.Windows.Tests;
+
+public class ExpressionTests
+{
+    [Fact]
+    public void TypeConverter_Get_ReturnsExpected()
+    {
+        Assert.IsType<ExpressionConverter>(TypeDescriptor.GetConverter(typeof(Expression)));
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/FreezableTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/FreezableTests.cs
new file mode 100644
index 00000000000..b4cae5ca7ce
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/FreezableTests.cs
@@ -0,0 +1,7140 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Reflection;
+using System.Windows.Threading;
+
+namespace System.Windows.Tests;
+
+public class FreezableTests
+{
+    [Fact]
+    public void Ctor_Default()
+    {
+        var freezable = new SubFreezable();
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void Changed_AddRemove_Success()
+    {
+        var freezable = new SubFreezable();
+
+        int callCount = 0;
+        EventHandler handler = (s, e) => callCount++;
+        freezable.Changed += handler;
+        Assert.Equal(0, callCount);
+
+        freezable.Changed -= handler;
+        Assert.Equal(0, callCount);
+
+        // Remove non existent.
+        Assert.Throws<ArgumentException>("handler", () => freezable.Changed -= handler);
+        Assert.Equal(0, callCount);
+
+        // Add null.
+        freezable.Changed += null;
+        Assert.Equal(0, callCount);
+
+        // Remove null.
+        freezable.Changed -= null;
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void Changed_AddRemoveFrozen_ThrowsInvalidOperationException()
+    {
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+
+        int callCount = 0;
+        EventHandler handler = (s, e) => callCount++;
+        Assert.Throws<InvalidOperationException>(() => freezable.Changed += handler);
+        Assert.Throws<InvalidOperationException>(() => freezable.Changed += null);
+        Assert.Throws<InvalidOperationException>(() => freezable.Changed -= handler);
+        Assert.Throws<InvalidOperationException>(() => freezable.Changed -= null);
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void Changed_AddRemoveOnDifferentThread_ThrowsInvalidOperationException()
+    {
+        var freezable = new SubFreezable();
+        int callCount = 0;
+        EventHandler handler = (s, e) => callCount++;
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => freezable.Changed += handler);
+            Assert.Throws<InvalidOperationException>(() => freezable.Changed += null);
+            Assert.Throws<InvalidOperationException>(() => freezable.Changed -= handler);
+            Assert.Throws<InvalidOperationException>(() => freezable.Changed -= null);
+            Assert.Equal(0, callCount);
+        });
+    }
+
+    [Fact]
+    public void Changed_AddRemoveFrozenOnDifferentThread_ThrowsInvalidOperationException()
+    {
+        var freezable = new SubFreezable();
+        int callCount = 0;
+        EventHandler handler = (s, e) => callCount++;
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => freezable.Changed += handler);
+            Assert.Throws<InvalidOperationException>(() => freezable.Changed += null);
+            Assert.Throws<InvalidOperationException>(() => freezable.Changed -= handler);
+            Assert.Throws<InvalidOperationException>(() => freezable.Changed -= null);
+            Assert.Equal(0, callCount);
+        });
+    }
+
+    [Fact]
+    public void CanFreeze_Get_ReturnsTrue()
+    {
+        var freezable = new SubFreezable();
+        Assert.True(freezable.CanFreeze);
+    }
+
+    [Fact]
+    public void CanFreeze_GetWithProperties_ReturnsTrue()
+    {
+        var freezable = new SubFreezable();
+        freezable.SetValue(SubFreezable.Property1, 10);
+        freezable.SetValue(SubFreezable.Property2, 20);
+        freezable.SetCurrentValue(SubFreezable.Property3, 30);
+        freezable.SetValue(SubFreezable.Property4, 40);
+        freezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        freezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        freezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        freezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+
+        Assert.True(freezable.CanFreeze);
+    }
+    
+    [Fact]
+    public void CanFreeze_GetWithUnfreezableProperties_ReturnsFalse()
+    {
+        var freezable = new SubFreezable();
+        Assert.True(freezable.CanFreeze);
+        
+        freezable.SetValue(SubFreezable.Property1, 10);
+        freezable.SetValue(SubFreezable.Property2, 20);
+        freezable.SetCurrentValue(SubFreezable.Property3, 30);
+        freezable.SetValue(SubFreezable.Property4, 40);
+        freezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        freezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        freezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        freezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+
+        var anotherFreezable4 = new CustomFreezable();
+        anotherFreezable4.SetValue(SubFreezable.Property1, 90);
+        anotherFreezable4.FreezeCoreAction = (checking) => false;
+        freezable.SetValue(SubFreezable.Property9, anotherFreezable4);
+
+        Assert.False(freezable.CanFreeze);
+    }
+
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void CanFreeze_GetCustomFreezeCore_ReturnsExpected(bool result)
+    {
+        var freezable = new CustomFreezable();
+        int callCount = 0;
+        freezable.FreezeCoreAction = (checking) =>
+        {
+            Assert.True(checking);
+            callCount++;
+            return result;
+        };
+
+        // Get once.
+        Assert.Equal(result, freezable.CanFreeze);
+        Assert.Equal(1, callCount);
+
+        // get again.
+        Assert.Equal(result, freezable.CanFreeze);
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void CanFreeze_GetFrozen_ReturnsTrue()
+    {
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+
+        Assert.True(freezable.CanFreeze);
+    }
+
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void CanFreeze_GetFrozenCustomFreezeCore_ReturnsTrue(bool result)
+    {
+        var freezable = new CustomFreezable();
+        freezable.Freeze();
+
+        int callCount = 0;
+        freezable.FreezeCoreAction = (checking) =>
+        {
+            callCount++;
+            return result;
+        };
+
+        // Get once.
+        Assert.True(freezable.CanFreeze);
+        Assert.Equal(0, callCount);
+
+        // get again.
+        Assert.True(freezable.CanFreeze);
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void CanFreeze_GetOnDifferentThread_ReturnsTrue()
+    {
+        var freezable = new SubFreezable();
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.True(freezable.CanFreeze);
+        });
+    }
+
+    [Fact]
+    public void CanFreeze_GetFrozenOnDifferentThread_ReturnsTrue()
+    {
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.True(freezable.CanFreeze);
+        });
+    }
+
+    [Fact]
+    public void DependencyObjectType_Get_ReturnsExpected()
+    {
+        var freezable = new SubFreezable();
+        DependencyObjectType dependencyObjectType = freezable.DependencyObjectType;
+        Assert.NotNull(dependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), dependencyObjectType);
+    }
+
+    [Fact]
+    public void DependencyObjectType_GetFrozen_ReturnsExpected()
+    {
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+
+        DependencyObjectType dependencyObjectType = freezable.DependencyObjectType;
+        Assert.NotNull(dependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), dependencyObjectType);
+    }
+
+    [Fact]
+    public void DependencyObjectType_GetOnDifferentThread_ReturnsExpected()
+    {
+        var freezable = new SubFreezable();
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            DependencyObjectType dependencyObjectType = freezable.DependencyObjectType;
+            Assert.NotNull(dependencyObjectType);
+            Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+            Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), dependencyObjectType);
+        });
+    }
+
+    [Fact]
+    public void DependencyObjectType_GetFrozenOnDifferentThread_ReturnsExpected()
+    {
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            DependencyObjectType dependencyObjectType = freezable.DependencyObjectType;
+            Assert.NotNull(dependencyObjectType);
+            Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+            Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), dependencyObjectType);
+        });
+    }
+
+    [Fact]
+    public void Dispatcher_GetFrozen_ReturnsNull()
+    {
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+
+        Assert.Null(freezable.Dispatcher);
+    }
+
+    [Fact]
+    public void Dispatcher_Get_ReturnsExpected()
+    {
+        var freezable = new SubFreezable();
+        Assert.NotNull(freezable.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+    }
+
+    [Fact]
+    public void Dispatcher_GetOnDifferentThread_ReturnsExpected()
+    {
+        var freezable = new SubFreezable();
+        Dispatcher expected = Dispatcher.CurrentDispatcher;
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Dispatcher? dispatcher = freezable.Dispatcher;
+            Assert.NotNull(dispatcher);
+            Assert.Same(expected, dispatcher);
+        });
+    }
+
+    [Fact]
+    public void Dispatcher_GetFrozenOnDifferentThread_ReturnsNull()
+    {
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Null(freezable.Dispatcher);
+        });
+    }
+
+    [Fact]
+    public void IsFrozen_Get_ReturnsFalse()
+    {
+        var freezable = new SubFreezable();
+        Assert.False(freezable.IsFrozen);
+    }
+
+    [Fact]
+    public void IsFrozen_GetFrozen_ReturnsTrue()
+    {
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+
+        Assert.True(freezable.IsFrozen);
+    }
+
+    [Fact]
+    public void IsFrozen_GetOnDifferentThread_ThrowsInvalidOperationException()
+    {
+        var freezable = new SubFreezable();
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => freezable.IsFrozen);
+        });
+    }
+
+    [Fact]
+    public void IsFrozen_GetFrozenOnDifferentThread_ReturnsTrue()
+    {
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.True(freezable.IsFrozen);
+        });
+    }
+
+    [Fact]
+    public void IsSealed_Get_ReturnsFalse()
+    {
+        var freezable = new SubFreezable();
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void IsSealed_GetFrozen_ReturnsTrue()
+    {
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+
+        Assert.True(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void IsSealed_GetOnDifferentThread_ReturnsFalse()
+    {
+        var freezable = new SubFreezable();
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.False(freezable.IsSealed);
+        });
+    }
+
+    [Fact]
+    public void IsSealed_GetFrozenOnDifferentThread_ReturnsTrue()
+    {
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.True(freezable.IsSealed);
+        });
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyValueType_GetValueReturnsExpected()
+    {
+        var obj = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject));
+
+        // Clear default.
+        obj.ClearValue(property);
+        Assert.False((bool)obj.GetValue(property));
+
+        // Set custom.
+        obj.SetValue(property, true);
+        Assert.True((bool)obj.GetValue(property));
+
+        // Clear custom.
+        obj.ClearValue(property);
+        Assert.False((bool)obj.GetValue(property));
+
+        // Clear again.
+        obj.ClearValue(property);
+        Assert.False((bool)obj.GetValue(property));
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyNullable_GetValueReturnsExpected()
+    {
+        var obj = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool?), typeof(DependencyObject));
+
+        // Clear default.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+
+        // Set custom.
+        obj.SetValue(property, true);
+        Assert.True((bool)obj.GetValue(property));
+
+        // Clear custom.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+
+        // Clear again.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyReferenceType_GetValueReturnsExpected()
+    {
+        var obj = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+
+        // Clear default.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+
+        // Set custom.
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Clear custom.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+
+        // Clear again.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyCustomDefaultValue_GetValueReturnsExpected()
+    {
+        var obj = new SubFreezable();
+        var typeMetadata = new PropertyMetadata("default");
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+
+        // Clear default.
+        obj.ClearValue(property);
+        Assert.Equal("default", obj.GetValue(property));
+
+        // Set custom.
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Clear custom.
+        obj.ClearValue(property);
+        Assert.Equal("default", obj.GetValue(property));
+
+        // Clear again.
+        obj.ClearValue(property);
+        Assert.Equal("default", obj.GetValue(property));
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyCustomPropertyChangedCallback_Success()
+    {
+        var obj = new SubFreezable();
+
+        int changedCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedOldValue = null;
+        object? expectedNewValue = null;
+        var typeMetadata = new PropertyMetadata(null, (d, e) =>
+        {
+            Assert.Same(obj, d);
+            Assert.Same(expectedProperty, e.Property);
+            Assert.Same(expectedOldValue, e.OldValue);
+            Assert.Same(expectedNewValue, e.NewValue);
+            Assert.Equal(expectedNewValue, obj.GetValue(e.Property));
+            changedCallCount++;
+        });
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        expectedProperty = property;
+
+        // Clear default.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(0, changedCallCount);
+
+        // Set custom.
+        expectedNewValue = "value";
+        expectedOldValue = null;
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+
+        // Clear custom.
+        expectedNewValue = null;
+        expectedOldValue = "value";
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+
+        // Clear again.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyCustomCoerceValueCallback_Success()
+    {
+        var obj = new SubFreezable();
+
+        int coerceValueCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedNewValue = null;
+        var typeMetadata = new PropertyMetadata(
+            null,
+            null,
+            (d, baseValue) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedNewValue, baseValue);
+                coerceValueCallCount++;
+                return baseValue;
+            });
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        expectedProperty = property;
+
+        // Clear default.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(0, coerceValueCallCount);
+
+        // Set custom.
+        expectedNewValue = "value";
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Clear custom.
+        expectedNewValue = null;
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Clear again.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallCount);
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyCustomPropertyChangedAndCoerceValueCallback_Success()
+    {
+        var obj = new SubFreezable();
+
+        int coerceValueCallCount = 0;
+        int changedCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedOldValue = null;
+        object? expectedNewValue = null;
+        var typeMetadata = new PropertyMetadata(
+            null,
+            (d, e) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedProperty, e.Property);
+                Assert.Same(expectedOldValue, e.OldValue);
+                Assert.Same(expectedNewValue, e.NewValue);
+                Assert.Equal(expectedNewValue, obj.GetValue(e.Property));
+                changedCallCount++;
+            },
+            (d, baseValue) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedNewValue, baseValue);
+                coerceValueCallCount++;
+                return baseValue;
+            });
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        expectedProperty = property;
+
+        // Clear default.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(0, changedCallCount);
+        Assert.Equal(0, coerceValueCallCount);
+
+        // Set custom.
+        expectedNewValue = "value";
+        expectedOldValue = null;
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Clear custom.
+        expectedNewValue = null;
+        expectedOldValue = "value";
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Clear again.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+        Assert.Equal(1, coerceValueCallCount);
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyCustomOnPropertyChanged_CallsOnPropertyChanged()
+    {
+        var obj = new CustomFreezable();
+
+        int onPropertyChangedCallCount = 0;
+        int changedCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedOldValue = null;
+        object? expectedNewValue = null;
+        obj.OnPropertyChangedAction = (e) =>
+        {
+            Assert.True(changedCallCount > onPropertyChangedCallCount);
+            Assert.Same(expectedProperty, e.Property);
+            Assert.Same(expectedOldValue, e.OldValue);
+            Assert.Same(expectedNewValue, e.NewValue);
+            Assert.Equal(expectedNewValue, obj.GetValue(e.Property));
+            onPropertyChangedCallCount++;
+        };
+        var typeMetadata = new PropertyMetadata(null, (d, e) =>
+        {
+            Assert.Equal(changedCallCount, onPropertyChangedCallCount);
+            Assert.Same(obj, d);
+            Assert.Same(expectedProperty, e.Property);
+            Assert.Same(expectedOldValue, e.OldValue);
+            Assert.Same(expectedNewValue, e.NewValue);
+            Assert.Equal(expectedNewValue, obj.GetValue(e.Property));
+            changedCallCount++;
+        });
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        expectedProperty = property;
+
+        // Clear default.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(0, changedCallCount);
+        Assert.Equal(0, onPropertyChangedCallCount);
+
+        // Set custom.
+        expectedNewValue = "value";
+        expectedOldValue = null;
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+        Assert.Equal(1, onPropertyChangedCallCount);
+
+        // Clear custom.
+        expectedNewValue = null;
+        expectedOldValue = "value";
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+        Assert.Equal(2, onPropertyChangedCallCount);
+
+        // Clear again.
+        obj.ClearValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+        Assert.Equal(2, onPropertyChangedCallCount);
+    }
+
+    [Fact]
+    public void ClearValue_InvokeWithHandler_CallsChanged()
+    {
+        var freezable = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject));
+
+        int callCount = 0;
+        EventHandler handler = (sender, e) =>
+        {
+            Assert.Same(freezable, sender);
+            Assert.Same(EventArgs.Empty, e);
+            callCount++;
+        }; 
+        freezable.Changed += handler;
+
+        // Clear.
+        freezable.ClearValue(property);
+        Assert.False((bool)freezable.GetValue(property));
+        Assert.Equal(0, callCount);
+
+        // Set.
+        freezable.SetValue(property, true);
+        Assert.True((bool)freezable.GetValue(property));
+        Assert.Equal(1, callCount);
+
+        // Clear.
+        freezable.ClearValue(property);
+        Assert.False((bool)freezable.GetValue(property));
+        Assert.Equal(2, callCount);
+
+        // Remove handler.
+        freezable.Changed -= handler;
+        freezable.SetValue(property, true);
+        Assert.True((bool)freezable.GetValue(property));
+        Assert.Equal(2, callCount);
+
+        freezable.ClearValue(property);
+        Assert.False((bool)freezable.GetValue(property));
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void ClearValue_InvokeWithCustomOnChanged_CallsChanged()
+    {
+        var freezable = new CustomFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject));
+
+        int onChangedCallCount = 0;
+        int changedCallCount = 0;
+        freezable.OnChangedAction = () =>
+        {
+            Assert.Equal(changedCallCount, onChangedCallCount);
+            onChangedCallCount++;
+        };
+        freezable.Changed += (sender, e) =>
+        {
+            Assert.True(onChangedCallCount > changedCallCount);
+            Assert.Same(freezable, sender);
+            Assert.Same(EventArgs.Empty, e);
+            changedCallCount++;
+        };
+
+        // Clear.
+        freezable.ClearValue(property);
+        Assert.False((bool)freezable.GetValue(property));
+        Assert.Equal(0, onChangedCallCount);
+        Assert.Equal(0, changedCallCount);
+
+        // Set.
+        freezable.SetValue(property, true);
+        Assert.True((bool)freezable.GetValue(property));
+        Assert.Equal(1, onChangedCallCount);
+        Assert.Equal(1, changedCallCount);
+
+        // Clear.
+        freezable.ClearValue(property);
+        Assert.False((bool)freezable.GetValue(property));
+        Assert.Equal(2, onChangedCallCount);
+        Assert.Equal(2, changedCallCount);
+
+        // Clear again.
+        freezable.ClearValue(property);
+        Assert.False((bool)freezable.GetValue(property));
+        Assert.Equal(2, onChangedCallCount);
+        Assert.Equal(2, changedCallCount);
+    }
+
+    [Fact]
+    public void ClearValue_DependencyPropertyNullDp_ThrowsArgumentNullException()
+    {
+        var obj = new SubFreezable();
+        Assert.Throws<ArgumentNullException>("dp", () => obj.ClearValue((DependencyProperty)null!));
+    }
+
+    [Fact]
+    public void ClearValue_DependencyPropertyReadOnly_ThrowsInvalidOperationException()
+    {
+        var obj = new SubFreezable();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+        Assert.Throws<InvalidOperationException>(() => obj.ClearValue(property));
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyFrozen_ThrowsInvalidOperationException()
+    {
+        var obj = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject));
+        obj.Freeze();
+
+        Assert.Throws<InvalidOperationException>(() => obj.ClearValue(property));
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyOnDifferentThread_ThrowsInvalidOperationException()
+    {
+        var obj = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject));
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => obj.ClearValue(property));
+        });
+    }
+
+    [Fact]
+    public void ClearValue_InvokePropertyFrozenOnDifferentThread_ThrowsInvalidOperationException()
+    {
+        var obj = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        obj.Freeze();
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => obj.ClearValue(property));
+        });
+    }
+
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyKeyValueType_GetValueReturnsExpected()
+    {
+        var obj = new SubFreezable();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+
+        // Clear default.
+        obj.ClearValue(key);
+        Assert.False((bool)obj.GetValue(property));
+
+        // Set custom.
+        obj.SetValue(key, true);
+        Assert.True((bool)obj.GetValue(property));
+
+        // Clear custom.
+        obj.ClearValue(key);
+        Assert.False((bool)obj.GetValue(property));
+
+        // Clear again.
+        obj.ClearValue(key);
+        Assert.False((bool)obj.GetValue(property));
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyKeyNullable_GetValueReturnsExpected()
+    {
+        var obj = new SubFreezable();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool?), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+
+        // Clear default.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+
+        // Set custom.
+        obj.SetValue(key, true);
+        Assert.True((bool)obj.GetValue(property));
+
+        // Clear custom.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+
+        // Clear again.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyKeyReferenceType_GetValueReturnsExpected()
+    {
+        var obj = new SubFreezable();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+
+        // Clear default.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+
+        // Set custom.
+        obj.SetValue(key, "value");
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Clear custom.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+
+        // Clear again.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyKeyObject_GetValueReturnsExpected()
+    {
+        var obj = new SubFreezable();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+
+        // Clear default.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+
+        // Set custom.
+        obj.SetValue(key, "value");
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Clear custom.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+
+        // Clear again.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyKeyCustomDefaultValue_GetValueReturnsExpected()
+    {
+        var obj = new SubFreezable();
+        var typeMetadata = new PropertyMetadata("default");
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        DependencyProperty property = key.DependencyProperty;
+
+        // Clear default.
+        obj.ClearValue(key);
+        Assert.Equal("default", obj.GetValue(property));
+
+        // Set custom.
+        obj.SetValue(key, "value");
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Clear custom.
+        obj.ClearValue(key);
+        Assert.Equal("default", obj.GetValue(property));
+
+        // Clear again.
+        obj.ClearValue(key);
+        Assert.Equal("default", obj.GetValue(property));
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyKeyCustomPropertyChangedCallback_Success()
+    {
+        var obj = new SubFreezable();
+
+        int changedCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedOldValue = null;
+        object? expectedNewValue = null;
+        var typeMetadata = new PropertyMetadata(null, (d, e) =>
+        {
+            Assert.Same(obj, d);
+            Assert.Same(expectedProperty, e.Property);
+            Assert.Same(expectedOldValue, e.OldValue);
+            Assert.Same(expectedNewValue, e.NewValue);
+            Assert.Equal(expectedNewValue, obj.GetValue(e.Property));
+            changedCallCount++;
+        });
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        DependencyProperty property = key.DependencyProperty;
+        expectedProperty = property;
+
+        // Clear default.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(0, changedCallCount);
+
+        // Set custom.
+        expectedNewValue = "value";
+        expectedOldValue = null;
+        obj.SetValue(key, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+
+        // Clear custom.
+        expectedNewValue = null;
+        expectedOldValue = "value";
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+
+        // Clear again.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyKeyCustomCoerceValueCallback_Success()
+    {
+        var obj = new SubFreezable();
+
+        int coerceValueCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedNewValue = null;
+        var typeMetadata = new PropertyMetadata(
+            null,
+            null,
+            (d, baseValue) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedNewValue, baseValue);
+                coerceValueCallCount++;
+                return baseValue;
+            });
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        DependencyProperty property = key.DependencyProperty;
+        expectedProperty = property;
+
+        // Clear default.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(0, coerceValueCallCount);
+
+        // Set custom.
+        expectedNewValue = "value";
+        obj.SetValue(key, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Clear custom.
+        expectedNewValue = null;
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Clear again.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallCount);
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyKeyCustomPropertyChangedAndCoerceValueCallback_Success()
+    {
+        var obj = new SubFreezable();
+
+        int coerceValueCallCount = 0;
+        int changedCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedOldValue = null;
+        object? expectedNewValue = null;
+        var typeMetadata = new PropertyMetadata(
+            null,
+            (d, e) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedProperty, e.Property);
+                Assert.Same(expectedOldValue, e.OldValue);
+                Assert.Same(expectedNewValue, e.NewValue);
+                Assert.Equal(expectedNewValue, obj.GetValue(e.Property));
+                changedCallCount++;
+            },
+            (d, baseValue) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedNewValue, baseValue);
+                coerceValueCallCount++;
+                return baseValue;
+            });
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        DependencyProperty property = key.DependencyProperty;
+        expectedProperty = property;
+
+        // Clear default.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(0, changedCallCount);
+        Assert.Equal(0, coerceValueCallCount);
+
+        // Set custom.
+        expectedNewValue = "value";
+        expectedOldValue = null;
+        obj.SetValue(key, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Clear custom.
+        expectedNewValue = null;
+        expectedOldValue = "value";
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Clear again.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+        Assert.Equal(1, coerceValueCallCount);
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyKeyCustomOnPropertyChanged_CallsOnPropertyChanged()
+    {
+        var obj = new CustomFreezable();
+
+        int onPropertyChangedCallCount = 0;
+        int changedCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedOldValue = null;
+        object? expectedNewValue = null;
+        obj.OnPropertyChangedAction = (e) =>
+        {
+            Assert.True(changedCallCount > onPropertyChangedCallCount);
+            Assert.Same(expectedProperty, e.Property);
+            Assert.Same(expectedOldValue, e.OldValue);
+            Assert.Same(expectedNewValue, e.NewValue);
+            Assert.Equal(expectedNewValue, obj.GetValue(e.Property));
+            onPropertyChangedCallCount++;
+        };
+        var typeMetadata = new PropertyMetadata(null, (d, e) =>
+        {
+            Assert.Equal(changedCallCount, onPropertyChangedCallCount);
+            Assert.Same(obj, d);
+            Assert.Same(expectedProperty, e.Property);
+            Assert.Same(expectedOldValue, e.OldValue);
+            Assert.Same(expectedNewValue, e.NewValue);
+            Assert.Equal(expectedNewValue, obj.GetValue(e.Property));
+            changedCallCount++;
+        });
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        DependencyProperty property = key.DependencyProperty;
+        expectedProperty = property;
+
+        // Clear default.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(0, changedCallCount);
+        Assert.Equal(0, onPropertyChangedCallCount);
+
+        // Set custom.
+        expectedNewValue = "value";
+        expectedOldValue = null;
+        obj.SetValue(key, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+        Assert.Equal(1, onPropertyChangedCallCount);
+
+        // Clear custom.
+        expectedNewValue = null;
+        expectedOldValue = "value";
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+        Assert.Equal(2, onPropertyChangedCallCount);
+
+        // Clear again.
+        obj.ClearValue(key);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(2, changedCallCount);
+        Assert.Equal(2, onPropertyChangedCallCount);
+    }
+
+    [Fact]
+    public void ClearValue_InvokePropertyKeyWithHandler_CallsChanged()
+    {
+        var freezable = new SubFreezable();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject), new PropertyMetadata());
+
+        int callCount = 0;
+        EventHandler handler = (sender, e) =>
+        {
+            Assert.Same(freezable, sender);
+            Assert.Same(EventArgs.Empty, e);
+            callCount++;
+        }; 
+        freezable.Changed += handler;
+
+        // Clear.
+        freezable.ClearValue(key);
+        Assert.False((bool)freezable.GetValue(key.DependencyProperty));
+        Assert.Equal(0, callCount);
+
+        // Set.
+        freezable.SetValue(key, true);
+        Assert.True((bool)freezable.GetValue(key.DependencyProperty));
+        Assert.Equal(1, callCount);
+
+        // Clear.
+        freezable.ClearValue(key);
+        Assert.False((bool)freezable.GetValue(key.DependencyProperty));
+        Assert.Equal(2, callCount);
+
+        // Remove handler.
+        freezable.Changed -= handler;
+        freezable.SetValue(key, true);
+        Assert.True((bool)freezable.GetValue(key.DependencyProperty));
+        Assert.Equal(2, callCount);
+
+        freezable.ClearValue(key);
+        Assert.False((bool)freezable.GetValue(key.DependencyProperty));
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void ClearValue_InvokePropertyKeyWithCustomOnChanged_CallsChanged()
+    {
+        var freezable = new CustomFreezable();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject), new PropertyMetadata());
+
+        int onChangedCallCount = 0;
+        int changedCallCount = 0;
+        freezable.OnChangedAction = () =>
+        {
+            Assert.Equal(changedCallCount, onChangedCallCount);
+            onChangedCallCount++;
+        };
+        freezable.Changed += (sender, e) =>
+        {
+            Assert.True(onChangedCallCount > changedCallCount);
+            Assert.Same(freezable, sender);
+            Assert.Same(EventArgs.Empty, e);
+            changedCallCount++;
+        };
+
+        // Clear.
+        freezable.ClearValue(key);
+        Assert.False((bool)freezable.GetValue(key.DependencyProperty));
+        Assert.Equal(0, onChangedCallCount);
+        Assert.Equal(0, changedCallCount);
+
+        // Set.
+        freezable.SetValue(key, true);
+        Assert.True((bool)freezable.GetValue(key.DependencyProperty));
+        Assert.Equal(1, onChangedCallCount);
+        Assert.Equal(1, changedCallCount);
+
+        // Clear.
+        freezable.ClearValue(key);
+        Assert.False((bool)freezable.GetValue(key.DependencyProperty));
+        Assert.Equal(2, onChangedCallCount);
+        Assert.Equal(2, changedCallCount);
+
+        // Clear again.
+        freezable.ClearValue(key);
+        Assert.False((bool)freezable.GetValue(key.DependencyProperty));
+        Assert.Equal(2, onChangedCallCount);
+        Assert.Equal(2, changedCallCount);
+    }
+
+    [Fact]
+    public void ClearValue_DependencyPropertyNullKey_ThrowsArgumentNullException()
+    {
+        var obj = new SubFreezable();
+        Assert.Throws<ArgumentNullException>("key", () => obj.ClearValue((DependencyPropertyKey)null!));
+    }
+
+    [Fact]
+    public void ClearValue_InvokeFrozen_ThrowsInvalidOperationException()
+    {
+        var obj = new SubFreezable();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), new PropertyMetadata(null));
+        obj.Freeze();
+
+        Assert.Throws<InvalidOperationException>(() => obj.ClearValue(key));
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyKeyOnDifferentThread_ThrowsInvalidOperationException()
+    {
+        var obj = new SubFreezable();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => obj.ClearValue(key));
+        });
+    }
+
+    [Fact]
+    public void ClearValue_InvokeDependencyPropertyKeyFrozenOnDifferentThread_ThrowsInvalidOperationException()
+    {
+        var obj = new SubFreezable();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), new PropertyMetadata(null));
+        obj.Freeze();
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => obj.ClearValue(key));
+        });
+    }
+
+    [Fact]
+    public void Clone_InvokeDefault_Success()
+    {
+        var freezable = new SubFreezable();
+        int createInstanceCallCount = 0;
+        freezable.CreateInstanceCoreAction = () =>
+        {
+            createInstanceCallCount++;
+            return new SubFreezable();
+        };
+
+        // Clone.
+        SubFreezable clone = Assert.IsType<SubFreezable>(freezable.Clone());
+        Assert.NotSame(freezable, clone);
+        Assert.True(clone.CanFreeze);
+        Assert.NotNull(clone.DependencyObjectType);
+        Assert.Same(clone.DependencyObjectType, clone.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), clone.DependencyObjectType);
+        Assert.NotNull(clone.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, clone.Dispatcher);
+        Assert.False(clone.IsFrozen);
+        Assert.False(clone.IsSealed);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+        Assert.True(freezable.CanFreeze);
+        Assert.Equal(1, createInstanceCallCount);
+
+        // Clone again.
+        SubFreezable clone2 = Assert.IsType<SubFreezable>(freezable.Clone());
+        Assert.NotSame(freezable, clone);
+        Assert.NotSame(clone, clone2);
+        Assert.True(clone2.CanFreeze);
+        Assert.NotNull(clone2.DependencyObjectType);
+        Assert.Same(clone2.DependencyObjectType, clone2.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), clone2.DependencyObjectType);
+        Assert.NotNull(clone2.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, clone2.Dispatcher);
+        Assert.False(clone2.IsFrozen);
+        Assert.False(clone2.IsSealed);
+        Assert.NotNull(clone.DependencyObjectType);
+        Assert.Same(clone.DependencyObjectType, clone.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), clone.DependencyObjectType);
+        Assert.NotNull(clone.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, clone.Dispatcher);
+        Assert.False(clone.IsFrozen);
+        Assert.False(clone.IsSealed);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+        Assert.True(freezable.CanFreeze);
+        Assert.Equal(2, createInstanceCallCount);
+    }
+
+    [Fact]
+    public void Clone_InvokeWithProperties_Success()
+    {
+        var freezable = new SubFreezable();
+        int createInstanceCallCount = 0;
+        freezable.CreateInstanceCoreAction = () =>
+        {
+            createInstanceCallCount++;
+            return new SubFreezable();
+        };
+
+        freezable.SetValue(SubFreezable.Property1, 10);
+        freezable.SetValue(SubFreezable.Property2, 20);
+        freezable.SetCurrentValue(SubFreezable.Property3, 30);
+        freezable.SetValue(SubFreezable.Property4, 40);
+        freezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        freezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        freezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        freezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+
+        // Clone.
+        SubFreezable clone = Assert.IsType<SubFreezable>(freezable.Clone());
+        Assert.NotSame(freezable, clone);
+        Assert.Equal(10, clone.GetValue(SubFreezable.Property1));
+        Assert.Equal(20, clone.GetValue(SubFreezable.Property2));
+        Assert.Equal(30, clone.GetValue(SubFreezable.Property3));
+        Assert.Equal(40, clone.GetValue(SubFreezable.Property4));
+        Assert.Equal(50, clone.GetValue(SubFreezable.Property5));
+        Assert.NotSame(anotherFreezable1, ((SubFreezable)clone.GetValue(SubFreezable.Property6)));
+        Assert.Equal(60, ((SubFreezable)clone.GetValue(SubFreezable.Property6)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)clone.GetValue(SubFreezable.Property6)).IsFrozen);
+        Assert.NotSame(anotherFreezable2, ((SubFreezable)clone.GetValue(SubFreezable.Property7)));
+        Assert.Equal(70, ((SubFreezable)clone.GetValue(SubFreezable.Property7)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)clone.GetValue(SubFreezable.Property7)).IsFrozen);
+        Assert.NotSame(anotherFreezable3, ((SubFreezable)clone.GetValue(SubFreezable.Property8)));
+        Assert.Equal(80, ((SubFreezable)clone.GetValue(SubFreezable.Property8)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)clone.GetValue(SubFreezable.Property8)).IsFrozen);
+        Assert.True(clone.CanFreeze);
+        Assert.NotNull(clone.DependencyObjectType);
+        Assert.Same(clone.DependencyObjectType, clone.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), clone.DependencyObjectType);
+        Assert.NotNull(clone.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, clone.Dispatcher);
+        Assert.False(clone.IsFrozen);
+        Assert.False(clone.IsSealed);
+    }
+
+    [Fact]
+    public void Clone_InvokeWithUnfreezableProperties_ThrowsInvalidOperationException()
+    {
+        var freezable = new SubFreezable();
+        freezable.CreateInstanceCoreAction = () => new SubFreezable();
+        freezable.SetValue(SubFreezable.Property1, 10);
+        freezable.SetValue(SubFreezable.Property2, 20);
+        freezable.SetCurrentValue(SubFreezable.Property3, 30);
+        freezable.SetValue(SubFreezable.Property4, 40);
+        freezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        freezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        freezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        freezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+
+        var anotherFreezable4 = new CustomFreezable();
+        anotherFreezable4.CreateInstanceCoreAction = () => new CustomFreezable();
+        anotherFreezable4.SetValue(SubFreezable.Property1, 90);
+        anotherFreezable4.FreezeCoreAction = (isChecking) => false;
+        freezable.SetValue(SubFreezable.Property9, anotherFreezable4);
+
+        SubFreezable clone = Assert.IsType<SubFreezable>(freezable.Clone());
+        Assert.NotSame(freezable, clone);
+        Assert.Equal(10, clone.GetValue(SubFreezable.Property1));
+        Assert.Equal(20, clone.GetValue(SubFreezable.Property2));
+        Assert.Equal(30, clone.GetValue(SubFreezable.Property3));
+        Assert.Equal(40, clone.GetValue(SubFreezable.Property4));
+        Assert.Equal(50, clone.GetValue(SubFreezable.Property5));
+        Assert.NotSame(anotherFreezable1, ((SubFreezable)clone.GetValue(SubFreezable.Property6)));
+        Assert.Equal(60, ((SubFreezable)clone.GetValue(SubFreezable.Property6)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)clone.GetValue(SubFreezable.Property6)).IsFrozen);
+        Assert.NotSame(anotherFreezable2, ((SubFreezable)clone.GetValue(SubFreezable.Property7)));
+        Assert.Equal(70, ((SubFreezable)clone.GetValue(SubFreezable.Property7)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)clone.GetValue(SubFreezable.Property7)).IsFrozen);
+        Assert.NotSame(anotherFreezable3, ((SubFreezable)clone.GetValue(SubFreezable.Property8)));
+        Assert.Equal(80, ((SubFreezable)clone.GetValue(SubFreezable.Property8)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)clone.GetValue(SubFreezable.Property8)).IsFrozen);
+        Assert.True(clone.CanFreeze);
+        Assert.NotNull(clone.DependencyObjectType);
+        Assert.Same(clone.DependencyObjectType, clone.DependencyObjectType);
+        Assert.NotNull(clone.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, clone.Dispatcher);
+        Assert.False(clone.IsFrozen);
+        Assert.False(clone.IsSealed);
+    }
+
+    [Fact]
+    public void Clone_InvokeWithReadOnlyProperty_DoesNotCopy()
+    {
+        var freezable = new SubFreezable();
+        freezable.CreateInstanceCoreAction = () => new SubFreezable();
+        DependencyPropertyKey propertyKey = DependencyProperty.RegisterReadOnly(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), new PropertyMetadata());
+        freezable.SetValue(propertyKey, "value");
+
+        // Clone.
+        SubFreezable clone = Assert.IsType<SubFreezable>(freezable.Clone());
+        Assert.Null(clone.GetValue(propertyKey.DependencyProperty));
+        Assert.Equal("value", freezable.GetValue(propertyKey.DependencyProperty));
+    }
+
+    [Fact]
+    public void Clone_InvokeFrozen_ReturnsExpected()
+    {
+        var freezable = new SubFreezable();
+        freezable.CreateInstanceCoreAction = () => new SubFreezable();
+        freezable.Freeze();
+
+        SubFreezable clone = Assert.IsType<SubFreezable>(freezable.Clone());
+        Assert.NotSame(freezable, clone);
+        Assert.True(clone.CanFreeze);
+        Assert.NotNull(clone.DependencyObjectType);
+        Assert.Same(clone.DependencyObjectType, clone.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), clone.DependencyObjectType);
+        Assert.NotNull(clone.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, clone.Dispatcher);
+        Assert.False(clone.IsFrozen);
+        Assert.False(clone.IsSealed);
+    }
+
+    [Fact]
+    public void Clone_InvokeNullCreateInstanceCore_ThrowsNullReferenceException()
+    {
+        var freezable = new CustomFreezable();
+        freezable.CreateInstanceCoreAction = () => null!;
+        Assert.Throws<NullReferenceException>(() => freezable.Clone());
+    }
+
+    [Fact]
+    public void Clone_InvokeDifferentCreateInstanceCore_Success()
+    {
+        var freezable = new CustomFreezable();
+        var clone = new SubFreezable();
+        freezable.CreateInstanceCoreAction = () => clone;
+        Assert.Same(clone, freezable.Clone());
+        Assert.False(freezable.IsFrozen);
+        Assert.False(clone.IsFrozen);
+    }
+
+    [Fact]
+    public void Clone_InvokeSameCreateInstanceCore_Success()
+    {
+        var freezable = new CustomFreezable();
+        freezable.CreateInstanceCoreAction = () => freezable;
+        Assert.Same(freezable, freezable.Clone());
+        Assert.False(freezable.IsFrozen);
+    }
+
+    [Fact]
+    public void Clone_InvokeFrozenCreateInstanceCore_Success()
+    {
+        var freezable = new CustomFreezable();
+        var clone = new CustomFreezable();
+        clone.Freeze();
+        freezable.CreateInstanceCoreAction = () => clone;
+        Assert.Same(clone, freezable.Clone());
+        Assert.False(freezable.IsFrozen);
+        Assert.True(clone.IsFrozen);
+    }
+
+    [Fact]
+    public void Clone_InvokeCantFreeze_ReturnsExpected()
+    {
+        var freezable = new CustomFreezable();
+        var clone = new CustomFreezable();
+        freezable.CreateInstanceCoreAction = () => clone;
+        int callCount = 0;
+        clone.FreezeCoreAction = (checking) =>
+        {
+            Assert.True(checking);
+            callCount++;
+            return false;
+        };
+
+        Assert.Same(clone, freezable.Clone());
+        Assert.NotSame(freezable, clone);
+        Assert.False(clone.CanFreeze);
+        Assert.NotNull(clone.DependencyObjectType);
+        Assert.Same(clone.DependencyObjectType, clone.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(CustomFreezable)), clone.DependencyObjectType);
+        Assert.NotNull(clone.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, clone.Dispatcher);
+        Assert.False(clone.IsFrozen);
+        Assert.False(clone.IsSealed);
+    }
+
+    [Fact]
+    public void Clone_InvokeOnDifferentThread_ThrowsInvalidOperationException()
+    {
+        var freezable = new SubFreezable();
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => freezable.Clone());
+        });
+    }
+
+    [Fact]
+    public void Clone_InvokeFrozenOnDifferentThread_ReturnsExpected()
+    {
+        var freezable = new SubFreezable();
+        freezable.CreateInstanceCoreAction = () => new SubFreezable();
+        freezable.Freeze();
+        
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            SubFreezable clone = Assert.IsType<SubFreezable>(freezable.Clone());    
+            Assert.NotSame(freezable, clone);
+            Assert.True(clone.CanFreeze);
+            Assert.NotNull(clone.DependencyObjectType);
+            Assert.Same(clone.DependencyObjectType, clone.DependencyObjectType);
+            Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), clone.DependencyObjectType);
+            Assert.NotNull(clone.Dispatcher);
+            Assert.Same(Dispatcher.CurrentDispatcher, clone.Dispatcher);
+            Assert.False(clone.IsFrozen);
+            Assert.False(clone.IsSealed);
+        });
+    }
+
+    [Fact]
+    public void CloneCore_InvokeDefault_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        // Clone.
+        freezable.CloneCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+
+        // Clone again.
+        freezable.CloneCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void CloneCore_InvokeWithProperties_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        sourceFreezable.SetValue(SubFreezable.Property1, 10);
+        sourceFreezable.SetValue(SubFreezable.Property2, 20);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property3, 30);
+        sourceFreezable.SetValue(SubFreezable.Property4, 40);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        sourceFreezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        sourceFreezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+
+        // Clone.
+        freezable.CloneCore(sourceFreezable);
+        Assert.Equal(10, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(20, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(30, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(40, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(50, freezable.GetValue(SubFreezable.Property5));
+        Assert.NotSame(anotherFreezable1, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)));
+        Assert.Equal(60, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)freezable.GetValue(SubFreezable.Property6)).IsFrozen);
+        Assert.NotSame(anotherFreezable2, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)));
+        Assert.Equal(70, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)freezable.GetValue(SubFreezable.Property7)).IsFrozen);
+        Assert.NotSame(anotherFreezable3, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)));
+        Assert.Equal(80, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)freezable.GetValue(SubFreezable.Property8)).IsFrozen);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void CloneCore_InvokeWithReadOnlyProperty_DoesNotCopy()
+    {
+        var freezable = new SubFreezable();
+        var sourceFreezable = new SubFreezable();
+        DependencyPropertyKey propertyKey = DependencyProperty.RegisterReadOnly(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), new PropertyMetadata());
+        sourceFreezable.SetValue(propertyKey, "value");
+
+        // Clone.
+        freezable.CloneCore(sourceFreezable);
+        Assert.Null(freezable.GetValue(propertyKey.DependencyProperty));
+        Assert.Equal("value", sourceFreezable.GetValue(propertyKey.DependencyProperty));
+    }
+
+    [Fact]
+    public void CloneCore_InvokeSourceFrozenDefault_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+        sourceFreezable.Freeze();
+
+        // Clone.
+        freezable.CloneCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+
+        // Clone again.
+        freezable.CloneCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void CloneCore_InvokeSourceFrozenWithProperties_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        sourceFreezable.SetValue(SubFreezable.Property1, 10);
+        sourceFreezable.SetValue(SubFreezable.Property2, 20);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property3, 30);
+        sourceFreezable.SetValue(SubFreezable.Property4, 40);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        sourceFreezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        sourceFreezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+        
+        sourceFreezable.Freeze();
+
+        // Clone.
+        freezable.CloneCore(sourceFreezable);
+        Assert.Equal(10, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(20, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(30, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(40, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(50, freezable.GetValue(SubFreezable.Property5));
+        Assert.NotSame(anotherFreezable1, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)));
+        Assert.Equal(60, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)freezable.GetValue(SubFreezable.Property6)).IsFrozen);
+        Assert.NotSame(anotherFreezable2, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)));
+        Assert.Equal(70, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)freezable.GetValue(SubFreezable.Property7)).IsFrozen);
+        Assert.NotSame(anotherFreezable3, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)));
+        Assert.Equal(80, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)freezable.GetValue(SubFreezable.Property8)).IsFrozen);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void CloneCore_InvokeDestinationFrozenDefault_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+
+        // Clone.
+        freezable.CloneCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Null(freezable.Dispatcher);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+
+        // Clone again.
+        freezable.CloneCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Null(freezable.Dispatcher);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void CloneCore_InvokeDestinationFrozenWithProperties_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        sourceFreezable.SetValue(SubFreezable.Property1, 10);
+        sourceFreezable.SetValue(SubFreezable.Property2, 20);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property3, 30);
+        sourceFreezable.SetValue(SubFreezable.Property4, 40);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        sourceFreezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        sourceFreezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+        
+        freezable.Freeze();
+
+        // Invoke.
+        Assert.Throws<InvalidOperationException>(() => freezable.CloneCore(sourceFreezable));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property5));
+        Assert.Null(freezable.GetValue(SubFreezable.Property6));
+        Assert.Null(freezable.GetValue(SubFreezable.Property7));
+        Assert.Null(freezable.GetValue(SubFreezable.Property8));
+        Assert.True(freezable.CanFreeze);
+        Assert.Null(freezable.Dispatcher);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void CloneCore_InvokeOnDifferentThreadDefault_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            freezable.CloneCore(sourceFreezable);
+        });
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+
+        // Clone again.
+        freezable.CloneCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void CloneCore_InvokeOnDifferentThreadWithProperties_ThrowsInvalidOperationException()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        sourceFreezable.SetValue(SubFreezable.Property1, 10);
+        sourceFreezable.SetValue(SubFreezable.Property2, 20);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property3, 30);
+        sourceFreezable.SetValue(SubFreezable.Property4, 40);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        sourceFreezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        sourceFreezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+
+        // Invoke.
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => freezable.CloneCore(sourceFreezable));
+        });
+
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property5));
+        Assert.Null(freezable.GetValue(SubFreezable.Property6));
+        Assert.Null(freezable.GetValue(SubFreezable.Property7));
+        Assert.Null(freezable.GetValue(SubFreezable.Property8));
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void CloneCore_InvokeSourceFrozenOnDifferentThreadDefault_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+        sourceFreezable.Freeze();
+        
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            freezable.CloneCore(sourceFreezable);
+        });
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+
+        // Clone again.
+        freezable.CloneCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void CloneCore_InvokeSourceFrozenOnDifferentThreadWithProperties_ThrowsInvalidOperationException()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        sourceFreezable.SetValue(SubFreezable.Property1, 10);
+        sourceFreezable.SetValue(SubFreezable.Property2, 20);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property3, 30);
+        sourceFreezable.SetValue(SubFreezable.Property4, 40);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        sourceFreezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        sourceFreezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+        
+        sourceFreezable.Freeze();
+
+        // Invoke.
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => freezable.CloneCore(sourceFreezable));
+        });
+
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property5));
+        Assert.Null(freezable.GetValue(SubFreezable.Property6));
+        Assert.Null(freezable.GetValue(SubFreezable.Property7));
+        Assert.Null(freezable.GetValue(SubFreezable.Property8));
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void CloneCore_InvokeDestinationFrozenOnDifferentThreadDefault_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+        
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            freezable.CloneCore(sourceFreezable);
+        });
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Null(freezable.Dispatcher);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+
+        // Clone again.
+        freezable.CloneCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Null(freezable.Dispatcher);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void CloneCore_InvokeDestinationFrozenOnDifferentThreadWithProperties_ThrowsInvalidOperationException()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        sourceFreezable.SetValue(SubFreezable.Property1, 10);
+        sourceFreezable.SetValue(SubFreezable.Property2, 20);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property3, 30);
+        sourceFreezable.SetValue(SubFreezable.Property4, 40);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        sourceFreezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        sourceFreezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+        
+        freezable.Freeze();
+
+        // Invoke.
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => freezable.CloneCore(sourceFreezable));
+        });
+
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property5));
+        Assert.Null(freezable.GetValue(SubFreezable.Property6));
+        Assert.Null(freezable.GetValue(SubFreezable.Property7));
+        Assert.Null(freezable.GetValue(SubFreezable.Property8));
+        Assert.True(freezable.CanFreeze);
+        Assert.Null(freezable.Dispatcher);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void CloneCore_NullSourceFreezable_ThrowsArgumentNullException()
+    {
+        var freezable = new SubFreezable();
+        // TODO: this should not throw NullReferenceException.
+        //Assert.Throws<ArgumentNullException>("sourceFreezable", () => freezable.CloneCore(null!));
+        Assert.Throws<NullReferenceException>(() => freezable.CloneCore(null!));
+    }
+
+    [Fact]
+    public void CloneCurrentValue_InvokeDefault_Success()
+    {
+        var freezable = new SubFreezable();
+        int createInstanceCallCount = 0;
+        freezable.CreateInstanceCoreAction = () =>
+        {
+            createInstanceCallCount++;
+            return new SubFreezable();
+        };
+
+        // Clone.
+        SubFreezable clone = Assert.IsType<SubFreezable>(freezable.CloneCurrentValue());
+        Assert.NotSame(freezable, clone);
+        Assert.True(clone.CanFreeze);
+        Assert.NotNull(clone.DependencyObjectType);
+        Assert.Same(clone.DependencyObjectType, clone.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), clone.DependencyObjectType);
+        Assert.NotNull(clone.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, clone.Dispatcher);
+        Assert.False(clone.IsFrozen);
+        Assert.False(clone.IsSealed);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+        Assert.True(freezable.CanFreeze);
+        Assert.Equal(1, createInstanceCallCount);
+
+        // Clone again.
+        SubFreezable clone2 = Assert.IsType<SubFreezable>(freezable.CloneCurrentValue());
+        Assert.NotSame(freezable, clone);
+        Assert.NotSame(clone, clone2);
+        Assert.True(clone2.CanFreeze);
+        Assert.NotNull(clone2.DependencyObjectType);
+        Assert.Same(clone2.DependencyObjectType, clone2.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), clone2.DependencyObjectType);
+        Assert.NotNull(clone2.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, clone2.Dispatcher);
+        Assert.False(clone2.IsFrozen);
+        Assert.False(clone2.IsSealed);
+        Assert.NotNull(clone.DependencyObjectType);
+        Assert.Same(clone.DependencyObjectType, clone.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), clone.DependencyObjectType);
+        Assert.NotNull(clone.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, clone.Dispatcher);
+        Assert.False(clone.IsFrozen);
+        Assert.False(clone.IsSealed);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+        Assert.True(freezable.CanFreeze);
+        Assert.Equal(2, createInstanceCallCount);
+    }
+
+    [Fact]
+    public void CloneCurrentValue_InvokeWithProperties_Success()
+    {
+        var freezable = new SubFreezable();
+        int createInstanceCallCount = 0;
+        freezable.CreateInstanceCoreAction = () =>
+        {
+            createInstanceCallCount++;
+            return new SubFreezable();
+        };
+
+        freezable.SetValue(SubFreezable.Property1, 10);
+        freezable.SetValue(SubFreezable.Property2, 20);
+        freezable.SetCurrentValue(SubFreezable.Property3, 30);
+        freezable.SetValue(SubFreezable.Property4, 40);
+        freezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        freezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        freezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        freezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+
+        // Clone.
+        SubFreezable clone = Assert.IsType<SubFreezable>(freezable.CloneCurrentValue());
+        Assert.NotSame(freezable, clone);
+        Assert.Equal(10, clone.GetValue(SubFreezable.Property1));
+        Assert.Equal(20, clone.GetValue(SubFreezable.Property2));
+        Assert.Equal(30, clone.GetValue(SubFreezable.Property3));
+        Assert.Equal(40, clone.GetValue(SubFreezable.Property4));
+        Assert.Equal(50, clone.GetValue(SubFreezable.Property5));
+        Assert.NotSame(anotherFreezable1, ((SubFreezable)clone.GetValue(SubFreezable.Property6)));
+        Assert.Equal(60, ((SubFreezable)clone.GetValue(SubFreezable.Property6)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)clone.GetValue(SubFreezable.Property6)).IsFrozen);
+        Assert.NotSame(anotherFreezable2, ((SubFreezable)clone.GetValue(SubFreezable.Property7)));
+        Assert.Equal(70, ((SubFreezable)clone.GetValue(SubFreezable.Property7)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)clone.GetValue(SubFreezable.Property7)).IsFrozen);
+        Assert.NotSame(anotherFreezable3, ((SubFreezable)clone.GetValue(SubFreezable.Property8)));
+        Assert.Equal(80, ((SubFreezable)clone.GetValue(SubFreezable.Property8)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)clone.GetValue(SubFreezable.Property8)).IsFrozen);
+        Assert.True(clone.CanFreeze);
+        Assert.NotNull(clone.DependencyObjectType);
+        Assert.Same(clone.DependencyObjectType, clone.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), clone.DependencyObjectType);
+        Assert.NotNull(clone.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, clone.Dispatcher);
+        Assert.False(clone.IsFrozen);
+        Assert.False(clone.IsSealed);
+    }
+
+    [Fact]
+    public void CloneCurrentValue_InvokeWithUnfreezableProperties_ThrowsInvalidOperationException()
+    {
+        var freezable = new SubFreezable();
+        freezable.CreateInstanceCoreAction = () => new SubFreezable();
+        freezable.SetValue(SubFreezable.Property1, 10);
+        freezable.SetValue(SubFreezable.Property2, 20);
+        freezable.SetCurrentValue(SubFreezable.Property3, 30);
+        freezable.SetValue(SubFreezable.Property4, 40);
+        freezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        freezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        freezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        freezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+
+        var anotherFreezable4 = new CustomFreezable();
+        anotherFreezable4.CreateInstanceCoreAction = () => new CustomFreezable();
+        anotherFreezable4.SetValue(SubFreezable.Property1, 90);
+        anotherFreezable4.FreezeCoreAction = (isChecking) => false;
+        freezable.SetValue(SubFreezable.Property9, anotherFreezable4);
+
+        SubFreezable clone = Assert.IsType<SubFreezable>(freezable.CloneCurrentValue());
+        Assert.NotSame(freezable, clone);
+        Assert.Equal(10, clone.GetValue(SubFreezable.Property1));
+        Assert.Equal(20, clone.GetValue(SubFreezable.Property2));
+        Assert.Equal(30, clone.GetValue(SubFreezable.Property3));
+        Assert.Equal(40, clone.GetValue(SubFreezable.Property4));
+        Assert.Equal(50, clone.GetValue(SubFreezable.Property5));
+        Assert.NotSame(anotherFreezable1, ((SubFreezable)clone.GetValue(SubFreezable.Property6)));
+        Assert.Equal(60, ((SubFreezable)clone.GetValue(SubFreezable.Property6)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)clone.GetValue(SubFreezable.Property6)).IsFrozen);
+        Assert.NotSame(anotherFreezable2, ((SubFreezable)clone.GetValue(SubFreezable.Property7)));
+        Assert.Equal(70, ((SubFreezable)clone.GetValue(SubFreezable.Property7)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)clone.GetValue(SubFreezable.Property7)).IsFrozen);
+        Assert.NotSame(anotherFreezable3, ((SubFreezable)clone.GetValue(SubFreezable.Property8)));
+        Assert.Equal(80, ((SubFreezable)clone.GetValue(SubFreezable.Property8)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)clone.GetValue(SubFreezable.Property8)).IsFrozen);
+        Assert.True(clone.CanFreeze);
+        Assert.NotNull(clone.DependencyObjectType);
+        Assert.Same(clone.DependencyObjectType, clone.DependencyObjectType);
+        Assert.NotNull(clone.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, clone.Dispatcher);
+        Assert.False(clone.IsFrozen);
+        Assert.False(clone.IsSealed);
+    }
+
+    [Fact]
+    public void CloneCurrentValue_InvokeWithReadOnlyProperty_DoesNotCopy()
+    {
+        var freezable = new SubFreezable();
+        freezable.CreateInstanceCoreAction = () => new SubFreezable();
+        DependencyPropertyKey propertyKey = DependencyProperty.RegisterReadOnly(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), new PropertyMetadata());
+        freezable.SetValue(propertyKey, "value");
+
+        // CloneCurrentValue.
+        SubFreezable clone = Assert.IsType<SubFreezable>(freezable.CloneCurrentValue());
+        Assert.Null(clone.GetValue(propertyKey.DependencyProperty));
+        Assert.Equal("value", freezable.GetValue(propertyKey.DependencyProperty));
+    }
+
+    [Fact]
+    public void CloneCurrentValue_InvokeFrozen_ReturnsExpected()
+    {
+        var freezable = new SubFreezable();
+        freezable.CreateInstanceCoreAction = () => new SubFreezable();
+        freezable.Freeze();
+
+        SubFreezable clone = Assert.IsType<SubFreezable>(freezable.CloneCurrentValue());
+        Assert.NotSame(freezable, clone);
+        Assert.True(clone.CanFreeze);
+        Assert.NotNull(clone.DependencyObjectType);
+        Assert.Same(clone.DependencyObjectType, clone.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), clone.DependencyObjectType);
+        Assert.NotNull(clone.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, clone.Dispatcher);
+        Assert.False(clone.IsFrozen);
+        Assert.False(clone.IsSealed);
+    }
+
+    [Fact]
+    public void CloneCurrentValue_InvokeNullCreateInstanceCore_ThrowsNullReferenceException()
+    {
+        var freezable = new CustomFreezable();
+        freezable.CreateInstanceCoreAction = () => null!;
+        Assert.Throws<NullReferenceException>(() => freezable.CloneCurrentValue());
+    }
+
+    [Fact]
+    public void CloneCurrentValue_InvokeCreateInstanceCore_Success()
+    {
+        var freezable = new CustomFreezable();
+        var clone = new SubFreezable();
+        freezable.CreateInstanceCoreAction = () => freezable;
+        Assert.Same(freezable, freezable.CloneCurrentValue());
+        Assert.False(clone.IsFrozen);
+    }
+
+    [Fact]
+    public void CloneCurrentValue_InvokeSameCreateInstanceCore_Success()
+    {
+        var freezable = new CustomFreezable();
+        freezable.CreateInstanceCoreAction = () => freezable;
+        Assert.Same(freezable, freezable.CloneCurrentValue());
+    }
+
+    [Fact]
+    public void CloneCurrentValue_InvokeFrozenCreateInstanceCore_Success()
+    {
+        var freezable = new CustomFreezable();
+        var clone = new CustomFreezable();
+        clone.Freeze();
+        freezable.CreateInstanceCoreAction = () => clone;
+        Assert.Same(clone, freezable.CloneCurrentValue());
+        Assert.True(clone.IsFrozen);
+    }
+
+    [Fact]
+    public void CloneCurrentValue_InvokeCantFreeze_ReturnsExpected()
+    {
+        var freezable = new CustomFreezable();
+        var clone = new CustomFreezable();
+        freezable.CreateInstanceCoreAction = () => clone;
+        int callCount = 0;
+        clone.FreezeCoreAction = (checking) =>
+        {
+            Assert.True(checking);
+            callCount++;
+            return false;
+        };
+
+        Assert.Same(clone, freezable.CloneCurrentValue());
+        Assert.NotSame(freezable, clone);
+        Assert.False(clone.CanFreeze);
+        Assert.NotNull(clone.DependencyObjectType);
+        Assert.Same(clone.DependencyObjectType, clone.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(CustomFreezable)), clone.DependencyObjectType);
+        Assert.NotNull(clone.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, clone.Dispatcher);
+        Assert.False(clone.IsFrozen);
+        Assert.False(clone.IsSealed);
+    }
+
+    [Fact]
+    public void CloneCurrentValue_InvokeOnDifferentThread_ThrowsInvalidOperationException()
+    {
+        var freezable = new SubFreezable();
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => freezable.CloneCurrentValue());
+        });
+    }
+
+    [Fact]
+    public void CloneCurrentValue_InvokeFrozenOnDifferentThread_ReturnsExpected()
+    {
+        var freezable = new SubFreezable();
+        freezable.CreateInstanceCoreAction = () => new SubFreezable();
+        freezable.Freeze();
+        
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            SubFreezable clone = Assert.IsType<SubFreezable>(freezable.CloneCurrentValue());    
+            Assert.NotSame(freezable, clone);
+            Assert.True(clone.CanFreeze);
+            Assert.NotNull(clone.DependencyObjectType);
+            Assert.Same(clone.DependencyObjectType, clone.DependencyObjectType);
+            Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), clone.DependencyObjectType);
+            Assert.NotNull(clone.Dispatcher);
+            Assert.Same(Dispatcher.CurrentDispatcher, clone.Dispatcher);
+            Assert.False(clone.IsFrozen);
+            Assert.False(clone.IsSealed);
+        });
+    }
+
+    [Fact]
+    public void CloneCurrentValueCore_InvokeDefault_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        // Clone.
+        freezable.CloneCurrentValueCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+
+        // Clone again.
+        freezable.CloneCurrentValueCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void CloneCurrentValueCore_InvokeWithProperties_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        sourceFreezable.SetValue(SubFreezable.Property1, 10);
+        sourceFreezable.SetValue(SubFreezable.Property2, 20);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property3, 30);
+        sourceFreezable.SetValue(SubFreezable.Property4, 40);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        sourceFreezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        sourceFreezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+
+        // Clone.
+        freezable.CloneCurrentValueCore(sourceFreezable);
+        Assert.Equal(10, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(20, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(30, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(40, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(50, freezable.GetValue(SubFreezable.Property5));
+        Assert.NotSame(anotherFreezable1, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)));
+        Assert.Equal(60, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)freezable.GetValue(SubFreezable.Property6)).IsFrozen);
+        Assert.NotSame(anotherFreezable2, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)));
+        Assert.Equal(70, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)freezable.GetValue(SubFreezable.Property7)).IsFrozen);
+        Assert.NotSame(anotherFreezable3, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)));
+        Assert.Equal(80, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)freezable.GetValue(SubFreezable.Property8)).IsFrozen);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void CloneCurrentValueCore_InvokeWithReadOnlyProperty_DoesNotCopy()
+    {
+        var freezable = new SubFreezable();
+        var sourceFreezable = new SubFreezable();
+        DependencyPropertyKey propertyKey = DependencyProperty.RegisterReadOnly(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), new PropertyMetadata());
+        sourceFreezable.SetValue(propertyKey, "value");
+
+        // Clone.
+        freezable.CloneCurrentValueCore(sourceFreezable);
+        Assert.Null(freezable.GetValue(propertyKey.DependencyProperty));
+        Assert.Equal("value", sourceFreezable.GetValue(propertyKey.DependencyProperty));
+    }
+
+    [Fact]
+    public void CloneCurrentValueCore_InvokeSourceFrozenDefault_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+        sourceFreezable.Freeze();
+
+        // Clone.
+        freezable.CloneCurrentValueCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+
+        // Clone again.
+        freezable.CloneCurrentValueCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void CloneCurrentValueCore_InvokeSourceFrozenWithProperties_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        sourceFreezable.SetValue(SubFreezable.Property1, 10);
+        sourceFreezable.SetValue(SubFreezable.Property2, 20);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property3, 30);
+        sourceFreezable.SetValue(SubFreezable.Property4, 40);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        sourceFreezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        sourceFreezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+        
+        sourceFreezable.Freeze();
+
+        // Clone.
+        freezable.CloneCurrentValueCore(sourceFreezable);
+        Assert.Equal(10, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(20, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(30, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(40, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(50, freezable.GetValue(SubFreezable.Property5));
+        Assert.NotSame(anotherFreezable1, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)));
+        Assert.Equal(60, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)freezable.GetValue(SubFreezable.Property6)).IsFrozen);
+        Assert.NotSame(anotherFreezable2, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)));
+        Assert.Equal(70, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)freezable.GetValue(SubFreezable.Property7)).IsFrozen);
+        Assert.NotSame(anotherFreezable3, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)));
+        Assert.Equal(80, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)freezable.GetValue(SubFreezable.Property8)).IsFrozen);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void CloneCurrentValueCore_InvokeDestinationFrozenDefault_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+
+        // Clone.
+        freezable.CloneCurrentValueCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Null(freezable.Dispatcher);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+
+        // Clone again.
+        freezable.CloneCurrentValueCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Null(freezable.Dispatcher);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void CloneCurrentValueCore_InvokeDestinationFrozenWithProperties_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        sourceFreezable.SetValue(SubFreezable.Property1, 10);
+        sourceFreezable.SetValue(SubFreezable.Property2, 20);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property3, 30);
+        sourceFreezable.SetValue(SubFreezable.Property4, 40);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        sourceFreezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        sourceFreezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+        
+        freezable.Freeze();
+
+        // Clone.
+        Assert.Throws<InvalidOperationException>(() => freezable.CloneCurrentValueCore(sourceFreezable));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property5));
+        Assert.Null(freezable.GetValue(SubFreezable.Property6));
+        Assert.Null(freezable.GetValue(SubFreezable.Property7));
+        Assert.Null(freezable.GetValue(SubFreezable.Property8));
+        Assert.True(freezable.CanFreeze);
+        Assert.Null(freezable.Dispatcher);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void CloneCurrentValueCore_InvokeOnDifferentThreadDefault_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+        
+        // Clone.
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            freezable.CloneCurrentValueCore(sourceFreezable);
+        });
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+
+        // Clone again.
+        freezable.CloneCurrentValueCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void CloneCurrentValueCore_InvokeOnDifferentThreadWithProperties_ThrowsInvalidOperationException()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        sourceFreezable.SetValue(SubFreezable.Property1, 10);
+        sourceFreezable.SetValue(SubFreezable.Property2, 20);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property3, 30);
+        sourceFreezable.SetValue(SubFreezable.Property4, 40);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        sourceFreezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        sourceFreezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+
+        // Clone.
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => freezable.CloneCurrentValueCore(sourceFreezable));
+        });
+
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property5));
+        Assert.Null(freezable.GetValue(SubFreezable.Property6));
+        Assert.Null(freezable.GetValue(SubFreezable.Property7));
+        Assert.Null(freezable.GetValue(SubFreezable.Property8));
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void CloneCurrentValueCore_InvokeSourceFrozenOnDifferentThreadDefault_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+        sourceFreezable.Freeze();
+        
+        // Clone.
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            freezable.CloneCurrentValueCore(sourceFreezable);
+        });
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+
+        // Clone again.
+        freezable.CloneCurrentValueCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void CloneCurrentValueCore_InvokeSourceFrozenOnDifferentThreadWithProperties_ThrowsInvalidOperationException()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        sourceFreezable.SetValue(SubFreezable.Property1, 10);
+        sourceFreezable.SetValue(SubFreezable.Property2, 20);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property3, 30);
+        sourceFreezable.SetValue(SubFreezable.Property4, 40);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        sourceFreezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        sourceFreezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+        
+        sourceFreezable.Freeze();
+
+        // Clone.
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => freezable.CloneCurrentValueCore(sourceFreezable));
+        });
+
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property5));
+        Assert.Null(freezable.GetValue(SubFreezable.Property6));
+        Assert.Null(freezable.GetValue(SubFreezable.Property7));
+        Assert.Null(freezable.GetValue(SubFreezable.Property8));
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void CloneCurrentValueCore_InvokeDestinationFrozenOnDifferentThreadDefault_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+        
+        // Clone.
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            freezable.CloneCurrentValueCore(sourceFreezable);
+        });
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Null(freezable.Dispatcher);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+
+        // Clone again.
+        freezable.CloneCurrentValueCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Null(freezable.Dispatcher);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void CloneCurrentValueCore_InvokeDestinationFrozenOnDifferentThreadWithProperties_ThrowsInvalidOperationException()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        sourceFreezable.SetValue(SubFreezable.Property1, 10);
+        sourceFreezable.SetValue(SubFreezable.Property2, 20);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property3, 30);
+        sourceFreezable.SetValue(SubFreezable.Property4, 40);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        sourceFreezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        sourceFreezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+        
+        freezable.Freeze();
+
+        // Clone.
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => freezable.CloneCurrentValueCore(sourceFreezable));
+        });
+
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property5));
+        Assert.Null(freezable.GetValue(SubFreezable.Property6));
+        Assert.Null(freezable.GetValue(SubFreezable.Property7));
+        Assert.Null(freezable.GetValue(SubFreezable.Property8));
+        Assert.True(freezable.CanFreeze);
+        Assert.Null(freezable.Dispatcher);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void CloneCurrentValueCore_NullSourceFreezable_ThrowsArgumentNullException()
+    {
+        var freezable = new SubFreezable();
+        // TODO: this should not throw NullReferenceException.
+        //Assert.Throws<ArgumentNullException>("sourceFreezable", () => freezable.CloneCurrentValueCore(null!));
+        Assert.Throws<NullReferenceException>(() => freezable.CloneCurrentValueCore(null!));
+    }
+
+    public static IEnumerable<object?[]> CreateInstance_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { new SubFreezable() };
+        yield return new object?[] { new SubFreezable2() };
+
+        var frozen = new SubFreezable2();
+        frozen.Freeze();
+        yield return new object?[] { frozen };
+    }
+
+    [Theory]
+    [MemberData(nameof(CreateInstance_TestData))]
+    public void CreateInstance_Invoke_ReturnsExpected(Freezable result)
+    {
+        var freezable = new SubFreezable();
+        int callCount = 0;
+        freezable.CreateInstanceCoreAction = () =>
+        {
+            callCount++;
+            return result;
+        };
+
+        Assert.Same(result, freezable.CreateInstance());
+        Assert.Equal(1, callCount);
+
+        // Call again.
+        Assert.Same(result, freezable.CreateInstance());
+        Assert.Equal(2, callCount);
+    }
+
+    [Theory]
+    [MemberData(nameof(CreateInstance_TestData))]
+    public void CreateInstance_InvokeFrozen_ReturnsExpected(Freezable result)
+    {
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+
+        int callCount = 0;
+        freezable.CreateInstanceCoreAction = () =>
+        {
+            callCount++;
+            return result;
+        };
+
+        Assert.Same(result, freezable.CreateInstance());
+        Assert.Equal(1, callCount);
+
+        // Call again.
+        Assert.Same(result, freezable.CreateInstance());
+        Assert.Equal(2, callCount);
+    }
+
+    [Theory]
+    [MemberData(nameof(CreateInstance_TestData))]
+    public void CreateInstance_InvokeOnDifferentThread_ReturnsExpected(Freezable result)
+    {
+        var freezable = new SubFreezable();
+        int callCount = 0;
+        freezable.CreateInstanceCoreAction = () =>
+        {
+            callCount++;
+            return result;
+        };
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Same(result, freezable.CreateInstance());
+            Assert.Equal(1, callCount);
+        });
+    }
+
+    [Theory]
+    [MemberData(nameof(CreateInstance_TestData))]
+    public void CreateInstance_InvokeFrozenOnDifferentThread_ReturnsExpected(Freezable result)
+    {
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+
+        int callCount = 0;
+        freezable.CreateInstanceCoreAction = () =>
+        {
+            callCount++;
+            return result;
+        };
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Same(result, freezable.CreateInstance());
+            Assert.Equal(1, callCount);
+        });
+    }
+
+
+
+    [Fact]
+    public void CoerceValue_InvokeValueType_GetValueReturnsExpected()
+    {
+        var obj = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject));
+
+        // Coerce default.
+        obj.CoerceValue(property);
+        Assert.False((bool)obj.GetValue(property));
+
+        // Set true.
+        obj.SetValue(property, true);
+        Assert.True((bool)obj.GetValue(property));
+
+        // Coerce true.
+        obj.CoerceValue(property);
+        Assert.True((bool)obj.GetValue(property));
+
+        // Coerce again.
+        obj.CoerceValue(property);
+        Assert.True((bool)obj.GetValue(property));
+    }
+
+    [Fact]
+    public void CoerceValue_InvokeNullable_GetValueReturnsExpected()
+    {
+        var obj = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool?), typeof(DependencyObject));
+
+        // Coerce default.
+        obj.CoerceValue(property);
+        Assert.Null(obj.GetValue(property));
+
+        // Set custom.
+        obj.SetValue(property, true);
+        Assert.True((bool)obj.GetValue(property));
+
+        // Coerce custom.
+        obj.CoerceValue(property);
+        Assert.True((bool)obj.GetValue(property));
+
+        // Coerce again.
+        obj.CoerceValue(property);
+        Assert.True((bool)obj.GetValue(property));
+    }
+
+    [Fact]
+    public void CoerceValue_InvokeReferenceType_GetValueReturnsExpected()
+    {
+        var obj = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+
+        // Coerce default.
+        obj.CoerceValue(property);
+        Assert.Null(obj.GetValue(property));
+
+        // Set custom.
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Coerce custom.
+        obj.CoerceValue(property);
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Coerce again.
+        obj.CoerceValue(property);
+        Assert.Equal("value", obj.GetValue(property));
+    }
+
+    [Fact]
+    public void CoerceValue_InvokeObject_GetValueReturnsExpected()
+    {
+        var obj = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(object), typeof(DependencyObject));
+
+        // Coerce default.
+        obj.CoerceValue(property);
+        Assert.Null(obj.GetValue(property));
+
+        // Set custom.
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Coerce custom.
+        obj.CoerceValue(property);
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Coerce again.
+        obj.CoerceValue(property);
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Set different.
+        obj.SetValue(property, 1);
+        Assert.Equal(1, obj.GetValue(property));
+
+        // Coerce custom.
+        obj.CoerceValue(property);
+        Assert.Equal(1, obj.GetValue(property));
+
+        // Coerce again.
+        obj.CoerceValue(property);
+        Assert.Equal(1, obj.GetValue(property));
+
+        // Set null.
+        obj.SetValue(property, null);
+        Assert.Null(obj.GetValue(property));
+
+        // Coerce custom.
+        obj.CoerceValue(property);
+        Assert.Null(obj.GetValue(property));
+
+        // Coerce again.
+        obj.CoerceValue(property);
+        Assert.Null(obj.GetValue(property));
+    }
+
+    [Fact]
+    public void CoerceValue_InvokeCustomPropertyChangeCallback_Success()
+    {
+        var obj = new SubFreezable();
+
+        int changedCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedOldValue = null;
+        object? expectedNewValue = null;
+        var typeMetadata = new PropertyMetadata(
+            null,
+            (d, e) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedProperty, e.Property);
+                Assert.Same(expectedOldValue, e.OldValue);
+                Assert.Same(expectedNewValue, e.NewValue);
+                Assert.Equal(expectedNewValue, obj.GetValue(e.Property));
+                changedCallCount++;
+            });
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        expectedProperty = property;
+
+        // Coerce default.
+        obj.CoerceValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(0, changedCallCount);
+
+        // Set custom.
+        expectedNewValue = "value";
+        expectedOldValue = null;
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+
+        // Coerce custom.
+        obj.CoerceValue(property);
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+
+        // Coerce again.
+        obj.CoerceValue(property);
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+    }
+
+    [Fact]
+    public void CoerceValue_InvokeCustomCoerceValueCallback_Success()
+    {
+        var obj = new SubFreezable();
+
+        int coerceValueCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedNewValue = null;
+        var typeMetadata = new PropertyMetadata(
+            null,
+            null,
+            (d, baseValue) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedNewValue, baseValue);
+                coerceValueCallCount++;
+                return baseValue;
+            }
+        );
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        expectedProperty = property;
+
+        // Coerce default.
+        obj.CoerceValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Set custom.
+        expectedNewValue = "value";
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(2, coerceValueCallCount);
+
+        // Coerce custom.
+        obj.CoerceValue(property);
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(3, coerceValueCallCount);
+
+        // Coerce again.
+        obj.CoerceValue(property);
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(4, coerceValueCallCount);
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("customCoercedValue")]
+    public void CoerceValue_InvokeCustomCoerceValueCallbackReturnsCustom_Success(object? customCoercedValue)
+    {
+        var obj = new SubFreezable();
+
+        int coerceValueCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedNewValue = null;
+        object? newBaseValue = "coercedValue";
+        var typeMetadata = new PropertyMetadata(
+            null,
+            null,
+            (d, baseValue) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedNewValue, baseValue);
+                coerceValueCallCount++;
+                return newBaseValue;
+            }
+        );
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name + customCoercedValue?.GetType().Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        expectedProperty = property;
+
+        // Coerce default.
+        obj.CoerceValue(property);
+        Assert.Equal("coercedValue", obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Set custom.
+        expectedNewValue = "value";
+        obj.SetValue(property, "value");
+        Assert.Equal("coercedValue", obj.GetValue(property));
+        Assert.Equal(2, coerceValueCallCount);
+
+        // Coerce custom.
+        newBaseValue = customCoercedValue;
+        obj.CoerceValue(property);
+        Assert.Equal(customCoercedValue, obj.GetValue(property));
+        Assert.Equal(3, coerceValueCallCount);
+
+        // Coerce again.
+        obj.CoerceValue(property);
+        Assert.Equal(customCoercedValue, obj.GetValue(property));
+        Assert.Equal(4, coerceValueCallCount);
+    }
+
+    [Fact]
+    public void CoerceValue_InvokeCustomCoerceValueCallbackReturnsUnset_Success()
+    {
+        var obj = new SubFreezable();
+
+        int coerceValueCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedBaseValue = null;
+        object? newBaseValue = null;
+        var typeMetadata = new PropertyMetadata(
+            null,
+            null,
+            (d, baseValue) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedBaseValue, baseValue);
+                coerceValueCallCount++;
+                return newBaseValue;
+            }
+        );
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        expectedProperty = property;
+
+        // Set custom.
+        expectedBaseValue = "value";
+        newBaseValue = "coercedValue";
+        obj.SetValue(property, "value");
+        Assert.Equal("coercedValue", obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Coerce.
+        expectedBaseValue = "value";
+        newBaseValue = DependencyProperty.UnsetValue;
+        obj.CoerceValue(property);
+        Assert.Equal("coercedValue", obj.GetValue(property));
+        Assert.Equal(2, coerceValueCallCount);
+    }
+
+    [Fact]
+    public void CoerceValue_InvokeChangeAndCoerceValueCallback_Success()
+    {
+        var obj = new SubFreezable();
+
+        int changedCallCount = 0;
+        int coerceValueCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedOldValue = null;
+        object? expectedNewValue = null;
+        var typeMetadata = new PropertyMetadata(
+            null,
+            (d, e) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedProperty, e.Property);
+                Assert.Same(expectedOldValue, e.OldValue);
+                Assert.Same(expectedNewValue, e.NewValue);
+                Assert.Equal(expectedNewValue, obj.GetValue(e.Property));
+                changedCallCount++;
+            },
+            (d, baseValue) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Same(expectedNewValue, baseValue);
+                coerceValueCallCount++;
+                return baseValue;
+            }
+        );
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        expectedProperty = property;
+
+        // Coerce default.
+        obj.CoerceValue(property);
+        Assert.Null(obj.GetValue(property));
+        Assert.Equal(0, changedCallCount);
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Set custom.
+        expectedNewValue = "value";
+        expectedOldValue = null;
+        obj.SetValue(property, "value");
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+        Assert.Equal(2, coerceValueCallCount);
+
+        // Coerce custom.
+        obj.CoerceValue(property);
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+        Assert.Equal(3, coerceValueCallCount);
+
+        // Coerce again.
+        obj.CoerceValue(property);
+        Assert.Equal("value", obj.GetValue(property));
+        Assert.Equal(1, changedCallCount);
+        Assert.Equal(4, coerceValueCallCount);
+    }
+
+    [Fact]
+    public void CoerceValue_InvokeReadOnly_GetValueReturnsExpected()
+    {
+        var obj = new SubFreezable();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+
+        // Coerce default.
+        obj.CoerceValue(property);
+        Assert.False((bool)obj.GetValue(property));
+
+        // Coerce again.
+        obj.CoerceValue(property);
+        Assert.False((bool)obj.GetValue(property));
+    }
+
+    [Fact]
+    public void CoerceValue_DependencyPropertyNullDp_ThrowsArgumentNullException()
+    {
+        var obj = new SubFreezable();
+        // TODO: this should throw ArgumentNullException
+        //Assert.Throws<ArgumentNullException>("dp", () => obj.CoerceValue(null!));
+        Assert.Throws<NullReferenceException>(() => obj.CoerceValue(null!));
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("value")]
+    public void CoerceValue_InvalidResultDefault_ThrowsArgumentException(object? invalidValue)
+    {
+        var obj = new SubFreezable();
+
+        int coerceValueCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedNewValue = null;
+        var typeMetadata = new PropertyMetadata(
+            0,
+            null,
+            (d, baseValue) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Equal(expectedNewValue, baseValue);
+                coerceValueCallCount++;
+                return invalidValue;
+            }
+        );
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name + invalidValue?.GetType().Name, typeof(int), typeof(DependencyObject), typeMetadata);
+        expectedProperty = property;
+
+        // Coerce default.
+        expectedNewValue = 0;
+        Assert.Throws<ArgumentException>(() => obj.CoerceValue(property));
+        Assert.Equal(0, obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallCount);
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("value")]
+    public void CoerceValue_InvalidResultCustom_ThrowsArgumentException(object? invalidValue)
+    {
+        var obj = new SubFreezable();
+
+        int coerceValueCallCount = 0;
+        DependencyProperty? expectedProperty = null;
+        object? expectedNewValue = null;
+        object? newBaseValue = 1;
+        var typeMetadata = new PropertyMetadata(
+            0,
+            null,
+            (d, baseValue) =>
+            {
+                Assert.Same(obj, d);
+                Assert.Equal(expectedNewValue, baseValue);
+                coerceValueCallCount++;
+                return newBaseValue;
+            }
+        );
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name + invalidValue?.GetType().Name, typeof(int), typeof(DependencyObject), typeMetadata);
+        expectedProperty = property;
+
+        // Set custom.
+        expectedNewValue = 2;
+        newBaseValue = 2;
+        obj.SetValue(property, 2);
+        Assert.Equal(2, obj.GetValue(property));
+        Assert.Equal(1, coerceValueCallCount);
+
+        // Coerce custom.
+        newBaseValue = invalidValue;
+        Assert.Throws<ArgumentException>(() => obj.CoerceValue(property));
+        Assert.Equal(2, coerceValueCallCount);
+    }
+
+    [Fact]
+    public void CoerceValue_InvokeFrozen_ThrowsInvalidOperationException()
+    {
+        var obj = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject));
+        obj.Freeze();
+
+        // Coerce default.
+        obj.CoerceValue(property);
+        Assert.False((bool)obj.GetValue(property));
+
+        // Coerce again.
+        obj.CoerceValue(property);
+        Assert.False((bool)obj.GetValue(property));
+    }
+
+    [Fact]
+    public void CoerceValue_InvokeOnDifferentThread_ThrowsInvalidOperationException()
+    {
+        var obj = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => obj.CoerceValue(property));
+        });
+    }
+
+    [Fact]
+    public void CoerceValue_InvokeFrozenOnDifferentThread_Nop()
+    {
+        var obj = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject));
+        obj.Freeze();
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            obj.CoerceValue(property);
+        });
+        Assert.False((bool)obj.GetValue(property));
+    }
+
+    [Fact]
+    public void CoerceValue_InvokeFrozenCustomOnDifferentThread_Nop()
+    {
+        var obj = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject));
+        obj.SetValue(property, true);
+        obj.Freeze();
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            obj.CoerceValue(property);
+        });
+        Assert.True((bool)obj.GetValue(property));
+    }
+
+    [Fact]
+    public void Freeze_Invoke_Success()
+    {
+        var freezable = new SubFreezable();
+
+        // Freeze once.
+        freezable.Freeze();
+        Assert.True(freezable.CanFreeze);
+        Assert.Null(freezable.Dispatcher);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+
+        // Freeze again.
+        freezable.Freeze();
+        Assert.True(freezable.CanFreeze);
+        Assert.Null(freezable.Dispatcher);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void Freeze_InvokeWithProperties_Success()
+    {
+        var freezable = new SubFreezable();
+        freezable.SetValue(SubFreezable.Property1, 10);
+        freezable.SetValue(SubFreezable.Property2, 20);
+        freezable.SetCurrentValue(SubFreezable.Property3, 30);
+        freezable.SetValue(SubFreezable.Property4, 40);
+        freezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        freezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        freezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        freezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+
+        // Freeze once.
+        freezable.Freeze();
+        Assert.Equal(10, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(20, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(30, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(40, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(50, freezable.GetValue(SubFreezable.Property5));
+        Assert.Same(anotherFreezable1, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)));
+        Assert.Equal(60, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)freezable.GetValue(SubFreezable.Property6)).IsFrozen);
+        Assert.Same(anotherFreezable2, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)));
+        Assert.Equal(70, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)freezable.GetValue(SubFreezable.Property7)).IsFrozen);
+        Assert.Same(anotherFreezable3, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)));
+        Assert.Equal(80, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)freezable.GetValue(SubFreezable.Property8)).IsFrozen);
+        Assert.True(freezable.CanFreeze);
+        Assert.Null(freezable.Dispatcher);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+
+        // Freeze again.
+        freezable.Freeze();
+        Assert.Equal(10, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(20, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(30, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(40, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(50, freezable.GetValue(SubFreezable.Property5));
+        Assert.Same(anotherFreezable1, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)));
+        Assert.Equal(60, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)freezable.GetValue(SubFreezable.Property6)).IsFrozen);
+        Assert.Same(anotherFreezable2, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)));
+        Assert.Equal(70, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)freezable.GetValue(SubFreezable.Property7)).IsFrozen);
+        Assert.Same(anotherFreezable3, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)));
+        Assert.Equal(80, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)freezable.GetValue(SubFreezable.Property8)).IsFrozen);
+        Assert.True(freezable.CanFreeze);
+        Assert.Null(freezable.Dispatcher);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void Freeze_InvokeWithUnfreezableProperties_Success()
+    {
+        var freezable = new SubFreezable();
+        freezable.SetValue(SubFreezable.Property1, 10);
+        freezable.SetValue(SubFreezable.Property2, 20);
+        freezable.SetCurrentValue(SubFreezable.Property3, 30);
+        freezable.SetValue(SubFreezable.Property4, 40);
+        freezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        freezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        freezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        freezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+
+        var anotherFreezable4 = new CustomFreezable();
+        anotherFreezable4.SetValue(SubFreezable.Property1, 90);
+        anotherFreezable4.FreezeCoreAction = (isChecking) => false;
+        freezable.SetValue(SubFreezable.Property9, anotherFreezable4);
+
+        // Freeze once.
+        Assert.Throws<InvalidOperationException>(() => freezable.Freeze());
+        Assert.Equal(10, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(20, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(30, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(40, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(50, freezable.GetValue(SubFreezable.Property5));
+        Assert.Same(anotherFreezable1, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)));
+        Assert.Equal(60, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)freezable.GetValue(SubFreezable.Property6)).IsFrozen);
+        Assert.Same(anotherFreezable2, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)));
+        Assert.Equal(70, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)freezable.GetValue(SubFreezable.Property7)).IsFrozen);
+        Assert.Same(anotherFreezable3, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)));
+        Assert.Equal(80, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)freezable.GetValue(SubFreezable.Property8)).IsFrozen);
+        Assert.False(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+
+        // Freeze again.
+        Assert.Throws<InvalidOperationException>(() => freezable.Freeze());
+        Assert.Equal(10, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(20, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(30, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(40, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(50, freezable.GetValue(SubFreezable.Property5));
+        Assert.False(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void Freeze_InvokeCustomFreezeCore_Success()
+    {
+        var freezable = new CustomFreezable();
+        int callCount = 0;
+        freezable.FreezeCoreAction = (checking) =>
+        {
+            Assert.Equal(callCount == 0, checking);
+            callCount++;
+            return true;
+        };
+
+        // Freeze once.
+        freezable.Freeze();
+        Assert.Equal(2, callCount);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(CustomFreezable)), freezable.DependencyObjectType);
+        Assert.Null(freezable.Dispatcher);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+
+        // Freeze again.
+        freezable.Freeze();
+        Assert.Equal(2, callCount);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(CustomFreezable)), freezable.DependencyObjectType);
+        Assert.Null(freezable.Dispatcher);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void Freeze_InvokeWithHandler_CallsChanged()
+    {
+        var freezable = new SubFreezable();
+
+        int callCount = 0;
+        EventHandler handler = (sender, e) =>
+        {
+            Assert.Same(freezable, sender);
+            Assert.Same(EventArgs.Empty, e);
+            Assert.Null(freezable.Dispatcher);
+            Assert.True(freezable.IsFrozen);
+            Assert.True(freezable.IsSealed);
+            callCount++;
+        }; 
+        freezable.Changed += handler;
+
+        // Freeze.
+        freezable.Freeze();
+        Assert.Equal(1, callCount);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Null(freezable.Dispatcher);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+        
+        // Freeze again.
+        freezable.Freeze();
+        Assert.Equal(1, callCount);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Null(freezable.Dispatcher);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void Freeze_InvokeCustomOnChanged_CallsChanged()
+    {
+        var freezable = new CustomFreezable();
+        int onChangedCallCount = 0;
+        int changedCallCount = 0;
+        freezable.OnChangedAction = () =>
+        {
+            Assert.Equal(changedCallCount, onChangedCallCount);
+            Assert.Null(freezable.Dispatcher);
+            Assert.True(freezable.IsFrozen);
+            Assert.True(freezable.IsSealed);
+            onChangedCallCount++;
+        };
+        freezable.Changed += (sender, e) =>
+        {
+            Assert.True(onChangedCallCount > changedCallCount);
+            Assert.Same(freezable, sender);
+            Assert.Same(EventArgs.Empty, e);
+            Assert.Null(freezable.Dispatcher);
+            Assert.True(freezable.IsFrozen);
+            Assert.True(freezable.IsSealed);
+            changedCallCount++;
+        }; 
+
+        // Freeze.
+        freezable.Freeze();
+        Assert.Equal(1, changedCallCount);
+        Assert.Equal(2, onChangedCallCount);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(CustomFreezable)), freezable.DependencyObjectType);
+        Assert.Null(freezable.Dispatcher);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+        
+        // Freeze again.
+        freezable.Freeze();
+        Assert.Equal(1, changedCallCount);
+        Assert.Equal(2, onChangedCallCount);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(CustomFreezable)), freezable.DependencyObjectType);
+        Assert.Null(freezable.Dispatcher);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void Freeze_InvokeWithRemovedHandler_CallsChanged()
+    {
+        var freezable = new SubFreezable();
+
+        int callCount = 0;
+        EventHandler handler = (sender, e) => callCount++;
+        freezable.Changed += handler;
+        freezable.Changed -= handler;
+
+        // Freeze.
+        freezable.Freeze();
+        Assert.Equal(0, callCount);
+        Assert.True(freezable.CanFreeze);
+        
+        // Freeze again.
+        freezable.Freeze();
+        Assert.Equal(0, callCount);
+        Assert.True(freezable.CanFreeze);
+    }
+
+    [Fact]
+    public void Freeze_InvokeCantFreeze_ThrowsInvalidOperationException()
+    {
+        var freezable = new CustomFreezable();
+        int callCount = 0;
+        freezable.FreezeCoreAction = (checking) =>
+        {
+            Assert.True(checking);
+            callCount++;
+            return false;
+        };
+
+        // Freeze.
+        Assert.Throws<InvalidOperationException>(() => freezable.Freeze());
+        Assert.Equal(1, callCount);
+        Assert.False(freezable.IsFrozen);
+    }
+
+    [Fact]
+    public void Freeze_InvokeFrozenCantFreeze_Nop()
+    {
+        var freezable = new CustomFreezable();
+        
+        // Freeze once.
+        freezable.Freeze();
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(CustomFreezable)), freezable.DependencyObjectType);
+        Assert.Null(freezable.Dispatcher);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+
+        int callCount = 0;
+        freezable.FreezeCoreAction = (checking) =>
+        {
+            Assert.True(checking);
+            callCount++;
+            return false;
+        };
+
+        // Freeze again.
+        freezable.Freeze();
+        Assert.Equal(0, callCount);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(CustomFreezable)), freezable.DependencyObjectType);
+        Assert.Null(freezable.Dispatcher);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void Freeze_InvokeOnDifferentThread_ThrowsInvalidOperationException()
+    {
+        var freezable = new SubFreezable();
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => freezable.Freeze());
+        });
+        Assert.False(freezable.IsFrozen);
+    }
+
+    [Fact]
+    public void Freeze_InvokeFrozenOnDifferentThread_Nop()
+    {
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            freezable.Freeze();
+        });
+        Assert.True(freezable.IsFrozen);
+    }
+
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void FreezeCore_InvokeDefault_Success(bool isChecking)
+    {
+        var freezable = new SubFreezable();
+
+        // Freeze once.
+        Assert.True(freezable.FreezeCore(isChecking));
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+
+        // Freeze again.
+        Assert.True(freezable.FreezeCore(isChecking));
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void FreezeCore_InvokeWithProperties_Success(bool isChecking)
+    {
+        var freezable = new SubFreezable();
+        freezable.SetValue(SubFreezable.Property1, 10);
+        freezable.SetValue(SubFreezable.Property2, 20);
+        freezable.SetCurrentValue(SubFreezable.Property3, 30);
+        freezable.SetValue(SubFreezable.Property4, 40);
+        freezable.SetCurrentValue(SubFreezable.Property5, 50);
+        
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        freezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        freezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        freezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+
+        // Freeze once.
+        Assert.True(freezable.FreezeCore(isChecking));
+        Assert.Equal(10, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(20, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(30, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(40, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(50, freezable.GetValue(SubFreezable.Property5));
+        Assert.Same(anotherFreezable1, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)));
+        Assert.Equal(60, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)).GetValue(SubFreezable.Property1));
+        Assert.Equal(!isChecking, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)).IsFrozen);
+        Assert.Same(anotherFreezable2, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)));
+        Assert.Equal(70, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)).GetValue(SubFreezable.Property1));
+        Assert.Equal(!isChecking, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)).IsFrozen);
+        Assert.Same(anotherFreezable3, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)));
+        Assert.Equal(80, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)freezable.GetValue(SubFreezable.Property8)).IsFrozen);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+
+        // Freeze again.
+        Assert.True(freezable.FreezeCore(isChecking));
+        Assert.Equal(10, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(20, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(30, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(40, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(50, freezable.GetValue(SubFreezable.Property5));
+        Assert.Same(anotherFreezable1, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)));
+        Assert.Equal(60, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)).GetValue(SubFreezable.Property1));
+        Assert.Equal(!isChecking, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)).IsFrozen);
+        Assert.Same(anotherFreezable2, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)));
+        Assert.Equal(70, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)).GetValue(SubFreezable.Property1));
+        Assert.Equal(!isChecking, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)).IsFrozen);
+        Assert.Same(anotherFreezable3, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)));
+        Assert.Equal(80, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)freezable.GetValue(SubFreezable.Property8)).IsFrozen);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void FreezeCore_InvokeWithUnfreezableProperties_Success(bool isChecking)
+    {
+        var freezable = new SubFreezable();
+        freezable.SetValue(SubFreezable.Property1, 10);
+        freezable.SetValue(SubFreezable.Property2, 20);
+        freezable.SetCurrentValue(SubFreezable.Property3, 30);
+        freezable.SetValue(SubFreezable.Property4, 40);
+        freezable.SetCurrentValue(SubFreezable.Property5, 50);
+        
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        freezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        freezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        freezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+
+        var anotherFreezable4 = new CustomFreezable();
+        anotherFreezable4.SetValue(SubFreezable.Property1, 90);
+        anotherFreezable4.FreezeCoreAction = (isChecking) => false;
+        freezable.SetValue(SubFreezable.Property9, anotherFreezable4);
+
+        // Freeze once.
+        Assert.Equal(!isChecking, freezable.FreezeCore(isChecking));
+        Assert.Equal(10, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(20, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(30, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(40, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(50, freezable.GetValue(SubFreezable.Property5));
+        Assert.Same(anotherFreezable1, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)));
+        Assert.Equal(60, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)).GetValue(SubFreezable.Property1));
+        Assert.Equal(!isChecking, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)).IsFrozen);
+        Assert.Same(anotherFreezable2, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)));
+        Assert.Equal(70, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)).GetValue(SubFreezable.Property1));
+        Assert.Equal(!isChecking, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)).IsFrozen);
+        Assert.Same(anotherFreezable3, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)));
+        Assert.Equal(80, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)freezable.GetValue(SubFreezable.Property8)).IsFrozen);
+        Assert.Same(anotherFreezable4, freezable.GetValue(SubFreezable.Property9));
+        Assert.Equal(90, ((CustomFreezable)freezable.GetValue(SubFreezable.Property9)).GetValue(SubFreezable.Property1));
+        Assert.Equal(!isChecking, ((CustomFreezable)freezable.GetValue(SubFreezable.Property9)).IsFrozen);
+        Assert.False(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+
+        // Freeze again.
+        Assert.Equal(!isChecking, freezable.FreezeCore(isChecking));
+        Assert.Equal(10, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(20, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(30, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(40, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(50, freezable.GetValue(SubFreezable.Property5));
+        Assert.Same(anotherFreezable1, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)));
+        Assert.Equal(60, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)).GetValue(SubFreezable.Property1));
+        Assert.Equal(!isChecking, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)).IsFrozen);
+        Assert.Same(anotherFreezable2, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)));
+        Assert.Equal(70, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)).GetValue(SubFreezable.Property1));
+        Assert.Equal(!isChecking, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)).IsFrozen);
+        Assert.Same(anotherFreezable3, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)));
+        Assert.Equal(80, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)freezable.GetValue(SubFreezable.Property8)).IsFrozen);
+        Assert.False(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void FreezeCore_InvokeWithHandler_DoesNotCallChanged(bool isChecking)
+    {
+        var freezable = new SubFreezable();
+
+        int callCount = 0;
+        EventHandler handler = (sender, e) => callCount++;
+        freezable.Changed += handler;
+
+        // Freeze.
+        Assert.True(freezable.FreezeCore(isChecking));
+        Assert.Equal(0, callCount);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+        
+        // Freeze again.
+        Assert.True(freezable.FreezeCore(isChecking));
+        Assert.Equal(0, callCount);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void FreezeCore_InvokeWithRemovedHandler_CallsChanged(bool isChecking)
+    {
+        var freezable = new SubFreezable();
+
+        int callCount = 0;
+        EventHandler handler = (sender, e) => callCount++;
+        freezable.Changed += handler;
+        freezable.Changed -= handler;
+
+        // Freeze.
+        Assert.True(freezable.FreezeCore(isChecking));
+        Assert.Equal(0, callCount);
+        Assert.True(freezable.CanFreeze);
+        
+        // Freeze again.
+        Assert.True(freezable.FreezeCore(isChecking));
+        Assert.Equal(0, callCount);
+        Assert.True(freezable.CanFreeze);
+    }
+
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void FreezeCore_InvokeOnDifferentThread_ReturnsTrue(bool isChecking)
+    {
+        var freezable = new SubFreezable();
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.True(freezable.FreezeCore(isChecking));
+        });
+        Assert.False(freezable.IsFrozen);
+    }
+
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void FreezeCore_InvokeFrozenOnDifferentThread_ReturnsTrue(bool isChecking)
+    {
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.True(freezable.FreezeCore(isChecking));
+        });
+        Assert.True(freezable.IsFrozen);
+    }
+
+    [Fact]
+    public void GetAsFrozen_InvokeDefault_Success()
+    {
+        var freezable = new SubFreezable();
+        int createInstanceCallCount = 0;
+        freezable.CreateInstanceCoreAction = () =>
+        {
+            createInstanceCallCount++;
+            return new SubFreezable();
+        };
+
+        // Clone.
+        SubFreezable clone = Assert.IsType<SubFreezable>(freezable.GetAsFrozen());
+        Assert.NotSame(freezable, clone);
+        Assert.True(clone.CanFreeze);
+        Assert.NotNull(clone.DependencyObjectType);
+        Assert.Same(clone.DependencyObjectType, clone.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), clone.DependencyObjectType);
+        Assert.Null(clone.Dispatcher);
+        Assert.True(clone.IsFrozen);
+        Assert.True(clone.IsSealed);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+        Assert.True(freezable.CanFreeze);
+        Assert.Equal(1, createInstanceCallCount);
+
+        // Clone again.
+        SubFreezable clone2 = Assert.IsType<SubFreezable>(freezable.GetAsFrozen());
+        Assert.NotSame(freezable, clone);
+        Assert.NotSame(clone, clone2);
+        Assert.True(clone2.CanFreeze);
+        Assert.NotNull(clone2.DependencyObjectType);
+        Assert.Same(clone2.DependencyObjectType, clone2.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), clone2.DependencyObjectType);
+        Assert.Null(clone2.Dispatcher);
+        Assert.True(clone2.IsFrozen);
+        Assert.True(clone2.IsSealed);
+        Assert.NotNull(clone.DependencyObjectType);
+        Assert.Same(clone.DependencyObjectType, clone.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), clone.DependencyObjectType);
+        Assert.Null(clone.Dispatcher);
+        Assert.True(clone.IsFrozen);
+        Assert.True(clone.IsSealed);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+        Assert.True(freezable.CanFreeze);
+        Assert.Equal(2, createInstanceCallCount);
+    }
+
+    [Fact]
+    public void GetAsFrozen_InvokeWithProperties_Success()
+    {
+        var freezable = new SubFreezable();
+        int createInstanceCallCount = 0;
+        freezable.CreateInstanceCoreAction = () =>
+        {
+            createInstanceCallCount++;
+            return new SubFreezable();
+        };
+
+        freezable.SetValue(SubFreezable.Property1, 10);
+        freezable.SetValue(SubFreezable.Property2, 20);
+        freezable.SetCurrentValue(SubFreezable.Property3, 30);
+        freezable.SetValue(SubFreezable.Property4, 40);
+        freezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        freezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        freezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        freezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+
+        // Clone.
+        SubFreezable clone = Assert.IsType<SubFreezable>(freezable.GetAsFrozen());
+        Assert.NotSame(freezable, clone);
+        Assert.Equal(10, clone.GetValue(SubFreezable.Property1));
+        Assert.Equal(20, clone.GetValue(SubFreezable.Property2));
+        Assert.Equal(30, clone.GetValue(SubFreezable.Property3));
+        Assert.Equal(40, clone.GetValue(SubFreezable.Property4));
+        Assert.Equal(50, clone.GetValue(SubFreezable.Property5));
+        Assert.NotSame(anotherFreezable1, ((SubFreezable)clone.GetValue(SubFreezable.Property6)));
+        Assert.Equal(60, ((SubFreezable)clone.GetValue(SubFreezable.Property6)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)clone.GetValue(SubFreezable.Property6)).IsFrozen);
+        Assert.NotSame(anotherFreezable2, ((SubFreezable)clone.GetValue(SubFreezable.Property7)));
+        Assert.Equal(70, ((SubFreezable)clone.GetValue(SubFreezable.Property7)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)clone.GetValue(SubFreezable.Property7)).IsFrozen);
+        Assert.Same(anotherFreezable3, ((SubFreezable)clone.GetValue(SubFreezable.Property8)));
+        Assert.Equal(80, ((SubFreezable)clone.GetValue(SubFreezable.Property8)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)clone.GetValue(SubFreezable.Property8)).IsFrozen);
+        Assert.True(clone.CanFreeze);
+        Assert.NotNull(clone.DependencyObjectType);
+        Assert.Same(clone.DependencyObjectType, clone.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), clone.DependencyObjectType);
+        Assert.Null(clone.Dispatcher);
+        Assert.True(clone.IsFrozen);
+        Assert.True(clone.IsSealed);
+    }
+
+    [Fact]
+    public void GetAsFrozen_InvokeWithUnfreezableProperties_ThrowsInvalidOperationException()
+    {
+        var freezable = new SubFreezable();
+        freezable.CreateInstanceCoreAction = () => new SubFreezable();
+        freezable.SetValue(SubFreezable.Property1, 10);
+        freezable.SetValue(SubFreezable.Property2, 20);
+        freezable.SetCurrentValue(SubFreezable.Property3, 30);
+        freezable.SetValue(SubFreezable.Property4, 40);
+        freezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        freezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        freezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        freezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+
+        var anotherFreezable4 = new CustomFreezable();
+        anotherFreezable4.CreateInstanceCoreAction = () => new CustomFreezable();
+        anotherFreezable4.SetValue(SubFreezable.Property1, 90);
+        anotherFreezable4.FreezeCoreAction = (isChecking) => false;
+        freezable.SetValue(SubFreezable.Property9, anotherFreezable4);
+
+        SubFreezable clone = Assert.IsType<SubFreezable>(freezable.GetAsFrozen());
+        Assert.NotSame(freezable, clone);
+        Assert.Equal(10, clone.GetValue(SubFreezable.Property1));
+        Assert.Equal(20, clone.GetValue(SubFreezable.Property2));
+        Assert.Equal(30, clone.GetValue(SubFreezable.Property3));
+        Assert.Equal(40, clone.GetValue(SubFreezable.Property4));
+        Assert.Equal(50, clone.GetValue(SubFreezable.Property5));
+        Assert.NotSame(anotherFreezable1, ((SubFreezable)clone.GetValue(SubFreezable.Property6)));
+        Assert.Equal(60, ((SubFreezable)clone.GetValue(SubFreezable.Property6)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)clone.GetValue(SubFreezable.Property6)).IsFrozen);
+        Assert.NotSame(anotherFreezable2, ((SubFreezable)clone.GetValue(SubFreezable.Property7)));
+        Assert.Equal(70, ((SubFreezable)clone.GetValue(SubFreezable.Property7)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)clone.GetValue(SubFreezable.Property7)).IsFrozen);
+        Assert.Same(anotherFreezable3, ((SubFreezable)clone.GetValue(SubFreezable.Property8)));
+        Assert.Equal(80, ((SubFreezable)clone.GetValue(SubFreezable.Property8)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)clone.GetValue(SubFreezable.Property8)).IsFrozen);
+        Assert.True(clone.CanFreeze);
+        Assert.NotNull(clone.DependencyObjectType);
+        Assert.Same(clone.DependencyObjectType, clone.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), clone.DependencyObjectType);
+        Assert.Null(clone.Dispatcher);
+        Assert.True(clone.IsFrozen);
+        Assert.True(clone.IsSealed);
+    }
+
+    [Fact]
+    public void GetAsFrozen_InvokeWithReadOnlyProperty_DoesNotCopy()
+    {
+        var freezable = new SubFreezable();
+        freezable.CreateInstanceCoreAction = () => new SubFreezable();
+        DependencyPropertyKey propertyKey = DependencyProperty.RegisterReadOnly(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), new PropertyMetadata());
+        freezable.SetValue(propertyKey, "value");
+
+        // Clone.
+        SubFreezable clone = Assert.IsType<SubFreezable>(freezable.GetAsFrozen());
+        Assert.Null(clone.GetValue(propertyKey.DependencyProperty));
+        Assert.Equal("value", freezable.GetValue(propertyKey.DependencyProperty));
+    }
+
+    [Fact]
+    public void GetAsFrozen_InvokeFrozen_ReturnsExpected()
+    {
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+        Assert.Same(freezable, freezable.GetAsFrozen());
+    }
+
+    [Fact]
+    public void GetAsFrozen_InvokeNullCreateInstanceCore_ThrowsNullReferenceException()
+    {
+        var freezable = new CustomFreezable();
+        freezable.CreateInstanceCoreAction = () => null!;
+        Assert.Throws<NullReferenceException>(() => freezable.GetAsFrozen());
+    }
+
+    [Fact]
+    public void GetAsFrozen_InvokeDifferentCreateInstanceCore_Success()
+    {
+        var freezable = new CustomFreezable();
+        var clone = new SubFreezable();
+        freezable.CreateInstanceCoreAction = () => clone;
+        Assert.Same(clone, freezable.GetAsFrozen());
+        Assert.False(freezable.IsFrozen);
+        Assert.True(clone.IsFrozen);
+    }
+
+    [Fact]
+    public void GetAsFrozen_InvokeSameCreateInstanceCore_Success()
+    {
+        var freezable = new CustomFreezable();
+        freezable.CreateInstanceCoreAction = () => freezable;
+        Assert.Same(freezable, freezable.GetAsFrozen());
+        Assert.True(freezable.IsFrozen);
+    }
+
+    [Fact]
+    public void GetAsFrozen_InvokeFrozenCreateInstanceCore_Success()
+    {
+        var freezable = new CustomFreezable();
+        var clone = new CustomFreezable();
+        clone.Freeze();
+        freezable.CreateInstanceCoreAction = () => clone;
+        Assert.Same(clone, freezable.GetAsFrozen());
+        Assert.False(freezable.IsFrozen);
+        Assert.True(clone.IsFrozen);
+    }
+
+    [Fact]
+    public void GetAsFrozen_InvokeCantFreeze_ThrowsInvalidOperationException()
+    {
+        var freezable = new CustomFreezable();
+        var clone = new CustomFreezable();
+        freezable.CreateInstanceCoreAction = () => clone;
+        int callCount = 0;
+        clone.FreezeCoreAction = (checking) =>
+        {
+            Assert.True(checking);
+            callCount++;
+            return false;
+        };
+
+        Assert.Throws<InvalidOperationException>(() => freezable.GetAsFrozen());
+    }
+
+    [Fact]
+    public void GetAsFrozen_InvokeOnDifferentThread_ThrowsInvalidOperationException()
+    {
+        var freezable = new SubFreezable();
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => freezable.GetAsFrozen());
+        });
+    }
+
+    [Fact]
+    public void GetAsFrozen_InvokeFrozenOnDifferentThread_ReturnsExpected()
+    {
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+        
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Same(freezable, freezable.GetAsFrozen());
+        });
+    }
+
+    [Fact]
+    public void GetAsFrozenCore_InvokeDefault_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        // Clone.
+        freezable.GetAsFrozenCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+
+        // Clone again.
+        freezable.GetAsFrozenCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void GetAsFrozenCore_InvokeWithProperties_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        sourceFreezable.SetValue(SubFreezable.Property1, 10);
+        sourceFreezable.SetValue(SubFreezable.Property2, 20);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property3, 30);
+        sourceFreezable.SetValue(SubFreezable.Property4, 40);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        sourceFreezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        sourceFreezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+
+        // Clone.
+        freezable.GetAsFrozenCore(sourceFreezable);
+        Assert.Equal(10, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(20, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(30, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(40, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(50, freezable.GetValue(SubFreezable.Property5));
+        Assert.NotSame(anotherFreezable1, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)));
+        Assert.Equal(60, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)freezable.GetValue(SubFreezable.Property6)).IsFrozen);
+        Assert.NotSame(anotherFreezable2, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)));
+        Assert.Equal(70, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)freezable.GetValue(SubFreezable.Property7)).IsFrozen);
+        Assert.Same(anotherFreezable3, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)));
+        Assert.Equal(80, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)freezable.GetValue(SubFreezable.Property8)).IsFrozen);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void GetAsFrozenCore_InvokeWithReadOnlyProperty_DoesNotCopy()
+    {
+        var freezable = new SubFreezable();
+        var sourceFreezable = new SubFreezable();
+        DependencyPropertyKey propertyKey = DependencyProperty.RegisterReadOnly(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), new PropertyMetadata());
+        sourceFreezable.SetValue(propertyKey, "value");
+
+        // Clone.
+        freezable.GetAsFrozenCore(sourceFreezable);
+        Assert.Null(freezable.GetValue(propertyKey.DependencyProperty));
+        Assert.Equal("value", sourceFreezable.GetValue(propertyKey.DependencyProperty));
+    }
+
+    [Fact]
+    public void GetAsFrozenCore_InvokeSourceFrozenDefault_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+        sourceFreezable.Freeze();
+
+        // Clone.
+        freezable.GetAsFrozenCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+
+        // Clone again.
+        freezable.GetAsFrozenCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void GetAsFrozenCore_InvokeSourceFrozenWithProperties_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        sourceFreezable.SetValue(SubFreezable.Property1, 10);
+        sourceFreezable.SetValue(SubFreezable.Property2, 20);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property3, 30);
+        sourceFreezable.SetValue(SubFreezable.Property4, 40);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        sourceFreezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        sourceFreezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+        
+        sourceFreezable.Freeze();
+
+        // Clone.
+        freezable.GetAsFrozenCore(sourceFreezable);
+        Assert.Equal(10, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(20, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(30, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(40, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(50, freezable.GetValue(SubFreezable.Property5));
+        Assert.Same(anotherFreezable1, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)));
+        Assert.Equal(60, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)freezable.GetValue(SubFreezable.Property6)).IsFrozen);
+        Assert.Same(anotherFreezable2, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)));
+        Assert.Equal(70, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)freezable.GetValue(SubFreezable.Property7)).IsFrozen);
+        Assert.Same(anotherFreezable3, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)));
+        Assert.Equal(80, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)freezable.GetValue(SubFreezable.Property8)).IsFrozen);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void GetAsFrozenCore_InvokeDestinationFrozenDefault_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+
+        // Clone.
+        freezable.GetAsFrozenCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Null(freezable.Dispatcher);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+
+        // Clone again.
+        freezable.GetAsFrozenCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Null(freezable.Dispatcher);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void GetAsFrozenCore_InvokeDestinationFrozenWithProperties_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        sourceFreezable.SetValue(SubFreezable.Property1, 10);
+        sourceFreezable.SetValue(SubFreezable.Property2, 20);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property3, 30);
+        sourceFreezable.SetValue(SubFreezable.Property4, 40);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        sourceFreezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        sourceFreezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+        
+        freezable.Freeze();
+
+        // Clone.
+        Assert.Throws<InvalidOperationException>(() => freezable.GetAsFrozenCore(sourceFreezable));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property5));
+        Assert.Null(freezable.GetValue(SubFreezable.Property6));
+        Assert.Null(freezable.GetValue(SubFreezable.Property7));
+        Assert.Null(freezable.GetValue(SubFreezable.Property8));
+        Assert.True(freezable.CanFreeze);
+        Assert.Null(freezable.Dispatcher);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void GetAsFrozenCore_InvokeOnDifferentThreadDefault_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        // Clone.
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            freezable.GetAsFrozenCore(sourceFreezable);
+        });
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+
+        // Clone again.
+        freezable.GetAsFrozenCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void GetAsFrozenCore_InvokeOnDifferentThreadWithProperties_ThrowsInvalidOperationException()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        sourceFreezable.SetValue(SubFreezable.Property1, 10);
+        sourceFreezable.SetValue(SubFreezable.Property2, 20);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property3, 30);
+        sourceFreezable.SetValue(SubFreezable.Property4, 40);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        sourceFreezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        sourceFreezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+
+        // Clone.
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => freezable.GetAsFrozenCore(sourceFreezable));
+        });
+
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property5));
+        Assert.Null(freezable.GetValue(SubFreezable.Property6));
+        Assert.Null(freezable.GetValue(SubFreezable.Property7));
+        Assert.Null(freezable.GetValue(SubFreezable.Property8));
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void GetAsFrozenCore_InvokeSourceFrozenOnDifferentThreadDefault_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+        sourceFreezable.Freeze();
+        
+        // Clone.
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            freezable.GetAsFrozenCore(sourceFreezable);
+        });
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+
+        // Clone again.
+        freezable.GetAsFrozenCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void GetAsFrozenCore_InvokeSourceFrozenOnDifferentThreadWithProperties_ThrowsInvalidOperationException()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        sourceFreezable.SetValue(SubFreezable.Property1, 10);
+        sourceFreezable.SetValue(SubFreezable.Property2, 20);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property3, 30);
+        sourceFreezable.SetValue(SubFreezable.Property4, 40);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        sourceFreezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        sourceFreezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+        
+        sourceFreezable.Freeze();
+
+        // Clone.
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => freezable.GetAsFrozenCore(sourceFreezable));
+        });
+
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property5));
+        Assert.Null(freezable.GetValue(SubFreezable.Property6));
+        Assert.Null(freezable.GetValue(SubFreezable.Property7));
+        Assert.Null(freezable.GetValue(SubFreezable.Property8));
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void GetAsFrozenCore_InvokeDestinationFrozenOnDifferentThreadDefault_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+        
+        // Clone.
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            freezable.GetAsFrozenCore(sourceFreezable);
+        });
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Null(freezable.Dispatcher);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+
+        // Clone again.
+        freezable.GetAsFrozenCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Null(freezable.Dispatcher);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void GetAsFrozenCore_InvokeDestinationFrozenOnDifferentThreadWithProperties_ThrowsInvalidOperationException()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        sourceFreezable.SetValue(SubFreezable.Property1, 10);
+        sourceFreezable.SetValue(SubFreezable.Property2, 20);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property3, 30);
+        sourceFreezable.SetValue(SubFreezable.Property4, 40);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        sourceFreezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        sourceFreezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+        
+        freezable.Freeze();
+
+        // Clone.
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => freezable.GetAsFrozenCore(sourceFreezable));
+        });
+
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property5));
+        Assert.Null(freezable.GetValue(SubFreezable.Property6));
+        Assert.Null(freezable.GetValue(SubFreezable.Property7));
+        Assert.Null(freezable.GetValue(SubFreezable.Property8));
+        Assert.True(freezable.CanFreeze);
+        Assert.Null(freezable.Dispatcher);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void GetAsFrozenCore_NullSourceFreezable_ThrowsArgumentNullException()
+    {
+        var freezable = new SubFreezable();
+        // TODO: this should not throw NullReferenceException.
+        //Assert.Throws<ArgumentNullException>("sourceFreezable", () => freezable.GetAsFrozenCore(null!));
+        Assert.Throws<NullReferenceException>(() => freezable.GetAsFrozenCore(null!));
+    }
+
+    [Fact]
+    public void GetCurrentValueAsFrozen_InvokeDefault_Success()
+    {
+        var freezable = new SubFreezable();
+        int createInstanceCallCount = 0;
+        freezable.CreateInstanceCoreAction = () =>
+        {
+            createInstanceCallCount++;
+            return new SubFreezable();
+        };
+
+        // Clone.
+        SubFreezable clone = Assert.IsType<SubFreezable>(freezable.GetCurrentValueAsFrozen());
+        Assert.NotSame(freezable, clone);
+        Assert.True(clone.CanFreeze);
+        Assert.NotNull(clone.DependencyObjectType);
+        Assert.Same(clone.DependencyObjectType, clone.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), clone.DependencyObjectType);
+        Assert.Null(clone.Dispatcher);
+        Assert.True(clone.IsFrozen);
+        Assert.True(clone.IsSealed);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+        Assert.True(freezable.CanFreeze);
+        Assert.Equal(1, createInstanceCallCount);
+
+        // Clone again.
+        SubFreezable clone2 = Assert.IsType<SubFreezable>(freezable.GetCurrentValueAsFrozen());
+        Assert.NotSame(freezable, clone);
+        Assert.NotSame(clone, clone2);
+        Assert.True(clone2.CanFreeze);
+        Assert.NotNull(clone2.DependencyObjectType);
+        Assert.Same(clone2.DependencyObjectType, clone2.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), clone2.DependencyObjectType);
+        Assert.Null(clone2.Dispatcher);
+        Assert.True(clone2.IsFrozen);
+        Assert.True(clone2.IsSealed);
+        Assert.NotNull(clone.DependencyObjectType);
+        Assert.Same(clone.DependencyObjectType, clone.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), clone.DependencyObjectType);
+        Assert.Null(clone.Dispatcher);
+        Assert.True(clone.IsFrozen);
+        Assert.True(clone.IsSealed);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+        Assert.True(freezable.CanFreeze);
+        Assert.Equal(2, createInstanceCallCount);
+    }
+
+    [Fact]
+    public void GetCurrentValueAsFrozen_InvokeWithProperties_Success()
+    {
+        var freezable = new SubFreezable();
+        int createInstanceCallCount = 0;
+        freezable.CreateInstanceCoreAction = () =>
+        {
+            createInstanceCallCount++;
+            return new SubFreezable();
+        };
+
+        freezable.SetValue(SubFreezable.Property1, 10);
+        freezable.SetValue(SubFreezable.Property2, 20);
+        freezable.SetCurrentValue(SubFreezable.Property3, 30);
+        freezable.SetValue(SubFreezable.Property4, 40);
+        freezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        freezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        freezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        freezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+
+        // Clone.
+        SubFreezable clone = Assert.IsType<SubFreezable>(freezable.GetCurrentValueAsFrozen());
+        Assert.NotSame(freezable, clone);
+        Assert.Equal(10, clone.GetValue(SubFreezable.Property1));
+        Assert.Equal(20, clone.GetValue(SubFreezable.Property2));
+        Assert.Equal(30, clone.GetValue(SubFreezable.Property3));
+        Assert.Equal(40, clone.GetValue(SubFreezable.Property4));
+        Assert.Equal(50, clone.GetValue(SubFreezable.Property5));
+        Assert.NotSame(anotherFreezable1, ((SubFreezable)clone.GetValue(SubFreezable.Property6)));
+        Assert.Equal(60, ((SubFreezable)clone.GetValue(SubFreezable.Property6)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)clone.GetValue(SubFreezable.Property6)).IsFrozen);
+        Assert.NotSame(anotherFreezable2, ((SubFreezable)clone.GetValue(SubFreezable.Property7)));
+        Assert.Equal(70, ((SubFreezable)clone.GetValue(SubFreezable.Property7)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)clone.GetValue(SubFreezable.Property7)).IsFrozen);
+        Assert.Same(anotherFreezable3, ((SubFreezable)clone.GetValue(SubFreezable.Property8)));
+        Assert.Equal(80, ((SubFreezable)clone.GetValue(SubFreezable.Property8)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)clone.GetValue(SubFreezable.Property8)).IsFrozen);
+        Assert.True(clone.CanFreeze);
+        Assert.NotNull(clone.DependencyObjectType);
+        Assert.Same(clone.DependencyObjectType, clone.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), clone.DependencyObjectType);
+        Assert.Null(clone.Dispatcher);
+        Assert.True(clone.IsFrozen);
+        Assert.True(clone.IsSealed);
+    }
+
+    [Fact]
+    public void GetCurrentValueAsFrozen_InvokeWithUnfreezableProperties_ThrowsInvalidOperationException()
+    {
+        var freezable = new SubFreezable();
+        freezable.CreateInstanceCoreAction = () => new SubFreezable();
+        freezable.SetValue(SubFreezable.Property1, 10);
+        freezable.SetValue(SubFreezable.Property2, 20);
+        freezable.SetCurrentValue(SubFreezable.Property3, 30);
+        freezable.SetValue(SubFreezable.Property4, 40);
+        freezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        freezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        freezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        freezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+
+        var anotherFreezable4 = new CustomFreezable();
+        anotherFreezable4.CreateInstanceCoreAction = () => new CustomFreezable();
+        anotherFreezable4.SetValue(SubFreezable.Property1, 90);
+        anotherFreezable4.FreezeCoreAction = (isChecking) => false;
+        freezable.SetValue(SubFreezable.Property9, anotherFreezable4);
+
+        SubFreezable clone = Assert.IsType<SubFreezable>(freezable.GetCurrentValueAsFrozen());
+        Assert.NotSame(freezable, clone);
+        Assert.Equal(10, clone.GetValue(SubFreezable.Property1));
+        Assert.Equal(20, clone.GetValue(SubFreezable.Property2));
+        Assert.Equal(30, clone.GetValue(SubFreezable.Property3));
+        Assert.Equal(40, clone.GetValue(SubFreezable.Property4));
+        Assert.Equal(50, clone.GetValue(SubFreezable.Property5));
+        Assert.NotSame(anotherFreezable1, ((SubFreezable)clone.GetValue(SubFreezable.Property6)));
+        Assert.Equal(60, ((SubFreezable)clone.GetValue(SubFreezable.Property6)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)clone.GetValue(SubFreezable.Property6)).IsFrozen);
+        Assert.NotSame(anotherFreezable2, ((SubFreezable)clone.GetValue(SubFreezable.Property7)));
+        Assert.Equal(70, ((SubFreezable)clone.GetValue(SubFreezable.Property7)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)clone.GetValue(SubFreezable.Property7)).IsFrozen);
+        Assert.Same(anotherFreezable3, ((SubFreezable)clone.GetValue(SubFreezable.Property8)));
+        Assert.Equal(80, ((SubFreezable)clone.GetValue(SubFreezable.Property8)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)clone.GetValue(SubFreezable.Property8)).IsFrozen);
+        Assert.True(clone.CanFreeze);
+        Assert.NotNull(clone.DependencyObjectType);
+        Assert.Same(clone.DependencyObjectType, clone.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), clone.DependencyObjectType);
+        Assert.Null(clone.Dispatcher);
+        Assert.True(clone.IsFrozen);
+        Assert.True(clone.IsSealed);
+    }
+
+    [Fact]
+    public void GetCurrentValueAsFrozen_InvokeWithReadOnlyProperty_DoesNotCopy()
+    {
+        var freezable = new SubFreezable();
+        freezable.CreateInstanceCoreAction = () => new SubFreezable();
+        DependencyPropertyKey propertyKey = DependencyProperty.RegisterReadOnly(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), new PropertyMetadata());
+        freezable.SetValue(propertyKey, "value");
+
+        // Clone.
+        SubFreezable clone = Assert.IsType<SubFreezable>(freezable.GetCurrentValueAsFrozen());
+        Assert.Null(clone.GetValue(propertyKey.DependencyProperty));
+        Assert.Equal("value", freezable.GetValue(propertyKey.DependencyProperty));
+    }
+
+    [Fact]
+    public void GetCurrentValueAsFrozen_InvokeFrozen_ReturnsExpected()
+    {
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+        Assert.Same(freezable, freezable.GetCurrentValueAsFrozen());
+    }
+
+    [Fact]
+    public void GetCurrentValueAsFrozen_InvokeNullCreateInstanceCore_ThrowsNullReferenceException()
+    {
+        var freezable = new CustomFreezable();
+        freezable.CreateInstanceCoreAction = () => null!;
+        Assert.Throws<NullReferenceException>(() => freezable.GetCurrentValueAsFrozen());
+    }
+
+    [Fact]
+    public void GetCurrentValueAsFrozen_InvokeDifferentCreateInstanceCore_Success()
+    {
+        var freezable = new CustomFreezable();
+        var clone = new SubFreezable();
+        freezable.CreateInstanceCoreAction = () => clone;
+        Assert.Same(clone, freezable.GetCurrentValueAsFrozen());
+        Assert.False(freezable.IsFrozen);
+        Assert.True(clone.IsFrozen);
+    }
+
+    [Fact]
+    public void GetCurrentValueAsFrozen_InvokeSameCreateInstanceCore_Success()
+    {
+        var freezable = new CustomFreezable();
+        freezable.CreateInstanceCoreAction = () => freezable;
+        Assert.Same(freezable, freezable.GetCurrentValueAsFrozen());
+        Assert.True(freezable.IsFrozen);
+    }
+
+    [Fact]
+    public void GetCurrentValueAsFrozen_InvokeFrozenCreateInstanceCore_Success()
+    {
+        var freezable = new CustomFreezable();
+        var clone = new CustomFreezable();
+        clone.Freeze();
+        freezable.CreateInstanceCoreAction = () => clone;
+        Assert.Same(clone, freezable.GetCurrentValueAsFrozen());
+        Assert.False(freezable.IsFrozen);
+        Assert.True(clone.IsFrozen);
+    }
+
+    [Fact]
+    public void GetCurrentValueAsFrozen_InvokeCantFreeze_ThrowsInvalidOperationException()
+    {
+        var freezable = new CustomFreezable();
+        var clone = new CustomFreezable();
+        freezable.CreateInstanceCoreAction = () => clone;
+        int callCount = 0;
+        clone.FreezeCoreAction = (checking) =>
+        {
+            Assert.True(checking);
+            callCount++;
+            return false;
+        };
+
+        Assert.Throws<InvalidOperationException>(() => freezable.GetCurrentValueAsFrozen());
+    }
+
+    [Fact]
+    public void GetCurrentValueAsFrozen_InvokeOnDifferentThread_ThrowsInvalidOperationException()
+    {
+        var freezable = new SubFreezable();
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => freezable.GetCurrentValueAsFrozen());
+        });
+    }
+
+    [Fact]
+    public void GetCurrentValueAsFrozen_InvokeFrozenOnDifferentThread_ReturnsExpected()
+    {
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+        
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Same(freezable, freezable.GetCurrentValueAsFrozen());
+        });
+    }
+
+    [Fact]
+    public void GetCurrentValueAsFrozenCore_InvokeDefault_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        // Invoke.
+        freezable.GetCurrentValueAsFrozenCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+
+        // Clone again.
+        freezable.GetCurrentValueAsFrozenCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void GetCurrentValueAsFrozenCore_InvokeWithProperties_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        sourceFreezable.SetValue(SubFreezable.Property1, 10);
+        sourceFreezable.SetValue(SubFreezable.Property2, 20);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property3, 30);
+        sourceFreezable.SetValue(SubFreezable.Property4, 40);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        sourceFreezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        sourceFreezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+
+        // Invoke.
+        freezable.GetCurrentValueAsFrozenCore(sourceFreezable);
+        Assert.Equal(10, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(20, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(30, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(40, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(50, freezable.GetValue(SubFreezable.Property5));
+        Assert.NotSame(anotherFreezable1, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)));
+        Assert.Equal(60, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)freezable.GetValue(SubFreezable.Property6)).IsFrozen);
+        Assert.NotSame(anotherFreezable2, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)));
+        Assert.Equal(70, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)).GetValue(SubFreezable.Property1));
+        Assert.False(((SubFreezable)freezable.GetValue(SubFreezable.Property7)).IsFrozen);
+        Assert.Same(anotherFreezable3, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)));
+        Assert.Equal(80, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)freezable.GetValue(SubFreezable.Property8)).IsFrozen);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void GetCurrentValueAsFrozenCore_InvokeWithReadOnlyProperty_DoesNotCopy()
+    {
+        var freezable = new SubFreezable();
+        var sourceFreezable = new SubFreezable();
+        DependencyPropertyKey propertyKey = DependencyProperty.RegisterReadOnly(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), new PropertyMetadata());
+        sourceFreezable.SetValue(propertyKey, "value");
+
+        // Clone.
+        freezable.GetCurrentValueAsFrozenCore(sourceFreezable);
+        Assert.Null(freezable.GetValue(propertyKey.DependencyProperty));
+        Assert.Equal("value", sourceFreezable.GetValue(propertyKey.DependencyProperty));
+    }
+
+    [Fact]
+    public void GetCurrentValueAsFrozenCore_InvokeSourceFrozenDefault_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+        sourceFreezable.Freeze();
+
+        // Invoke.
+        freezable.GetCurrentValueAsFrozenCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+
+        // Clone again.
+        freezable.GetCurrentValueAsFrozenCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void GetCurrentValueAsFrozenCore_InvokeSourceFrozenWithProperties_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        sourceFreezable.SetValue(SubFreezable.Property1, 10);
+        sourceFreezable.SetValue(SubFreezable.Property2, 20);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property3, 30);
+        sourceFreezable.SetValue(SubFreezable.Property4, 40);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        sourceFreezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        sourceFreezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+        
+        sourceFreezable.Freeze();
+
+        // Invoke.
+        freezable.GetCurrentValueAsFrozenCore(sourceFreezable);
+        Assert.Equal(10, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(20, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(30, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(40, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(50, freezable.GetValue(SubFreezable.Property5));
+        Assert.Same(anotherFreezable1, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)));
+        Assert.Equal(60, ((SubFreezable)freezable.GetValue(SubFreezable.Property6)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)freezable.GetValue(SubFreezable.Property6)).IsFrozen);
+        Assert.Same(anotherFreezable2, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)));
+        Assert.Equal(70, ((SubFreezable)freezable.GetValue(SubFreezable.Property7)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)freezable.GetValue(SubFreezable.Property7)).IsFrozen);
+        Assert.Same(anotherFreezable3, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)));
+        Assert.Equal(80, ((SubFreezable)freezable.GetValue(SubFreezable.Property8)).GetValue(SubFreezable.Property1));
+        Assert.True(((SubFreezable)freezable.GetValue(SubFreezable.Property8)).IsFrozen);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void GetCurrentValueAsFrozenCore_InvokeDestinationFrozenDefault_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+
+        // Invoke.
+        freezable.GetCurrentValueAsFrozenCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Null(freezable.Dispatcher);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+
+        // Clone again.
+        freezable.GetCurrentValueAsFrozenCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Null(freezable.Dispatcher);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void GetCurrentValueAsFrozenCore_InvokeDestinationFrozenWithProperties_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        sourceFreezable.SetValue(SubFreezable.Property1, 10);
+        sourceFreezable.SetValue(SubFreezable.Property2, 20);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property3, 30);
+        sourceFreezable.SetValue(SubFreezable.Property4, 40);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        sourceFreezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        sourceFreezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+        
+        freezable.Freeze();
+
+        // Invoke.
+        Assert.Throws<InvalidOperationException>(() => freezable.GetCurrentValueAsFrozenCore(sourceFreezable));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property5));
+        Assert.Null(freezable.GetValue(SubFreezable.Property6));
+        Assert.Null(freezable.GetValue(SubFreezable.Property7));
+        Assert.Null(freezable.GetValue(SubFreezable.Property8));
+        Assert.True(freezable.CanFreeze);
+        Assert.Null(freezable.Dispatcher);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void GetCurrentValueAsFrozenCore_InvokeOnDifferentThreadDefault_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        // Clone.
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            freezable.GetCurrentValueAsFrozenCore(sourceFreezable);
+        });
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+
+        // Clone again.
+        freezable.GetCurrentValueAsFrozenCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void GetCurrentValueAsFrozenCore_InvokeOnDifferentThreadWithProperties_ThrowsInvalidOperationException()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        sourceFreezable.SetValue(SubFreezable.Property1, 10);
+        sourceFreezable.SetValue(SubFreezable.Property2, 20);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property3, 30);
+        sourceFreezable.SetValue(SubFreezable.Property4, 40);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        sourceFreezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        sourceFreezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+
+        // Clone.
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => freezable.GetCurrentValueAsFrozenCore(sourceFreezable));
+        });
+
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property5));
+        Assert.Null(freezable.GetValue(SubFreezable.Property6));
+        Assert.Null(freezable.GetValue(SubFreezable.Property7));
+        Assert.Null(freezable.GetValue(SubFreezable.Property8));
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void GetCurrentValueAsFrozenCore_InvokeSourceFrozenOnDifferentThreadDefault_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+        sourceFreezable.Freeze();
+        
+        // Clone.
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            freezable.GetCurrentValueAsFrozenCore(sourceFreezable);
+        });
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+
+        // Clone again.
+        freezable.GetCurrentValueAsFrozenCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void GetCurrentValueAsFrozenCore_InvokeSourceFrozenOnDifferentThreadWithProperties_ThrowsInvalidOperationException()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        sourceFreezable.SetValue(SubFreezable.Property1, 10);
+        sourceFreezable.SetValue(SubFreezable.Property2, 20);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property3, 30);
+        sourceFreezable.SetValue(SubFreezable.Property4, 40);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        sourceFreezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        sourceFreezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+        
+        sourceFreezable.Freeze();
+
+        // Clone.
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => freezable.GetCurrentValueAsFrozenCore(sourceFreezable));
+        });
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property5));
+        Assert.Null(freezable.GetValue(SubFreezable.Property6));
+        Assert.Null(freezable.GetValue(SubFreezable.Property7));
+        Assert.Null(freezable.GetValue(SubFreezable.Property8));
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, freezable.Dispatcher);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.False(freezable.IsFrozen);
+        Assert.False(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void GetCurrentValueAsFrozenCore_InvokeDestinationFrozenOnDifferentThreadDefault_Success()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+        
+        // Clone.
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            freezable.GetCurrentValueAsFrozenCore(sourceFreezable);
+        });
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Null(freezable.Dispatcher);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+
+        // Clone again.
+        freezable.GetCurrentValueAsFrozenCore(sourceFreezable);
+        Assert.True(freezable.CanFreeze);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.Null(freezable.Dispatcher);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void GetCurrentValueAsFrozenCore_InvokeDestinationFrozenOnDifferentThreadWithProperties_ThrowsInvalidOperationException()
+    {
+        var sourceFreezable = new SubFreezable();
+        var freezable = new SubFreezable();
+
+        sourceFreezable.SetValue(SubFreezable.Property1, 10);
+        sourceFreezable.SetValue(SubFreezable.Property2, 20);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property3, 30);
+        sourceFreezable.SetValue(SubFreezable.Property4, 40);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property5, 50);
+
+        var anotherFreezable1 = new SubFreezable();
+        anotherFreezable1.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable1.SetValue(SubFreezable.Property1, 60);
+        sourceFreezable.SetValue(SubFreezable.Property6, anotherFreezable1);
+        
+        var anotherFreezable2 = new SubFreezable();
+        anotherFreezable2.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable2.SetValue(SubFreezable.Property1, 70);
+        sourceFreezable.SetCurrentValue(SubFreezable.Property7, anotherFreezable2);
+        
+        var anotherFreezable3 = new SubFreezable();
+        anotherFreezable3.CreateInstanceCoreAction = () => new SubFreezable();
+        anotherFreezable3.SetValue(SubFreezable.Property1, 80);
+        anotherFreezable3.Freeze();
+        sourceFreezable.SetCurrentValue(SubFreezable.Property8, anotherFreezable3);
+        
+        freezable.Freeze();
+
+        // Clone.
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => freezable.GetCurrentValueAsFrozenCore(sourceFreezable));
+        });
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property1));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property2));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property3));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property4));
+        Assert.Equal(0, freezable.GetValue(SubFreezable.Property5));
+        Assert.Null(freezable.GetValue(SubFreezable.Property6));
+        Assert.Null(freezable.GetValue(SubFreezable.Property7));
+        Assert.Null(freezable.GetValue(SubFreezable.Property8));
+        Assert.True(freezable.CanFreeze);
+        Assert.Null(freezable.Dispatcher);
+        Assert.NotNull(freezable.DependencyObjectType);
+        Assert.Same(freezable.DependencyObjectType, freezable.DependencyObjectType);
+        Assert.Same(DependencyObjectType.FromSystemType(typeof(SubFreezable)), freezable.DependencyObjectType);
+        Assert.True(freezable.IsFrozen);
+        Assert.True(freezable.IsSealed);
+    }
+
+    [Fact]
+    public void GetCurrentValueAsFrozenCore_NullSourceFreezable_ThrowsArgumentNullException()
+    {
+        var freezable = new SubFreezable();
+        // TODO: this should not throw NullReferenceException.
+        //Assert.Throws<ArgumentNullException>("sourceFreezable", () => freezable.GetCurrentValueAsFrozenCore(null!));
+        Assert.Throws<NullReferenceException>(() => freezable.GetCurrentValueAsFrozenCore(null!));
+    }
+
+    [Fact]
+    public void GetValue_Invoke_ReturnsExpected()
+    {
+        var obj = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+
+        Assert.Null(obj.GetValue(property));
+
+        // Call again to test caching.
+        Assert.Null(obj.GetValue(property));
+    }
+
+    [Fact]
+    public void GetValue_InvokeSetValue_ReturnsExpected()
+    {
+        var obj = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        obj.SetValue(property, "value");
+
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Call again to test caching.
+        Assert.Equal("value", obj.GetValue(property));
+    }
+
+    [Fact]
+    public void GetValue_InvokeCustomDefaultValue_ReturnsExpected()
+    {
+        var obj = new SubFreezable();
+        var typeMetadata = new PropertyMetadata("value");
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Call again to test caching.
+        Assert.Equal("value", obj.GetValue(property));
+    }
+
+    [Fact]
+    public void GetValue_InvokeReadOnlyProperty_ReturnsExpected()
+    {
+        var obj = new SubFreezable();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+
+        Assert.False((bool)obj.GetValue(property));
+
+        // Call again to test caching.
+        Assert.False((bool)obj.GetValue(property));
+    }
+
+    [Fact]
+    public void GetValue_InvokeFrozen_ReturnsExpected()
+    {
+        var obj = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        obj.Freeze();
+
+        Assert.Null(obj.GetValue(property));
+
+        // Call again to test caching.
+        Assert.Null(obj.GetValue(property));
+    }
+
+    [Fact]
+    public void GetValue_InvokeFrozenSetValue_ReturnsExpected()
+    {
+        var obj = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        obj.SetValue(property, "value");
+        obj.Freeze();
+
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Call again to test caching.
+        Assert.Equal("value", obj.GetValue(property));
+    }
+
+    [Fact]
+    public void GetValue_InvokeFrozenCustomDefaultValue_ReturnsExpected()
+    {
+        var obj = new SubFreezable();
+        var typeMetadata = new PropertyMetadata("value");
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), typeMetadata);
+        obj.Freeze();
+
+        Assert.Equal("value", obj.GetValue(property));
+
+        // Call again to test caching.
+        Assert.Equal("value", obj.GetValue(property));
+    }
+
+    [Fact]
+    public void GetValue_InvokeFrozenReadOnlyProperty_ReturnsExpected()
+    {
+        var obj = new SubFreezable();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+        obj.Freeze();
+
+        Assert.False((bool)obj.GetValue(property));
+
+        // Call again to test caching.
+        Assert.False((bool)obj.GetValue(property));
+    }
+
+    [Fact]
+    public void GetValue_NullProperty_ThrowsArgumentNullException()
+    {
+        var obj = new SubFreezable();
+        Assert.Throws<ArgumentNullException>("dp", () => obj.GetValue(null!));
+    }
+
+    [Fact]
+    public void GetValue_InvokeOnDifferentThread_ThrowsInvalidOperationException()
+    {
+        var obj = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => obj.GetValue(property));
+        });
+    }
+
+    [Fact]
+    public void GetValue_InvokeFrozenOnDifferentThread_ReturnsExpected()
+    {
+        var obj = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject));
+        obj.Freeze();
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.False((bool)obj.GetValue(property));
+        });
+    }
+
+    [Fact]
+    public void ReadPreamble_InvokeSuccess()
+    {
+        var freezable = new SubFreezable();
+
+        // Call.
+        freezable.ReadPreamble();
+
+        // Call again.
+        freezable.ReadPreamble();
+    }
+
+    [Fact]
+    public void ReadPreamble_InvokeWithHandler_DoesNotCallChanged()
+    {
+        var freezable = new CustomFreezable();
+        int onChangedCallCount = 0;
+        freezable.OnChangedAction = () => onChangedCallCount++;
+        int changedCallCount = 0;
+        freezable.Changed += (sender, e) => changedCallCount++;
+        freezable.ReadPreamble();
+        Assert.Equal(0, onChangedCallCount);
+        Assert.Equal(0, changedCallCount);
+    }
+
+    [Fact]
+    public void ReadPreamble_InvokeFrozen_Nop()
+    {
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+
+        // Call.
+        freezable.ReadPreamble();
+        
+        // Call again.
+        freezable.ReadPreamble();
+    }
+
+    [Fact]
+    public void ReadPreamble_InvokeOnDifferentThread_ThrowsInvalidOperationException()
+    {
+        var freezable = new SubFreezable();
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => freezable.ReadPreamble());
+        });
+    }
+
+    [Fact]
+    public void ReadPreamble_InvokeFrozenOnDifferentThread_Nop()
+    {
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            freezable.ReadPreamble();
+        });
+    }
+
+    [Fact]
+    public void OnChanged_Invoke_Nop()
+    {
+        var freezable = new SubFreezable();
+        freezable.OnChanged();
+    }
+
+    [Fact]
+    public void OnChanged_InvokeWithHandler_DoesNotCallChanged()
+    {
+        var freezable = new SubFreezable();
+        int callCount = 0;
+        freezable.Changed += (sender, e) => callCount++;
+        
+        freezable.OnChanged();
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void OnChanged_InvokeFrozen_Nop()
+    {
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+
+        freezable.OnChanged();
+    }
+
+    [Fact]
+    public void OnChanged_InvokeOnDifferentThread_Nop()
+    {
+        var freezable = new SubFreezable();
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            freezable.OnChanged();
+        });
+    }
+
+    [Fact]
+    public void OnChanged_InvokeFrozenOnDifferentThread_Nop()
+    {
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            freezable.OnChanged();
+        });
+    }
+
+    [Fact]
+    public void OnFreezablePropertyChanged_Invoke_Nop()
+    {
+        var freezable = new SubFreezable();
+        var value1 = new SubDependencyObject();
+        var value2 = new SubDependencyObject();
+        freezable.OnFreezablePropertyChanged(value1, value2);
+        freezable.OnFreezablePropertyChanged(value1, null!);
+        freezable.OnFreezablePropertyChanged(null!, value2);
+    }
+
+    [Fact]
+    public void OnFreezablePropertyChanged_InvokeFrozen_Nop()
+    {
+        var freezable = new SubFreezable();
+        var value1 = new SubDependencyObject();
+        var value2 = new SubDependencyObject();
+        freezable.Freeze();
+        freezable.OnFreezablePropertyChanged(value1, value2);
+        freezable.OnFreezablePropertyChanged(value1, null!);
+        freezable.OnFreezablePropertyChanged(null!, value2);
+    }
+
+    [Fact]
+    public void OnFreezablePropertyChanged_InvokeOnDifferentThread_Nop()
+    {
+        var freezable = new SubFreezable();
+        var value1 = new SubDependencyObject();
+        var value2 = new SubDependencyObject();
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            freezable.OnFreezablePropertyChanged(value1, value2);
+            freezable.OnFreezablePropertyChanged(value1, null!);
+            freezable.OnFreezablePropertyChanged(null!, value2);
+        });
+    }
+
+    [Fact]
+    public void OnFreezablePropertyChanged_InvokeFrozenOnDifferentThread_Nop()
+    {
+        var freezable = new SubFreezable();
+        var value1 = new SubDependencyObject();
+        var value2 = new SubDependencyObject();
+        freezable.Freeze();
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            freezable.OnFreezablePropertyChanged(value1, value2);
+            freezable.OnFreezablePropertyChanged(value1, null!);
+            freezable.OnFreezablePropertyChanged(null!, value2);
+        });
+    }
+
+    [Fact]
+    public void OnFreezablePropertyChanged_InvokeDifferentThread_ThrowsInvalidOperationException()
+    {
+        var freezable = new SubFreezable();
+        var value1 = Helpers.ExecuteOnDifferentThread(() => new SubDependencyObject());
+        var value2 = new SubDependencyObject();
+        var value3 = Helpers.ExecuteOnDifferentThread(() => new SubDependencyObject());
+        var value4 = new SubFreezable();
+        value4.Freeze();
+
+        Assert.Throws<InvalidOperationException>(() => freezable.OnFreezablePropertyChanged(null!, value1));
+        Assert.Throws<InvalidOperationException>(() => freezable.OnFreezablePropertyChanged(null!, value3));
+        freezable.OnFreezablePropertyChanged(null!, value4);
+        freezable.OnFreezablePropertyChanged(value1, value2);
+        Assert.Throws<InvalidOperationException>(() => freezable.OnFreezablePropertyChanged(value1, value3));
+        freezable.OnFreezablePropertyChanged(value1, value4);
+        Assert.Throws<InvalidOperationException>(() => freezable.OnFreezablePropertyChanged(value2, value1));
+        Assert.Throws<InvalidOperationException>(() => freezable.OnFreezablePropertyChanged(value2, value3));
+        freezable.OnFreezablePropertyChanged(value2, value4);
+        Assert.Throws<InvalidOperationException>(() => freezable.OnFreezablePropertyChanged(value3, value1));
+        freezable.OnFreezablePropertyChanged(value3, value2);
+        freezable.OnFreezablePropertyChanged(value3, value4);
+    }
+
+    [Fact]
+    public void OnFreezablePropertyChanged_InvokeDifferentThreadFrozen_Nop()
+    {
+        var freezable = new SubFreezable();
+        var value1 = Helpers.ExecuteOnDifferentThread(() => new SubDependencyObject());
+        var value2 = new SubDependencyObject();
+        var value3 = Helpers.ExecuteOnDifferentThread(() => new SubDependencyObject());
+        freezable.Freeze();
+        var value4 = new SubFreezable();
+        value4.Freeze();
+
+        freezable.OnFreezablePropertyChanged(null!, value1);
+        freezable.OnFreezablePropertyChanged(null!, value2);
+        freezable.OnFreezablePropertyChanged(null!, value3);
+        freezable.OnFreezablePropertyChanged(null!, value4);
+        freezable.OnFreezablePropertyChanged(value1, value1);
+        freezable.OnFreezablePropertyChanged(value1, value2);
+        freezable.OnFreezablePropertyChanged(value1, value3);
+        freezable.OnFreezablePropertyChanged(value1, value4);
+        freezable.OnFreezablePropertyChanged(value2, value1);
+        freezable.OnFreezablePropertyChanged(value2, value2);
+        freezable.OnFreezablePropertyChanged(value2, value3);
+        freezable.OnFreezablePropertyChanged(value2, value4);
+        freezable.OnFreezablePropertyChanged(value3, value1);
+        freezable.OnFreezablePropertyChanged(value3, value2);
+        freezable.OnFreezablePropertyChanged(value3, value3);
+        freezable.OnFreezablePropertyChanged(value3, value4);
+    }
+
+    [Fact]
+    public void OnFreezablePropertyChanged_InvokeDifferentThreadOnDifferentThread_ThrowsInvalidOperationException()
+    {
+        var freezable = new SubFreezable();
+        var value1 = Helpers.ExecuteOnDifferentThread(() => new SubDependencyObject());
+        var value2 = new SubDependencyObject();
+        var value3 = Helpers.ExecuteOnDifferentThread(() => new SubDependencyObject());
+        var value4 = new SubFreezable();
+        value4.Freeze();
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => freezable.OnFreezablePropertyChanged(null!, value1));
+            Assert.Throws<InvalidOperationException>(() => freezable.OnFreezablePropertyChanged(null!, value3));
+            freezable.OnFreezablePropertyChanged(null!, value4);
+            freezable.OnFreezablePropertyChanged(value1, value2);
+            Assert.Throws<InvalidOperationException>(() => freezable.OnFreezablePropertyChanged(value1, value3));
+            freezable.OnFreezablePropertyChanged(value1, value4);
+            Assert.Throws<InvalidOperationException>(() => freezable.OnFreezablePropertyChanged(value2, value1));
+            Assert.Throws<InvalidOperationException>(() => freezable.OnFreezablePropertyChanged(value2, value3));
+            freezable.OnFreezablePropertyChanged(value2, value4);
+            Assert.Throws<InvalidOperationException>(() => freezable.OnFreezablePropertyChanged(value3, value1));
+            freezable.OnFreezablePropertyChanged(value3, value2);
+            freezable.OnFreezablePropertyChanged(value3, value4);
+        });
+    }
+
+    [Fact]
+    public void OnFreezablePropertyChanged_InvokeDifferentThreadFrozenOnDifferentThread_Nop()
+    {
+        var freezable = new SubFreezable();
+        var value1 = Helpers.ExecuteOnDifferentThread(() => new SubDependencyObject());
+        var value2 = new SubDependencyObject();
+        var value3 = Helpers.ExecuteOnDifferentThread(() => new SubDependencyObject());
+        freezable.Freeze();
+        var value4 = new SubFreezable();
+        value4.Freeze();
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            freezable.OnFreezablePropertyChanged(null!, value1);
+            freezable.OnFreezablePropertyChanged(null!, value2);
+            freezable.OnFreezablePropertyChanged(null!, value3);
+            freezable.OnFreezablePropertyChanged(null!, value4);
+            freezable.OnFreezablePropertyChanged(value1, value1);
+            freezable.OnFreezablePropertyChanged(value1, value2);
+            freezable.OnFreezablePropertyChanged(value1, value3);
+            freezable.OnFreezablePropertyChanged(value1, value4);
+            freezable.OnFreezablePropertyChanged(value2, value1);
+            freezable.OnFreezablePropertyChanged(value2, value2);
+            freezable.OnFreezablePropertyChanged(value2, value3);
+            freezable.OnFreezablePropertyChanged(value2, value4);
+            freezable.OnFreezablePropertyChanged(value3, value1);
+            freezable.OnFreezablePropertyChanged(value3, value2);
+            freezable.OnFreezablePropertyChanged(value3, value3);
+            freezable.OnFreezablePropertyChanged(value3, value4);
+        });
+    }
+    public static IEnumerable<object?[]> OnFreezablePropertyChanged_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { SubFreezable.Property1 };
+    }
+
+    [Theory]
+    [MemberData(nameof(OnFreezablePropertyChanged_TestData))]
+    public void OnFreezablePropertyChanged_InvokeDependencyProperty_Nop(DependencyProperty property)
+    {
+        var freezable = new SubFreezable();
+        var value1 = new SubDependencyObject();
+        var value2 = new SubDependencyObject();
+        freezable.OnFreezablePropertyChanged(value1, value2, property);
+        freezable.OnFreezablePropertyChanged(value1, null!, property);
+        freezable.OnFreezablePropertyChanged(null!, value2, property);
+    }
+
+    [Theory]
+    [MemberData(nameof(OnFreezablePropertyChanged_TestData))]
+    public void OnFreezablePropertyChanged_InvokeDependencyPropertyFrozen_Nop(DependencyProperty property)
+    {
+        var freezable = new SubFreezable();
+        var value1 = new SubDependencyObject();
+        var value2 = new SubDependencyObject();
+        freezable.Freeze();
+        freezable.OnFreezablePropertyChanged(value1, value2, property);
+        freezable.OnFreezablePropertyChanged(value1, null!, property);
+        freezable.OnFreezablePropertyChanged(null!, value2, property);
+    }
+
+    [Theory]
+    [MemberData(nameof(OnFreezablePropertyChanged_TestData))]
+    public void OnFreezablePropertyChanged_InvokeDependencyPropertyOnDifferentThread_Nop(DependencyProperty property)
+    {
+        var freezable = new SubFreezable();
+        var value1 = new SubDependencyObject();
+        var value2 = new SubDependencyObject();
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            freezable.OnFreezablePropertyChanged(value1, value2, property);
+            freezable.OnFreezablePropertyChanged(value1, null!, property);
+            freezable.OnFreezablePropertyChanged(null!, value2, property);
+        });
+    }
+
+    [Theory]
+    [MemberData(nameof(OnFreezablePropertyChanged_TestData))]
+    public void OnFreezablePropertyChanged_InvokeDependencyPropertyFrozenOnDifferentThread_Nop(DependencyProperty property)
+    {
+        var freezable = new SubFreezable();
+        var value1 = new SubDependencyObject();
+        var value2 = new SubDependencyObject();
+        freezable.Freeze();
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            freezable.OnFreezablePropertyChanged(value1, value2, property);
+            freezable.OnFreezablePropertyChanged(value1, null!, property);
+            freezable.OnFreezablePropertyChanged(null!, value2, property);
+        });
+    }
+
+    [Theory]
+    [MemberData(nameof(OnFreezablePropertyChanged_TestData))]
+    public void OnFreezablePropertyChanged_InvokeDependencyPropertyDifferentThread_ThrowsInvalidOperationException(DependencyProperty property)
+    {
+        var freezable = new SubFreezable();
+        var value1 = Helpers.ExecuteOnDifferentThread(() => new SubDependencyObject());
+        var value2 = new SubDependencyObject();
+        var value3 = Helpers.ExecuteOnDifferentThread(() => new SubDependencyObject());
+        var value4 = new SubFreezable();
+        value4.Freeze();
+
+        Assert.Throws<InvalidOperationException>(() => freezable.OnFreezablePropertyChanged(null!, value1, property));
+        Assert.Throws<InvalidOperationException>(() => freezable.OnFreezablePropertyChanged(null!, value3, property));
+        freezable.OnFreezablePropertyChanged(null!, value4, property);
+        freezable.OnFreezablePropertyChanged(value1, value2, property);
+        Assert.Throws<InvalidOperationException>(() => freezable.OnFreezablePropertyChanged(value1, value3, property));
+        freezable.OnFreezablePropertyChanged(value1, value4, property);
+        Assert.Throws<InvalidOperationException>(() => freezable.OnFreezablePropertyChanged(value2, value1, property));
+        Assert.Throws<InvalidOperationException>(() => freezable.OnFreezablePropertyChanged(value2, value3, property));
+        freezable.OnFreezablePropertyChanged(value2, value4, property);
+        Assert.Throws<InvalidOperationException>(() => freezable.OnFreezablePropertyChanged(value3, value1, property));
+        freezable.OnFreezablePropertyChanged(value3, value2, property);
+        freezable.OnFreezablePropertyChanged(value3, value4, property);
+    }
+
+    [Theory]
+    [MemberData(nameof(OnFreezablePropertyChanged_TestData))]
+    public void OnFreezablePropertyChanged_InvokeDependencyPropertyDifferentThreadFrozen_Nop(DependencyProperty property)
+    {
+        var freezable = new SubFreezable();
+        var value1 = Helpers.ExecuteOnDifferentThread(() => new SubDependencyObject());
+        var value2 = new SubDependencyObject();
+        var value3 = Helpers.ExecuteOnDifferentThread(() => new SubDependencyObject());
+        freezable.Freeze();
+        var value4 = new SubFreezable();
+        value4.Freeze();
+
+        freezable.OnFreezablePropertyChanged(null!, value1, property);
+        freezable.OnFreezablePropertyChanged(null!, value2, property);
+        freezable.OnFreezablePropertyChanged(null!, value3, property);
+        freezable.OnFreezablePropertyChanged(null!, value4, property);
+        freezable.OnFreezablePropertyChanged(value1, value1, property);
+        freezable.OnFreezablePropertyChanged(value1, value2, property);
+        freezable.OnFreezablePropertyChanged(value1, value3, property);
+        freezable.OnFreezablePropertyChanged(value1, value4, property);
+        freezable.OnFreezablePropertyChanged(value2, value1, property);
+        freezable.OnFreezablePropertyChanged(value2, value2, property);
+        freezable.OnFreezablePropertyChanged(value2, value3, property);
+        freezable.OnFreezablePropertyChanged(value2, value4, property);
+        freezable.OnFreezablePropertyChanged(value3, value1, property);
+        freezable.OnFreezablePropertyChanged(value3, value2, property);
+        freezable.OnFreezablePropertyChanged(value3, value3, property);
+        freezable.OnFreezablePropertyChanged(value3, value4, property);
+    }
+
+    [Theory]
+    [MemberData(nameof(OnFreezablePropertyChanged_TestData))]
+    public void OnFreezablePropertyChanged_InvokeDependencyPropertyDifferentThreadOnDifferentThread_ThrowsInvalidOperationException(DependencyProperty property)
+    {
+        var freezable = new SubFreezable();
+        var value1 = Helpers.ExecuteOnDifferentThread(() => new SubDependencyObject());
+        var value2 = new SubDependencyObject();
+        var value3 = Helpers.ExecuteOnDifferentThread(() => new SubDependencyObject());
+        var value4 = new SubFreezable();
+        value4.Freeze();
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => freezable.OnFreezablePropertyChanged(null!, value1, property));
+            Assert.Throws<InvalidOperationException>(() => freezable.OnFreezablePropertyChanged(null!, value3, property));
+            freezable.OnFreezablePropertyChanged(null!, value4, property);
+            freezable.OnFreezablePropertyChanged(value1, value2, property);
+            Assert.Throws<InvalidOperationException>(() => freezable.OnFreezablePropertyChanged(value1, value3, property));
+            freezable.OnFreezablePropertyChanged(value1, value4, property);
+            Assert.Throws<InvalidOperationException>(() => freezable.OnFreezablePropertyChanged(value2, value1, property));
+            Assert.Throws<InvalidOperationException>(() => freezable.OnFreezablePropertyChanged(value2, value3, property));
+            freezable.OnFreezablePropertyChanged(value2, value4, property);
+            Assert.Throws<InvalidOperationException>(() => freezable.OnFreezablePropertyChanged(value3, value1, property));
+            freezable.OnFreezablePropertyChanged(value3, value2, property);
+            freezable.OnFreezablePropertyChanged(value3, value4, property);
+        });
+    }
+
+    [Theory]
+    [MemberData(nameof(OnFreezablePropertyChanged_TestData))]
+    public void OnFreezablePropertyChanged_InvokeDependencyPropertyDifferentThreadFrozenOnDifferentThread_Nop(DependencyProperty property)
+    {
+        var freezable = new SubFreezable();
+        var value1 = Helpers.ExecuteOnDifferentThread(() => new SubDependencyObject());
+        var value2 = new SubDependencyObject();
+        var value3 = Helpers.ExecuteOnDifferentThread(() => new SubDependencyObject());
+        freezable.Freeze();
+        var value4 = new SubFreezable();
+        value4.Freeze();
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            freezable.OnFreezablePropertyChanged(null!, value1, property);
+            freezable.OnFreezablePropertyChanged(null!, value2, property);
+            freezable.OnFreezablePropertyChanged(null!, value3, property);
+            freezable.OnFreezablePropertyChanged(null!, value4, property);
+            freezable.OnFreezablePropertyChanged(value1, value1, property);
+            freezable.OnFreezablePropertyChanged(value1, value2, property);
+            freezable.OnFreezablePropertyChanged(value1, value3, property);
+            freezable.OnFreezablePropertyChanged(value1, value4, property);
+            freezable.OnFreezablePropertyChanged(value2, value1, property);
+            freezable.OnFreezablePropertyChanged(value2, value2, property);
+            freezable.OnFreezablePropertyChanged(value2, value3, property);
+            freezable.OnFreezablePropertyChanged(value2, value4, property);
+            freezable.OnFreezablePropertyChanged(value3, value1, property);
+            freezable.OnFreezablePropertyChanged(value3, value2, property);
+            freezable.OnFreezablePropertyChanged(value3, value3, property);
+            freezable.OnFreezablePropertyChanged(value3, value4, property);
+        });
+    }
+
+    [Fact]
+    public void OnPropertyChanged_InvokeNoMetadata_Nop()
+    {
+        var obj = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        obj.OnPropertyChanged(new DependencyPropertyChangedEventArgs(property, new object(), new object()));
+    }
+
+    [Fact]
+    public void OnPropertyChanged_InvokeEmptyMetadata_Nop()
+    {
+        var obj = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), new PropertyMetadata());
+        obj.OnPropertyChanged(new DependencyPropertyChangedEventArgs(property, new object(), new object()));
+    }
+
+    [Fact]
+    public void OnPropertyChanged_InvokeMetadataHasPropertyChangedCallback_Nop()
+    {
+        var obj = new SubFreezable();
+        int callCount = 0;
+        var metadata = new PropertyMetadata(null, (d, actualE) => callCount++);
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), metadata);
+        var e = new DependencyPropertyChangedEventArgs(property, new object(), new object());
+        obj.OnPropertyChanged(e);
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void OnPropertyChanged_InvokeOnDifferentThread_Nop()
+    {
+        var obj = new SubFreezable();
+        int callCount = 0;
+        var metadata = new PropertyMetadata(null, (d, actualE) => callCount++);
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject), metadata);
+        var e = new DependencyPropertyChangedEventArgs(property, new object(), new object());
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            obj.OnPropertyChanged(e);
+            Assert.Equal(0, callCount);
+        });
+    }
+
+    [Fact]
+    public void OnPropertyChanged_NullEProperty_ThrowsArgumentException()
+    {
+        var obj = new SubFreezable();
+        DependencyPropertyChangedEventArgs e = default;
+        Assert.Throws<ArgumentException>("e", () => obj.OnPropertyChanged(e));
+    }
+
+    [Fact]
+    public void SetValue_InvokeDependencyProperty_GetValueReturnsExpected()
+    {
+        var freezable = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject));
+
+        // Set true.
+        freezable.SetValue(property, true);
+        Assert.True((bool)freezable.GetValue(property));
+
+        // Set same.
+        freezable.SetValue(property, true);
+        Assert.True((bool)freezable.GetValue(property));
+
+        // Set false.
+        freezable.SetValue(property, false);
+        Assert.False((bool)freezable.GetValue(property));
+    }
+
+    [Fact]
+    public void SetValue_InvokeDependencyPropertyWithHandler_CallsChanged()
+    {
+        var freezable = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject));
+
+        int callCount = 0;
+        EventHandler handler = (sender, e) =>
+        {
+            Assert.Same(freezable, sender);
+            Assert.Same(EventArgs.Empty, e);
+            callCount++;
+        }; 
+        freezable.Changed += handler;
+
+        // Set.
+        freezable.SetValue(property, true);
+        Assert.True((bool)freezable.GetValue(property));
+        Assert.Equal(1, callCount);
+
+        // Set same.
+        freezable.SetValue(property, true);
+        Assert.True((bool)freezable.GetValue(property));
+        Assert.Equal(1, callCount);
+
+        // Set different.
+        freezable.SetValue(property, false);
+        Assert.False((bool)freezable.GetValue(property));
+        Assert.Equal(2, callCount);
+
+        // Remove handler.
+        freezable.Changed -= handler;
+        freezable.SetValue(property, true);
+        Assert.True((bool)freezable.GetValue(property));
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void SetValue_InvokeWithCustomOnChanged_CallsChanged()
+    {
+        var freezable = new CustomFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject));
+
+        int onChangedCallCount = 0;
+        int changedCallCount = 0;
+        freezable.OnChangedAction = () =>
+        {
+            Assert.Equal(changedCallCount, onChangedCallCount);
+            onChangedCallCount++;
+        };
+        freezable.Changed += (sender, e) =>
+        {
+            Assert.True(onChangedCallCount > changedCallCount);
+            Assert.Same(freezable, sender);
+            Assert.Same(EventArgs.Empty, e);
+            changedCallCount++;
+        }; 
+
+        // Set.
+        freezable.SetValue(property, true);
+        Assert.True((bool)freezable.GetValue(property));
+        Assert.Equal(1, onChangedCallCount);
+        Assert.Equal(1, changedCallCount);
+
+        // Set same.
+        freezable.SetValue(property, true);
+        Assert.True((bool)freezable.GetValue(property));
+        Assert.Equal(1, onChangedCallCount);
+        Assert.Equal(1, changedCallCount);
+
+        // Set different.
+        freezable.SetValue(property, false);
+        Assert.False((bool)freezable.GetValue(property));
+        Assert.Equal(2, onChangedCallCount);
+        Assert.Equal(2, changedCallCount);
+    }
+
+
+    [Fact]
+    public void SetValue_DependencyPropertyNullDp_ThrowsArgumentNullException()
+    {
+        var obj = new SubFreezable();
+        Assert.Throws<ArgumentNullException>("dp", () => obj.SetValue((DependencyProperty)null!, true));
+    }
+
+    [Fact]
+    public void SetValue_DependencyPropertyReadOnly_ThrowsInvalidOperationException()
+    {
+        var obj = new SubFreezable();
+        DependencyPropertyKey key = DependencyProperty.RegisterReadOnly(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject), new PropertyMetadata());
+        DependencyProperty property = key.DependencyProperty;
+        Assert.Throws<InvalidOperationException>(() => obj.SetValue(property, "value"));
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("value")]
+    [InlineData(1)]
+    public void SetValue_DependencyPropertyInvalidValueValueType_ThrowsArgumentException(object? value)
+    {
+        var obj = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name + value?.GetType().Name, typeof(bool), typeof(DependencyObject));
+        // TODO: add paramName
+        Assert.Throws<ArgumentException>(() => obj.SetValue(property, value));
+    }
+
+    [Theory]
+    [InlineData("value")]
+    [InlineData(1)]
+    public void SetValue_DependencyPropertyInvalidValueNullable_ThrowsArgumentException(object value)
+    {
+        var obj = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name + value?.GetType().Name, typeof(bool?), typeof(DependencyObject));
+        // TODO: add paramName
+        Assert.Throws<ArgumentException>(() => obj.SetValue(property, value));
+    }
+
+    public static IEnumerable<object[]> SetValue_DependencyPropertyInvalidValueReferenceType_TestData()
+    {
+        yield return new object[] { new object() };
+        yield return new object[] { 1 };
+    }
+
+    [Theory]
+    [MemberData(nameof(SetValue_DependencyPropertyInvalidValueReferenceType_TestData))]
+    public void SetValue_DependencyPropertyInvalidValueReferenceType_ThrowsArgumentException(object value)
+    {
+        var obj = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name + value?.GetType().Name, typeof(string), typeof(DependencyObject));
+        // TODO: add paramName
+        Assert.Throws<ArgumentException>(() => obj.SetValue(property, value));
+    }
+
+    [Fact]
+    public void SetValue_InvokeDependencyPropertyFrozen_ThrowsInvalidOperationException()
+    {
+        var freezable = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject));
+        freezable.SetValue(property, true);
+        freezable.Freeze();
+
+        // Set true.
+        Assert.Throws<InvalidOperationException>(() => freezable.SetValue(property, true));
+        Assert.True((bool)freezable.GetValue(property));
+
+        // Set same.
+        Assert.Throws<InvalidOperationException>(() => freezable.SetValue(property, true));
+        Assert.True((bool)freezable.GetValue(property));
+
+        // Set false.
+        Assert.Throws<InvalidOperationException>(() => freezable.SetValue(property, false));
+        Assert.True((bool)freezable.GetValue(property));
+    }
+
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void SetValue_InvokeDifferentThread_ThrowsInvalidOperationException(bool value)
+    {
+        var freezable = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name + value.ToString(), typeof(bool), typeof(DependencyObject));
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => freezable.SetValue(property, value));
+        });
+    }
+
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void SetValue_InvokeFrozenOnDifferentThread_ThrowsInvalidOperationException(bool value)
+    {
+        var freezable = new SubFreezable();
+        DependencyProperty property = DependencyProperty.Register(nameof(FreezableTests) + MethodBase.GetCurrentMethod()!.Name + value.ToString(), typeof(bool), typeof(DependencyObject));
+        freezable.Freeze();
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => freezable.SetValue(property, value));
+        });
+    }
+
+    [Fact]
+    public void WritePostscript_Invoke_Success()
+    {
+        var freezable = new SubFreezable();
+
+        // Call.
+        freezable.WritePostscript();
+        
+        // Call again.
+        freezable.WritePostscript();
+    }
+
+    [Fact]
+    public void WritePostscript_InvokeWithHandler_CallsChanged()
+    {
+        var freezable = new CustomFreezable();
+        int onChangedCallCount = 0;
+        int changedCallCount = 0;
+        freezable.OnChangedAction = () =>
+        {
+            Assert.Equal(changedCallCount, onChangedCallCount);
+            onChangedCallCount++;
+        };
+        freezable.Changed += (sender, e) =>
+        {
+            Assert.True(onChangedCallCount > changedCallCount);
+            Assert.Same(freezable, sender);
+            Assert.Same(EventArgs.Empty, e);
+            changedCallCount++;
+        };
+
+        // Call.
+        freezable.WritePostscript();
+        Assert.Equal(1, onChangedCallCount);
+        Assert.Equal(1, changedCallCount);
+        
+        // Call again.
+        freezable.WritePostscript();
+        Assert.Equal(2, onChangedCallCount);
+        Assert.Equal(2, changedCallCount);
+    }
+
+    [Fact]
+    public void WritePostscript_InvokeWithRemovedHandler_DoesNotCallChanged()
+    {
+        var freezable = new CustomFreezable();
+        int onChangedCallCount = 0;
+        int changedCallCount = 0;
+        freezable.OnChangedAction = () =>
+        {
+            onChangedCallCount++;
+        };
+        EventHandler handler = (sender, e) => changedCallCount++;
+        freezable.Changed += handler;
+        freezable.Changed -= handler;
+
+        // Call.
+        freezable.WritePostscript();
+        Assert.Equal(1, onChangedCallCount);
+        Assert.Equal(0, changedCallCount);
+        
+        // Call again.
+        freezable.WritePostscript();
+        Assert.Equal(2, onChangedCallCount);
+        Assert.Equal(0, changedCallCount);
+    }
+
+    [Fact]
+    public void WritePostscript_InvokeWithMultipleHandlers_CallsChanged()
+    {
+        var freezable = new CustomFreezable();
+        int onChangedCallCount = 0;
+        int changedCallCount1 = 0;
+        int changedCallCount2 = 0;
+        int changedCallCount3 = 0;
+        freezable.OnChangedAction = () =>
+        {
+            onChangedCallCount++;
+        };
+        freezable.Changed += (sender, e) =>
+        {
+            Assert.Same(freezable, sender);
+            Assert.Same(EventArgs.Empty, e);
+            changedCallCount1++;
+        };
+        freezable.Changed += (sender, e) =>
+        {
+            Assert.Same(freezable, sender);
+            Assert.Same(EventArgs.Empty, e);
+            changedCallCount2++;
+        };
+        freezable.Changed += (sender, e) =>
+        {
+            Assert.Same(freezable, sender);
+            Assert.Same(EventArgs.Empty, e);
+            changedCallCount3++;
+        };
+
+        // Call.
+        freezable.WritePostscript();
+        Assert.Equal(1, onChangedCallCount);
+        Assert.Equal(1, changedCallCount1);
+        Assert.Equal(1, changedCallCount2);
+        Assert.Equal(1, changedCallCount3);
+        
+        // Call again.
+        freezable.WritePostscript();
+        Assert.Equal(2, onChangedCallCount);
+        Assert.Equal(2, changedCallCount1);
+        Assert.Equal(2, changedCallCount2);
+        Assert.Equal(2, changedCallCount3);
+    }
+
+    [Fact]
+    public void WritePostscript_InvokeWithMultipleHandlersRemovedOne_DoesNotCallChanged()
+    {
+        var freezable = new CustomFreezable();
+        int onChangedCallCount = 0;
+        int changedCallCount1 = 0;
+        int changedCallCount2 = 0;
+        int changedCallCount3 = 0;
+        freezable.OnChangedAction = () =>
+        {
+            onChangedCallCount++;
+        };
+        EventHandler handler1 = (sender, e) =>
+        {
+            Assert.Same(freezable, sender);
+            Assert.Same(EventArgs.Empty, e);
+            changedCallCount1++;
+        };
+        freezable.Changed += handler1;
+        EventHandler handler2 = (sender, e) =>
+        {
+            Assert.Same(freezable, sender);
+            Assert.Same(EventArgs.Empty, e);
+            changedCallCount2++;
+        };
+        freezable.Changed += handler2;
+        EventHandler handler3 = (sender, e) => changedCallCount3++;
+        freezable.Changed += handler3;
+        freezable.Changed -= handler3;
+
+        // Call.
+        freezable.WritePostscript();
+        Assert.Equal(1, onChangedCallCount);
+        Assert.Equal(1, changedCallCount1);
+        Assert.Equal(1, changedCallCount2);
+        Assert.Equal(0, changedCallCount3);
+        
+        // Call again.
+        freezable.WritePostscript();
+        Assert.Equal(2, onChangedCallCount);
+        Assert.Equal(2, changedCallCount1);
+        Assert.Equal(2, changedCallCount2);
+        Assert.Equal(0, changedCallCount3);
+    }
+
+    [Fact]
+    public void WritePostscript_InvokeWithMultipleHandlersRemovedAllButOne_DoesNotCallChanged()
+    {
+        var freezable = new CustomFreezable();
+        int onChangedCallCount = 0;
+        int changedCallCount1 = 0;
+        int changedCallCount2 = 0;
+        int changedCallCount3 = 0;
+        freezable.OnChangedAction = () =>
+        {
+            onChangedCallCount++;
+        };
+        EventHandler handler1 = (sender, e) => changedCallCount1++;
+        freezable.Changed += handler1;
+        EventHandler handler2 = (sender, e) =>
+        {
+            Assert.Same(freezable, sender);
+            Assert.Same(EventArgs.Empty, e);
+            changedCallCount2++;
+        };
+        freezable.Changed += handler2;
+        EventHandler handler3 = (sender, e) => changedCallCount3++;
+        freezable.Changed += handler3;
+        freezable.Changed -= handler3;
+        freezable.Changed -= handler1;
+
+        // Call.
+        freezable.WritePostscript();
+        Assert.Equal(1, onChangedCallCount);
+        Assert.Equal(0, changedCallCount1);
+        Assert.Equal(1, changedCallCount2);
+        Assert.Equal(0, changedCallCount3);
+        
+        // Call again.
+        freezable.WritePostscript();
+        Assert.Equal(2, onChangedCallCount);
+        Assert.Equal(0, changedCallCount1);
+        Assert.Equal(2, changedCallCount2);
+        Assert.Equal(0, changedCallCount3);
+    }
+
+    [Fact]
+    public void WritePostscript_InvokeWithMultipleHandlersRemovedAll_DoesNotCallChanged()
+    {
+        var freezable = new CustomFreezable();
+        int onChangedCallCount = 0;
+        int changedCallCount1 = 0;
+        int changedCallCount2 = 0;
+        int changedCallCount3 = 0;
+        freezable.OnChangedAction = () =>
+        {
+            onChangedCallCount++;
+        };
+        EventHandler handler1 = (sender, e) => changedCallCount1++;
+        freezable.Changed += handler1;
+        EventHandler handler2 = (sender, e) => changedCallCount2++;
+        freezable.Changed += handler2;
+        EventHandler handler3 = (sender, e) => changedCallCount3++;
+        freezable.Changed += handler3;
+        freezable.Changed -= handler3;
+        freezable.Changed -= handler1;
+
+        // Call.
+        freezable.WritePostscript();
+        Assert.Equal(1, onChangedCallCount);
+        Assert.Equal(0, changedCallCount1);
+        Assert.Equal(1, changedCallCount2);
+        Assert.Equal(0, changedCallCount3);
+        
+        // Call again.
+        freezable.WritePostscript();
+        Assert.Equal(2, onChangedCallCount);
+        Assert.Equal(0, changedCallCount1);
+        Assert.Equal(2, changedCallCount2);
+        Assert.Equal(0, changedCallCount3);
+    }
+
+    [Fact]
+    public void WritePostscript_InvokeFrozen_Success()
+    {
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+
+        // Call.
+        freezable.WritePostscript();
+
+        // Call again.
+        freezable.WritePostscript();
+    }
+
+    [Fact]
+    public void WritePostscript_InvokeFrozenWithHandler_DoesNotCallChanged()
+    {
+        var freezable = new CustomFreezable();
+        bool shouldTrack = false;
+        int onChangedCallCount = 0;
+        int changedCallCount = 0;
+        freezable.OnChangedAction = () =>
+        {
+            if (shouldTrack)
+            {
+                onChangedCallCount++;
+            }
+        };
+        freezable.Changed += (sender, e) =>
+        {
+            if (shouldTrack)
+            {
+                Assert.Same(freezable, sender);
+                Assert.Same(EventArgs.Empty, e);
+                changedCallCount++;
+            }
+        };
+        freezable.Freeze();
+        shouldTrack = true;
+
+        // Call.
+        freezable.WritePostscript();
+        Assert.Equal(1, onChangedCallCount);
+        Assert.Equal(0, changedCallCount);
+        
+        // Call again.
+        freezable.WritePostscript();
+        Assert.Equal(2, onChangedCallCount);
+        Assert.Equal(0, changedCallCount);
+    }
+
+    [Fact]
+    public void WritePostscript_InvokeOnDifferentThread_Success()
+    {
+        var freezable = new SubFreezable();
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            freezable.WritePostscript();
+        });
+    }
+
+    [Fact]
+    public void WritePostscript_InvokeFrozenOnDifferentThread_Success()
+    {
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            freezable.WritePostscript();
+        });
+    }
+
+    [Fact]
+    public void WritePreamble_Invoke_Success()
+    {
+        var freezable = new SubFreezable();
+
+        // Call.
+        freezable.WritePreamble();
+
+        // Call again.
+        freezable.WritePreamble();
+    }
+
+    [Fact]
+    public void WritePreamble_InvokeWithHandler_DoesNotCallChanged()
+    {
+        var freezable = new CustomFreezable();
+        int onChangedCallCount = 0;
+        freezable.OnChangedAction = () => onChangedCallCount++;
+        int changedCallCount = 0;
+        freezable.Changed += (sender, e) => changedCallCount++;
+        
+        // Call.
+        freezable.WritePreamble();
+        Assert.Equal(0, onChangedCallCount);
+        Assert.Equal(0, changedCallCount);
+        
+        // Call again.
+        freezable.WritePreamble();
+        Assert.Equal(0, onChangedCallCount);
+        Assert.Equal(0, changedCallCount);
+    }
+
+    [Fact]
+    public void WritePreamble_InvokeFrozen_ThrowsInvalidOperationException()
+    {
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+
+        // Call.
+        Assert.Throws<InvalidOperationException>(() => freezable.WritePreamble());
+        
+        // Call again.
+        Assert.Throws<InvalidOperationException>(() => freezable.WritePreamble());
+    }
+
+    [Fact]
+    public void WritePreamble_InvokeOnDifferentThread_ThrowsInvalidOperationException()
+    {
+        var freezable = new SubFreezable();
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => freezable.WritePreamble());
+        });
+    }
+
+    [Fact]
+    public void WritePreamble_InvokeFrozenOnDifferentThread_ThrowsInvalidOperationException()
+    {
+        var freezable = new SubFreezable();
+        freezable.Freeze();
+
+        Helpers.ExecuteOnDifferentThread(() =>
+        {
+            Assert.Throws<InvalidOperationException>(() => freezable.WritePreamble());
+        });
+    }
+
+    private class SubDependencyObject : DependencyObject
+    {
+    }
+
+    private class CustomFreezable : Freezable
+    {
+        public Func<Freezable>? CreateInstanceCoreAction { get; set; }
+
+        protected override Freezable CreateInstanceCore()
+        {
+            if (CreateInstanceCoreAction is null)
+            {
+                throw new NotImplementedException();
+            }
+
+            return CreateInstanceCoreAction();
+        }
+
+        public Func<bool, bool>? FreezeCoreAction { get; set; }
+
+        protected override bool FreezeCore(bool isChecking)
+        {
+            if (FreezeCoreAction != null)
+            {
+                return FreezeCoreAction(isChecking);
+            }
+
+            return base.FreezeCore(isChecking);
+        }
+
+        public Action? OnChangedAction { get; set; }
+
+        protected override void OnChanged()
+        {
+            if (OnChangedAction != null)
+            {
+                OnChangedAction();
+            }
+
+            base.OnChanged();
+        }
+
+        public Action<DependencyPropertyChangedEventArgs>? OnPropertyChangedAction { get; set; }
+
+        protected override void OnPropertyChanged(DependencyPropertyChangedEventArgs e)
+        {
+            base.OnPropertyChanged(e);
+            OnPropertyChangedAction?.Invoke(e);
+        }
+
+        public new void ReadPreamble() => base.ReadPreamble();
+
+        public new void WritePreamble() => base.WritePreamble();
+
+        public new void WritePostscript() => base.WritePostscript();
+    }
+
+    private class SubFreezable : Freezable
+    {
+        public static DependencyProperty Property1 { get; } = DependencyProperty.Register($"{nameof(SubFreezable)}_{nameof(Property1)}", typeof(int), typeof(SubFreezable));
+        public static DependencyProperty Property2 { get; } = DependencyProperty.Register($"{nameof(SubFreezable)}_{nameof(Property2)}", typeof(int), typeof(SubFreezable));
+        public static DependencyProperty Property3 { get; } = DependencyProperty.Register($"{nameof(SubFreezable)}_{nameof(Property3)}", typeof(int), typeof(SubFreezable));
+        public static DependencyProperty Property4 { get; } = DependencyProperty.RegisterAttached($"{nameof(SubFreezable)}_{nameof(Property4)}", typeof(int), typeof(SubFreezable));
+        public static DependencyProperty Property5 { get; } = DependencyProperty.RegisterAttached($"{nameof(SubFreezable)}_{nameof(Property5)}", typeof(int), typeof(SubFreezable));
+        public static DependencyProperty Property6 { get; } = DependencyProperty.Register($"{nameof(SubFreezable)}_{nameof(Property6)}", typeof(DependencyObject), typeof(SubFreezable));
+        public static DependencyProperty Property7 { get; } = DependencyProperty.Register($"{nameof(SubFreezable)}_{nameof(Property7)}", typeof(DependencyObject), typeof(SubFreezable));
+        public static DependencyProperty Property8 { get; } = DependencyProperty.Register($"{nameof(SubFreezable)}_{nameof(Property8)}", typeof(DependencyObject), typeof(SubFreezable));
+        public static DependencyProperty Property9 { get; } = DependencyProperty.Register($"{nameof(SubFreezable)}_{nameof(Property9)}", typeof(DependencyObject), typeof(SubFreezable));
+        public static DependencyPropertyKey ReadOnlyProperty { get; } = DependencyProperty.RegisterReadOnly($"{nameof(SubFreezable)}_{nameof(ReadOnlyProperty)}", typeof(int), typeof(SubFreezable), new PropertyMetadata(1));
+
+        public new Freezable CreateInstance() => base.CreateInstance();
+
+        public Func<Freezable>? CreateInstanceCoreAction { get; set; }
+
+        protected override Freezable CreateInstanceCore()
+        {
+            if (CreateInstanceCoreAction is null)
+            {
+                throw new NotImplementedException();
+            }
+
+            return CreateInstanceCoreAction();
+        }
+
+        public new void CloneCore(Freezable sourceFreezable) => base.CloneCore(sourceFreezable);
+
+        public new void CloneCurrentValueCore(Freezable sourceFreezable) => base.CloneCurrentValueCore(sourceFreezable);
+
+        public new bool FreezeCore(bool isChecking) => base.FreezeCore(isChecking);
+
+        public new void GetAsFrozenCore(Freezable sourceFreezable) => base.GetAsFrozenCore(sourceFreezable);
+        
+        public new void GetCurrentValueAsFrozenCore(Freezable sourceFreezable) => base.GetCurrentValueAsFrozenCore(sourceFreezable);
+
+        public new void ReadPreamble() => base.ReadPreamble();
+
+        public new void OnChanged() => base.OnChanged();
+        
+        public new void OnFreezablePropertyChanged(DependencyObject oldValue, DependencyObject newValue) => base.OnFreezablePropertyChanged(oldValue, newValue, Property1);
+
+        public new void OnFreezablePropertyChanged(DependencyObject oldValue, DependencyObject newValue, DependencyProperty property) => base.OnFreezablePropertyChanged(oldValue, newValue, property);
+
+        public new void OnPropertyChanged(DependencyPropertyChangedEventArgs e) => base.OnPropertyChanged(e);
+
+        public new void WritePreamble() => base.WritePreamble();
+
+        public new void WritePostscript() => base.WritePostscript();
+    }
+
+    private class SubFreezable2 : Freezable
+    {
+        public SubFreezable2() : base()
+        {
+        }
+
+        protected override Freezable CreateInstanceCore() => throw new NotImplementedException();
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Input/KeyConverterTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Input/KeyConverterTests.cs
new file mode 100644
index 00000000000..b1465705334
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Input/KeyConverterTests.cs
@@ -0,0 +1,444 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.ComponentModel.Design.Serialization;
+using System.Globalization;
+
+namespace System.Windows.Input.Tests;
+
+public class KeyConverterTests
+{
+    public static IEnumerable<object?[]> CanConvertTo_TestData()
+    {
+        yield return new object?[] { null, null, false };
+        yield return new object?[] { null, typeof(object), false };
+        yield return new object?[] { null, typeof(string), false };
+        yield return new object?[] { null, typeof(InstanceDescriptor), false };
+        yield return new object?[] { null, typeof(Key), false };
+        yield return new object?[] { new CustomTypeDescriptorContext(), null, false };
+        yield return new object?[] { new CustomTypeDescriptorContext(), typeof(object), false };
+        yield return new object?[] { new CustomTypeDescriptorContext(), typeof(string), false };
+        yield return new object?[] { new CustomTypeDescriptorContext(), typeof(InstanceDescriptor), false };
+        yield return new object?[] { new CustomTypeDescriptorContext(), typeof(Key), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = new object() }, null, false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = new object() }, typeof(object), false };
+        // TODO: this should not throw.
+        //yield return new object?[] { new CustomTypeDescriptorContext { Instance = new object() }, typeof(string), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = new object() }, typeof(InstanceDescriptor), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = new object() }, typeof(Key), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.None }, null, false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.None }, typeof(object), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.None }, typeof(string), true };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.None }, typeof(InstanceDescriptor), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.None }, typeof(Key), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.Cancel }, null, false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.Cancel }, typeof(object), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.Cancel }, typeof(string), true };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.Cancel }, typeof(InstanceDescriptor), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.Cancel }, typeof(Key), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.A }, null, false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.A }, typeof(object), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.A }, typeof(string), true };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.A }, typeof(InstanceDescriptor), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.A }, typeof(Key), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.OemClear }, null, false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.OemClear }, typeof(object), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.OemClear }, typeof(string), true };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.OemClear }, typeof(InstanceDescriptor), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.OemClear }, typeof(Key), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.DeadCharProcessed }, null, false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.DeadCharProcessed }, typeof(object), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.DeadCharProcessed }, typeof(string), true };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.DeadCharProcessed }, typeof(InstanceDescriptor), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.DeadCharProcessed }, typeof(Key), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.None - 1 }, null, false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.None - 1 }, typeof(object), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.None - 1 }, typeof(string), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.None - 1 }, typeof(InstanceDescriptor), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.None - 1 }, typeof(Key), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.DeadCharProcessed + 1 }, null, false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.DeadCharProcessed + 1 }, typeof(object), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.DeadCharProcessed + 1 }, typeof(string), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.DeadCharProcessed + 1 }, typeof(InstanceDescriptor), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = Key.DeadCharProcessed + 1 }, typeof(Key), false };
+    }
+
+    [Theory]
+    [MemberData(nameof(CanConvertTo_TestData))]
+    public void CanConvertTo_Invoke_ReturnsExpected(ITypeDescriptorContext context, Type destinationType, bool expected)
+    {
+        var converter = new KeyConverter();
+        Assert.Equal(expected, converter.CanConvertTo(context, destinationType));
+    }
+
+    [Fact]
+    public void CanConvertTo_InvokeToStringInstanceNotKey_ThrowsInvalidCastException()
+    {
+        // TODO: this should return false.
+        var converter = new KeyConverter();
+        var context = new CustomTypeDescriptorContext { Instance = new object() };
+        Assert.Throws<InvalidCastException>(() => converter.CanConvertTo(context, typeof(string)));
+    }
+
+    public static IEnumerable<object[]> ConvertTo_KeyToString_TestData()
+    {
+        yield return new object[] { Key.None, "" };
+        yield return new object[] { Key.Cancel, "Cancel" };
+        yield return new object[] { Key.Back, "Backspace" };
+        yield return new object[] { Key.Tab, "Tab" };
+        yield return new object[] { Key.LineFeed, "Clear" };
+        yield return new object[] { Key.Return, "Return" };
+        yield return new object[] { Key.HanjaMode, "HanjaMode" };
+        yield return new object[] { Key.Escape, "Esc" };
+        yield return new object[] { Key.ImeConvert, "ImeConvert" };
+        yield return new object[] { Key.Help, "Help" };
+        yield return new object[] { Key.D0, "0" };
+        yield return new object[] { Key.D1, "1" };
+        yield return new object[] { Key.D2, "2" };
+        yield return new object[] { Key.D3, "3" };
+        yield return new object[] { Key.D4, "4" };
+        yield return new object[] { Key.D5, "5" };
+        yield return new object[] { Key.D6, "6" };
+        yield return new object[] { Key.D7, "7" };
+        yield return new object[] { Key.D8, "8" };
+        yield return new object[] { Key.D9, "9" };
+        yield return new object[] { Key.A, "A" };
+        yield return new object[] { Key.B, "B" };
+        yield return new object[] { Key.C, "C" };
+        yield return new object[] { Key.D, "D" };
+        yield return new object[] { Key.E, "E" };
+        yield return new object[] { Key.F, "F" };
+        yield return new object[] { Key.G, "G" };
+        yield return new object[] { Key.H, "H" };
+        yield return new object[] { Key.I, "I" };
+        yield return new object[] { Key.J, "J" };
+        yield return new object[] { Key.K, "K" };
+        yield return new object[] { Key.L, "L" };
+        yield return new object[] { Key.M, "M" };
+        yield return new object[] { Key.N, "N" };
+        yield return new object[] { Key.O, "O" };
+        yield return new object[] { Key.P, "P" };
+        yield return new object[] { Key.Q, "Q" };
+        yield return new object[] { Key.R, "R" };
+        yield return new object[] { Key.S, "S" };
+        yield return new object[] { Key.T, "T" };
+        yield return new object[] { Key.U, "U" };
+        yield return new object[] { Key.V, "V" };
+        yield return new object[] { Key.W, "W" };
+        yield return new object[] { Key.X, "X" };
+        yield return new object[] { Key.Y, "Y" };
+        yield return new object[] { Key.Z, "Z" };
+        yield return new object[] { Key.LWin, "LWin" };
+        yield return new object[] { Key.DeadCharProcessed, "DeadCharProcessed" };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertTo_KeyToString_TestData))]
+    public void ConvertTo_InvokeKeyToString_ReturnsExpected(Key value, string expected)
+    {
+        var converter = new KeyConverter();
+        Assert.Equal(expected, converter.ConvertTo(value, typeof(string)));
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), null, value, typeof(string)));
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value, typeof(string)));
+    }
+    
+    [Theory]
+    [InlineData((Key)int.MinValue)]
+    [InlineData((Key)(-1))]
+    [InlineData(Key.DeadCharProcessed + 1)]
+    [InlineData((Key)int.MaxValue)]
+    public void ConvertTo_InvalidKey_ThrowsNotSupportedException(Key value)
+    {
+        var converter = new KeyConverter();
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(value, typeof(string)));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(new CustomTypeDescriptorContext(), null, value, typeof(string)));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value, typeof(string)));
+    }
+
+    [Theory]
+    [InlineData(null)]
+    // TODO: this should not throw InvalidCastException.
+    //[InlineData("", "")]
+    //[InlineData("value", "value")]
+    public void ConvertTo_InvokeNotKeyToStringNull_ThrowsNotSupportedException(object? value)
+    {
+        var converter = new KeyConverter();
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(value, typeof(string)));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(new CustomTypeDescriptorContext(), null, value, typeof(string)));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value, typeof(string)));
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData("value")]
+    public void ConvertTo_InvokeNotKeyToStringNotNull_ThrowsInvalidCastException(object value)
+    {
+        // TODO: this should not throw InvalidCastException.
+        var converter = new KeyConverter();
+        Assert.Throws<InvalidCastException>(() => converter.ConvertTo(value, typeof(string)));
+        Assert.Throws<InvalidCastException>(() => converter.ConvertTo(new CustomTypeDescriptorContext(), null, value, typeof(string)));
+        Assert.Throws<InvalidCastException>(() => converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value, typeof(string)));
+    }
+
+    public static IEnumerable<object?[]> ConvertTo_CantConvert_TestData()
+    {
+        yield return new object?[] { null, typeof(object) };
+        yield return new object?[] { string.Empty, typeof(object) };
+        yield return new object?[] { "value", typeof(object) };
+        yield return new object?[] { new object(), typeof(object) };
+        yield return new object?[] { Key.None, typeof(object) };
+        
+        yield return new object?[] { null, typeof(Key) };
+        yield return new object?[] { string.Empty, typeof(Key) };
+        yield return new object?[] { "value", typeof(Key) };
+        yield return new object?[] { new object(), typeof(Key) };
+        yield return new object?[] { Key.None, typeof(Key) };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertTo_CantConvert_TestData))]
+    public void ConvertTo_CantConvert_ThrowsNotSupportedException(object value, Type destinationType)
+    {
+        var converter = new KeyConverter();
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(value, destinationType));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(null, null, value, destinationType));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value, destinationType));
+    }
+
+    public static IEnumerable<object?[]> ConvertTo_NullDestinationType_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { string.Empty };
+        yield return new object?[] { "value" };
+        yield return new object?[] { new object() };
+        yield return new object?[] { Key.None };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertTo_NullDestinationType_TestData))]
+    public void ConvertTo_NullDestinationType_ThrowsArgumentNullException(object value)
+    {
+        var converter = new KeyConverter();
+        Assert.Throws<ArgumentNullException>("destinationType", () => converter.ConvertTo(value, null!));
+        Assert.Throws<ArgumentNullException>("destinationType", () => converter.ConvertTo(null, null, Key.None, null!));
+        Assert.Throws<ArgumentNullException>("destinationType", () => converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, Key.None, null!));
+    }
+
+    [Theory]
+    [InlineData(null, false)]
+    [InlineData(typeof(object), false)]
+    [InlineData(typeof(string), true)]
+    [InlineData(typeof(InstanceDescriptor), false)]
+    [InlineData(typeof(Key), false)]
+    public void CanConvertFrom_Invoke_ReturnsExpected(Type? sourceType, bool expected)
+    {
+        var converter = new KeyConverter();
+        Assert.Equal(expected, converter.CanConvertFrom(sourceType!));
+        Assert.Equal(expected, converter.CanConvertFrom(null, sourceType));
+        Assert.Equal(expected, converter.CanConvertFrom(new CustomTypeDescriptorContext(), sourceType));
+    }
+
+    public static IEnumerable<object[]> ConvertFrom_TestData()
+    {
+        yield return new object[] { "", Key.None };
+        yield return new object[] { "  ", Key.None };
+        yield return new object[] { "0", Key.D0 };
+        yield return new object[] { " 0 ", Key.D0 };
+        yield return new object[] { "1", Key.D1 };
+        yield return new object[] { "2", Key.D2 };
+        yield return new object[] { "3", Key.D3 };
+        yield return new object[] { "4", Key.D4 };
+        yield return new object[] { "5", Key.D5 };
+        yield return new object[] { "6", Key.D6 };
+        yield return new object[] { "7", Key.D7 };
+        yield return new object[] { "8", Key.D8 };
+        yield return new object[] { "9", Key.D9 };
+        yield return new object[] { "A", Key.A };
+        yield return new object[] { "B", Key.B };
+        yield return new object[] { "C", Key.C };
+        yield return new object[] { "D", Key.D };
+        yield return new object[] { "E", Key.E };
+        yield return new object[] { "F", Key.F };
+        yield return new object[] { "G", Key.G };
+        yield return new object[] { "H", Key.H };
+        yield return new object[] { "I", Key.I };
+        yield return new object[] { "J", Key.J };
+        yield return new object[] { "K", Key.K };
+        yield return new object[] { "L", Key.L };
+        yield return new object[] { "M", Key.M };
+        yield return new object[] { "N", Key.N };
+        yield return new object[] { "O", Key.O };
+        yield return new object[] { "P", Key.P };
+        yield return new object[] { "Q", Key.Q };
+        yield return new object[] { "R", Key.R };
+        yield return new object[] { "S", Key.S };
+        yield return new object[] { "T", Key.T };
+        yield return new object[] { "U", Key.U };
+        yield return new object[] { "V", Key.V };
+        yield return new object[] { "W", Key.W };
+        yield return new object[] { "X", Key.X };
+        yield return new object[] { "Y", Key.Y };
+        yield return new object[] { "Z", Key.Z };
+        yield return new object[] { "a", Key.A };
+        yield return new object[] { "b", Key.B };
+        yield return new object[] { "c", Key.C };
+        yield return new object[] { "d", Key.D };
+        yield return new object[] { "e", Key.E };
+        yield return new object[] { "f", Key.F };
+        yield return new object[] { "g", Key.G };
+        yield return new object[] { "h", Key.H };
+        yield return new object[] { "i", Key.I };
+        yield return new object[] { "j", Key.J };
+        yield return new object[] { "k", Key.K };
+        yield return new object[] { "l", Key.L };
+        yield return new object[] { "m", Key.M };
+        yield return new object[] { "n", Key.N };
+        yield return new object[] { "o", Key.O };
+        yield return new object[] { "p", Key.P };
+        yield return new object[] { "q", Key.Q };
+        yield return new object[] { "r", Key.R };
+        yield return new object[] { "s", Key.S };
+        yield return new object[] { "t", Key.T };
+        yield return new object[] { "u", Key.U };
+        yield return new object[] { "v", Key.V };
+        yield return new object[] { "w", Key.W };
+        yield return new object[] { "x", Key.X };
+        yield return new object[] { "y", Key.Y };
+        yield return new object[] { "z", Key.Z };
+        yield return new object[] { "ENTER", Key.Return };
+        yield return new object[] { " ENTER ", Key.Return };
+        yield return new object[] { " eNtEr ", Key.Return };
+        yield return new object[] { "ESC", Key.Escape };
+        yield return new object[] { "PGUP", Key.PageUp };
+        yield return new object[] { "PGDN", Key.PageDown };
+        yield return new object[] { "PRTSC", Key.PrintScreen };
+        yield return new object[] { "INS", Key.Insert };
+        yield return new object[] { "DEL", Key.Delete };
+        yield return new object[] { "WINDOWS", Key.LWin };
+        yield return new object[] { "WIN", Key.LWin };
+        yield return new object[] { "LEFTWINDOWS", Key.LWin };
+        yield return new object[] { "RIGHTWINDOWS", Key.RWin };
+        yield return new object[] { "APPS", Key.Apps };
+        yield return new object[] { "APPLICATION", Key.Apps };
+        yield return new object[] { "BREAK", Key.Cancel };
+        yield return new object[] { "BACKSPACE", Key.Back };
+        yield return new object[] { "BKSP", Key.Back };
+        yield return new object[] { "BS", Key.Back };
+        yield return new object[] { "SHIFT", Key.LeftShift };
+        yield return new object[] { "LEFTSHIFT", Key.LeftShift };
+        yield return new object[] { "RIGHTSHIFT", Key.RightShift };
+        yield return new object[] { "CONTROL", Key.LeftCtrl };
+        yield return new object[] { "CTRL", Key.LeftCtrl };
+        yield return new object[] { "LEFTCTRL", Key.LeftCtrl };
+        yield return new object[] { "RIGHTCTRL", Key.RightCtrl };
+        yield return new object[] { "ALT", Key.LeftAlt };
+        yield return new object[] { "LEFTALT", Key.LeftAlt };
+        yield return new object[] { "RIGHTALT", Key.RightAlt };
+        yield return new object[] { "SEMICOLON", Key.OemSemicolon };
+        yield return new object[] { "PLUS", Key.OemPlus };
+        yield return new object[] { "COMMA", Key.OemComma };
+        yield return new object[] { "MINUS", Key.OemMinus };
+        yield return new object[] { "PERIOD", Key.OemPeriod };
+        yield return new object[] { "QUESTION", Key.OemQuestion };
+        yield return new object[] { "TILDE", Key.OemTilde };
+        yield return new object[] { "OPENBRACKETS", Key.OemOpenBrackets };
+        yield return new object[] { "PIPE", Key.OemPipe };
+        yield return new object[] { "CLOSEBRACKETS", Key.OemCloseBrackets };
+        yield return new object[] { "QUOTES", Key.OemQuotes };
+        yield return new object[] { "BACKSLASH", Key.OemBackslash };
+        yield return new object[] { "FINISH", Key.OemFinish };
+        yield return new object[] { "ATTN", Key.Attn };
+        yield return new object[] { "CRSEL", Key.CrSel };
+        yield return new object[] { "EXSEL", Key.ExSel };
+        yield return new object[] { "ERASEEOF", Key.EraseEof };
+        yield return new object[] { "PLAY", Key.Play };
+        yield return new object[] { "ZOOM", Key.Zoom };
+        yield return new object[] { "PA1", Key.Pa1 };
+        
+        yield return new object[] { "Cancel", Key.Cancel };
+        yield return new object[] { "CANCEL", Key.Cancel };
+        yield return new object[] { " CANCEL ", Key.Cancel };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertFrom_TestData))]
+    public void ConvertFrom_InvokeStringValue_ReturnsExpected(string value, Key expected)
+    {
+        var converter = new KeyConverter();
+        Assert.Equal(expected, converter.ConvertFrom(value));
+        Assert.Equal(expected, converter.ConvertFrom(null, null, value));
+        Assert.Equal(expected, converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    [Fact]
+    public void ConvertFrom_NullValue_ThrowsNotSupportedException()
+    {
+        var converter = new KeyConverter();
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(null!));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(null, null, null));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, null));
+    }
+
+    public static IEnumerable<object[]> ConvertFrom_InvalidValue_TestData()
+    {
+        yield return new object[] { "_" };
+        yield return new object[] { " _ " };
+        yield return new object[] { "\u0663" };
+        yield return new object[] { " \u0663 " };
+        yield return new object[] { "\u0409" };
+        yield return new object[] { " \u0409 " };
+        yield return new object[] { "NOSUCHKEY" };
+        yield return new object[] { " NOSUCHKEY " };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertFrom_InvalidValue_TestData))]
+    public void ConvertFrom_InvokeInvalidValue_ThrowsArgumentException(string value)
+    {
+        var converter = new KeyConverter();
+        // TODO: add paramName.
+        Assert.Throws<ArgumentException>(() => converter.ConvertFrom(value));
+        Assert.Throws<ArgumentException>(() => converter.ConvertFrom(null, null, value));
+        Assert.Throws<ArgumentException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+    
+    public static IEnumerable<object[]> ConvertFrom_CantConvert_TestData()
+    {
+        yield return new object[] { new object() };
+        yield return new object[] { Key.A };
+        yield return new object[] { ModifierKeys.None };
+    }
+    
+    [Theory]
+    [MemberData(nameof(ConvertFrom_CantConvert_TestData))]
+    public void ConvertFrom_CantConvert_ThrowsNotSupportedException(object value)
+    {
+        var converter = new KeyConverter();
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(value));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(null, null, value));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    private class CustomTypeDescriptorContext : ITypeDescriptorContext
+    {
+        public IContainer Container => throw new NotImplementedException();
+
+        private object? _instance;
+
+        public object Instance
+        {
+            get => _instance!;
+            set => _instance = value;
+        }
+
+        public PropertyDescriptor PropertyDescriptor => throw new NotImplementedException();
+
+        public object? GetService(Type serviceType) => throw new NotImplementedException();
+
+        public void OnComponentChanged() => throw new NotImplementedException();
+
+        public bool OnComponentChanging() => throw new NotImplementedException();
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Input/KeyInteropTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Input/KeyInteropTests.cs
new file mode 100644
index 00000000000..929cbf5dcbf
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Input/KeyInteropTests.cs
@@ -0,0 +1,688 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Windows.Input.Tests;
+
+public class KeyInteropTests
+{
+    [Theory]
+    [InlineData(VK_LBUTTON, Key.None)]
+    [InlineData(VK_RBUTTON, Key.None)]
+    [InlineData(VK_CANCEL, Key.Cancel)]
+    [InlineData(VK_MBUTTON, Key.None)]
+    [InlineData(VK_XBUTTON1, Key.None)]
+    [InlineData(VK_XBUTTON2, Key.None)]
+    [InlineData(0x07, Key.None)]
+    [InlineData(VK_BACK, Key.Back)]
+    [InlineData(VK_TAB, Key.Tab)]
+    [InlineData(0x0A, Key.None)]
+    [InlineData(0x0B, Key.None)]
+    [InlineData(VK_CLEAR, Key.Clear)]
+    [InlineData(VK_RETURN, Key.Return)]
+    [InlineData(0x0E, Key.None)]
+    [InlineData(0x0F, Key.None)]
+    [InlineData(VK_SHIFT, Key.LeftShift)]
+    [InlineData(VK_CONTROL, Key.LeftCtrl)]
+    [InlineData(VK_MENU, Key.LeftAlt)]
+    [InlineData(VK_PAUSE, Key.Pause)]
+    [InlineData(VK_CAPITAL, Key.Capital)]
+    [InlineData(VK_KANA, Key.KanaMode)]
+    [InlineData(0x16, Key.None)]
+    [InlineData(VK_JUNJA, Key.JunjaMode)]
+    [InlineData(VK_FINAL, Key.FinalMode)]
+    [InlineData(VK_KANJI, Key.KanjiMode)]
+    [InlineData(0x1A, Key.None)]
+    [InlineData(VK_ESCAPE, Key.Escape)]
+    [InlineData(VK_CONVERT, Key.ImeConvert)]
+    [InlineData(VK_NONCONVERT, Key.ImeNonConvert)]
+    [InlineData(VK_ACCEPT, Key.ImeAccept)]
+    [InlineData(VK_MODECHANGE, Key.ImeModeChange)]
+    [InlineData(VK_SPACE, Key.Space)]
+    [InlineData(VK_PRIOR, Key.Prior)]
+    [InlineData(VK_NEXT, Key.Next)]
+    [InlineData(VK_END, Key.End)]
+    [InlineData(VK_HOME, Key.Home)]
+    [InlineData(VK_LEFT, Key.Left)]
+    [InlineData(VK_UP, Key.Up)]
+    [InlineData(VK_RIGHT, Key.Right)]
+    [InlineData(VK_DOWN, Key.Down)]
+    [InlineData(VK_SELECT, Key.Select)]
+    [InlineData(VK_PRINT, Key.Print)]
+    [InlineData(VK_EXECUTE, Key.Execute)]
+    [InlineData(VK_SNAPSHOT, Key.Snapshot)]
+    [InlineData(VK_INSERT, Key.Insert)]
+    [InlineData(VK_DELETE, Key.Delete)]
+    [InlineData(VK_HELP, Key.Help)]
+    [InlineData(VK_0, Key.D0)]
+    [InlineData(VK_1, Key.D1)]
+    [InlineData(VK_2, Key.D2)]
+    [InlineData(VK_3, Key.D3)]
+    [InlineData(VK_4, Key.D4)]
+    [InlineData(VK_5, Key.D5)]
+    [InlineData(VK_6, Key.D6)]
+    [InlineData(VK_7, Key.D7)]
+    [InlineData(VK_8, Key.D8)]
+    [InlineData(VK_9, Key.D9)]
+    [InlineData(0x3A, Key.None)]
+    [InlineData(0x3B, Key.None)]
+    [InlineData(0x3C, Key.None)]
+    [InlineData(0x3D, Key.None)]
+    [InlineData(0x3E, Key.None)]
+    [InlineData(0x3F, Key.None)]
+    [InlineData(VK_A, Key.A)]
+    [InlineData(VK_B, Key.B)]
+    [InlineData(VK_C, Key.C)]
+    [InlineData(VK_D, Key.D)]
+    [InlineData(VK_E, Key.E)]
+    [InlineData(VK_F, Key.F)]
+    [InlineData(VK_G, Key.G)]
+    [InlineData(VK_H, Key.H)]
+    [InlineData(VK_I, Key.I)]
+    [InlineData(VK_J, Key.J)]
+    [InlineData(VK_K, Key.K)]
+    [InlineData(VK_L, Key.L)]
+    [InlineData(VK_M, Key.M)]
+    [InlineData(VK_N, Key.N)]
+    [InlineData(VK_O, Key.O)]
+    [InlineData(VK_P, Key.P)]
+    [InlineData(VK_Q, Key.Q)]
+    [InlineData(VK_R, Key.R)]
+    [InlineData(VK_S, Key.S)]
+    [InlineData(VK_T, Key.T)]
+    [InlineData(VK_U, Key.U)]
+    [InlineData(VK_V, Key.V)]
+    [InlineData(VK_W, Key.W)]
+    [InlineData(VK_X, Key.X)]
+    [InlineData(VK_Y, Key.Y)]
+    [InlineData(VK_Z, Key.Z)]
+    [InlineData(VK_LWIN, Key.LWin)]
+    [InlineData(VK_RWIN, Key.RWin)]
+    [InlineData(VK_APPS, Key.Apps)]
+    [InlineData(0x5E, Key.None)]
+    [InlineData(VK_SLEEP, Key.Sleep)]
+    [InlineData(VK_NUMPAD0, Key.NumPad0)]
+    [InlineData(VK_NUMPAD1, Key.NumPad1)]
+    [InlineData(VK_NUMPAD2, Key.NumPad2)]
+    [InlineData(VK_NUMPAD3, Key.NumPad3)]
+    [InlineData(VK_NUMPAD4, Key.NumPad4)]
+    [InlineData(VK_NUMPAD5, Key.NumPad5)]
+    [InlineData(VK_NUMPAD6, Key.NumPad6)]
+    [InlineData(VK_NUMPAD7, Key.NumPad7)]
+    [InlineData(VK_NUMPAD8, Key.NumPad8)]
+    [InlineData(VK_NUMPAD9, Key.NumPad9)]
+    [InlineData(VK_MULTIPLY, Key.Multiply)]
+    [InlineData(VK_ADD, Key.Add)]
+    [InlineData(VK_SEPARATOR, Key.Separator)]
+    [InlineData(VK_SUBTRACT, Key.Subtract)]
+    [InlineData(VK_DECIMAL, Key.Decimal)]
+    [InlineData(VK_DIVIDE, Key.Divide)]
+    [InlineData(VK_F1, Key.F1)]
+    [InlineData(VK_F2, Key.F2)]
+    [InlineData(VK_F3, Key.F3)]
+    [InlineData(VK_F4, Key.F4)]
+    [InlineData(VK_F5, Key.F5)]
+    [InlineData(VK_F6, Key.F6)]
+    [InlineData(VK_F7, Key.F7)]
+    [InlineData(VK_F8, Key.F8)]
+    [InlineData(VK_F9, Key.F9)]
+    [InlineData(VK_F10, Key.F10)]
+    [InlineData(VK_F11, Key.F11)]
+    [InlineData(VK_F12, Key.F12)]
+    [InlineData(VK_F13, Key.F13)]
+    [InlineData(VK_F14, Key.F14)]
+    [InlineData(VK_F15, Key.F15)]
+    [InlineData(VK_F16, Key.F16)]
+    [InlineData(VK_F17, Key.F17)]
+    [InlineData(VK_F18, Key.F18)]
+    [InlineData(VK_F19, Key.F19)]
+    [InlineData(VK_F20, Key.F20)]
+    [InlineData(VK_F21, Key.F21)]
+    [InlineData(VK_F22, Key.F22)]
+    [InlineData(VK_F23, Key.F23)]
+    [InlineData(VK_F24, Key.F24)]
+    [InlineData(VK_NUMLOCK, Key.NumLock)]
+    [InlineData(VK_SCROLL, Key.Scroll)]
+    [InlineData(VK_OEM_NEC_EQUAL, Key.None)]
+    //[InlineData(VK_OEM_FJ_JISHO, Key.None)]
+    [InlineData(VK_OEM_FJ_MASSHOU, Key.None)]
+    [InlineData(VK_OEM_FJ_TOUROKU, Key.None)]
+    [InlineData(VK_OEM_FJ_LOYA, Key.None)]
+    [InlineData(VK_OEM_FJ_ROYA, Key.None)]
+    [InlineData(VK_LSHIFT, Key.LeftShift)]
+    [InlineData(VK_RSHIFT, Key.RightShift)]
+    [InlineData(VK_LCONTROL, Key.LeftCtrl)]
+    [InlineData(VK_RCONTROL, Key.RightCtrl)]
+    [InlineData(VK_LMENU, Key.LeftAlt)]
+    [InlineData(VK_RMENU, Key.RightAlt)]
+    [InlineData(VK_BROWSER_BACK, Key.BrowserBack)]
+    [InlineData(VK_BROWSER_FORWARD, Key.BrowserForward)]
+    [InlineData(VK_BROWSER_REFRESH, Key.BrowserRefresh)]
+    [InlineData(VK_BROWSER_STOP, Key.BrowserStop)]
+    [InlineData(VK_BROWSER_SEARCH, Key.BrowserSearch)]
+    [InlineData(VK_BROWSER_FAVORITES, Key.BrowserFavorites)]
+    [InlineData(VK_BROWSER_HOME, Key.BrowserHome)]
+    [InlineData(VK_VOLUME_MUTE, Key.VolumeMute)]
+    [InlineData(VK_VOLUME_DOWN, Key.VolumeDown)]
+    [InlineData(VK_VOLUME_UP, Key.VolumeUp)]
+    [InlineData(VK_MEDIA_NEXT_TRACK, Key.MediaNextTrack)]
+    [InlineData(VK_MEDIA_PREV_TRACK, Key.MediaPreviousTrack)]
+    [InlineData(VK_MEDIA_STOP, Key.MediaStop)]
+    [InlineData(VK_MEDIA_PLAY_PAUSE, Key.MediaPlayPause)]
+    [InlineData(VK_LAUNCH_MAIL, Key.LaunchMail)]
+    [InlineData(VK_LAUNCH_MEDIA_SELECT, Key.SelectMedia)]
+    [InlineData(VK_LAUNCH_APP1, Key.LaunchApplication1)]
+    [InlineData(VK_LAUNCH_APP2, Key.LaunchApplication2)]
+    [InlineData(0xB8, Key.None)]
+    [InlineData(0xB9, Key.None)]
+    [InlineData(VK_OEM_1, Key.OemSemicolon)]
+    [InlineData(VK_OEM_PLUS, Key.OemPlus)]
+    [InlineData(VK_OEM_COMMA, Key.OemComma)]
+    [InlineData(VK_OEM_MINUS, Key.OemMinus)]
+    [InlineData(VK_OEM_PERIOD, Key.OemPeriod)]
+    [InlineData(VK_OEM_2, Key.OemQuestion)]
+    [InlineData(VK_OEM_3, Key.OemTilde)]
+    [InlineData(VK_C1, Key.AbntC1)]
+    [InlineData(VK_C2, Key.AbntC2)]
+    [InlineData(VK_GAMEPAD_A, Key.None)]
+    [InlineData(VK_GAMEPAD_B, Key.None)]
+    [InlineData(VK_GAMEPAD_X, Key.None)]
+    [InlineData(VK_GAMEPAD_Y, Key.None)]
+    [InlineData(VK_GAMEPAD_RIGHT_SHOULDER, Key.None)]
+    [InlineData(VK_GAMEPAD_LEFT_SHOULDER, Key.None)]
+    [InlineData(VK_GAMEPAD_LEFT_TRIGGER, Key.None)]
+    [InlineData(VK_GAMEPAD_RIGHT_TRIGGER, Key.None)]
+    [InlineData(VK_GAMEPAD_DPAD_UP, Key.None)]
+    [InlineData(VK_GAMEPAD_DPAD_DOWN, Key.None)]
+    [InlineData(VK_GAMEPAD_DPAD_LEFT, Key.None)]
+    [InlineData(VK_GAMEPAD_DPAD_RIGHT, Key.None)]
+    [InlineData(VK_GAMEPAD_MENU, Key.None)]
+    [InlineData(VK_GAMEPAD_VIEW, Key.None)]
+    [InlineData(VK_GAMEPAD_LEFT_THUMBSTICK_BUTTON, Key.None)]
+    [InlineData(VK_GAMEPAD_RIGHT_THUMBSTICK_BUTTON, Key.None)]
+    [InlineData(VK_GAMEPAD_LEFT_THUMBSTICK_UP, Key.None)]
+    [InlineData(VK_GAMEPAD_LEFT_THUMBSTICK_DOWN, Key.None)]
+    [InlineData(VK_GAMEPAD_LEFT_THUMBSTICK_RIGHT, Key.None)]
+    [InlineData(VK_GAMEPAD_LEFT_THUMBSTICK_LEFT, Key.None)]
+    [InlineData(VK_GAMEPAD_RIGHT_THUMBSTICK_UP, Key.None)]
+    [InlineData(VK_GAMEPAD_RIGHT_THUMBSTICK_DOWN, Key.None)]
+    [InlineData(VK_GAMEPAD_RIGHT_THUMBSTICK_RIGHT, Key.None)]
+    [InlineData(VK_GAMEPAD_RIGHT_THUMBSTICK_LEFT, Key.None)]
+    [InlineData(VK_OEM_4, Key.OemOpenBrackets)]
+    [InlineData(VK_OEM_5, Key.OemPipe)]
+    [InlineData(VK_OEM_6, Key.OemCloseBrackets)]
+    [InlineData(VK_OEM_7, Key.OemQuotes)]
+    [InlineData(VK_OEM_8, Key.Oem8)]
+    [InlineData(0xE0, Key.None)]
+    [InlineData(VK_OEM_AX, Key.None)]
+    [InlineData(VK_OEM_102, Key.OemBackslash)]
+    [InlineData(VK_ICO_HELP, Key.None)]
+    [InlineData(VK_ICO_00, Key.None)]
+    [InlineData(VK_PROCESSKEY, Key.ImeProcessed)]
+    [InlineData(VK_ICO_CLEAR, Key.None)]
+    [InlineData(VK_PACKET, Key.None)]
+    [InlineData(0xE8, Key.None)]
+    [InlineData(VK_OEM_RESET, Key.None)]
+    [InlineData(VK_OEM_JUMP, Key.None)]
+    [InlineData(VK_OEM_PA1, Key.None)]
+    [InlineData(VK_OEM_PA2, Key.None)]
+    [InlineData(VK_OEM_PA3, Key.None)]
+    [InlineData(VK_OEM_WSCTRL, Key.None)]
+    [InlineData(VK_OEM_CUSEL, Key.None)]
+    [InlineData(VK_OEM_ATTN, Key.OemAttn)]
+    [InlineData(VK_OEM_FINISH, Key.OemFinish)]
+    [InlineData(VK_OEM_COPY, Key.OemCopy)]
+    [InlineData(VK_OEM_AUTO, Key.OemAuto)]
+    [InlineData(VK_OEM_ENLW, Key.OemEnlw)]
+    [InlineData(VK_OEM_BACKTAB, Key.OemBackTab)]
+    [InlineData(VK_ATTN, Key.Attn)]
+    [InlineData(VK_CRSEL, Key.CrSel)]
+    [InlineData(VK_EXSEL, Key.ExSel)]
+    [InlineData(VK_EREOF, Key.EraseEof)]
+    [InlineData(VK_PLAY, Key.Play)]
+    [InlineData(VK_ZOOM, Key.Zoom)]
+    [InlineData(VK_NONAME, Key.NoName)]
+    [InlineData(VK_PA1, Key.Pa1)]
+    [InlineData(VK_OEM_CLEAR, Key.OemClear)]
+    [InlineData(0xFF, Key.None)]
+    [InlineData(0x100, Key.None)]
+    [InlineData(int.MinValue, Key.None)]
+    [InlineData(-1, Key.None)]
+    [InlineData(int.MaxValue, Key.None)]
+    public void KeyFromVirtualKey_Invoke_ReturnsExpected(int virtualKey, Key expected)
+    {
+        Assert.Equal(expected, KeyInterop.KeyFromVirtualKey(virtualKey));
+    }
+
+    [Theory]
+    [InlineData(Key.None, 0)]
+    [InlineData(Key.Cancel, VK_CANCEL)]
+    [InlineData(Key.Back, VK_BACK)]
+    [InlineData(Key.Tab, VK_TAB)]
+    [InlineData(Key.Clear, VK_CLEAR)]
+    [InlineData(Key.Return, VK_RETURN)]
+    //[InlineData(Key.Enter, VK_RETURN)]
+    [InlineData(Key.Pause, VK_PAUSE)]
+    [InlineData(Key.Capital, VK_CAPITAL)]
+    //[InlineData(Key.CapsLock, VK_CAPITAL)]
+    [InlineData(Key.KanaMode, VK_KANA)]
+    //[InlineData(Key.HangulMode, VK_KANA)]
+    [InlineData(Key.JunjaMode, VK_JUNJA)]
+    [InlineData(Key.FinalMode, VK_FINAL)]
+    [InlineData(Key.HanjaMode, VK_KANJI)]
+    //[InlineData(Key.KanjiMode, VK_KANJI)]
+    [InlineData(Key.Escape, VK_ESCAPE)]
+    [InlineData(Key.ImeConvert, VK_CONVERT)]
+    [InlineData(Key.ImeNonConvert, VK_NONCONVERT)]
+    [InlineData(Key.ImeAccept, VK_ACCEPT)]
+    [InlineData(Key.ImeModeChange, VK_MODECHANGE)]
+    [InlineData(Key.Space, VK_SPACE)]
+    [InlineData(Key.Prior, VK_PRIOR)]
+    [InlineData(Key.Next, VK_NEXT)]
+    //[InlineData(Key.PageDown, VK_NEXT)]
+    [InlineData(Key.End, VK_END)]
+    [InlineData(Key.Home, VK_HOME)]
+    [InlineData(Key.Left, VK_LEFT)]
+    [InlineData(Key.Up, VK_UP)]
+    [InlineData(Key.Right, VK_RIGHT)]
+    [InlineData(Key.Down, VK_DOWN)]
+    [InlineData(Key.Select, VK_SELECT)]
+    [InlineData(Key.Print, VK_PRINT)]
+    [InlineData(Key.Execute, VK_EXECUTE)]
+    [InlineData(Key.Snapshot, VK_SNAPSHOT)]
+    //[InlineData(Key.PrintScreen, VK_SNAPSHOT)]
+    [InlineData(Key.Insert, VK_INSERT)]
+    [InlineData(Key.Delete, VK_DELETE)]
+    [InlineData(Key.Help, VK_HELP)]
+    [InlineData(Key.D0, VK_0)]
+    [InlineData(Key.D1, VK_1)]
+    [InlineData(Key.D2, VK_2)]
+    [InlineData(Key.D3, VK_3)]
+    [InlineData(Key.D4, VK_4)]
+    [InlineData(Key.D5, VK_5)]
+    [InlineData(Key.D6, VK_6)]
+    [InlineData(Key.D7, VK_7)]
+    [InlineData(Key.D8, VK_8)]
+    [InlineData(Key.D9, VK_9)]
+    [InlineData(Key.A, VK_A)]
+    [InlineData(Key.B, VK_B)]
+    [InlineData(Key.C, VK_C)]
+    [InlineData(Key.D, VK_D)]
+    [InlineData(Key.E, VK_E)]
+    [InlineData(Key.F, VK_F)]
+    [InlineData(Key.G, VK_G)]
+    [InlineData(Key.H, VK_H)]
+    [InlineData(Key.I, VK_I)]
+    [InlineData(Key.J, VK_J)]
+    [InlineData(Key.K, VK_K)]
+    [InlineData(Key.L, VK_L)]
+    [InlineData(Key.M, VK_M)]
+    [InlineData(Key.N, VK_N)]
+    [InlineData(Key.O, VK_O)]
+    [InlineData(Key.P, VK_P)]
+    [InlineData(Key.Q, VK_Q)]
+    [InlineData(Key.R, VK_R)]
+    [InlineData(Key.S, VK_S)]
+    [InlineData(Key.T, VK_T)]
+    [InlineData(Key.U, VK_U)]
+    [InlineData(Key.V, VK_V)]
+    [InlineData(Key.W, VK_W)]
+    [InlineData(Key.X, VK_X)]
+    [InlineData(Key.Y, VK_Y)]
+    [InlineData(Key.Z, VK_Z)]
+    [InlineData(Key.LWin, VK_LWIN)]
+    [InlineData(Key.RWin, VK_RWIN)]
+    [InlineData(Key.Apps, VK_APPS)]
+    [InlineData(Key.Sleep, VK_SLEEP)]
+    [InlineData(Key.NumPad0, VK_NUMPAD0)]
+    [InlineData(Key.NumPad1, VK_NUMPAD1)]
+    [InlineData(Key.NumPad2, VK_NUMPAD2)]
+    [InlineData(Key.NumPad3, VK_NUMPAD3)]
+    [InlineData(Key.NumPad4, VK_NUMPAD4)]
+    [InlineData(Key.NumPad5, VK_NUMPAD5)]
+    [InlineData(Key.NumPad6, VK_NUMPAD6)]
+    [InlineData(Key.NumPad7, VK_NUMPAD7)]
+    [InlineData(Key.NumPad8, VK_NUMPAD8)]
+    [InlineData(Key.NumPad9, VK_NUMPAD9)]
+    [InlineData(Key.Multiply, VK_MULTIPLY)]
+    [InlineData(Key.Add, VK_ADD)]
+    [InlineData(Key.Separator, VK_SEPARATOR)]
+    [InlineData(Key.Subtract, VK_SUBTRACT)]
+    [InlineData(Key.Decimal, VK_DECIMAL)]
+    [InlineData(Key.Divide, VK_DIVIDE)]
+    [InlineData(Key.F1, VK_F1)]
+    [InlineData(Key.F2, VK_F2)]
+    [InlineData(Key.F3, VK_F3)]
+    [InlineData(Key.F4, VK_F4)]
+    [InlineData(Key.F5, VK_F5)]
+    [InlineData(Key.F6, VK_F6)]
+    [InlineData(Key.F7, VK_F7)]
+    [InlineData(Key.F8, VK_F8)]
+    [InlineData(Key.F9, VK_F9)]
+    [InlineData(Key.F10, VK_F10)]
+    [InlineData(Key.F11, VK_F11)]
+    [InlineData(Key.F12, VK_F12)]
+    [InlineData(Key.F13, VK_F13)]
+    [InlineData(Key.F14, VK_F14)]
+    [InlineData(Key.F15, VK_F15)]
+    [InlineData(Key.F16, VK_F16)]
+    [InlineData(Key.F17, VK_F17)]
+    [InlineData(Key.F18, VK_F18)]
+    [InlineData(Key.F19, VK_F19)]
+    [InlineData(Key.F20, VK_F20)]
+    [InlineData(Key.F21, VK_F21)]
+    [InlineData(Key.F22, VK_F22)]
+    [InlineData(Key.F23, VK_F23)]
+    [InlineData(Key.F24, VK_F24)]
+    [InlineData(Key.NumLock, VK_NUMLOCK)]
+    [InlineData(Key.Scroll, VK_SCROLL)]
+    [InlineData(Key.LeftShift, VK_LSHIFT)]
+    [InlineData(Key.RightShift, VK_RSHIFT)]
+    [InlineData(Key.LeftCtrl, VK_LCONTROL)]
+    [InlineData(Key.RightCtrl, VK_RCONTROL)]
+    [InlineData(Key.LeftAlt, VK_LMENU)]
+    [InlineData(Key.RightAlt, VK_RMENU)]
+    [InlineData(Key.BrowserBack, VK_BROWSER_BACK)]
+    [InlineData(Key.BrowserForward, VK_BROWSER_FORWARD)]
+    [InlineData(Key.BrowserRefresh, VK_BROWSER_REFRESH)]
+    [InlineData(Key.BrowserStop, VK_BROWSER_STOP)]
+    [InlineData(Key.BrowserSearch, VK_BROWSER_SEARCH)]
+    [InlineData(Key.BrowserFavorites, VK_BROWSER_FAVORITES)]
+    [InlineData(Key.BrowserHome, VK_BROWSER_HOME)]
+    [InlineData(Key.VolumeMute, VK_VOLUME_MUTE)]
+    [InlineData(Key.VolumeDown, VK_VOLUME_DOWN)]
+    [InlineData(Key.VolumeUp, VK_VOLUME_UP)]
+    [InlineData(Key.MediaNextTrack, VK_MEDIA_NEXT_TRACK)]
+    [InlineData(Key.MediaPreviousTrack, VK_MEDIA_PREV_TRACK)]
+    [InlineData(Key.MediaStop, VK_MEDIA_STOP)]
+    [InlineData(Key.MediaPlayPause, VK_MEDIA_PLAY_PAUSE)]
+    [InlineData(Key.LaunchMail, VK_LAUNCH_MAIL)]
+    [InlineData(Key.SelectMedia, VK_LAUNCH_MEDIA_SELECT)]
+    [InlineData(Key.LaunchApplication1, VK_LAUNCH_APP1)]
+    [InlineData(Key.LaunchApplication2, VK_LAUNCH_APP2)]
+    [InlineData(Key.OemSemicolon, VK_OEM_1)]
+    [InlineData(Key.OemPlus, VK_OEM_PLUS)]
+    [InlineData(Key.OemComma, VK_OEM_COMMA)]
+    [InlineData(Key.OemMinus, VK_OEM_MINUS)]
+    [InlineData(Key.OemPeriod, VK_OEM_PERIOD)]
+    [InlineData(Key.Oem2, VK_OEM_2)]
+    //[InlineData(Key.OemQuestion, VK_OEM_2)]
+    [InlineData(Key.Oem3, VK_OEM_3)]
+    //[InlineData(Key.OemTilde, VK_OEM_3)]
+    [InlineData(Key.AbntC1, VK_C1)]
+    [InlineData(Key.AbntC2, VK_C2)]
+    [InlineData(Key.Oem4, VK_OEM_4)]
+    //[InlineData(Key.OemOpenBrackets, VK_OEM_4)]
+    //[InlineData(Key.Oem5, VK_OEM_5)]
+    [InlineData(Key.OemPipe, VK_OEM_5)]
+    [InlineData(Key.Oem6, VK_OEM_6)]
+    //[InlineData(Key.OemCloseBrackets, VK_OEM_6)]
+    [InlineData(Key.Oem7, VK_OEM_7)]
+    //[InlineData(Key.OemQuotes, VK_OEM_7)]
+    [InlineData(Key.Oem8, VK_OEM_8)]
+    [InlineData(Key.Oem102, VK_OEM_102)]
+    //[InlineData(Key.OemBackslash, VK_OEM_102)]
+    [InlineData(Key.ImeProcessed, VK_PROCESSKEY)]
+    [InlineData(Key.OemAttn, VK_OEM_ATTN)]
+    //[InlineData(Key.DbeAlphanumeric, VK_OEM_ATTN)]
+    [InlineData(Key.OemFinish, VK_OEM_FINISH)]
+    //[InlineData(Key.DbeKatakana, VK_OEM_FINISH)]
+    [InlineData(Key.OemCopy, VK_OEM_COPY)]
+    //[InlineData(Key.DbeHiragana, VK_OEM_COPY)]
+    [InlineData(Key.OemAuto, VK_OEM_AUTO)]
+    //[InlineData(Key.DbeSbcsChar, VK_OEM_AUTO)]
+    [InlineData(Key.OemEnlw, VK_OEM_ENLW)]
+    //[InlineData(Key.DbeDbcsChar, VK_OEM_ENLW)]
+    [InlineData(Key.OemBackTab, VK_OEM_BACKTAB)]
+    //[InlineData(Key.DbeRoman, VK_OEM_BACKTAB)]
+    [InlineData(Key.Attn, VK_ATTN)]
+    //[InlineData(Key.DbeNoRoman, VK_ATTN)]
+    [InlineData(Key.CrSel, VK_CRSEL)]
+    //[InlineData(Key.DbeEnterWordRegisterMode, VK_CRSEL)]
+    [InlineData(Key.ExSel, VK_EXSEL)]
+    //[InlineData(Key.DbeEnterImeConfigureMode, VK_EXSEL)]
+    [InlineData(Key.EraseEof, VK_EREOF)]
+    //[InlineData(Key.DbeFlushString, VK_EREOF)]
+    [InlineData(Key.Play, VK_PLAY)]
+    //[InlineData(Key.DbeCodeInput, VK_PLAY)]
+    [InlineData(Key.Zoom, VK_ZOOM)]
+    //[InlineData(Key.DbeNoCodeInput, VK_ZOOM)]
+    [InlineData(Key.NoName, VK_NONAME)]
+    //[InlineData(Key.DbeDetermineString, VK_NONAME)]
+    [InlineData(Key.Pa1, VK_PA1)]
+    //[InlineData(Key.DbeEnterDialogConversionMode, VK_PA1)]
+    [InlineData(Key.OemClear, VK_OEM_CLEAR)]
+    [InlineData(Key.DeadCharProcessed, 0)]
+    [InlineData((Key)int.MinValue, 0)]
+    [InlineData((Key)(-1), 0)]
+    [InlineData(Key.DeadCharProcessed + 1, 0)]
+    [InlineData((Key)int.MaxValue, 0)]
+    public void VirtualKeyFromKey_Invoke_ReturnsExpected(Key key, int expected)
+    {
+        Assert.Equal(expected, KeyInterop.VirtualKeyFromKey(key));
+    }
+
+    private const int VK_LBUTTON = 0x01;
+    private const int VK_RBUTTON = 0x02;
+    private const int VK_CANCEL = 0x03;
+    private const int VK_MBUTTON = 0x04;
+    private const int VK_XBUTTON1 = 0x05;
+    private const int VK_XBUTTON2 = 0x06;
+    private const int VK_BACK = 0x08;
+    private const int VK_TAB = 0x09;
+    private const int VK_CLEAR = 0x0C;
+    private const int VK_RETURN = 0x0D;
+    private const int VK_SHIFT = 0x10;
+    private const int VK_CONTROL = 0x11;
+    private const int VK_MENU = 0x12;
+    private const int VK_PAUSE = 0x13;
+    private const int VK_CAPITAL = 0x14;
+    private const int VK_KANA = 0x15;
+    private const int VK_HANGEUL = 0x15;
+    private const int VK_HANGUL = 0x15;
+    private const int VK_JUNJA = 0x17;
+    private const int VK_FINAL = 0x18;
+    private const int VK_HANJA = 0x19;
+    private const int VK_KANJI = 0x19;
+    private const int VK_ESCAPE = 0x1B;
+    private const int VK_CONVERT = 0x1C;
+    private const int VK_NONCONVERT = 0x1D;
+    private const int VK_ACCEPT = 0x1E;
+    private const int VK_MODECHANGE = 0x1F;
+    private const int VK_SPACE = 0x20;
+    private const int VK_PRIOR = 0x21;
+    private const int VK_NEXT = 0x22;
+    private const int VK_END = 0x23;
+    private const int VK_HOME = 0x24;
+    private const int VK_LEFT = 0x25;
+    private const int VK_UP = 0x26;
+    private const int VK_RIGHT = 0x27;
+    private const int VK_DOWN = 0x28;
+    private const int VK_SELECT = 0x29;
+    private const int VK_PRINT = 0x2A;
+    private const int VK_EXECUTE = 0x2B;
+    private const int VK_SNAPSHOT = 0x2C;
+    private const int VK_INSERT = 0x2D;
+    private const int VK_DELETE = 0x2E;
+    private const int VK_HELP = 0x2F;
+    private const int VK_0 = 0x30;
+    private const int VK_1 = 0x31;
+    private const int VK_2 = 0x32;
+    private const int VK_3 = 0x33;
+    private const int VK_4 = 0x34;
+    private const int VK_5 = 0x35;
+    private const int VK_6 = 0x36;
+    private const int VK_7 = 0x37;
+    private const int VK_8 = 0x38;
+    private const int VK_9 = 0x39;
+    private const int VK_A = 0x41;
+    private const int VK_B = 0x42;
+    private const int VK_C = 0x43;
+    private const int VK_D = 0x44;
+    private const int VK_E = 0x45;
+    private const int VK_F = 0x46;
+    private const int VK_G = 0x47;
+    private const int VK_H = 0x48;
+    private const int VK_I = 0x49;
+    private const int VK_J = 0x4A;
+    private const int VK_K = 0x4B;
+    private const int VK_L = 0x4C;
+    private const int VK_M = 0x4D;
+    private const int VK_N = 0x4E;
+    private const int VK_O = 0x4F;
+    private const int VK_P = 0x50;
+    private const int VK_Q = 0x51;
+    private const int VK_R = 0x52;
+    private const int VK_S = 0x53;
+    private const int VK_T = 0x54;
+    private const int VK_U = 0x55;
+    private const int VK_V = 0x56;
+    private const int VK_W = 0x57;
+    private const int VK_X = 0x58;
+    private const int VK_Y = 0x59;
+    private const int VK_Z = 0x5A;
+    private const int VK_LWIN = 0x5B;
+    private const int VK_RWIN = 0x5C;
+    private const int VK_APPS = 0x5D;
+    private const int VK_POWER = 0x5E;
+    private const int VK_SLEEP = 0x5F;
+    private const int VK_NUMPAD0 = 0x60;
+    private const int VK_NUMPAD1 = 0x61;
+    private const int VK_NUMPAD2 = 0x62;
+    private const int VK_NUMPAD3 = 0x63;
+    private const int VK_NUMPAD4 = 0x64;
+    private const int VK_NUMPAD5 = 0x65;
+    private const int VK_NUMPAD6 = 0x66;
+    private const int VK_NUMPAD7 = 0x67;
+    private const int VK_NUMPAD8 = 0x68;
+    private const int VK_NUMPAD9 = 0x69;
+    private const int VK_MULTIPLY = 0x6A;
+    private const int VK_ADD = 0x6B;
+    private const int VK_SEPARATOR = 0x6C;
+    private const int VK_SUBTRACT = 0x6D;
+    private const int VK_DECIMAL = 0x6E;
+    private const int VK_DIVIDE = 0x6F;
+    private const int VK_F1 = 0x70;
+    private const int VK_F2 = 0x71;
+    private const int VK_F3 = 0x72;
+    private const int VK_F4 = 0x73;
+    private const int VK_F5 = 0x74;
+    private const int VK_F6 = 0x75;
+    private const int VK_F7 = 0x76;
+    private const int VK_F8 = 0x77;
+    private const int VK_F9 = 0x78;
+    private const int VK_F10 = 0x79;
+    private const int VK_F11 = 0x7A;
+    private const int VK_F12 = 0x7B;
+    private const int VK_F13 = 0x7C;
+    private const int VK_F14 = 0x7D;
+    private const int VK_F15 = 0x7E;
+    private const int VK_F16 = 0x7F;
+    private const int VK_F17 = 0x80;
+    private const int VK_F18 = 0x81;
+    private const int VK_F19 = 0x82;
+    private const int VK_F20 = 0x83;
+    private const int VK_F21 = 0x84;
+    private const int VK_F22 = 0x85;
+    private const int VK_F23 = 0x86;
+    private const int VK_F24 = 0x87;
+    private const int VK_NUMLOCK = 0x90;
+    private const int VK_SCROLL = 0x91;
+    private const int VK_OEM_NEC_EQUAL = 0x92;
+    private const int VK_OEM_FJ_JISHO = 0x92;
+    private const int VK_OEM_FJ_MASSHOU = 0x93;
+    private const int VK_OEM_FJ_TOUROKU = 0x94;
+    private const int VK_OEM_FJ_LOYA = 0x95;
+    private const int VK_OEM_FJ_ROYA = 0x96;
+    private const int VK_LSHIFT = 0xA0;
+    private const int VK_RSHIFT = 0xA1;
+    private const int VK_LCONTROL = 0xA2;
+    private const int VK_RCONTROL = 0xA3;
+    private const int VK_RMENU = 0xA5;
+    private const int VK_LMENU = 0xA4;
+    private const int VK_BROWSER_BACK = 0xA6;
+    private const int VK_BROWSER_FORWARD = 0xA7;
+    private const int VK_BROWSER_REFRESH = 0xA8;
+    private const int VK_BROWSER_STOP = 0xA9;
+    private const int VK_BROWSER_SEARCH = 0xAA;
+    private const int VK_BROWSER_FAVORITES = 0xAB;
+    private const int VK_BROWSER_HOME = 0xAC;
+    private const int VK_VOLUME_MUTE = 0xAD;
+    private const int VK_VOLUME_DOWN = 0xAE;
+    private const int VK_VOLUME_UP = 0xAF;
+    private const int VK_MEDIA_NEXT_TRACK = 0xB0;
+    private const int VK_MEDIA_PREV_TRACK = 0xB1;
+    private const int VK_MEDIA_STOP = 0xB2;
+    private const int VK_MEDIA_PLAY_PAUSE = 0xB3;
+    private const int VK_LAUNCH_MAIL = 0xB4;
+    private const int VK_LAUNCH_MEDIA_SELECT = 0xB5;
+    private const int VK_LAUNCH_APP1 = 0xB6;
+    private const int VK_LAUNCH_APP2 = 0xB7;
+    private const int VK_OEM_1 = 0xBA;
+    private const int VK_OEM_PLUS = 0xBB;
+    private const int VK_OEM_COMMA = 0xBC;
+    private const int VK_OEM_MINUS = 0xBD;
+    private const int VK_OEM_PERIOD = 0xBE;
+    private const int VK_OEM_2 = 0xBF;
+    private const int VK_OEM_3 = 0xC0;
+    private const int VK_C1 = 0xC1;   // Brazilian ABNT_C1 key (not defined in winuser.h).
+    private const int VK_C2 = 0xC2;   // Brazilian ABNT_C2 key (not defined in winuser.h).
+    private const int VK_GAMEPAD_A = 0xC3;
+    private const int VK_GAMEPAD_B = 0xC4;
+    private const int VK_GAMEPAD_X = 0xC5;
+    private const int VK_GAMEPAD_Y = 0xC6;
+    private const int VK_GAMEPAD_RIGHT_SHOULDER = 0xC7;
+    private const int VK_GAMEPAD_LEFT_SHOULDER = 0xC8;
+    private const int VK_GAMEPAD_LEFT_TRIGGER = 0xC9;
+    private const int VK_GAMEPAD_RIGHT_TRIGGER = 0xCA;
+    private const int VK_GAMEPAD_DPAD_UP = 0xCB;
+    private const int VK_GAMEPAD_DPAD_DOWN = 0xCC;
+    private const int VK_GAMEPAD_DPAD_LEFT = 0xCD;
+    private const int VK_GAMEPAD_DPAD_RIGHT = 0xCE;
+    private const int VK_GAMEPAD_MENU = 0xCF;
+    private const int VK_GAMEPAD_VIEW = 0xD0;
+    private const int VK_GAMEPAD_LEFT_THUMBSTICK_BUTTON = 0xD1;
+    private const int VK_GAMEPAD_RIGHT_THUMBSTICK_BUTTON = 0xD2;
+    private const int VK_GAMEPAD_LEFT_THUMBSTICK_UP = 0xD3;
+    private const int VK_GAMEPAD_LEFT_THUMBSTICK_DOWN = 0xD4;
+    private const int VK_GAMEPAD_LEFT_THUMBSTICK_RIGHT = 0xD5;
+    private const int VK_GAMEPAD_LEFT_THUMBSTICK_LEFT = 0xD6;
+    private const int VK_GAMEPAD_RIGHT_THUMBSTICK_UP = 0xD7;
+    private const int VK_GAMEPAD_RIGHT_THUMBSTICK_DOWN = 0xD8;
+    private const int VK_GAMEPAD_RIGHT_THUMBSTICK_RIGHT = 0xD9;
+    private const int VK_GAMEPAD_RIGHT_THUMBSTICK_LEFT = 0xDA;
+    private const int VK_OEM_4 = 0xDB;
+    private const int VK_OEM_5 = 0xDC;
+    private const int VK_OEM_6 = 0xDD;
+    private const int VK_OEM_7 = 0xDE;
+    private const int VK_OEM_8 = 0xDF;
+    private const int VK_OEM_AX = 0xE1;
+    private const int VK_OEM_102 = 0xE2;
+    private const int VK_ICO_HELP = 0xE3;
+    private const int VK_ICO_00= 0xE4;
+    private const int VK_PROCESSKEY = 0xE5;
+    private const int VK_ICO_CLEAR = 0xE6;
+    private const int VK_PACKET = 0xE7;
+    private const int VK_OEM_RESET = 0xE9;
+    private const int VK_OEM_JUMP = 0xEA;
+    private const int VK_OEM_PA1 = 0xEB;
+    private const int VK_OEM_PA2 = 0xEC;
+    private const int VK_OEM_PA3 = 0xED;
+    private const int VK_OEM_WSCTRL = 0xEE;
+    private const int VK_OEM_CUSEL = 0xEF;
+    private const int VK_OEM_ATTN = 0xF0;
+    private const int VK_OEM_FINISH = 0xF1;
+    private const int VK_OEM_COPY = 0xF2;
+    private const int VK_OEM_AUTO = 0xF3;
+    private const int VK_OEM_ENLW = 0xF4;
+    private const int VK_OEM_BACKTAB = 0xF5;
+    private const int VK_ATTN = 0xF6;
+    private const int VK_CRSEL = 0xF7;
+    private const int VK_EXSEL = 0xF8;
+    private const int VK_EREOF = 0xF9;
+    private const int VK_PLAY = 0xFA;
+    private const int VK_ZOOM = 0xFB;
+    private const int VK_NONAME = 0xFC;
+    private const int VK_PA1 = 0xFD;
+    private const int VK_OEM_CLEAR = 0xFE;
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Input/KeyTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Input/KeyTests.cs
new file mode 100644
index 00000000000..c876e777ecb
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Input/KeyTests.cs
@@ -0,0 +1,23 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.Windows.Markup;
+
+namespace System.Windows.Input.Tests;
+
+public class KeyTests
+{
+    [Fact]
+    public void TypeConverter_Get_ReturnsExpected()
+    {
+        Assert.IsType<KeyConverter>(TypeDescriptor.GetConverter(typeof(Key)));
+    }
+
+    [Fact]
+    public void ValueSerializer_Get_ReturnsExpected()
+    {
+        Assert.IsType<KeyValueSerializer>(ValueSerializer.GetSerializerFor(typeof(Key)));
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Input/KeyValueSerializerTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Input/KeyValueSerializerTests.cs
new file mode 100644
index 00000000000..d3a2ebdc484
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Input/KeyValueSerializerTests.cs
@@ -0,0 +1,144 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.Windows.Markup;
+
+namespace System.Windows.Input.Tests;
+
+public class KeyValueSerializerTests
+{
+    public static IEnumerable<object?[]> CanConvertToString_TestData()
+    {
+        yield return new object?[] { null, false };
+        yield return new object?[] { string.Empty, false };
+        yield return new object?[] { "value", false };
+        yield return new object?[] { new object(), false };
+        yield return new object?[] { ModifierKeys.None, false };
+
+        yield return new object?[] { Key.None, true };
+        yield return new object?[] { Key.Cancel, true };
+        yield return new object?[] { Key.A, true };
+        yield return new object?[] { Key.Pa1, true };
+        yield return new object?[] { Key.OemClear, true };
+        yield return new object?[] { Key.DeadCharProcessed, false };
+        yield return new object?[] { Key.None - 1, false };
+        yield return new object?[] { Key.DeadCharProcessed + 1, false };
+    }
+
+    [Theory]
+    [MemberData(nameof(CanConvertToString_TestData))]
+    public void CanConvertToString_Invoke_ReturnsExpected(object value, bool expected)
+    {
+        var serializer = new KeyValueSerializer();
+        Assert.Equal(expected, serializer.CanConvertToString(value, null));
+        Assert.Equal(expected, serializer.CanConvertToString(value, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [MemberData(nameof(KeyConverterTests.ConvertTo_KeyToString_TestData), MemberType = typeof(KeyConverterTests))]
+    public void ConvertToString_Invoke_ReturnsExpected(Key key, string expected)
+    {
+        var serializer = new KeyValueSerializer();
+        Assert.Equal(expected, serializer.ConvertToString(key, null));
+        Assert.Equal(expected, serializer.ConvertToString(key, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [InlineData((Key)int.MinValue)]
+    [InlineData((Key)(-1))]
+    [InlineData(Key.DeadCharProcessed + 1)]
+    [InlineData((Key)int.MaxValue)]
+    public void ConvertToString_InvalidKey_ThrowsNotSupportedException(Key key)
+    {
+        var serializer = new KeyValueSerializer();
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertToString(key, null));
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertToString(key, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [InlineData(null)]
+    // TODO: this should not throw InvalidCastException.
+    //[InlineData("", "")]
+    //[InlineData("value", "value")]
+    public void ConvertToString_InvokeNotKeyToStringNull_ThrowsNotSupportedException(object? value)
+    {
+        var serializer = new KeyValueSerializer();
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertToString(value, null));
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertToString(value, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData("value")]
+    public void ConvertToString_InvokeNotKeyNotNull_ThrowsInvalidCastException(object value)
+    {
+        // TODO: this should not throw InvalidCastException.
+        var serializer = new KeyValueSerializer();
+        Assert.Throws<InvalidCastException>(() => serializer.ConvertToString(value, null));
+        Assert.Throws<InvalidCastException>(() => serializer.ConvertToString(value, new CustomValueSerializerContext()));
+    }
+
+    public static IEnumerable<object?[]> CanConvertFromString_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { string.Empty };
+        yield return new object?[] { "value" };
+    }
+
+    [Theory]
+    [MemberData(nameof(CanConvertFromString_TestData))]
+    public void CanConvertFromString_Invoke_ReturnsTrue(string value)
+    {
+        var serializer = new KeyValueSerializer();
+        Assert.True(serializer.CanConvertFromString(value, null));
+        Assert.True(serializer.CanConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [MemberData(nameof(KeyConverterTests.ConvertFrom_TestData), MemberType = typeof(KeyConverterTests))]
+    public void ConvertFromString_Invoke_ReturnsExpected(string value, Key expected)
+    {
+        var serializer = new KeyValueSerializer();
+        Assert.Equal(expected, serializer.ConvertFromString(value, null));
+        Assert.Equal(expected, serializer.ConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    [Fact]
+    public void ConvertFromString_NullValue_ThrowsNotSupportedException()
+    {
+        var serializer = new KeyValueSerializer();
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertFromString(null, null));
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertFromString(null, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [MemberData(nameof(KeyConverterTests.ConvertFrom_InvalidValue_TestData), MemberType = typeof(KeyConverterTests))]
+    public void ConvertFromString_InvalidValue_ThrowsInvalidOperationException(string value)
+    {
+        var serializer = new KeyValueSerializer();
+        // TODO: add paramName.
+        Assert.Throws<ArgumentException>(() => serializer.ConvertFromString(value, null));
+        Assert.Throws<ArgumentException>(() => serializer.ConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    private class CustomValueSerializerContext : IValueSerializerContext
+    {
+        public IContainer Container => throw new NotImplementedException();
+
+        public object Instance => throw new NotImplementedException();
+
+        public PropertyDescriptor PropertyDescriptor => throw new NotImplementedException();
+
+        public object? GetService(Type serviceType) => throw new NotImplementedException();
+
+        public ValueSerializer GetValueSerializerFor(PropertyDescriptor descriptor) => throw new NotImplementedException();
+
+        public ValueSerializer GetValueSerializerFor(Type type) => throw new NotImplementedException();
+
+        public void OnComponentChanged() => throw new NotImplementedException();
+
+        public bool OnComponentChanging() => throw new NotImplementedException();
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Input/ModifierKeysConverterTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Input/ModifierKeysConverterTests.cs
new file mode 100644
index 00000000000..14688c7cad5
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Input/ModifierKeysConverterTests.cs
@@ -0,0 +1,318 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.ComponentModel.Design.Serialization;
+using System.Globalization;
+
+namespace System.Windows.Input.Tests;
+
+public class ModifierKeysConverterTests
+{
+    public static IEnumerable<object?[]> CanConvertTo_TestData()
+    {
+        yield return new object?[] { null, null, false };
+        yield return new object?[] { null, typeof(object), false };
+        yield return new object?[] { null, typeof(string), false };
+        yield return new object?[] { null, typeof(InstanceDescriptor), false };
+        yield return new object?[] { null, typeof(Key), false };
+        yield return new object?[] { null, typeof(ModifierKeys), false };
+        yield return new object?[] { new CustomTypeDescriptorContext(), null, false };
+        yield return new object?[] { new CustomTypeDescriptorContext(), typeof(object), false };
+        yield return new object?[] { new CustomTypeDescriptorContext(), typeof(string), false };
+        yield return new object?[] { new CustomTypeDescriptorContext(), typeof(InstanceDescriptor), false };
+        yield return new object?[] { new CustomTypeDescriptorContext(), typeof(Key), false };
+        yield return new object?[] { new CustomTypeDescriptorContext(), typeof(ModifierKeys), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = new object() }, null, false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = new object() }, typeof(object), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = new object() }, typeof(string), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = new object() }, typeof(InstanceDescriptor), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = new object() }, typeof(Key), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = new object() }, typeof(ModifierKeys), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = ModifierKeys.None }, null, false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = ModifierKeys.None }, typeof(object), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = ModifierKeys.None }, typeof(string), true };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = ModifierKeys.None }, typeof(InstanceDescriptor), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = ModifierKeys.None }, typeof(Key), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = ModifierKeys.None }, typeof(ModifierKeys), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = ModifierKeys.Control }, null, false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = ModifierKeys.Control }, typeof(object), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = ModifierKeys.Control }, typeof(string), true };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = ModifierKeys.Control }, typeof(InstanceDescriptor), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = ModifierKeys.Control }, typeof(Key), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = ModifierKeys.Control }, typeof(ModifierKeys), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = ModifierKeys.Control | ModifierKeys.Alt | ModifierKeys.Windows | ModifierKeys.Shift }, null, false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = ModifierKeys.Control | ModifierKeys.Alt | ModifierKeys.Windows | ModifierKeys.Shift }, typeof(object), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = ModifierKeys.Control | ModifierKeys.Alt | ModifierKeys.Windows | ModifierKeys.Shift }, typeof(string), true };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = ModifierKeys.Control | ModifierKeys.Alt | ModifierKeys.Windows | ModifierKeys.Shift }, typeof(InstanceDescriptor), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = ModifierKeys.Control | ModifierKeys.Alt | ModifierKeys.Windows | ModifierKeys.Shift }, typeof(Key), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = ModifierKeys.Control | ModifierKeys.Alt | ModifierKeys.Windows | ModifierKeys.Shift }, typeof(ModifierKeys), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = (ModifierKeys)(-1) }, null, false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = (ModifierKeys)(-1) }, typeof(object), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = (ModifierKeys)(-1) }, typeof(string), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = (ModifierKeys)(-1) }, typeof(InstanceDescriptor), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = (ModifierKeys)(-1) }, typeof(Key), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = (ModifierKeys)(-1) }, typeof(ModifierKeys), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = (ModifierKeys)0x10 }, null, false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = (ModifierKeys)0x10 }, typeof(object), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = (ModifierKeys)0x10 }, typeof(string), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = (ModifierKeys)0x10 }, typeof(InstanceDescriptor), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = (ModifierKeys)0x10 }, typeof(Key), false };
+        yield return new object?[] { new CustomTypeDescriptorContext { Instance = (ModifierKeys)0x10 }, typeof(ModifierKeys), false };
+    }
+
+    [Theory]
+    [MemberData(nameof(CanConvertTo_TestData))]
+    public void CanConvertTo_Invoke_ReturnsExpected(ITypeDescriptorContext context, Type destinationType, bool expected)
+    {
+        var converter = new ModifierKeysConverter();
+        Assert.Equal(expected, converter.CanConvertTo(context, destinationType));
+    }
+
+    public static IEnumerable<object[]> ConvertTo_ModifierKeysToString_TestData()
+    {
+        yield return new object[] { ModifierKeys.None, "" };
+        yield return new object[] { ModifierKeys.Alt, "Alt" };
+        yield return new object[] { ModifierKeys.Control, "Ctrl" };
+        yield return new object[] { ModifierKeys.Shift, "Shift" };
+        yield return new object[] { ModifierKeys.Windows, "Windows" };
+        
+        yield return new object[] { ModifierKeys.Control | ModifierKeys.Alt, "Ctrl+Alt" };
+        yield return new object[] { ModifierKeys.Control | ModifierKeys.Windows, "Ctrl+Windows" };
+        yield return new object[] { ModifierKeys.Control | ModifierKeys.Shift, "Ctrl+Shift" };
+        yield return new object[] { ModifierKeys.Control | ModifierKeys.Alt | ModifierKeys.Windows, "Ctrl+Alt+Windows" };
+        yield return new object[] { ModifierKeys.Control | ModifierKeys.Alt | ModifierKeys.Windows | ModifierKeys.Shift, "Ctrl+Alt+Windows+Shift" };
+        yield return new object[] { ModifierKeys.Control | ModifierKeys.Alt | ModifierKeys.Shift, "Ctrl+Alt+Shift" };
+        yield return new object[] { ModifierKeys.Control | ModifierKeys.Windows | ModifierKeys.Shift, "Ctrl+Windows+Shift" };
+        yield return new object[] { ModifierKeys.Alt | ModifierKeys.Windows, "Alt+Windows" };
+        yield return new object[] { ModifierKeys.Alt | ModifierKeys.Windows | ModifierKeys.Shift, "Alt+Windows+Shift" };
+        yield return new object[] { ModifierKeys.Alt | ModifierKeys.Shift, "Alt+Shift" };
+        yield return new object[] { ModifierKeys.Windows | ModifierKeys.Shift, "Windows+Shift" };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertTo_ModifierKeysToString_TestData))]
+    public void ConvertTo_InvokeModifierKeysToString_ReturnsExpected(ModifierKeys value, string expected)
+    {
+        var converter = new ModifierKeysConverter();
+        Assert.Equal(expected, converter.ConvertTo(value, typeof(string)));
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), null, value, typeof(string)));
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value, typeof(string)));
+    }
+
+    public static IEnumerable<object[]> ConvertTo_InvalidModifierKeys_TestData()
+    {
+        yield return new object[] { (ModifierKeys)int.MinValue };
+        yield return new object[] { (ModifierKeys)(-1) };
+        yield return new object[] { (ModifierKeys)32 };
+        yield return new object[] { (ModifierKeys)int.MaxValue };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertTo_InvalidModifierKeys_TestData))]
+    public void ConvertTo_InvalidModifierKeys_ThrowsInvalidEnumArgumentException(ModifierKeys value)
+    {
+        var converter = new ModifierKeysConverter();
+        Assert.Throws<InvalidEnumArgumentException>("value", () => converter.ConvertTo(value, typeof(string)));
+        Assert.Throws<InvalidEnumArgumentException>("value", () => converter.ConvertTo(new CustomTypeDescriptorContext(), null, value, typeof(string)));
+        Assert.Throws<InvalidEnumArgumentException>("value", () => converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value, typeof(string)));
+    }
+
+    [Theory]
+    [InlineData(null)]
+    // TODO: this should not throw InvalidCastException.
+    //[InlineData("", "")]
+    //[InlineData("value", "value")]
+    public void ConvertTo_InvokeNotModifierKeysToStringNull_ThrowsNotSupportedException(object? value)
+    {
+        var converter = new ModifierKeysConverter();
+        // TODO: should not throw NullReferenceException
+        //Assert.Throws<NotSupportedException>(() => converter.ConvertTo(value, typeof(string)));
+        //Assert.Throws<NotSupportedException>(() => converter.ConvertTo(new CustomTypeDescriptorContext(), null, value, typeof(string)));
+        //Assert.Throws<NotSupportedException>(() => converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value, typeof(string)));
+        Assert.Throws<NullReferenceException>(() => converter.ConvertTo(value, typeof(string)));
+        Assert.Throws<NullReferenceException>(() => converter.ConvertTo(new CustomTypeDescriptorContext(), null, value, typeof(string)));
+        Assert.Throws<NullReferenceException>(() => converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value, typeof(string)));
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData("value")]
+    public void ConvertTo_InvokeNotModifierKeysToStringNotNull_ThrowsInvalidCastException(object value)
+    {
+        // TODO: this should not throw InvalidCastException.
+        var converter = new ModifierKeysConverter();
+        Assert.Throws<InvalidCastException>(() => converter.ConvertTo(value, typeof(string)));
+        Assert.Throws<InvalidCastException>(() => converter.ConvertTo(new CustomTypeDescriptorContext(), null, value, typeof(string)));
+        Assert.Throws<InvalidCastException>(() => converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value, typeof(string)));
+    }
+
+    public static IEnumerable<object?[]> ConvertTo_CantConvert_TestData()
+    {
+        yield return new object?[] { null, typeof(object) };
+        yield return new object?[] { string.Empty, typeof(object) };
+        yield return new object?[] { "value", typeof(object) };
+        yield return new object?[] { new object(), typeof(object) };
+        yield return new object?[] { Key.None, typeof(object) };
+        
+        yield return new object?[] { null, typeof(Key) };
+        yield return new object?[] { string.Empty, typeof(Key) };
+        yield return new object?[] { "value", typeof(Key) };
+        yield return new object?[] { new object(), typeof(Key) };
+        yield return new object?[] { Key.None, typeof(Key) };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertTo_CantConvert_TestData))]
+    public void ConvertTo_CantConvert_ThrowsNotSupportedException(object value, Type destinationType)
+    {
+        var converter = new ModifierKeysConverter();
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(value, destinationType));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(null, null, value, destinationType));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value, destinationType));
+    }
+
+    public static IEnumerable<object?[]> ConvertTo_NullDestinationType_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { string.Empty };
+        yield return new object?[] { "value" };
+        yield return new object?[] { new object() };
+        yield return new object?[] { ModifierKeys.None };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertTo_NullDestinationType_TestData))]
+    public void ConvertTo_NullDestinationType_ThrowsArgumentNullException(object value)
+    {
+        var converter = new ModifierKeysConverter();
+        Assert.Throws<ArgumentNullException>("destinationType", () => converter.ConvertTo(value, null!));
+        Assert.Throws<ArgumentNullException>("destinationType", () => converter.ConvertTo(null, null, Key.None, null!));
+        Assert.Throws<ArgumentNullException>("destinationType", () => converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, Key.None, null!));
+    }
+
+    [Theory]
+    [InlineData(null, false)]
+    [InlineData(typeof(object), false)]
+    [InlineData(typeof(string), true)]
+    [InlineData(typeof(InstanceDescriptor), false)]
+    [InlineData(typeof(Key), false)]
+    public void CanConvertFrom_Invoke_ReturnsExpected(Type? sourceType, bool expected)
+    {
+        var converter = new ModifierKeysConverter();
+        Assert.Equal(expected, converter.CanConvertFrom(sourceType!));
+        Assert.Equal(expected, converter.CanConvertFrom(null, sourceType));
+        Assert.Equal(expected, converter.CanConvertFrom(new CustomTypeDescriptorContext(), sourceType));
+    }
+
+    public static IEnumerable<object[]> ConvertFrom_TestData()
+    {
+        yield return new object[] { "", ModifierKeys.None };
+        yield return new object[] { "  ", ModifierKeys.None };
+        yield return new object[] { "+", ModifierKeys.None };
+        yield return new object[] { " + ", ModifierKeys.None };
+        yield return new object[] { "Alt", ModifierKeys.Alt };
+        yield return new object[] { "ALT", ModifierKeys.Alt };
+        yield return new object[] { " Alt ", ModifierKeys.Alt };
+        yield return new object[] { "Ctrl", ModifierKeys.Control };
+        yield return new object[] { "Control", ModifierKeys.Control };
+        yield return new object[] { "Shift", ModifierKeys.Shift };
+        yield return new object[] { "Windows", ModifierKeys.Windows };
+        yield return new object[] { "Win", ModifierKeys.Windows };
+        
+        yield return new object[] { "Ctrl+Alt", ModifierKeys.Control | ModifierKeys.Alt };
+        yield return new object[] { "  Ctrl  +  Alt  ", ModifierKeys.Control | ModifierKeys.Alt };
+        yield return new object[] { "Ctrl+Windows", ModifierKeys.Control | ModifierKeys.Windows };
+        yield return new object[] { "Control+Win", ModifierKeys.Control | ModifierKeys.Windows };
+        yield return new object[] { "Ctrl+Shift", ModifierKeys.Control | ModifierKeys.Shift };
+        yield return new object[] { "Ctrl+Alt+Windows", ModifierKeys.Control | ModifierKeys.Alt | ModifierKeys.Windows };
+        yield return new object[] { "Ctrl+Alt+Windows+Shift", ModifierKeys.Control | ModifierKeys.Alt | ModifierKeys.Windows | ModifierKeys.Shift };
+        yield return new object[] { "Ctrl+Alt+Shift", ModifierKeys.Control | ModifierKeys.Alt | ModifierKeys.Shift };
+        yield return new object[] { "Ctrl+Windows+Shift", ModifierKeys.Control | ModifierKeys.Windows | ModifierKeys.Shift };
+        yield return new object[] { "Alt+Windows", ModifierKeys.Alt | ModifierKeys.Windows };
+        yield return new object[] { "Alt+Windows+Shift", ModifierKeys.Alt | ModifierKeys.Windows | ModifierKeys.Shift };
+        yield return new object[] { "Alt+Shift", ModifierKeys.Alt | ModifierKeys.Shift };
+        yield return new object[] { "Windows+Shift", ModifierKeys.Windows | ModifierKeys.Shift };
+
+        yield return new object[] { "Ctrl+", ModifierKeys.Control };
+        yield return new object[] { "Ctrl+Windows+", ModifierKeys.Control | ModifierKeys.Windows };
+        yield return new object[] { "Ctrl+Ctrl+Ctrl", ModifierKeys.Control };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertFrom_TestData))]
+    public void ConvertFrom_InvokeStringValue_ReturnsExpected(string value, ModifierKeys expected)
+    {
+        var converter = new ModifierKeysConverter();
+        Assert.Equal(expected, converter.ConvertFrom(value));
+        Assert.Equal(expected, converter.ConvertFrom(null, null, value));
+        Assert.Equal(expected, converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    [Fact]
+    public void ConvertFrom_NullValue_ThrowsNotSupportedException()
+    {
+        var converter = new ModifierKeysConverter();
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(null!));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(null, null, null));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, null));
+    }
+
+    public static IEnumerable<object[]> ConvertFrom_InvalidValue_TestData()
+    {
+        yield return new object[] { "_" };
+        yield return new object[] { " _ " };
+        yield return new object[] { "NOSUCHKEY" };
+        yield return new object[] { " NOSUCHKEY " };
+        yield return new object[] { "Control+NOSUCHKEY" };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertFrom_InvalidValue_TestData))]
+    public void ConvertFrom_InvokeInvalidValue_ThrowsNotSupportedException(string value)
+    {
+        var converter = new ModifierKeysConverter();
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(value));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(null, null, value));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    public static IEnumerable<object[]> ConvertFrom_CantConvert_TestData()
+    {
+        yield return new object[] { new object() };
+        yield return new object[] { Key.A };
+        yield return new object[] { ModifierKeys.None };
+    }
+    
+    [Theory]
+    [MemberData(nameof(ConvertFrom_CantConvert_TestData))]
+    public void ConvertFrom_CantConvert_ThrowsNotSupportedException(object value)
+    {
+        var converter = new ModifierKeysConverter();
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(value));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(null, null, value));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    private class CustomTypeDescriptorContext : ITypeDescriptorContext
+    {
+        public IContainer Container => throw new NotImplementedException();
+
+        private object? _instance;
+
+        public object Instance
+        {
+            get => _instance!;
+            set => _instance = value;
+        }
+
+        public PropertyDescriptor PropertyDescriptor => throw new NotImplementedException();
+
+        public object? GetService(Type serviceType) => throw new NotImplementedException();
+
+        public void OnComponentChanged() => throw new NotImplementedException();
+
+        public bool OnComponentChanging() => throw new NotImplementedException();
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Input/ModifierKeysTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Input/ModifierKeysTests.cs
new file mode 100644
index 00000000000..4bcc92d1985
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Input/ModifierKeysTests.cs
@@ -0,0 +1,23 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.Windows.Markup;
+
+namespace System.Windows.Input.Tests;
+
+public class ModifierKeysTests
+{
+    [Fact]
+    public void TypeConverter_Get_ReturnsExpected()
+    {
+        Assert.IsType<ModifierKeysConverter>(TypeDescriptor.GetConverter(typeof(ModifierKeys)));
+    }
+
+    [Fact]
+    public void ValueSerializer_Get_ReturnsExpected()
+    {
+        Assert.IsType<ModifierKeysValueSerializer>(ValueSerializer.GetSerializerFor(typeof(ModifierKeys)));
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Input/ModifierKeysValueSerializerTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Input/ModifierKeysValueSerializerTests.cs
new file mode 100644
index 00000000000..6289eb9c505
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Input/ModifierKeysValueSerializerTests.cs
@@ -0,0 +1,139 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.Windows.Markup;
+
+namespace System.Windows.Input.Tests;
+
+public class ModifierKeysValueSerializerTests
+{
+    public static IEnumerable<object?[]> CanConvertToString_TestData()
+    {
+        yield return new object?[] { null, false };
+        yield return new object?[] { string.Empty, false };
+        yield return new object?[] { "value", false };
+        yield return new object?[] { new object(), false };
+
+        yield return new object?[] { ModifierKeys.None, true };
+        yield return new object?[] { ModifierKeys.Control, true };
+        yield return new object?[] { ModifierKeys.Control | ModifierKeys.Alt | ModifierKeys.Windows | ModifierKeys.Shift, true };
+        yield return new object?[] { (ModifierKeys)(-1), false };
+        yield return new object?[] { (ModifierKeys)0x10, false };
+    }
+
+    [Theory]
+    [MemberData(nameof(CanConvertToString_TestData))]
+    public void CanConvertToString_Invoke_ReturnsExpected(object value, bool expected)
+    {
+        var serializer = new ModifierKeysValueSerializer();
+        Assert.Equal(expected, serializer.CanConvertToString(value, null));
+        Assert.Equal(expected, serializer.CanConvertToString(value, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [MemberData(nameof(ModifierKeysConverterTests.ConvertTo_ModifierKeysToString_TestData), MemberType = typeof(ModifierKeysConverterTests))]
+    public void ConvertToString_Invoke_ReturnsExpected(ModifierKeys key, string expected)
+    {
+        var serializer = new ModifierKeysValueSerializer();
+        Assert.Equal(expected, serializer.ConvertToString(key, null));
+        Assert.Equal(expected, serializer.ConvertToString(key, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [MemberData(nameof(ModifierKeysConverterTests.ConvertTo_InvalidModifierKeys_TestData), MemberType = typeof(ModifierKeysConverterTests))]
+    public void ConvertToString_InvalidModifierKeys_ThrowsInvalidEnumArgumentException(ModifierKeys key)
+    {
+        var serializer = new ModifierKeysValueSerializer();
+        Assert.Throws<InvalidEnumArgumentException>("value", () => serializer.ConvertToString(key, null));
+        Assert.Throws<InvalidEnumArgumentException>("value", () => serializer.ConvertToString(key, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [InlineData(null)]
+    // TODO: this should not throw InvalidCastException.
+    //[InlineData("", "")]
+    //[InlineData("value", "value")]
+    public void ConvertToString_InvokeNotModifierKeysToStringNull_ThrowsNotSupportedException(object? value)
+    {
+        var serializer = new ModifierKeysValueSerializer();
+        // TODO: should not throw NullReferenceException
+        //Assert.Throws<NotSupportedException>(() => serializer.ConvertToString(value, null));
+        //Assert.Throws<NotSupportedException>(() => serializer.ConvertToString(value, new CustomValueSerializerContext()));
+        Assert.Throws<NullReferenceException>(() => serializer.ConvertToString(value, null));
+        Assert.Throws<NullReferenceException>(() => serializer.ConvertToString(value, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData("value")]
+    public void ConvertToString_InvokeNotModifierKeysNotNull_ThrowsInvalidCastException(object value)
+    {
+        // TODO: this should not throw InvalidCastException.
+        var serializer = new ModifierKeysValueSerializer();
+        Assert.Throws<InvalidCastException>(() => serializer.ConvertToString(value, null));
+        Assert.Throws<InvalidCastException>(() => serializer.ConvertToString(value, new CustomValueSerializerContext()));
+    }
+
+    public static IEnumerable<object?[]> CanConvertFromString_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { string.Empty };
+        yield return new object?[] { "value" };
+    }
+
+    [Theory]
+    [MemberData(nameof(CanConvertFromString_TestData))]
+    public void CanConvertFromString_Invoke_ReturnsTrue(string value)
+    {
+        var serializer = new ModifierKeysValueSerializer();
+        Assert.True(serializer.CanConvertFromString(value, null));
+        Assert.True(serializer.CanConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [MemberData(nameof(ModifierKeysConverterTests.ConvertFrom_TestData), MemberType = typeof(ModifierKeysConverterTests))]
+    public void ConvertFromString_Invoke_ReturnsExpected(string value, ModifierKeys expected)
+    {
+        var serializer = new ModifierKeysValueSerializer();
+        Assert.Equal(expected, serializer.ConvertFromString(value, null));
+        Assert.Equal(expected, serializer.ConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    [Fact]
+    public void ConvertFromString_NullValue_ThrowsNotSupportedException()
+    {
+        var serializer = new ModifierKeysValueSerializer();
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertFromString(null, null));
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertFromString(null, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [MemberData(nameof(ModifierKeysConverterTests.ConvertFrom_InvalidValue_TestData), MemberType = typeof(ModifierKeysConverterTests))]
+    public void ConvertFromString_InvalidValue_ThrowsNotSupportedException(string value)
+    {
+        var serializer = new ModifierKeysValueSerializer();
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertFromString(value, null));
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    private class CustomValueSerializerContext : IValueSerializerContext
+    {
+        public IContainer Container => throw new NotImplementedException();
+
+        public object Instance => throw new NotImplementedException();
+
+        public PropertyDescriptor PropertyDescriptor => throw new NotImplementedException();
+
+        public object? GetService(Type serviceType) => throw new NotImplementedException();
+
+        public ValueSerializer GetValueSerializerFor(PropertyDescriptor descriptor) => throw new NotImplementedException();
+
+        public ValueSerializer GetValueSerializerFor(Type type) => throw new NotImplementedException();
+
+        public void OnComponentChanged() => throw new NotImplementedException();
+
+        public bool OnComponentChanging() => throw new NotImplementedException();
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Input/TraversalRequestTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Input/TraversalRequestTests.cs
new file mode 100644
index 00000000000..97a78085277
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Input/TraversalRequestTests.cs
@@ -0,0 +1,54 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+
+namespace System.Windows.Input.Tests;
+
+public class TraversalRequestTests
+{
+    [Theory]
+    [InlineData(FocusNavigationDirection.Next)]
+    [InlineData(FocusNavigationDirection.Previous)]
+    [InlineData(FocusNavigationDirection.First)]
+    [InlineData(FocusNavigationDirection.Last)]
+    [InlineData(FocusNavigationDirection.Left)]
+    [InlineData(FocusNavigationDirection.Right)]
+    [InlineData(FocusNavigationDirection.Up)]
+    [InlineData(FocusNavigationDirection.Down)]
+    public void Ctor_FocusNavigationDirection(FocusNavigationDirection focusNavigationDirection)
+    {
+        var request = new TraversalRequest(focusNavigationDirection);
+        Assert.Equal(focusNavigationDirection, request.FocusNavigationDirection);
+        Assert.False(request.Wrapped);
+    }
+
+    [Theory]
+    [InlineData(FocusNavigationDirection.Next - 1)]
+    [InlineData(FocusNavigationDirection.Down + 1)]
+    public void Ctor_InvalidFocusNavigationDirection_ThrowsInvalidEnumArgumentException(FocusNavigationDirection focusNavigationDirection)
+    {
+        Assert.Throws<InvalidEnumArgumentException>("focusNavigationDirection", () => new TraversalRequest(focusNavigationDirection));
+    }
+
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void Wrapped_Set_GetReturnsExpected(bool value)
+    {
+        var request = new TraversalRequest(FocusNavigationDirection.Next);
+
+        // Set.
+        request.Wrapped = value;
+        Assert.Equal(value, request.Wrapped);
+
+        // Set same.
+        request.Wrapped = value;
+        Assert.Equal(value, request.Wrapped);
+
+        // Set different.
+        request.Wrapped = !value;
+        Assert.Equal(!value, request.Wrapped);
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Int32RectConverterTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Int32RectConverterTests.cs
new file mode 100644
index 00000000000..b0b7fc6800b
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Int32RectConverterTests.cs
@@ -0,0 +1,188 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.ComponentModel.Design.Serialization;
+using System.Globalization;
+
+namespace System.Windows.Tests;
+
+public class Int32RectConverterTests
+{
+    [Theory]
+    [InlineData(null, false)]
+    [InlineData(typeof(object), false)]
+    [InlineData(typeof(string), true)]
+    [InlineData(typeof(InstanceDescriptor), false)]
+    [InlineData(typeof(Int32Rect), false)]
+    public void CanConvertTo_Invoke_ReturnsExpected(Type? destinationType, bool expected)
+    {
+        var converter = new Int32RectConverter();
+        Assert.Equal(expected, converter.CanConvertTo(null, destinationType));
+        Assert.Equal(expected, converter.CanConvertTo(new CustomTypeDescriptorContext(), destinationType));
+    }
+    
+    [Theory]
+    [MemberData(nameof(Int32RectTests.ToString_TestData), MemberType = typeof(Int32RectTests))]
+    public void ConvertTo_InvokeInt32RectToString_ReturnsExpected(Int32Rect matrix, string expected)
+    {
+        var converter = new Int32RectConverter();
+        Assert.Equal(expected, converter.ConvertTo(matrix, typeof(string)));
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), null, matrix, typeof(string)));
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, matrix, typeof(string)));
+    }
+    
+    [Theory]
+    [MemberData(nameof(Int32RectTests.ToString_IFormatProviderCustom_TestData), MemberType = typeof(Int32RectTests))]
+    public void ConvertTo_InvokeInt32RectToStringCustomCulture_ReturnsExpected(Int32Rect matrix, string numberDecimalSeparator, string expected)
+    {
+        var culture = new CultureInfo("en-US");
+        NumberFormatInfo formatInfo = culture.NumberFormat;
+        formatInfo.NumberDecimalSeparator = numberDecimalSeparator;
+
+        var converter = new Int32RectConverter();
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), culture, matrix, typeof(string)));
+    }
+
+    [Theory]
+    [InlineData(null, "")]
+    [InlineData("", "")]
+    [InlineData("value", "value")]
+    [InlineData(1, "1")]
+    public void ConvertTo_InvokeNotInt32RectToString_ReturnsExpected(object? value, string expected)
+    {
+        var converter = new Int32RectConverter();
+        Assert.Equal(expected, converter.ConvertTo(value, typeof(string)));
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), null, value, typeof(string)));
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value, typeof(string)));
+    }
+
+    public static IEnumerable<object?[]> ConvertTo_CantConvert_TestData()
+    {
+        yield return new object?[] { null, typeof(object) };
+        yield return new object?[] { string.Empty, typeof(object) };
+        yield return new object?[] { "value", typeof(object) };
+        yield return new object?[] { new object(), typeof(object) };
+        yield return new object?[] { new Int32Rect(), typeof(object) };
+        
+        yield return new object?[] { null, typeof(Int32Rect) };
+        yield return new object?[] { string.Empty, typeof(Int32Rect) };
+        yield return new object?[] { "value", typeof(Int32Rect) };
+        yield return new object?[] { new object(), typeof(Int32Rect) };
+        yield return new object?[] { new Int32Rect(), typeof(Int32Rect) };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertTo_CantConvert_TestData))]
+    public void ConvertTo_CantConvert_ThrowsNotSupportedException(object value, Type destinationType)
+    {
+        var converter = new Int32RectConverter();
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(value, destinationType));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(null, null, value, destinationType));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value, destinationType));
+    }
+
+    public static IEnumerable<object?[]> ConvertTo_NullDestinationType_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { string.Empty };
+        yield return new object?[] { "value" };
+        yield return new object?[] { new object() };
+        yield return new object?[] { new Int32Rect() };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertTo_NullDestinationType_TestData))]
+    public void ConvertTo_NullDestinationType_ThrowsArgumentNullException(object value)
+    {
+        var converter = new Int32RectConverter();
+        Assert.Throws<ArgumentNullException>("destinationType", () => converter.ConvertTo(value, null!));
+        Assert.Throws<ArgumentNullException>("destinationType", () => converter.ConvertTo(null, null, new Int32Rect(), null!));
+        Assert.Throws<ArgumentNullException>("destinationType", () => converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, new Int32Rect(), null!));
+    }
+
+    [Theory]
+    [InlineData(null, false)]
+    [InlineData(typeof(object), false)]
+    [InlineData(typeof(string), true)]
+    [InlineData(typeof(InstanceDescriptor), true)]
+    [InlineData(typeof(Int32Rect), false)]
+    public void CanConvertFrom_Invoke_ReturnsExpected(Type? sourceType, bool expected)
+    {
+        var converter = new Int32RectConverter();
+        Assert.Equal(expected, converter.CanConvertFrom(sourceType!));
+        Assert.Equal(expected, converter.CanConvertFrom(null, sourceType));
+        Assert.Equal(expected, converter.CanConvertFrom(new CustomTypeDescriptorContext(), sourceType));
+    }
+
+    [Theory]
+    [MemberData(nameof(Int32RectTests.Parse_TestData), MemberType = typeof(Int32RectTests))]
+    public void ConvertFrom_InvokeStringValue_ReturnsExpected(object value, Int32Rect expected)
+    {
+        var converter = new Int32RectConverter();
+        Assert.Equal(expected, converter.ConvertFrom(value));
+        Assert.Equal(expected, converter.ConvertFrom(null, null, value));
+        Assert.Equal(expected, converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    [Fact]
+    public void ConvertFrom_NullValue_ThrowsNotSupportedException()
+    {
+        var converter = new Int32RectConverter();
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(null!));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(null, null, null));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, null));
+    }
+
+    [Theory]
+    [MemberData(nameof(Int32RectTests.Parse_InvalidSource_TestData), MemberType = typeof(Int32RectTests))]
+    public void ConvertFrom_InvalidStringValue_ThrowsInvalidOperationException(object value)
+    {
+        var converter = new Int32RectConverter();
+        Assert.Throws<InvalidOperationException>(() => converter.ConvertFrom(value));
+        Assert.Throws<InvalidOperationException>(() => converter.ConvertFrom(null, null, value));
+        Assert.Throws<InvalidOperationException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    [Theory]
+    [MemberData(nameof(Int32RectTests.Parse_NotInt32_TestData), MemberType = typeof(Int32RectTests))]
+    public void ConvertFrom_NotInt_ThrowsFormatException(object value)
+    {
+        var converter = new Int32RectConverter();
+        Assert.Throws<FormatException>(() => converter.ConvertFrom(value));
+        Assert.Throws<FormatException>(() => converter.ConvertFrom(null, null, value));
+        Assert.Throws<FormatException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    public static IEnumerable<object[]> ConvertFrom_CantConvert_TestData()
+    {
+        yield return new object[] { new object() };
+        yield return new object[] { new Int32Rect() };
+    }
+    
+    [Theory]
+    [MemberData(nameof(ConvertFrom_CantConvert_TestData))]
+    public void ConvertFrom_CantConvert_ThrowsNotSupportedException(object value)
+    {
+        var converter = new Int32RectConverter();
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(value));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(null, null, value));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    private class CustomTypeDescriptorContext : ITypeDescriptorContext
+    {
+        public IContainer Container => throw new NotImplementedException();
+
+        public object Instance => throw new NotImplementedException();
+
+        public PropertyDescriptor PropertyDescriptor => throw new NotImplementedException();
+
+        public object? GetService(Type serviceType) => throw new NotImplementedException();
+
+        public void OnComponentChanged() => throw new NotImplementedException();
+
+        public bool OnComponentChanging() => throw new NotImplementedException();
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Int32RectTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Int32RectTests.cs
new file mode 100644
index 00000000000..5a34be40743
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Int32RectTests.cs
@@ -0,0 +1,459 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.Globalization;
+using System.Windows.Converters;
+using System.Windows.Markup;
+
+namespace System.Windows.Tests;
+
+public class Int32RectTests
+{
+    [Fact]
+    public void Ctor_Default()
+    {
+        var rect = new Int32Rect();
+        Assert.Equal(0, rect.X);
+        Assert.Equal(0, rect.Y);
+        Assert.Equal(0, rect.Width);
+        Assert.Equal(0, rect.Height);
+        Assert.True(rect.IsEmpty);
+        Assert.False(rect.HasArea);
+    }
+
+    [Theory]
+    [InlineData(-1, -2, -3, -4, false, false)]
+    [InlineData(0, 0, 0, 0, true, false)]
+    [InlineData(1, 0, 0, 0, false, false)]
+    [InlineData(-1, 0, 0, 0, false, false)]
+    [InlineData(0, 1, 0, 0, false, false)]
+    [InlineData(0, -1, 0, 0, false, false)]
+    [InlineData(0, 0, 1, 0, false, false)]
+    [InlineData(0, 0, -1, 0, false, false)]
+    [InlineData(0, 0, 0, 1, false, false)]
+    [InlineData(0, 0, 0, -1, false, false)]
+    [InlineData(1, 2, -1, 4, false, false)]
+    [InlineData(1, 2, 0, 4, false, false)]
+    [InlineData(1, 2, 3, -1, false, false)]
+    [InlineData(1, 2, 3, 0, false, false)]
+    [InlineData(1, 2, 3, 4, false, true)]
+    [InlineData(0, 0, 3, 4, false, true)]
+    public void Ctor_Int_Int_Int_Int(int x, int y, int width, int height, bool expectedIsEmpty, bool expectedHasArea)
+    {
+        var rect = new Int32Rect(x, y, width, height);
+        Assert.Equal(x, rect.X);
+        Assert.Equal(y, rect.Y);
+        Assert.Equal(width, rect.Width);
+        Assert.Equal(height, rect.Height);
+        Assert.Equal(expectedIsEmpty, rect.IsEmpty);
+        Assert.Equal(expectedHasArea, rect.HasArea);
+    }
+
+    [Fact]
+    public void Empty_Get_ReturnsExpected()
+    {
+        Int32Rect rect = Int32Rect.Empty;
+        Assert.Equal(0, rect.X);
+        Assert.Equal(0, rect.Y);
+        Assert.Equal(0, rect.Width);
+        Assert.Equal(0, rect.Height);
+        Assert.True(rect.IsEmpty);
+        Assert.False(rect.HasArea);
+        Assert.Equal(rect, Int32Rect.Empty);
+    }
+
+    [Theory]
+    [InlineData(-1)]
+    [InlineData(0)]
+    [InlineData(1)]
+    [InlineData(2)]
+    [InlineData(3)]
+    [InlineData(4   )]
+    public void X_Set_GetReturnsExpected(int value)
+    {
+        var rect = new Int32Rect(1, 2, 3, 4);
+
+        // Set.
+        rect.X = value;
+        Assert.Equal(value, rect.X);
+        Assert.Equal(2, rect.Y);
+        Assert.Equal(3, rect.Width);
+        Assert.Equal(4, rect.Height);
+        Assert.False(rect.IsEmpty);
+        Assert.True(rect.HasArea);
+
+        // Set again.
+        rect.X = value;
+        Assert.Equal(value, rect.X);
+        Assert.Equal(2, rect.Y);
+        Assert.Equal(3, rect.Width);
+        Assert.Equal(4, rect.Height);
+        Assert.False(rect.IsEmpty);
+        Assert.True(rect.HasArea);
+    }
+
+
+    [Theory]
+    [InlineData(-1)]
+    [InlineData(0)]
+    [InlineData(1)]
+    [InlineData(2)]
+    [InlineData(3)]
+    [InlineData(4   )]
+    public void Y_Set_GetReturnsExpected(int value)
+    {
+        var rect = new Int32Rect(1, 2, 3, 4);
+
+        // Set.
+        rect.Y = value;
+        Assert.Equal(1, rect.X);
+        Assert.Equal(value, rect.Y);
+        Assert.Equal(3, rect.Width);
+        Assert.Equal(4, rect.Height);
+        Assert.False(rect.IsEmpty);
+        Assert.True(rect.HasArea);
+
+        // Set again.
+        rect.Y = value;
+        Assert.Equal(1, rect.X);
+        Assert.Equal(value, rect.Y);
+        Assert.Equal(3, rect.Width);
+        Assert.Equal(4, rect.Height);
+        Assert.False(rect.IsEmpty);
+        Assert.True(rect.HasArea);
+    }
+
+
+    [Theory]
+    [InlineData(-1, false)]
+    [InlineData(0, false)]
+    [InlineData(1, true)]
+    [InlineData(2, true)]
+    [InlineData(3, true)]
+    [InlineData(4, true)]
+    public void Width_Set_GetReturnsExpected(int value, bool expectedHasArea)
+    {
+        var rect = new Int32Rect(1, 2, 3, 4);
+
+        // Set.
+        rect.Width = value;
+        Assert.Equal(1, rect.X);
+        Assert.Equal(2, rect.Y);
+        Assert.Equal(value, rect.Width);
+        Assert.Equal(4, rect.Height);
+        Assert.False(rect.IsEmpty);
+        Assert.Equal(expectedHasArea, rect.HasArea);
+
+        // Set again.
+        rect.Width = value;
+        Assert.Equal(1, rect.X);
+        Assert.Equal(2, rect.Y);
+        Assert.Equal(value, rect.Width);
+        Assert.Equal(4, rect.Height);
+        Assert.False(rect.IsEmpty);
+        Assert.Equal(expectedHasArea, rect.HasArea);
+    }
+
+    [Theory]
+    [InlineData(-1, false)]
+    [InlineData(0, false)]
+    [InlineData(1, true)]
+    [InlineData(2, true)]
+    [InlineData(3, true)]
+    [InlineData(4, true)]
+    public void Height_Set_GetReturnsExpected(int value, bool expectedHasArea)
+    {
+        var rect = new Int32Rect(1, 2, 3, 4);
+
+        // Set.
+        rect.Height = value;
+        Assert.Equal(1, rect.X);
+        Assert.Equal(2, rect.Y);
+        Assert.Equal(3, rect.Width);
+        Assert.Equal(value, rect.Height);
+        Assert.False(rect.IsEmpty);
+        Assert.Equal(expectedHasArea, rect.HasArea);
+
+        // Set again.
+        rect.Height = value;
+        Assert.Equal(1, rect.X);
+        Assert.Equal(2, rect.Y);
+        Assert.Equal(3, rect.Width);
+        Assert.Equal(value, rect.Height);
+        Assert.False(rect.IsEmpty);
+        Assert.Equal(expectedHasArea, rect.HasArea);
+    }
+
+    public static IEnumerable<object?[]> Equals_TestData()
+    {
+        // Zero.
+        yield return new object?[] { new Int32Rect(1, 2, 3, 4), new Int32Rect(1, 2, 3, 4), true };
+        yield return new object?[] { new Int32Rect(1, 2, 3, 4), new Int32Rect(2, 2, 3, 4), false };
+        yield return new object?[] { new Int32Rect(1, 2, 3, 4), new Int32Rect(1, 3, 3, 4), false };
+        yield return new object?[] { new Int32Rect(1, 2, 3, 4), new Int32Rect(1, 2, 4, 4), false };
+        yield return new object?[] { new Int32Rect(1, 2, 3, 4), new Int32Rect(1, 2, 3, 5), false };
+        yield return new object?[] { new Int32Rect(1, 2, 3, 4), new Int32Rect(0, 0, 0, 0), false };
+        yield return new object?[] { new Int32Rect(1, 2, 3, 4), new Int32Rect(), false };
+        yield return new object?[] { new Int32Rect(1, 2, 3, 4), Int32Rect.Empty, false };
+        yield return new object?[] { new Int32Rect(1, 2, 3, 4), new object(), false };
+        yield return new object?[] { new Int32Rect(1, 2, 3, 4), null, false };
+
+        // Zero.
+        yield return new object?[] { new Int32Rect(0, 0, 0, 0), Int32Rect.Empty, true };
+        yield return new object?[] { new Int32Rect(0, 0, 0, 0), new Int32Rect(), true };
+        yield return new object?[] { new Int32Rect(0, 0, 0, 0), new Int32Rect(0, 0, 0, 0), true };
+        yield return new object?[] { new Int32Rect(0, 0, 0, 0), new Int32Rect(1, 0, 0, 0), false };
+        yield return new object?[] { new Int32Rect(0, 0, 0, 0), new Int32Rect(0, 2, 0, 0), false };
+        yield return new object?[] { new Int32Rect(0, 0, 0, 0), new Int32Rect(0, 0, 3, 0), false };
+        yield return new object?[] { new Int32Rect(0, 0, 0, 0), new Int32Rect(0, 0, 0, 4), false };
+        yield return new object?[] { new Int32Rect(0, 0, 0, 0), new Int32Rect(1, 2, 3, 4), false };
+        yield return new object?[] { new Int32Rect(0, 0, 0, 0), new object(), false };
+        yield return new object?[] { new Int32Rect(0, 0, 0, 0), null, false };
+
+        // Default.
+        yield return new object?[] { new Int32Rect(), Int32Rect.Empty, true };
+        yield return new object?[] { new Int32Rect(), new Int32Rect(), true };
+        yield return new object?[] { new Int32Rect(), new Int32Rect(0, 0, 0, 0), true };
+        yield return new object?[] { new Int32Rect(), new Int32Rect(1, 0, 0, 0), false };
+        yield return new object?[] { new Int32Rect(), new Int32Rect(0, 2, 0, 0), false };
+        yield return new object?[] { new Int32Rect(), new Int32Rect(0, 0, 3, 0), false };
+        yield return new object?[] { new Int32Rect(), new Int32Rect(0, 0, 0, 4), false };
+        yield return new object?[] { new Int32Rect(), new Int32Rect(1, 2, 3, 4), false };
+        yield return new object?[] { new Int32Rect(), new object(), false };
+        yield return new object?[] { new Int32Rect(), null, false };
+
+        // Empty.
+        yield return new object?[] { Int32Rect.Empty, Int32Rect.Empty, true };
+        yield return new object?[] { Int32Rect.Empty, new Int32Rect(), true };
+        yield return new object?[] { Int32Rect.Empty, new Int32Rect(0, 0, 0, 0), true };
+        yield return new object?[] { Int32Rect.Empty, new Int32Rect(1, 0, 0, 0), false };
+        yield return new object?[] { Int32Rect.Empty, new Int32Rect(0, 2, 0, 0), false };
+        yield return new object?[] { Int32Rect.Empty, new Int32Rect(0, 0, 3, 0), false };
+        yield return new object?[] { Int32Rect.Empty, new Int32Rect(0, 0, 0, 4), false };
+        yield return new object?[] { Int32Rect.Empty, new Int32Rect(1, 2, 3, 4), false };
+        yield return new object?[] { Int32Rect.Empty, new object(), false };
+        yield return new object?[] { Int32Rect.Empty, null, false };
+    }
+
+    [Theory]
+    [MemberData(nameof(Equals_TestData))]
+    public void Equals_Invoke_ReturnsExpected(Int32Rect rect, object o, bool expected)
+    {
+        Assert.Equal(expected, rect.Equals(o));
+        if (o is Int32Rect value)
+        {
+            Assert.Equal(expected, rect.Equals(value));
+            Assert.Equal(expected, value.Equals(rect));
+            Assert.Equal(expected, rect == value);
+            Assert.Equal(expected, value == rect);
+            Assert.Equal(!expected, rect != value);
+            Assert.Equal(!expected, value != rect);
+            Assert.Equal(expected, rect.GetHashCode().Equals(value.GetHashCode()));
+        }
+    }
+
+    [Fact]
+    public void GetHashCode_InvokeDefault_ReturnsEqual()
+    {
+        var rect = new Int32Rect();
+        Assert.Equal(0, rect.GetHashCode());
+        Assert.Equal(rect.GetHashCode(), rect.GetHashCode());
+    }
+
+    [Fact]
+    public void GetHashCode_InvokeEmpty_ReturnsEqual()
+    {
+        Int32Rect rect = Int32Rect.Empty;
+        Assert.Equal(0, rect.GetHashCode());
+        Assert.Equal(rect.GetHashCode(), rect.GetHashCode());
+    }
+
+    [Fact]
+    public void GetHashCode_InvokeNormal_ReturnsEqual()
+    {
+        var rect = new Int32Rect(1, 2, 3, 4);
+        Assert.NotEqual(0, rect.GetHashCode());
+        Assert.Equal(rect.GetHashCode(), rect.GetHashCode());
+    }
+
+    public static IEnumerable<object[]> Parse_TestData()
+    {
+        yield return new object[] { "Empty", Int32Rect.Empty };
+        yield return new object[] { "  Empty  ", Int32Rect.Empty };
+        yield return new object[] { "Empty", new Int32Rect() };
+        yield return new object[] { "1,2,3,4", new Int32Rect(1, 2, 3, 4) };
+        yield return new object[] { "   1   ,   2  ,  3,  4", new Int32Rect(1, 2, 3, 4) };
+        yield return new object[] { "-1,-2,-3,-4", new Int32Rect(-1, -2, -3, -4) };
+    }
+
+    [Theory]
+    [MemberData(nameof(Parse_TestData))]
+    public void Parse_Invoke_Success(string source, Int32Rect expected)
+    {
+        Int32Rect result = Int32Rect.Parse(source);
+        Assert.Equal(expected.X, result.X);
+        Assert.Equal(expected.Y, result.Y);
+        Assert.Equal(expected.Width, result.Width);
+        Assert.Equal(expected.Height, result.Height);
+    }
+
+    [Fact]
+    public void Parse_NullSource_ThrowsInvalidOperationException()
+    {
+        Assert.Throws<InvalidOperationException>(() => Int32Rect.Parse(null));
+    }
+
+    public static IEnumerable<object[]> Parse_InvalidSource_TestData()
+    {
+        yield return new object[] { "" };
+        yield return new object[] { "  " };
+        yield return new object[] { "," };
+        yield return new object[] { "1" };
+        yield return new object[] { "1," };
+        yield return new object[] { "1,2" };
+        yield return new object[] { "1,2," };
+        yield return new object[] { "1,2,3" };
+        yield return new object[] { "1,2,3," };
+        yield return new object[] { "1,2,3,4," };
+        yield return new object[] { "1,2,3,4,5" };
+        yield return new object[] { "1,2,4,5,test" };
+        yield return new object[] { "Empty," };
+        yield return new object[] { "Empty,2,3,4" };
+        yield return new object[] { "Identity," };
+    }
+
+    [Theory]
+    [MemberData(nameof(Parse_InvalidSource_TestData))]
+    public void Parse_InvalidSource_ThrowsInvalidOperationException(string source)
+    {
+        Assert.Throws<InvalidOperationException>(() => Int32Rect.Parse(source));
+    }
+
+    public static IEnumerable<object[]> Parse_NotInt32_TestData()
+    {
+        yield return new object[] { "Identity" };
+        yield return new object[] { " Identity " };
+        yield return new object[] { "Identity,2,3,4" };
+        yield return new object[] { "test" };
+        yield return new object[] { "test,2,3,4" };
+        yield return new object[] { "1,test,3,4" };
+        yield return new object[] { "1,2,test,4" };
+        yield return new object[] { "1,2,3,test" };
+        yield return new object[] { "1;2;3;4" };
+        yield return new object[] { """1"",""2"",""3"",""4""" };
+        yield return new object[] { "1.1,2,3,4" };
+    }
+
+    [Theory]
+    [MemberData(nameof(Parse_NotInt32_TestData))]
+    public void Parse_NotInt_ThrowsFormatException(string source)
+    {
+        Assert.Throws<FormatException>(() => Int32Rect.Parse(source));
+    }
+
+    public static IEnumerable<object[]> ToString_TestData()
+    {
+        yield return new object[] { Int32Rect.Empty, "Empty" };
+        yield return new object[] { new Int32Rect(), "Empty" };
+        yield return new object[] { new Int32Rect(0, 0, 0, 0), "Empty" };
+        yield return new object[] { new Int32Rect(1, 2, 3, 4), "1,2,3,4" };
+        yield return new object[] { new Int32Rect(-1, -2, 3, 4), "-1,-2,3,4" };
+    }
+
+    [Theory]
+    [MemberData(nameof(ToString_TestData))]
+    public void ToString_Invoke_ReturnsExpected(Int32Rect rect, string expected)
+    {
+        Assert.Equal(expected, rect.ToString());
+    }
+
+    [Theory]
+    [MemberData(nameof(ToString_TestData))]
+    public void ToString_InvokeIFormatProviderInvariantCulture_ReturnsExpected(Int32Rect rect, string expected)
+    {
+        Assert.Equal(expected, rect.ToString(CultureInfo.InvariantCulture));
+    }
+
+    public static IEnumerable<object[]> ToString_IFormatProviderCustom_TestData()
+    {
+        yield return new object[] { new Int32Rect(), "|", "Empty" };
+        yield return new object[] { new Int32Rect(), "|_", "Empty" };
+        yield return new object[] { new Int32Rect(), ",_", "Empty" };
+        yield return new object[] { new Int32Rect(), ",", "Empty" };
+        yield return new object[] { new Int32Rect(), ";", "Empty" };
+        yield return new object[] { new Int32Rect(), " ", "Empty" };
+
+        yield return new object[] { new Int32Rect(0, 0, 0, 0), "|", "Empty" };
+        yield return new object[] { new Int32Rect(0, 0, 0, 0), "|_", "Empty" };
+        yield return new object[] { new Int32Rect(0, 0, 0, 0), ",_", "Empty" };
+        yield return new object[] { new Int32Rect(0, 0, 0, 0), ",", "Empty" };
+        yield return new object[] { new Int32Rect(0, 0, 0, 0), ";", "Empty" };
+        yield return new object[] { new Int32Rect(0, 0, 0, 0), " ", "Empty" };
+
+        yield return new object[] { new Int32Rect(1, 2, 3, 4), "|", "1,2,3,4" };
+        yield return new object[] { new Int32Rect(1, 2, 3, 4), "|_", "1,2,3,4" };
+        yield return new object[] { new Int32Rect(1, 2, 3, 4), ",_", "1;2;3;4" };
+        yield return new object[] { new Int32Rect(1, 2, 3, 4), ",", "1;2;3;4" };
+        yield return new object[] { new Int32Rect(1, 2, 3, 4), ";", "1,2,3,4" };
+        yield return new object[] { new Int32Rect(1, 2, 3, 4), " ", "1,2,3,4" };
+
+        yield return new object[] { new Int32Rect(-1, -2, -3, -4), "|", "-1,-2,-3,-4" };
+        yield return new object[] { new Int32Rect(-1, -2, -3, -4), "|_", "-1,-2,-3,-4" };
+        yield return new object[] { new Int32Rect(-1, -2, -3, -4), ",_", "-1;-2;-3;-4" };
+        yield return new object[] { new Int32Rect(-1, -2, -3, -4), ",", "-1;-2;-3;-4" };
+        yield return new object[] { new Int32Rect(-1, -2, -3, -4), ";", "-1,-2,-3,-4" };
+        yield return new object[] { new Int32Rect(-1, -2, -3, -4), " ", "-1,-2,-3,-4" };
+    }
+
+    [Theory]
+    [MemberData(nameof(ToString_IFormatProviderCustom_TestData))]
+    public void ToString_InvokeIFormatProviderCustom_ReturnsExpected(Int32Rect rect, string numberDecimalSeparator, string expected)
+    {
+        var culture = new CultureInfo("en-US");
+        NumberFormatInfo formatInfo = culture.NumberFormat;
+        formatInfo.NumberDecimalSeparator = numberDecimalSeparator;
+
+        Assert.Equal(expected, rect.ToString(formatInfo));
+    }
+
+    [Theory]
+    [MemberData(nameof(ToString_TestData))]
+    public void ToString_InvokeIFormattableInvariantCulture_ReturnsExpected(Int32Rect rect, string expected)
+    {
+        IFormattable formattable = rect;
+        Assert.Equal(expected, formattable.ToString(null, null));
+        Assert.Equal(expected, formattable.ToString(null, CultureInfo.InvariantCulture));
+    }
+
+    [Theory]
+    [InlineData("|", "1|00,2|00,3|00,4|00")]
+    [InlineData("|_", "1|_00,2|_00,3|_00,4|_00")]
+    [InlineData(",_", "1,_00;2,_00;3,_00;4,_00")]
+    [InlineData(",", "1,00;2,00;3,00;4,00")]
+    [InlineData(";", "1;00,2;00,3;00,4;00")]
+    [InlineData(" ", "1 00,2 00,3 00,4 00")]
+    public void ToString_InvokeIFormattableCustomFormat_ReturnsExpected(string numberDecimalSeparator, string expected)
+    {
+        var rect = new Int32Rect(1, 2, 3, 4);
+        IFormattable formattable = rect;
+
+        var culture = new CultureInfo("en-US");
+        NumberFormatInfo formatInfo = culture.NumberFormat;
+        formatInfo.NumberDecimalSeparator = numberDecimalSeparator;
+        Assert.Equal(expected, formattable.ToString("F2", formatInfo));
+    }
+
+    [Fact]
+    public void TypeConverter_Get_ReturnsExpected()
+    {
+        Assert.IsType<Int32RectConverter>(TypeDescriptor.GetConverter(typeof(Int32Rect)));
+    }
+
+    [Fact]
+    public void ValueSerializer_Get_ReturnsExpected()
+    {
+        Assert.IsType<Int32RectValueSerializer>(ValueSerializer.GetSerializerFor(typeof(Int32Rect)));
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Interop/ComponentDispatcherTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Interop/ComponentDispatcherTests.cs
new file mode 100644
index 00000000000..61377b82898
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Interop/ComponentDispatcherTests.cs
@@ -0,0 +1,279 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Windows.Interop.Tests;
+
+public class ComponentDispatcherTests
+{
+    // TODO:
+    // - Invoke tests (needs RemoteExecutor)
+
+    [Fact]
+    public void CurrentKeyboardMessage_Get_ReturnsExpected()
+    {
+        MSG msg = ComponentDispatcher.CurrentKeyboardMessage;
+        Assert.Equal(msg, ComponentDispatcher.CurrentKeyboardMessage);
+    }
+
+    [Fact]
+    public void IsThreadModal_Get_ReturnsExpected()
+    {
+        bool isThreadModal = ComponentDispatcher.IsThreadModal;
+        Assert.False(isThreadModal);
+        Assert.Equal(isThreadModal, ComponentDispatcher.IsThreadModal);
+    }
+
+    [Fact]
+    public void EnterThreadModal_AddRemove_Success()
+    {
+        int callCount = 0;
+        EventHandler handler = (s, e) => callCount++;
+        ComponentDispatcher.EnterThreadModal += handler;
+        Assert.Equal(0, callCount);
+
+        ComponentDispatcher.EnterThreadModal -= handler;
+        Assert.Equal(0, callCount);
+
+        // Remove non existent.
+        ComponentDispatcher.EnterThreadModal -= handler;
+        Assert.Equal(0, callCount);
+
+        // Add null.
+        ComponentDispatcher.EnterThreadModal += null;
+        Assert.Equal(0, callCount);
+
+        // Remove null.
+        ComponentDispatcher.EnterThreadModal -= null;
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void LeaveThreadModal_AddRemove_Success()
+    {
+        int callCount = 0;
+        EventHandler handler = (s, e) => callCount++;
+        ComponentDispatcher.LeaveThreadModal += handler;
+        Assert.Equal(0, callCount);
+
+        ComponentDispatcher.LeaveThreadModal -= handler;
+        Assert.Equal(0, callCount);
+
+        // Remove non existent.
+        ComponentDispatcher.LeaveThreadModal -= handler;
+        Assert.Equal(0, callCount);
+
+        // Add null.
+        ComponentDispatcher.LeaveThreadModal += null;
+        Assert.Equal(0, callCount);
+
+        // Remove null.
+        ComponentDispatcher.LeaveThreadModal -= null;
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void ThreadFilterMessage_AddRemove_Success()
+    {
+        int callCount = 0;
+        ThreadMessageEventHandler handler = (ref MSG m, ref bool h) => callCount++;
+        ComponentDispatcher.ThreadFilterMessage += handler;
+        Assert.Equal(0, callCount);
+
+        ComponentDispatcher.ThreadFilterMessage -= handler;
+        Assert.Equal(0, callCount);
+
+        // Remove non existent.
+        ComponentDispatcher.ThreadFilterMessage -= handler;
+        Assert.Equal(0, callCount);
+
+        // Add null.
+        ComponentDispatcher.ThreadFilterMessage += null;
+        Assert.Equal(0, callCount);
+
+        // Remove null.
+        ComponentDispatcher.ThreadFilterMessage -= null;
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void ThreadPreprocessMessage_AddRemove_Success()
+    {
+        int callCount = 0;
+        ThreadMessageEventHandler handler = (ref MSG m, ref bool h) => callCount++;
+        ComponentDispatcher.ThreadPreprocessMessage += handler;
+        Assert.Equal(0, callCount);
+
+        ComponentDispatcher.ThreadPreprocessMessage -= handler;
+        Assert.Equal(0, callCount);
+
+        // Remove non existent.
+        ComponentDispatcher.ThreadPreprocessMessage -= handler;
+        Assert.Equal(0, callCount);
+
+        // Add null.
+        ComponentDispatcher.ThreadPreprocessMessage += null;
+        Assert.Equal(0, callCount);
+
+        // Remove null.
+        ComponentDispatcher.ThreadPreprocessMessage -= null;
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void ThreadIdle_AddRemove_Success()
+    {
+        int callCount = 0;
+        EventHandler handler = (s, e) => callCount++;
+        ComponentDispatcher.ThreadIdle += handler;
+        Assert.Equal(0, callCount);
+
+        ComponentDispatcher.ThreadIdle -= handler;
+        Assert.Equal(0, callCount);
+
+        // Remove non existent.
+        ComponentDispatcher.ThreadIdle -= handler;
+        Assert.Equal(0, callCount);
+
+        // Add null.
+        ComponentDispatcher.ThreadIdle += null;
+        Assert.Equal(0, callCount);
+
+        // Remove null.
+        ComponentDispatcher.ThreadIdle -= null;
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void RaiseIdle_Invoke_Success()
+    {
+        // Raise.
+        ComponentDispatcher.RaiseIdle();
+
+        // Raise again.
+        ComponentDispatcher.RaiseIdle();
+    }
+
+    [Fact]
+    public void RaiseIdle_InvokeWithHandler_Success()
+    {
+        int callCount = 0;
+        EventHandler handler = (s, e) =>
+        {
+            Assert.Null(s);
+            Assert.Same(EventArgs.Empty, e);
+            callCount++;
+        };
+        ComponentDispatcher.ThreadIdle += handler;
+
+        // Raise.
+        ComponentDispatcher.RaiseIdle();
+        Assert.Equal(1, callCount);
+
+        // Raise again.
+        ComponentDispatcher.RaiseIdle();
+        Assert.Equal(2, callCount);
+
+        // Remove handler.
+        ComponentDispatcher.ThreadIdle -= handler;
+        ComponentDispatcher.RaiseIdle();
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void RaiseThreadMessage_Invoke_Success()
+    {
+        var msg = new MSG();
+
+        // Raise.
+        ComponentDispatcher.RaiseThreadMessage(ref msg);
+
+        // Raise again.
+        ComponentDispatcher.RaiseThreadMessage(ref msg);
+    }
+
+    [Fact]
+    public void PushModal_Invoke_Success()
+    {
+        bool original = ComponentDispatcher.IsThreadModal;
+
+        // Push.
+        ComponentDispatcher.PushModal();
+        Assert.True(ComponentDispatcher.IsThreadModal);
+        
+        // Pop.
+        ComponentDispatcher.PopModal();
+        Assert.Equal(original, ComponentDispatcher.IsThreadModal);
+    }
+
+    [Fact]
+    public void PushModal_InvokeMultipleTimes_Success()
+    {
+        bool original = ComponentDispatcher.IsThreadModal;
+
+        // Push.
+        ComponentDispatcher.PushModal();
+        Assert.True(ComponentDispatcher.IsThreadModal);
+
+        // Push again.
+        ComponentDispatcher.PushModal();
+        Assert.True(ComponentDispatcher.IsThreadModal);
+        
+        // Pop.
+        ComponentDispatcher.PopModal();
+        Assert.Equal(original, ComponentDispatcher.IsThreadModal);
+
+        // Pop again.
+        ComponentDispatcher.PopModal();
+        Assert.False(ComponentDispatcher.IsThreadModal);
+    }
+
+    [Fact]
+    public void PopModal_Invoke_Success()
+    {
+        // Push.
+        ComponentDispatcher.PushModal();
+        Assert.True(ComponentDispatcher.IsThreadModal);
+
+        // Pop.
+        ComponentDispatcher.PopModal();
+        Assert.False(ComponentDispatcher.IsThreadModal);
+        
+        // Pop again.
+        ComponentDispatcher.PopModal();
+        Assert.False(ComponentDispatcher.IsThreadModal);
+    }
+
+    [Fact]
+    public void PopModal_InvokeNoPush_Success()
+    {
+        // Pop.
+        ComponentDispatcher.PopModal();
+        Assert.False(ComponentDispatcher.IsThreadModal);
+        
+        // Pop again.
+        ComponentDispatcher.PopModal();
+        Assert.False(ComponentDispatcher.IsThreadModal);
+
+        // Push.
+        ComponentDispatcher.PushModal();
+        Assert.True(ComponentDispatcher.IsThreadModal);
+
+        // Push again.
+        ComponentDispatcher.PushModal();
+        Assert.True(ComponentDispatcher.IsThreadModal);
+    }
+
+    [Fact]
+    public void PopModal_InvokeMultipleTimes_Success()
+    {
+        // Push.
+        ComponentDispatcher.PushModal();
+
+        // Pop.
+        ComponentDispatcher.PopModal();
+        
+        // Pop again.
+        ComponentDispatcher.PopModal();
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Interop/MSGTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Interop/MSGTests.cs
new file mode 100644
index 00000000000..1fb03716878
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Interop/MSGTests.cs
@@ -0,0 +1,141 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Windows.Interop.Tests;
+
+public class MSGTests
+{
+    [Fact]
+    public void Ctor_Default()
+    {
+        var msg = new MSG();
+        Assert.Equal(IntPtr.Zero, msg.hwnd);
+        Assert.Equal(0, msg.message);
+        Assert.Equal(IntPtr.Zero, msg.wParam);
+        Assert.Equal(IntPtr.Zero, msg.lParam);
+        Assert.Equal(0, msg.time);
+        Assert.Equal(0, msg.pt_x);
+        Assert.Equal(0, msg.pt_y);
+    }
+
+    public static IEnumerable<object[]> IntPtr_TestData()
+    {
+        yield return new object[] { (IntPtr)(-1) };
+        yield return new object[] { IntPtr.Zero };
+        yield return new object[] { (IntPtr)1 };
+    }
+
+    [Theory]
+    [MemberData(nameof(IntPtr_TestData))]
+    public void hwnd_Set_GetReturnsExpected(IntPtr value)
+    {
+        var msg = new MSG();
+        
+        // Set.
+        msg.hwnd = value;
+        Assert.Equal(value, msg.hwnd);
+
+        // Set same.
+        msg.hwnd = value;
+        Assert.Equal(value, msg.hwnd);
+    }
+
+    [Theory]
+    [InlineData(-1)]
+    [InlineData(0)]
+    [InlineData(1)]
+    public void message_Set_GetReturnsExpected(int value)
+    {
+        var msg = new MSG();
+        
+        // Set.
+        msg.message = value;
+        Assert.Equal(value, msg.message);
+
+        // Set same.
+        msg.message = value;
+        Assert.Equal(value, msg.message);
+    }
+
+    [Theory]
+    [MemberData(nameof(IntPtr_TestData))]
+    public void wParam_Set_GetReturnsExpected(IntPtr value)
+    {
+        var msg = new MSG();
+        
+        // Set.
+        msg.wParam = value;
+        Assert.Equal(value, msg.wParam);
+
+        // Set same.
+        msg.wParam = value;
+        Assert.Equal(value, msg.wParam);
+    }
+
+    [Theory]
+    [MemberData(nameof(IntPtr_TestData))]
+    public void lParam_Set_GetReturnsExpected(IntPtr value)
+    {
+        var msg = new MSG();
+        
+        // Set.
+        msg.lParam = value;
+        Assert.Equal(value, msg.lParam);
+
+        // Set same.
+        msg.lParam = value;
+        Assert.Equal(value, msg.lParam);
+    }
+
+    [Theory]
+    [InlineData(-1)]
+    [InlineData(0)]
+    [InlineData(1)]
+    public void time_Set_GetReturnsExpected(int value)
+    {
+        var msg = new MSG();
+        
+        // Set.
+        msg.time = value;
+        Assert.Equal(value, msg.time);
+
+        // Set same.
+        msg.time = value;
+        Assert.Equal(value, msg.time);
+    }
+
+    [Theory]
+    [InlineData(-1)]
+    [InlineData(0)]
+    [InlineData(1)]
+    public void pt_x_Set_GetReturnsExpected(int value)
+    {
+        var msg = new MSG();
+        
+        // Set.
+        msg.pt_x = value;
+        Assert.Equal(value, msg.pt_x);
+
+        // Set same.
+        msg.pt_x = value;
+        Assert.Equal(value, msg.pt_x);
+    }
+
+    [Theory]
+    [InlineData(-1)]
+    [InlineData(0)]
+    [InlineData(1)]
+    public void pt_y_Set_GetReturnsExpected(int value)
+    {
+        var msg = new MSG();
+        
+        // Set.
+        msg.pt_y = value;
+        Assert.Equal(value, msg.pt_y);
+
+        // Set same.
+        msg.pt_y = value;
+        Assert.Equal(value, msg.pt_y);
+    }
+}
\ No newline at end of file
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/LocalValueEntryTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/LocalValueEntryTests.cs
new file mode 100644
index 00000000000..72f8195940f
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/LocalValueEntryTests.cs
@@ -0,0 +1,115 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Reflection;
+
+namespace System.Windows.Tests;
+
+public class LocalValueEntryTests
+{
+    [Fact]
+    public void Ctor_Default()
+    {
+        var entry = new LocalValueEntry();
+        Assert.Null(entry.Property);
+        Assert.Null(entry.Value);
+    }
+
+    public static IEnumerable<object?[]> Equals_TestData()
+    {
+        yield return new object?[] { new LocalValueEntry(), new LocalValueEntry(), true };
+        //yield return new object?[] { new LocalValueEntry(), new object(), false };
+        //yield return new object?[] { new LocalValueEntry(), null, false };
+    }
+
+    [Theory]
+    [MemberData(nameof(Equals_TestData))]
+    public void Equals_Invoke_ReturnsExpected(LocalValueEntry entry, object? obj, bool expected)
+    {
+        Assert.Equal(expected, entry.Equals(obj));
+        if (obj is LocalValueEntry other)
+        {
+            Assert.Equal(expected, other.Equals(entry));
+            Assert.Equal(expected, entry == other);
+            Assert.Equal(expected, other == entry);
+            Assert.Equal(!expected, entry != other);
+            Assert.Equal(!expected, other != entry);
+        }
+    }
+
+    [Fact]
+    public void Equals_InvokeCustom_ReturnsExpected()
+    {
+        DependencyProperty property1 = DependencyProperty.Register(nameof(LocalValueEntryTests) + MethodBase.GetCurrentMethod()!.Name + "1", typeof(string), typeof(DependencyObject));
+        DependencyProperty property2 = DependencyProperty.Register(nameof(LocalValueEntryTests) + MethodBase.GetCurrentMethod()!.Name + "2", typeof(string), typeof(DependencyObject));
+        var obj1 = new DependencyObject();
+        var obj2 = new DependencyObject();
+        var obj3 = new DependencyObject();
+        var obj4 = new DependencyObject();
+        obj1.SetValue(property1, "a");
+        obj2.SetValue(property1, "a");
+        obj3.SetValue(property1, "b");
+        obj4.SetValue(property2, "a");
+        
+        LocalValueEnumerator enumerator1 = obj1.GetLocalValueEnumerator();
+        enumerator1.MoveNext();
+        LocalValueEnumerator enumerator1Copy = obj1.GetLocalValueEnumerator();
+        enumerator1Copy.MoveNext();
+        LocalValueEnumerator enumerator2 = obj2.GetLocalValueEnumerator();
+        enumerator2.MoveNext();
+        LocalValueEnumerator enumerator3 = obj3.GetLocalValueEnumerator();
+        enumerator3.MoveNext();
+        LocalValueEnumerator enumerator4 = obj4.GetLocalValueEnumerator();
+        enumerator4.MoveNext();
+
+        Equals_Invoke_ReturnsExpected(enumerator1.Current, enumerator1.Current, true);
+        Equals_Invoke_ReturnsExpected(enumerator1.Current, enumerator1Copy.Current, true);
+        Equals_Invoke_ReturnsExpected(enumerator1.Current, enumerator2.Current, true);
+        Equals_Invoke_ReturnsExpected(enumerator1.Current, enumerator3.Current, false);
+        Equals_Invoke_ReturnsExpected(enumerator1.Current, enumerator4.Current, false);
+        Equals_Invoke_ReturnsExpected(enumerator1.Current, new LocalValueEntry(), false);
+        Equals_Invoke_ReturnsExpected(new LocalValueEntry(), enumerator1.Current, false);
+        // TODO: should return false.
+        //Equals_Invoke_ReturnsExpected(enumerator1.Current, new object(), false);
+        //Equals_Invoke_ReturnsExpected(enumerator1.Current, null!, false);
+    }
+
+    [Fact]
+    public void Equals_ObjNull_ThrowsNullReferenceException()
+    {
+        var entry = new LocalValueEntry();
+        // TODO: should return false.
+        Assert.Throws<NullReferenceException>(() => entry.Equals(null));
+    }
+
+    [Fact]
+    public void Equals_ObjNotLocalValueEntry_ThrowsInvalidCastException()
+    {
+        var entry = new LocalValueEntry();
+        Assert.Throws<InvalidCastException>(() => entry.Equals(new object()));
+    }
+
+    [Fact]
+    public void GetHashCode_InvokeDefault_ReturnsExpected()
+    {
+        var entry = new LocalValueEntry();
+        Assert.NotEqual(0, entry.GetHashCode());
+        Assert.Equal(entry.GetHashCode(), entry.GetHashCode());
+    }
+
+    [Fact]
+    public void GetHashCode_InvokeCustom_ReturnsExpected()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(LocalValueEntryTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+        obj.SetValue(property, "a");
+
+        LocalValueEnumerator enumerator = obj.GetLocalValueEnumerator();
+        enumerator.MoveNext();
+
+        LocalValueEntry entry = enumerator.Current;
+        Assert.NotEqual(0, entry.GetHashCode());
+        Assert.Equal(entry.GetHashCode(), entry.GetHashCode());
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/LocalValueEnumeratorTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/LocalValueEnumeratorTests.cs
new file mode 100644
index 00000000000..0f8821a5084
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/LocalValueEnumeratorTests.cs
@@ -0,0 +1,302 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections;
+using System.Reflection;
+
+namespace System.Windows.Tests;
+
+public class LocalValueEnumeratorTests
+{
+    [Fact]
+    public void Ctor_Default()
+    {
+        var enumerator = new LocalValueEnumerator();
+        Assert.Equal(0, enumerator.Count);
+        Assert.Throws<InvalidOperationException>(() => enumerator.Current);
+    }
+
+    [Fact]
+    public void Current_GetDefault_ThrowsInvalidOperationException()
+    {
+        var enumerator = new LocalValueEnumerator();
+        Assert.Throws<InvalidOperationException>(() => enumerator.Current);
+    }
+
+    [Fact]
+    public void Current_GetDefaultFinished_ThrowsInvalidOperationException()
+    {
+        var enumerator = new LocalValueEnumerator();
+        enumerator.MoveNext();
+
+        Assert.Throws<InvalidOperationException>(() => enumerator.Current);
+    }
+
+    [Fact]
+    public void Current_GetDefaultReset_ThrowsInvalidOperationException()
+    {
+        var enumerator = new LocalValueEnumerator();
+        enumerator.Reset();
+
+        Assert.Throws<InvalidOperationException>(() => enumerator.Current);
+    }
+
+    [Fact]
+    public void Current_GetCustom_ThrowsInvalidOperationException()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(LocalValueEnumeratorTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+        obj.SetValue(property, "a");
+
+        LocalValueEnumerator enumerator = obj.GetLocalValueEnumerator();
+        Assert.Throws<InvalidOperationException>(() => enumerator.Current);
+    }
+
+    [Fact]
+    public void Current_GetCustomFinished_ThrowsInvalidOperationException()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(LocalValueEnumeratorTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+        obj.SetValue(property, "a");
+
+        LocalValueEnumerator enumerator = obj.GetLocalValueEnumerator();
+        enumerator.MoveNext();
+        enumerator.MoveNext();
+        Assert.Throws<InvalidOperationException>(() => enumerator.Current);
+    }
+
+    [Fact]
+    public void Current_GetCustomReset_ThrowsInvalidOperationException()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(LocalValueEnumeratorTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+        obj.SetValue(property, "a");
+
+        LocalValueEnumerator enumerator = obj.GetLocalValueEnumerator();
+        enumerator.Reset();
+        Assert.Throws<InvalidOperationException>(() => enumerator.Current);
+    }
+
+    [Fact]
+    public void IEnumeratorCurrent_GetDefault_ThrowsInvalidOperationException()
+    {
+        IEnumerator enumerator = new LocalValueEnumerator();
+        Assert.Throws<InvalidOperationException>(() => ((IEnumerator)enumerator).Current);
+    }
+
+    [Fact]
+    public void IEnumeratorCurrent_GetDefaultFinished_ThrowsInvalidOperationException()
+    {
+        IEnumerator enumerator = new LocalValueEnumerator();
+        enumerator.MoveNext();
+
+        Assert.Throws<InvalidOperationException>(() => ((IEnumerator)enumerator).Current);
+    }
+
+    [Fact]
+    public void IEnumeratorCurrent_GetDefaultReset_ThrowsInvalidOperationException()
+    {
+        IEnumerator enumerator = new LocalValueEnumerator();
+        enumerator.Reset();
+
+        Assert.Throws<InvalidOperationException>(() => ((IEnumerator)enumerator).Current);
+    }
+
+    [Fact]
+    public void IEnumeratorCurrent_GetCustom_ThrowsInvalidOperationException()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(LocalValueEnumeratorTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+        obj.SetValue(property, "a");
+
+        LocalValueEnumerator enumerator = obj.GetLocalValueEnumerator();
+        Assert.Throws<InvalidOperationException>(() => ((IEnumerator)enumerator).Current);
+    }
+
+    [Fact]
+    public void IEnumeratorCurrent_GetCustomFinished_ThrowsInvalidOperationException()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(LocalValueEnumeratorTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+        obj.SetValue(property, "a");
+
+        LocalValueEnumerator enumerator = obj.GetLocalValueEnumerator();
+        enumerator.MoveNext();
+        enumerator.MoveNext();
+        Assert.Throws<InvalidOperationException>(() => ((IEnumerator)enumerator).Current);
+    }
+
+    [Fact]
+    public void IEnumeratorCurrent_GetCustomReset_ThrowsInvalidOperationException()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(LocalValueEnumeratorTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+        obj.SetValue(property, "a");
+
+        LocalValueEnumerator enumerator = obj.GetLocalValueEnumerator();
+        enumerator.Reset();
+        Assert.Throws<InvalidOperationException>(() => ((IEnumerator)enumerator).Current);
+    }
+
+    public static IEnumerable<object?[]> Equals_TestData()
+    {
+        yield return new object?[] { new LocalValueEnumerator(), new LocalValueEnumerator(), true, true };
+        
+        var enumerator1 = new LocalValueEnumerator();
+        enumerator1.MoveNext();
+        yield return new object?[] { new LocalValueEnumerator(), enumerator1, false, false };
+        
+        var enumerator2 = new LocalValueEnumerator();
+        enumerator2.MoveNext();
+        var enumerator3 = new LocalValueEnumerator();
+        enumerator3.MoveNext();
+        enumerator3.MoveNext();
+        yield return new object?[] { enumerator2, enumerator2, true, true };
+        yield return new object?[] { enumerator2, enumerator1, true, true };
+        yield return new object?[] { enumerator2, enumerator3, false, false };
+        
+        yield return new object?[] { new LocalValueEnumerator(), new object(), false, false };
+        yield return new object?[] { new LocalValueEnumerator(), null, false, false };
+    }
+
+    [Theory]
+    [MemberData(nameof(Equals_TestData))]
+    public void Equals_Invoke_ReturnsExpected(LocalValueEnumerator enumerator, object? obj, bool expected, bool expectedHashCode)
+    {
+        Assert.Equal(expected, enumerator.Equals(obj));
+        if (obj is LocalValueEnumerator other)
+        {
+            Assert.Equal(expected, other.Equals(enumerator));
+            Assert.Equal(expected, enumerator == other);
+            Assert.Equal(expected, other == enumerator);
+            Assert.Equal(!expected, enumerator != other);
+            Assert.Equal(!expected, other != enumerator);
+            Assert.Equal(expectedHashCode, enumerator.GetHashCode().Equals(other.GetHashCode()));
+        }
+    }
+
+    [Fact]
+    public void Equals_InvokeCustom_ReturnsExpected()
+    {
+        DependencyProperty property1 = DependencyProperty.Register(nameof(LocalValueEnumeratorTests) + MethodBase.GetCurrentMethod()!.Name + "1", typeof(string), typeof(DependencyObject));
+        DependencyProperty property2 = DependencyProperty.Register(nameof(LocalValueEnumeratorTests) + MethodBase.GetCurrentMethod()!.Name + "2", typeof(string), typeof(DependencyObject));
+        var obj1 = new DependencyObject();
+        var obj2 = new DependencyObject();
+        var obj3 = new DependencyObject();
+        var obj4 = new DependencyObject();
+        var obj5 = new DependencyObject();
+        obj1.SetValue(property1, "a");
+        obj2.SetValue(property1, "a");
+        obj3.SetValue(property1, "b");
+        obj4.SetValue(property1, "a");
+        obj4.SetValue(property2, "b");
+        obj5.SetValue(property2, "a");
+
+        LocalValueEnumerator enumerator1 = obj1.GetLocalValueEnumerator();
+        enumerator1.MoveNext();
+        LocalValueEnumerator enumerator1Copy1 = obj1.GetLocalValueEnumerator();
+        enumerator1Copy1.MoveNext();
+        LocalValueEnumerator enumerator1Copy2 = enumerator1;
+        LocalValueEnumerator enumerator1Copy3 = enumerator1;
+        enumerator1Copy3.MoveNext();
+        LocalValueEnumerator enumerator2 = obj2.GetLocalValueEnumerator();
+        enumerator2.MoveNext();
+        LocalValueEnumerator enumerator3 = obj3.GetLocalValueEnumerator();
+        enumerator3.MoveNext();
+        LocalValueEnumerator enumerator4 = obj4.GetLocalValueEnumerator();
+        enumerator4.MoveNext();
+        LocalValueEnumerator enumerator5 = obj5.GetLocalValueEnumerator();
+        enumerator5.MoveNext();
+
+        Equals_Invoke_ReturnsExpected(enumerator1, enumerator1, true, true);
+        Equals_Invoke_ReturnsExpected(enumerator1, enumerator1Copy1, false, true);
+        Equals_Invoke_ReturnsExpected(enumerator1, enumerator1Copy2, true, true);
+        Equals_Invoke_ReturnsExpected(enumerator1, enumerator1Copy3, false, false);
+        Equals_Invoke_ReturnsExpected(enumerator1, enumerator2, false, true);
+        Equals_Invoke_ReturnsExpected(enumerator1, enumerator3, false, true);
+        Equals_Invoke_ReturnsExpected(enumerator1, enumerator4, false, true);
+        Equals_Invoke_ReturnsExpected(enumerator1, enumerator5, false, true);
+        Equals_Invoke_ReturnsExpected(enumerator1, new LocalValueEnumerator(), false, true);
+        Equals_Invoke_ReturnsExpected(new LocalValueEnumerator(), enumerator1, false, true);
+        Equals_Invoke_ReturnsExpected(enumerator1, new object(), false, false);
+        Equals_Invoke_ReturnsExpected(enumerator1, null, false, false);
+    }
+
+    [Fact]
+    public void GetHashCode_InvokeDefault_ReturnsExpected()
+    {
+        var enumerator = new LocalValueEnumerator();
+        Assert.NotEqual(0, enumerator.GetHashCode());
+        Assert.Equal(enumerator.GetHashCode(), enumerator.GetHashCode());
+    }
+
+    [Fact]
+    public void GetHashCode_InvokeCustom_ReturnsExpected()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(LocalValueEnumeratorTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+        obj.SetValue(property, "a");
+
+        LocalValueEnumerator enumerator = obj.GetLocalValueEnumerator();
+        Assert.NotEqual(0, enumerator.GetHashCode());
+        Assert.Equal(enumerator.GetHashCode(), enumerator.GetHashCode());
+    }
+
+    [Fact]
+    public void MoveNext_InvokeDefault_ReturnsFalse()
+    {
+        var enumerator = new LocalValueEnumerator();
+        
+        // Move end.
+        Assert.False(enumerator.MoveNext());
+
+        // Move again.
+        Assert.False(enumerator.MoveNext());
+    }
+
+    [Fact]
+    public void MoveNext_InvokeCustom_ReturnsExpected()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(LocalValueEnumeratorTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+        obj.SetValue(property, "a");
+
+        LocalValueEnumerator enumerator = obj.GetLocalValueEnumerator();
+        Assert.True(enumerator.MoveNext());
+
+        // Move end.
+        Assert.False(enumerator.MoveNext());
+
+        // Move again.
+        Assert.False(enumerator.MoveNext());
+    }
+
+    [Fact]
+    public void Reset_InvokeDefault_Success()
+    {
+        var enumerator = new LocalValueEnumerator();
+        enumerator.Reset();
+        Assert.Throws<InvalidOperationException>(() => enumerator.Current);
+
+        // Reset again.
+        enumerator.Reset();
+        Assert.Throws<InvalidOperationException>(() => enumerator.Current);
+    }
+
+    [Fact]
+    public void Reset_InvokeCustom_Success()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(LocalValueEnumeratorTests) + MethodBase.GetCurrentMethod()!.Name, typeof(string), typeof(DependencyObject));
+        var obj = new DependencyObject();
+        obj.SetValue(property, "a");
+
+        LocalValueEnumerator enumerator = obj.GetLocalValueEnumerator();
+        enumerator.Reset();
+        Assert.Throws<InvalidOperationException>(() => enumerator.Current);
+
+        // Reset again.
+        enumerator.Reset();
+        Assert.Throws<InvalidOperationException>(() => enumerator.Current);
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Markup/InternalTypeHelperTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Markup/InternalTypeHelperTests.cs
new file mode 100644
index 00000000000..6dcee3c2f48
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Markup/InternalTypeHelperTests.cs
@@ -0,0 +1,36 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Globalization;
+using System.Reflection;
+
+namespace System.Windows.Markup.Tests;
+
+public class InternalTypeHelperTests
+{
+    [Fact]
+    public void Ctor_Default()
+    {
+        // Verify doesn't throw.
+        new SubInternalTypeHelper();
+    }
+
+    private class SubInternalTypeHelper : InternalTypeHelper
+    {
+        protected override void AddEventHandler(EventInfo eventInfo, object target, Delegate handler)
+            => throw new NotImplementedException();
+
+        protected override Delegate CreateDelegate(Type delegateType, object target, string handler)
+            => throw new NotImplementedException();
+
+        protected override object CreateInstance(Type type, CultureInfo culture)
+            => throw new NotImplementedException();
+
+        protected override object GetPropertyValue(PropertyInfo propertyInfo, object target, CultureInfo culture)
+            => throw new NotImplementedException();
+
+        protected override void SetPropertyValue(PropertyInfo propertyInfo, object target, object value, CultureInfo culture)
+            => throw new NotImplementedException();
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Markup/Primitives/MarkupObjectTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Markup/Primitives/MarkupObjectTests.cs
new file mode 100644
index 00000000000..e7a6e7ceb05
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Markup/Primitives/MarkupObjectTests.cs
@@ -0,0 +1,531 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections;
+using System.ComponentModel;
+using System.ComponentModel.Design.Serialization;
+using System.Globalization;
+using System.Linq;
+
+namespace System.Windows.Markup.Primitives.Tests;
+
+public class MarkupObjectTests
+{
+    [Fact]
+    public void Properties_GetObject_ReturnsExpected()
+    {
+        var instance = new object();
+        MarkupObject obj = MarkupWriter.GetMarkupObjectFor(instance);
+        Assert.NotNull(obj);
+        Assert.NotEmpty(obj.Attributes);
+        Assert.Same(obj.Attributes, obj.Attributes);
+        Assert.Same(instance, obj.Instance);
+        Assert.Equal(typeof(object), obj.ObjectType);
+        Assert.Empty(obj.Properties);
+        Assert.NotSame(obj.Properties, obj.Properties);
+    }
+
+    [Fact]
+    public void Properties_GetConvertableToString_ReturnsExpected()
+    {
+        var instance = Rect.Empty;
+        MarkupObject obj = MarkupWriter.GetMarkupObjectFor(instance);
+        Assert.NotNull(obj);
+        Assert.NotEmpty(obj.Attributes);
+        Assert.Same(obj.Attributes, obj.Attributes);
+        Assert.Equal(instance, obj.Instance);
+        Assert.Equal(typeof(Rect), obj.ObjectType);
+        Assert.NotEmpty(obj.Properties);
+        Assert.NotSame(obj.Properties, obj.Properties);
+
+        List<MarkupProperty> properties = obj.Properties.ToList();
+        Assert.Single(properties);
+        Assert.Empty(properties[0].Attributes);
+        Assert.Same(properties[0].Attributes, properties[0].Attributes);
+        Assert.Null(properties[0].DependencyProperty);
+        Assert.False(properties[0].IsAttached);
+        Assert.False(properties[0].IsComposite);
+        Assert.False(properties[0].IsConstructorArgument);
+        Assert.False(properties[0].IsContent);
+        Assert.False(properties[0].IsKey);
+        Assert.True(properties[0].IsValueAsString);
+        Assert.Equal("StringValue", properties[0].Name);
+        Assert.Null(properties[0].PropertyDescriptor);
+        Assert.Equal(typeof(string), properties[0].PropertyType);
+        Assert.Equal("Empty", properties[0].StringValue);
+        Assert.Empty(properties[0].TypeReferences);
+        Assert.Same(properties[0].TypeReferences, properties[0].TypeReferences);
+        Assert.Null(properties[0].Items);
+        Assert.Equal("Empty", properties[0].Value);
+    }
+
+    [Fact]
+    public void Properties_GetArray_ReturnsExpected()
+    {
+        var instance = new int[] { 1, 2, 3 };
+        MarkupObject obj = MarkupWriter.GetMarkupObjectFor(instance);
+        Assert.NotNull(obj);
+        Assert.NotEmpty(obj.Attributes);
+        Assert.Same(obj.Attributes, obj.Attributes);
+        Assert.Equal(instance, obj.Instance);
+        Assert.Equal(typeof(int[]), obj.ObjectType);
+        Assert.NotEmpty(obj.Properties);
+        Assert.NotSame(obj.Properties, obj.Properties);
+
+        List<MarkupProperty> properties = obj.Properties.ToList();
+        Assert.Single(properties);
+        Assert.Empty(properties[0].Attributes);
+        Assert.Same(properties[0].Attributes, properties[0].Attributes);
+        Assert.Null(properties[0].DependencyProperty);
+        Assert.False(properties[0].IsAttached);
+        Assert.True(properties[0].IsComposite);
+        Assert.False(properties[0].IsConstructorArgument);
+        Assert.True(properties[0].IsContent);
+        Assert.False(properties[0].IsKey);
+        Assert.False(properties[0].IsValueAsString);
+        Assert.Equal("Items", properties[0].Name);
+        Assert.Null(properties[0].PropertyDescriptor);
+        Assert.Equal(typeof(IEnumerable), properties[0].PropertyType);
+        Assert.Equal("", properties[0].StringValue);
+        Assert.Empty(properties[0].TypeReferences);
+        Assert.Same(properties[0].TypeReferences, properties[0].TypeReferences);
+        Assert.Equal(instance.Length, properties[0].Items.Count());
+        Assert.NotSame(properties[0].Items, properties[0].Items);
+        Assert.Equal(instance, Assert.IsType<ArrayExtension>(properties[0].Value).Items);
+    }
+
+    [Fact]
+    public void Properties_GetList_ReturnsExpected()
+    {
+        var instance = new List<int> { 1, 2, 3 };
+        MarkupObject obj = MarkupWriter.GetMarkupObjectFor(instance);
+        Assert.NotNull(obj);
+        Assert.NotEmpty(obj.Attributes);
+        Assert.Same(obj.Attributes, obj.Attributes);
+        Assert.Equal(instance, obj.Instance);
+        Assert.Equal(typeof(List<int>), obj.ObjectType);
+        Assert.NotEmpty(obj.Properties);
+        Assert.NotSame(obj.Properties, obj.Properties);
+
+        List<MarkupProperty> properties = obj.Properties.ToList();
+        Assert.Equal(2, properties.Count);
+        Assert.NotEmpty(properties[0].Attributes);
+        Assert.Same(properties[0].Attributes, properties[0].Attributes);
+        Assert.Null(properties[0].DependencyProperty);
+        Assert.False(properties[0].IsAttached);
+        Assert.False(properties[0].IsComposite);
+        Assert.False(properties[0].IsConstructorArgument);
+        Assert.False(properties[0].IsContent);
+        Assert.False(properties[0].IsKey);
+        Assert.False(properties[0].IsValueAsString);
+        Assert.Equal("Capacity", properties[0].Name);
+        Assert.NotNull(properties[0].PropertyDescriptor);
+        Assert.Equal(typeof(int), properties[0].PropertyType);
+        Assert.NotEmpty(properties[0].StringValue);
+        Assert.Empty(properties[0].TypeReferences);
+        Assert.Same(properties[0].TypeReferences, properties[0].TypeReferences);
+        Assert.NotSame(obj, Assert.Single(properties[0].Items));
+        Assert.NotSame(properties[0].Items, properties[0].Items);
+        Assert.NotEqual(0, properties[0].Value);
+
+        Assert.Empty(properties[1].Attributes);
+        Assert.Same(properties[1].Attributes, properties[1].Attributes);
+        Assert.Null(properties[1].DependencyProperty);
+        Assert.False(properties[1].IsAttached);
+        Assert.True(properties[1].IsComposite);
+        Assert.False(properties[1].IsConstructorArgument);
+        Assert.True(properties[1].IsContent);
+        Assert.False(properties[1].IsKey);
+        Assert.False(properties[1].IsValueAsString);
+        Assert.Equal("Items", properties[1].Name);
+        Assert.Null(properties[1].PropertyDescriptor);
+        Assert.Equal(typeof(IEnumerable), properties[1].PropertyType);
+        Assert.Empty(properties[1].StringValue);
+        Assert.Empty(properties[1].TypeReferences);
+        Assert.Same(properties[1].TypeReferences, properties[1].TypeReferences);
+        Assert.Equal(instance.Count, properties[1].Items.Count());
+        Assert.NotSame(properties[1].Items, properties[1].Items);
+        Assert.Same(instance, properties[1].Value);
+    }
+
+    [Fact]
+    public void Properties_GetDictionary_ReturnsExpected()
+    {
+        var instance = new Dictionary<int, string>
+        {
+            { 1, "value1" },
+            { 2, "value2" },
+            { 3, "value3" }
+        };
+        MarkupObject obj = MarkupWriter.GetMarkupObjectFor(instance);
+        Assert.NotNull(obj);
+        Assert.NotEmpty(obj.Attributes);
+        Assert.Same(obj.Attributes, obj.Attributes);
+        Assert.Equal(instance, obj.Instance);
+        Assert.Equal(typeof(Dictionary<int, string>), obj.ObjectType);
+        Assert.NotEmpty(obj.Properties);
+        Assert.NotSame(obj.Properties, obj.Properties);
+
+        List<MarkupProperty> properties = obj.Properties.ToList();
+        Assert.Single(properties);
+        Assert.Empty(properties[0].Attributes);
+        Assert.Same(properties[0].Attributes, properties[0].Attributes);
+        Assert.Null(properties[0].DependencyProperty);
+        Assert.False(properties[0].IsAttached);
+        Assert.True(properties[0].IsComposite);
+        Assert.False(properties[0].IsConstructorArgument);
+        Assert.True(properties[0].IsContent);
+        Assert.False(properties[0].IsKey);
+        Assert.False(properties[0].IsValueAsString);
+        Assert.Equal("Entries", properties[0].Name);
+        Assert.Null(properties[0].PropertyDescriptor);
+        Assert.Equal(typeof(IDictionary), properties[0].PropertyType);
+        Assert.Equal("", properties[0].StringValue);
+        Assert.Empty(properties[0].TypeReferences);
+        Assert.Same(properties[0].TypeReferences, properties[0].TypeReferences);
+        Assert.Equal(instance.Count, properties[0].Items.Count());
+        Assert.NotSame(properties[0].Items, properties[0].Items);
+        Assert.Same(instance, properties[0].Value);
+    }
+
+    [Fact]
+    public void Properties_GetEnumerable_ReturnsExpected()
+    {
+        var list = new List<int> { 1, 2, 3 };
+        var instance = new IEnumerableWrapper(list);
+        MarkupObject obj = MarkupWriter.GetMarkupObjectFor(instance);
+        Assert.NotNull(obj);
+        Assert.NotEmpty(obj.Attributes);
+        Assert.Same(obj.Attributes, obj.Attributes);
+        Assert.Equal(instance, obj.Instance);
+        Assert.Equal(typeof(IEnumerableWrapper), obj.ObjectType);
+        Assert.NotEmpty(obj.Properties);
+        Assert.NotSame(obj.Properties, obj.Properties);
+
+        List<MarkupProperty> properties = obj.Properties.ToList();
+        Assert.Single(properties);
+        Assert.Empty(properties[0].Attributes);
+        Assert.Same(properties[0].Attributes, properties[0].Attributes);
+        Assert.Null(properties[0].DependencyProperty);
+        Assert.False(properties[0].IsAttached);
+        Assert.True(properties[0].IsComposite);
+        Assert.False(properties[0].IsConstructorArgument);
+        Assert.True(properties[0].IsContent);
+        Assert.False(properties[0].IsKey);
+        Assert.False(properties[0].IsValueAsString);
+        Assert.Equal("Items", properties[0].Name);
+        Assert.Null(properties[0].PropertyDescriptor);
+        Assert.Equal(typeof(IEnumerable), properties[0].PropertyType);
+        Assert.Equal("", properties[0].StringValue);
+        Assert.Empty(properties[0].TypeReferences);
+        Assert.Same(properties[0].TypeReferences, properties[0].TypeReferences);
+        Assert.Equal(list.Count, properties[0].Items.Count());
+        Assert.NotSame(properties[0].Items, properties[0].Items);
+        Assert.Same(instance, properties[0].Value);
+    }
+
+    [Fact]
+    public void Properties_GetNormalProperty_ReturnsExpected()
+    {
+        var instance = new CustomClass
+        {
+            Property = 1
+        };
+        MarkupObject obj = MarkupWriter.GetMarkupObjectFor(instance);
+        Assert.NotNull(obj);
+        Assert.Empty(obj.Attributes);
+        Assert.Same(obj.Attributes, obj.Attributes);
+        Assert.Same(instance, obj.Instance);
+        Assert.Equal(typeof(CustomClass), obj.ObjectType);
+        Assert.NotEmpty(obj.Properties);
+        Assert.NotSame(obj.Properties, obj.Properties);
+
+        List<MarkupProperty> properties = obj.Properties.ToList();
+        Assert.Single(properties);
+        Assert.NotEmpty(properties[0].Attributes);
+        Assert.Same(properties[0].Attributes, properties[0].Attributes);
+        Assert.Null(properties[0].DependencyProperty);
+        Assert.False(properties[0].IsAttached);
+        Assert.False(properties[0].IsComposite);
+        Assert.False(properties[0].IsConstructorArgument);
+        Assert.False(properties[0].IsContent);
+        Assert.False(properties[0].IsKey);
+        Assert.False(properties[0].IsValueAsString);
+        Assert.Equal(nameof(CustomClass.Property), properties[0].Name);
+        Assert.NotNull(properties[0].PropertyDescriptor);
+        Assert.Equal(typeof(int), properties[0].PropertyType);
+        Assert.Equal("1", properties[0].StringValue);
+        Assert.Empty(properties[0].TypeReferences);
+        Assert.Same(properties[0].TypeReferences, properties[0].TypeReferences);
+        Assert.NotSame(obj, Assert.Single(properties[0].Items));
+        Assert.NotSame(properties[0].Items, properties[0].Items);
+        Assert.Equal(1, properties[0].Value);
+    }
+
+    [Fact]
+    public void Properties_GetArrayProperty_ReturnsExpected()
+    {
+        var array = new int[] { 1, 2, 3 };
+        var instance = new ArrayClass
+        {
+            Property = array
+        };
+        MarkupObject obj = MarkupWriter.GetMarkupObjectFor(instance);
+        Assert.NotNull(obj);
+        Assert.NotEmpty(obj.Attributes);
+        Assert.Same(obj.Attributes, obj.Attributes);
+        Assert.Same(instance, obj.Instance);
+        Assert.Equal(typeof(ArrayClass), obj.ObjectType);
+        Assert.NotEmpty(obj.Properties);
+        Assert.NotSame(obj.Properties, obj.Properties);
+
+        List<MarkupProperty> properties = obj.Properties.ToList();
+        Assert.Single(properties);
+        Assert.NotEmpty(properties[0].Attributes);
+        Assert.Same(properties[0].Attributes, properties[0].Attributes);
+        Assert.Null(properties[0].DependencyProperty);
+        Assert.False(properties[0].IsAttached);
+        Assert.True(properties[0].IsComposite);
+        Assert.False(properties[0].IsConstructorArgument);
+        Assert.False(properties[0].IsContent);
+        Assert.False(properties[0].IsKey);
+        Assert.False(properties[0].IsValueAsString);
+        Assert.Equal(nameof(ArrayClass.Property), properties[0].Name);
+        Assert.NotNull(properties[0].PropertyDescriptor);
+        Assert.Equal(typeof(int[]), properties[0].PropertyType);
+        Assert.Empty(properties[0].StringValue);
+        Assert.Empty(properties[0].TypeReferences);
+        Assert.Same(properties[0].TypeReferences, properties[0].TypeReferences);
+        Assert.NotSame(obj, Assert.Single(properties[0].Items));
+        Assert.NotSame(properties[0].Items, properties[0].Items);
+        Assert.Equal(array, Assert.IsType<ArrayExtension>(properties[0].Value).Items);
+    }
+
+    [Fact]
+    public void Properties_GetListProperty_ReturnsExpected()
+    {
+        var list = new List<int> { 1, 2, 3 };
+        var instance = new ListClass
+        {
+            Property = list
+        };
+        MarkupObject obj = MarkupWriter.GetMarkupObjectFor(instance);
+        Assert.NotNull(obj);
+        Assert.NotEmpty(obj.Attributes);
+        Assert.Same(obj.Attributes, obj.Attributes);
+        Assert.Same(instance, obj.Instance);
+        Assert.Equal(typeof(ListClass), obj.ObjectType);
+        Assert.NotEmpty(obj.Properties);
+        Assert.NotSame(obj.Properties, obj.Properties);
+
+        List<MarkupProperty> properties = obj.Properties.ToList();
+        Assert.Single(properties);
+        Assert.NotEmpty(properties[0].Attributes);
+        Assert.Same(properties[0].Attributes, properties[0].Attributes);
+        Assert.Null(properties[0].DependencyProperty);
+        Assert.False(properties[0].IsAttached);
+        Assert.True(properties[0].IsComposite);
+        Assert.False(properties[0].IsConstructorArgument);
+        Assert.False(properties[0].IsContent);
+        Assert.False(properties[0].IsKey);
+        Assert.False(properties[0].IsValueAsString);
+        Assert.Equal(nameof(ListClass.Property), properties[0].Name);
+        Assert.NotNull(properties[0].PropertyDescriptor);
+        Assert.Equal(typeof(IList), properties[0].PropertyType);
+        Assert.Empty(properties[0].StringValue);
+        Assert.Empty(properties[0].TypeReferences);
+        Assert.Same(properties[0].TypeReferences, properties[0].TypeReferences);
+        Assert.NotSame(obj, Assert.Single(properties[0].Items));
+        Assert.NotSame(properties[0].Items, properties[0].Items);
+        Assert.Equal(list, properties[0].Value);
+    }
+
+    [Fact]
+    public void Properties_GetDictionaryProperty_ReturnsExpected()
+    {
+        var dictionary = new Dictionary<int, string>
+        {
+            { 1, "value1" },
+            { 2, "value2" },
+            { 3, "value3" }
+        };
+        var instance = new DictionaryClass
+        {
+            Property = dictionary
+        };
+        MarkupObject obj = MarkupWriter.GetMarkupObjectFor(instance);
+        Assert.NotNull(obj);
+        Assert.NotEmpty(obj.Attributes);
+        Assert.Same(obj.Attributes, obj.Attributes);
+        Assert.Same(instance, obj.Instance);
+        Assert.Equal(typeof(DictionaryClass), obj.ObjectType);
+        Assert.NotEmpty(obj.Properties);
+        Assert.NotSame(obj.Properties, obj.Properties);
+
+        List<MarkupProperty> properties = obj.Properties.ToList();
+        Assert.Single(properties);
+        Assert.NotEmpty(properties[0].Attributes);
+        Assert.Same(properties[0].Attributes, properties[0].Attributes);
+        Assert.Null(properties[0].DependencyProperty);
+        Assert.False(properties[0].IsAttached);
+        Assert.True(properties[0].IsComposite);
+        Assert.False(properties[0].IsConstructorArgument);
+        Assert.False(properties[0].IsContent);
+        Assert.False(properties[0].IsKey);
+        Assert.False(properties[0].IsValueAsString);
+        Assert.Equal(nameof(DictionaryClass.Property), properties[0].Name);
+        Assert.NotNull(properties[0].PropertyDescriptor);
+        Assert.Equal(typeof(IDictionary), properties[0].PropertyType);
+        Assert.Empty(properties[0].StringValue);
+        Assert.Empty(properties[0].TypeReferences);
+        Assert.Same(properties[0].TypeReferences, properties[0].TypeReferences);
+        Assert.NotSame(obj, Assert.Single(properties[0].Items));
+        Assert.NotSame(properties[0].Items, properties[0].Items);
+        Assert.Equal(dictionary, properties[0].Value);
+    }
+
+    [Fact]
+    public void Properties_GetMarkupExtensionDefault_ReturnsExpected()
+    {
+        var instance = new DefaultMarkupExtension();
+        MarkupObject obj = MarkupWriter.GetMarkupObjectFor(instance);
+        Assert.NotNull(obj);
+        Assert.NotEmpty(obj.Attributes);
+        Assert.Same(obj.Attributes, obj.Attributes);
+        Assert.Same(instance, obj.Instance);
+        Assert.Equal(typeof(DefaultMarkupExtension), obj.ObjectType);
+        Assert.Empty(obj.Properties);
+        Assert.NotSame(obj.Properties, obj.Properties);
+    }
+
+    [Fact]
+    public void Properties_GetMarkupExtensionWithTypeConverter_ReturnsExpected()
+    {
+        var instance = new MarkupExtensionWithTypeConverter();
+        MarkupObject obj = MarkupWriter.GetMarkupObjectFor(instance);
+        Assert.NotNull(obj);
+        Assert.NotEmpty(obj.Attributes);
+        Assert.Same(obj.Attributes, obj.Attributes);
+        Assert.Same(instance, obj.Instance);
+        Assert.Equal(typeof(MarkupExtensionWithTypeConverter), obj.ObjectType);
+        Assert.NotEmpty(obj.Properties);
+        Assert.NotSame(obj.Properties, obj.Properties);
+
+        List<MarkupProperty> properties = obj.Properties.ToList();
+        Assert.Equal(2, properties.Count);
+        Assert.Empty(properties[0].Attributes);
+        Assert.Same(properties[0].Attributes, properties[0].Attributes);
+        Assert.Null(properties[0].DependencyProperty);
+        Assert.False(properties[0].IsAttached);
+        Assert.False(properties[0].IsComposite);
+        Assert.True(properties[0].IsConstructorArgument);
+        Assert.False(properties[0].IsContent);
+        Assert.False(properties[0].IsKey);
+        Assert.False(properties[0].IsValueAsString);
+        Assert.Equal("Argument", properties[0].Name);
+        Assert.Null(properties[0].PropertyDescriptor);
+        Assert.Equal(typeof(int), properties[0].PropertyType);
+        Assert.Equal("1", properties[0].StringValue);
+        Assert.Empty(properties[0].TypeReferences);
+        Assert.Same(properties[0].TypeReferences, properties[0].TypeReferences);
+        Assert.NotSame(obj, Assert.Single(properties[0].Items));
+        Assert.NotSame(properties[0].Items, properties[0].Items);
+        Assert.Equal(1, properties[0].Value);
+
+        Assert.Empty(properties[1].Attributes);
+        Assert.Same(properties[1].Attributes, properties[1].Attributes);
+        Assert.Null(properties[1].DependencyProperty);
+        Assert.False(properties[1].IsAttached);
+        Assert.False(properties[1].IsComposite);
+        Assert.True(properties[1].IsConstructorArgument);
+        Assert.False(properties[1].IsContent);
+        Assert.False(properties[1].IsKey);
+        Assert.False(properties[1].IsValueAsString);
+        Assert.Equal("Argument", properties[1].Name);
+        Assert.Null(properties[1].PropertyDescriptor);
+        Assert.Equal(typeof(int), properties[1].PropertyType);
+        Assert.Equal("2", properties[1].StringValue);
+        Assert.Empty(properties[1].TypeReferences);
+        Assert.Same(properties[1].TypeReferences, properties[1].TypeReferences);
+        Assert.NotSame(obj, Assert.Single(properties[1].Items));
+        Assert.NotSame(properties[1].Items, properties[1].Items);
+        Assert.Equal(2, properties[1].Value);
+    }
+
+    private class DefaultMarkupExtension : MarkupExtension
+    {
+        public override object ProvideValue(IServiceProvider serviceProvider) => throw new NotImplementedException();
+    }
+
+    private class CustomTypeConverter : TypeConverter
+    {
+        public override bool CanConvertTo(ITypeDescriptorContext? context, Type? destinationType)
+        {
+            if (destinationType == typeof(InstanceDescriptor))
+            {
+                return true;
+            }
+
+            return base.CanConvertTo(context, destinationType);
+        }
+
+        public override object? ConvertTo(ITypeDescriptorContext? context, CultureInfo? culture, object? value, Type destinationType)
+        {
+            if (destinationType == typeof(InstanceDescriptor))
+            {
+                var ctor = typeof(MarkupExtensionWithTypeConverter).GetConstructor(new[] { typeof(int), typeof(int) });
+                Assert.NotNull(ctor);
+                return new InstanceDescriptor(ctor, new object[] { 1, 2 });
+            }
+
+            return base.ConvertTo(context, culture, value, destinationType);
+        }
+    }
+
+    [TypeConverter(typeof(CustomTypeConverter))]
+    private class MarkupExtensionWithTypeConverter : MarkupExtension
+    {
+        public MarkupExtensionWithTypeConverter()
+        {
+        }
+
+        public MarkupExtensionWithTypeConverter(int property1, int property2)
+        {
+        }
+
+        public override object ProvideValue(IServiceProvider serviceProvider) => throw new NotImplementedException();
+    }
+
+    private class CustomClass
+    {
+        public int Property { get; set; }
+    }
+
+    private class ArrayClass
+    {
+        public int[]? Property { get; set; }
+    }
+
+    private class ListClass
+    {
+        public IList? Property { get; set; }
+    }
+
+    private class DictionaryClass
+    {
+        public IDictionary? Property { get; set; }
+    }
+
+    private class IEnumerableWrapper : IEnumerable
+    {
+        private IEnumerable _enumerable;
+
+        public IEnumerableWrapper(IEnumerable enumerable)
+        {
+            _enumerable = enumerable;
+        }
+
+        public IEnumerator GetEnumerator() => _enumerable.GetEnumerator();
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Markup/Primitives/MarkupPropertyTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Markup/Primitives/MarkupPropertyTests.cs
new file mode 100644
index 00000000000..beac30b6741
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Markup/Primitives/MarkupPropertyTests.cs
@@ -0,0 +1,619 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections;
+using System.ComponentModel;
+using System.ComponentModel.Design.Serialization;
+using System.Globalization;
+using System.Linq;
+using System.Windows.Markup.Primitives.Tests.InternalClasses;
+
+namespace System.Windows.Markup.Primitives.Tests
+{
+    public class MarkupPropertyTests
+    {
+        [Fact]
+        public void Properties_GetConvertableToString_ReturnsExpected()
+        {
+            var instance = Rect.Empty;
+            MarkupObject obj = MarkupWriter.GetMarkupObjectFor(instance);
+            Assert.NotNull(obj);
+            Assert.NotEmpty(obj.Attributes);
+            Assert.Same(obj.Attributes, obj.Attributes);
+            Assert.Equal(instance, obj.Instance);
+            Assert.Equal(typeof(Rect), obj.ObjectType);
+            Assert.NotEmpty(obj.Properties);
+            Assert.NotSame(obj.Properties, obj.Properties);
+
+            List<MarkupProperty> properties = obj.Properties.ToList();
+            Assert.Single(properties);
+            Assert.Empty(properties[0].Attributes);
+            Assert.Same(properties[0].Attributes, properties[0].Attributes);
+            Assert.Null(properties[0].DependencyProperty);
+            Assert.False(properties[0].IsAttached);
+            Assert.False(properties[0].IsComposite);
+            Assert.False(properties[0].IsConstructorArgument);
+            Assert.False(properties[0].IsContent);
+            Assert.False(properties[0].IsKey);
+            Assert.True(properties[0].IsValueAsString);
+            Assert.Equal("StringValue", properties[0].Name);
+            Assert.Null(properties[0].PropertyDescriptor);
+            Assert.Equal(typeof(string), properties[0].PropertyType);
+            Assert.Equal("Empty", properties[0].StringValue);
+            Assert.Empty(properties[0].TypeReferences);
+            Assert.Same(properties[0].TypeReferences, properties[0].TypeReferences);
+            Assert.Null(properties[0].Items);
+            Assert.Equal("Empty", properties[0].Value);
+        }
+
+        [Fact]
+        public void Properties_GetArray_ReturnsExpected()
+        {
+            var instance = new int[] { 1, 2, 3 };
+            MarkupObject obj = MarkupWriter.GetMarkupObjectFor(instance);
+            Assert.NotNull(obj);
+            Assert.NotEmpty(obj.Attributes);
+            Assert.Same(obj.Attributes, obj.Attributes);
+            Assert.Equal(instance, obj.Instance);
+            Assert.Equal(typeof(int[]), obj.ObjectType);
+            Assert.NotEmpty(obj.Properties);
+            Assert.NotSame(obj.Properties, obj.Properties);
+
+            List<MarkupProperty> properties = obj.Properties.ToList();
+            Assert.Single(properties);
+            Assert.Empty(properties[0].Attributes);
+            Assert.Same(properties[0].Attributes, properties[0].Attributes);
+            Assert.Null(properties[0].DependencyProperty);
+            Assert.False(properties[0].IsAttached);
+            Assert.True(properties[0].IsComposite);
+            Assert.False(properties[0].IsConstructorArgument);
+            Assert.True(properties[0].IsContent);
+            Assert.False(properties[0].IsKey);
+            Assert.False(properties[0].IsValueAsString);
+            Assert.Equal("Items", properties[0].Name);
+            Assert.Null(properties[0].PropertyDescriptor);
+            Assert.Equal(typeof(IEnumerable), properties[0].PropertyType);
+            Assert.Empty(properties[0].StringValue);
+            Assert.Empty(properties[0].TypeReferences);
+            Assert.Same(properties[0].TypeReferences, properties[0].TypeReferences);
+            Assert.Equal(instance.Length, properties[0].Items.Count());
+            Assert.NotSame(properties[0].Items, properties[0].Items);
+            Assert.Equal(instance, Assert.IsType<ArrayExtension>(properties[0].Value).Items);
+        }
+
+        [Fact]
+        public void Properties_GetList_ReturnsExpected()
+        {
+            var instance = new List<int> { 1, 2, 3 };
+            MarkupObject obj = MarkupWriter.GetMarkupObjectFor(instance);
+            Assert.NotNull(obj);
+            Assert.NotEmpty(obj.Attributes);
+            Assert.Same(obj.Attributes, obj.Attributes);
+            Assert.Equal(instance, obj.Instance);
+            Assert.Equal(typeof(List<int>), obj.ObjectType);
+            Assert.NotEmpty(obj.Properties);
+            Assert.NotSame(obj.Properties, obj.Properties);
+
+            List<MarkupProperty> properties = obj.Properties.ToList();
+            Assert.Equal(2, properties.Count);
+            Assert.NotEmpty(properties[0].Attributes);
+            Assert.Same(properties[0].Attributes, properties[0].Attributes);
+            Assert.Null(properties[0].DependencyProperty);
+            Assert.False(properties[0].IsAttached);
+            Assert.False(properties[0].IsComposite);
+            Assert.False(properties[0].IsConstructorArgument);
+            Assert.False(properties[0].IsContent);
+            Assert.False(properties[0].IsKey);
+            Assert.False(properties[0].IsValueAsString);
+            Assert.Equal("Capacity", properties[0].Name);
+            Assert.NotNull(properties[0].PropertyDescriptor);
+            Assert.Equal(typeof(int), properties[0].PropertyType);
+            Assert.NotEmpty(properties[0].StringValue);
+            Assert.Empty(properties[0].TypeReferences);
+            Assert.Same(properties[0].TypeReferences, properties[0].TypeReferences);
+            Assert.NotSame(obj, Assert.Single(properties[0].Items));
+            Assert.NotSame(properties[0].Items, properties[0].Items);
+            Assert.NotEqual(0, properties[0].Value);
+
+            Assert.Empty(properties[1].Attributes);
+            Assert.Same(properties[1].Attributes, properties[1].Attributes);
+            Assert.Null(properties[1].DependencyProperty);
+            Assert.False(properties[1].IsAttached);
+            Assert.True(properties[1].IsComposite);
+            Assert.False(properties[1].IsConstructorArgument);
+            Assert.True(properties[1].IsContent);
+            Assert.False(properties[1].IsKey);
+            Assert.False(properties[1].IsValueAsString);
+            Assert.Equal("Items", properties[1].Name);
+            Assert.Null(properties[1].PropertyDescriptor);
+            Assert.Equal(typeof(IEnumerable), properties[1].PropertyType);
+            Assert.Empty(properties[1].StringValue);
+            Assert.Empty(properties[1].TypeReferences);
+            Assert.Same(properties[1].TypeReferences, properties[1].TypeReferences);
+            Assert.Equal(instance.Count, properties[1].Items.Count());
+            Assert.NotSame(properties[1].Items, properties[1].Items);
+            Assert.Same(instance, properties[1].Value);
+        }
+
+        [Fact]
+        public void Properties_GetDictionary_ReturnsExpected()
+        {
+            var instance = new Dictionary<int, string>
+            {
+                { 1, "value1" },
+                { 2, "value2" },
+                { 3, "value3" }
+            };
+            MarkupObject obj = MarkupWriter.GetMarkupObjectFor(instance);
+            Assert.NotNull(obj);
+            Assert.NotEmpty(obj.Attributes);
+            Assert.Same(obj.Attributes, obj.Attributes);
+            Assert.Equal(instance, obj.Instance);
+            Assert.Equal(typeof(Dictionary<int, string>), obj.ObjectType);
+            Assert.NotEmpty(obj.Properties);
+            Assert.NotSame(obj.Properties, obj.Properties);
+
+            List<MarkupProperty> properties = obj.Properties.ToList();
+            Assert.Single(properties);
+            Assert.Empty(properties[0].Attributes);
+            Assert.Same(properties[0].Attributes, properties[0].Attributes);
+            Assert.Null(properties[0].DependencyProperty);
+            Assert.False(properties[0].IsAttached);
+            Assert.True(properties[0].IsComposite);
+            Assert.False(properties[0].IsConstructorArgument);
+            Assert.True(properties[0].IsContent);
+            Assert.False(properties[0].IsKey);
+            Assert.False(properties[0].IsValueAsString);
+            Assert.Equal("Entries", properties[0].Name);
+            Assert.Null(properties[0].PropertyDescriptor);
+            Assert.Equal(typeof(IDictionary), properties[0].PropertyType);
+            Assert.Empty(properties[0].StringValue);
+            Assert.Empty(properties[0].TypeReferences);
+            Assert.Same(properties[0].TypeReferences, properties[0].TypeReferences);
+            Assert.Equal(instance.Count, properties[0].Items.Count());
+            Assert.NotSame(properties[0].Items, properties[0].Items);
+            Assert.Same(instance, properties[0].Value);
+        }
+
+        [Fact]
+        public void Properties_GetEnumerable_ReturnsExpected()
+        {
+            var list = new List<int> { 1, 2, 3 };
+            var instance = new IEnumerableWrapper(list);
+            MarkupObject obj = MarkupWriter.GetMarkupObjectFor(instance);
+            Assert.NotNull(obj);
+            Assert.NotEmpty(obj.Attributes);
+            Assert.Same(obj.Attributes, obj.Attributes);
+            Assert.Equal(instance, obj.Instance);
+            Assert.Equal(typeof(IEnumerableWrapper), obj.ObjectType);
+            Assert.NotEmpty(obj.Properties);
+            Assert.NotSame(obj.Properties, obj.Properties);
+
+            List<MarkupProperty> properties = obj.Properties.ToList();
+            Assert.Single(properties);
+            Assert.Empty(properties[0].Attributes);
+            Assert.Same(properties[0].Attributes, properties[0].Attributes);
+            Assert.Null(properties[0].DependencyProperty);
+            Assert.False(properties[0].IsAttached);
+            Assert.True(properties[0].IsComposite);
+            Assert.False(properties[0].IsConstructorArgument);
+            Assert.True(properties[0].IsContent);
+            Assert.False(properties[0].IsKey);
+            Assert.False(properties[0].IsValueAsString);
+            Assert.Equal("Items", properties[0].Name);
+            Assert.Null(properties[0].PropertyDescriptor);
+            Assert.Equal(typeof(IEnumerable), properties[0].PropertyType);
+            Assert.Empty(properties[0].StringValue);
+            Assert.Empty(properties[0].TypeReferences);
+            Assert.Same(properties[0].TypeReferences, properties[0].TypeReferences);
+            Assert.Equal(list.Count, properties[0].Items.Count());
+            Assert.NotSame(properties[0].Items, properties[0].Items);
+            Assert.Same(instance, properties[0].Value);
+        }
+
+        [Fact]
+        public void Properties_GetNormalProperty_ReturnsExpected()
+        {
+            var instance = new CustomClass
+            {
+                Property = 1
+            };
+            MarkupObject obj = MarkupWriter.GetMarkupObjectFor(instance);
+            Assert.NotNull(obj);
+            Assert.Empty(obj.Attributes);
+            Assert.Same(obj.Attributes, obj.Attributes);
+            Assert.Same(instance, obj.Instance);
+            Assert.Equal(typeof(CustomClass), obj.ObjectType);
+            Assert.NotEmpty(obj.Properties);
+            Assert.NotSame(obj.Properties, obj.Properties);
+
+            List<MarkupProperty> properties = obj.Properties.ToList();
+            Assert.Single(properties);
+            Assert.NotEmpty(properties[0].Attributes);
+            Assert.Same(properties[0].Attributes, properties[0].Attributes);
+            Assert.Null(properties[0].DependencyProperty);
+            Assert.False(properties[0].IsAttached);
+            Assert.False(properties[0].IsComposite);
+            Assert.False(properties[0].IsConstructorArgument);
+            Assert.False(properties[0].IsContent);
+            Assert.False(properties[0].IsKey);
+            Assert.False(properties[0].IsValueAsString);
+            Assert.Equal(nameof(CustomClass.Property), properties[0].Name);
+            Assert.NotNull(properties[0].PropertyDescriptor);
+            Assert.Equal(typeof(int), properties[0].PropertyType);
+            Assert.Equal("1", properties[0].StringValue);
+            Assert.Empty(properties[0].TypeReferences);
+            Assert.Same(properties[0].TypeReferences, properties[0].TypeReferences);
+            Assert.NotSame(obj, Assert.Single(properties[0].Items));
+            Assert.NotSame(properties[0].Items, properties[0].Items);
+            Assert.Equal(1, properties[0].Value);
+        }
+
+        [Fact]
+        public void Properties_GetArrayProperty_ReturnsExpected()
+        {
+            var array = new int[] { 1, 2, 3 };
+            var instance = new ArrayClass
+            {
+                Property = array
+            };
+            MarkupObject obj = MarkupWriter.GetMarkupObjectFor(instance);
+            Assert.NotNull(obj);
+            Assert.NotEmpty(obj.Attributes);
+            Assert.Same(obj.Attributes, obj.Attributes);
+            Assert.Same(instance, obj.Instance);
+            Assert.Equal(typeof(ArrayClass), obj.ObjectType);
+            Assert.NotEmpty(obj.Properties);
+            Assert.NotSame(obj.Properties, obj.Properties);
+
+            List<MarkupProperty> properties = obj.Properties.ToList();
+            Assert.Single(properties);
+            Assert.NotEmpty(properties[0].Attributes);
+            Assert.Same(properties[0].Attributes, properties[0].Attributes);
+            Assert.Null(properties[0].DependencyProperty);
+            Assert.False(properties[0].IsAttached);
+            Assert.True(properties[0].IsComposite);
+            Assert.False(properties[0].IsConstructorArgument);
+            Assert.False(properties[0].IsContent);
+            Assert.False(properties[0].IsKey);
+            Assert.False(properties[0].IsValueAsString);
+            Assert.Equal(nameof(ArrayClass.Property), properties[0].Name);
+            Assert.NotNull(properties[0].PropertyDescriptor);
+            Assert.Equal(typeof(int[]), properties[0].PropertyType);
+            Assert.Empty(properties[0].StringValue);
+            Assert.Empty(properties[0].TypeReferences);
+            Assert.Same(properties[0].TypeReferences, properties[0].TypeReferences);
+            Assert.NotSame(obj, Assert.Single(properties[0].Items));
+            Assert.NotSame(properties[0].Items, properties[0].Items);
+            Assert.Equal(array, Assert.IsType<ArrayExtension>(properties[0].Value).Items);
+        }
+
+        [Fact]
+        public void Properties_GetListProperty_ReturnsExpected()
+        {
+            var list = new List<int> { 1, 2, 3 };
+            var instance = new ListClass
+            {
+                Property = list
+            };
+            MarkupObject obj = MarkupWriter.GetMarkupObjectFor(instance);
+            Assert.NotNull(obj);
+            Assert.NotEmpty(obj.Attributes);
+            Assert.Same(obj.Attributes, obj.Attributes);
+            Assert.Same(instance, obj.Instance);
+            Assert.Equal(typeof(ListClass), obj.ObjectType);
+            Assert.NotEmpty(obj.Properties);
+            Assert.NotSame(obj.Properties, obj.Properties);
+
+            List<MarkupProperty> properties = obj.Properties.ToList();
+            Assert.Single(properties);
+            Assert.NotEmpty(properties[0].Attributes);
+            Assert.Same(properties[0].Attributes, properties[0].Attributes);
+            Assert.Null(properties[0].DependencyProperty);
+            Assert.False(properties[0].IsAttached);
+            Assert.True(properties[0].IsComposite);
+            Assert.False(properties[0].IsConstructorArgument);
+            Assert.False(properties[0].IsContent);
+            Assert.False(properties[0].IsKey);
+            Assert.False(properties[0].IsValueAsString);
+            Assert.Equal(nameof(ListClass.Property), properties[0].Name);
+            Assert.NotNull(properties[0].PropertyDescriptor);
+            Assert.Equal(typeof(IList), properties[0].PropertyType);
+            Assert.Empty(properties[0].StringValue);
+            Assert.Empty(properties[0].TypeReferences);
+            Assert.Same(properties[0].TypeReferences, properties[0].TypeReferences);
+            Assert.NotSame(obj, Assert.Single(properties[0].Items));
+            Assert.NotSame(properties[0].Items, properties[0].Items);
+            Assert.Equal(list, properties[0].Value);
+        }
+
+        [Fact]
+        public void Properties_GetDictionaryProperty_ReturnsExpected()
+        {
+            var dictionary = new Dictionary<int, string>
+            {
+                { 1, "value1" },
+                { 2, "value2" },
+                { 3, "value3" }
+            };
+            var instance = new DictionaryClass
+            {
+                Property = dictionary
+            };
+            MarkupObject obj = MarkupWriter.GetMarkupObjectFor(instance);
+            Assert.NotNull(obj);
+            Assert.NotEmpty(obj.Attributes);
+            Assert.Same(obj.Attributes, obj.Attributes);
+            Assert.Same(instance, obj.Instance);
+            Assert.Equal(typeof(DictionaryClass), obj.ObjectType);
+            Assert.NotEmpty(obj.Properties);
+            Assert.NotSame(obj.Properties, obj.Properties);
+
+            List<MarkupProperty> properties = obj.Properties.ToList();
+            Assert.Single(properties);
+            Assert.NotEmpty(properties[0].Attributes);
+            Assert.Same(properties[0].Attributes, properties[0].Attributes);
+            Assert.Null(properties[0].DependencyProperty);
+            Assert.False(properties[0].IsAttached);
+            Assert.True(properties[0].IsComposite);
+            Assert.False(properties[0].IsConstructorArgument);
+            Assert.False(properties[0].IsContent);
+            Assert.False(properties[0].IsKey);
+            Assert.False(properties[0].IsValueAsString);
+            Assert.Equal(nameof(DictionaryClass.Property), properties[0].Name);
+            Assert.NotNull(properties[0].PropertyDescriptor);
+            Assert.Equal(typeof(IDictionary), properties[0].PropertyType);
+            Assert.Empty(properties[0].StringValue);
+            Assert.Empty(properties[0].TypeReferences);
+            Assert.Same(properties[0].TypeReferences, properties[0].TypeReferences);
+            Assert.NotSame(obj, Assert.Single(properties[0].Items));
+            Assert.NotSame(properties[0].Items, properties[0].Items);
+            Assert.Equal(dictionary, properties[0].Value);
+        }
+
+        [Fact]
+        public void Properties_GetMarkupExtensionWithTypeConverter_ReturnsExpected()
+        {
+            var instance = new MarkupExtensionWithTypeConverter();
+            MarkupObject obj = MarkupWriter.GetMarkupObjectFor(instance);
+            Assert.NotNull(obj);
+            Assert.NotEmpty(obj.Attributes);
+            Assert.Same(obj.Attributes, obj.Attributes);
+            Assert.Same(instance, obj.Instance);
+            Assert.Equal(typeof(MarkupExtensionWithTypeConverter), obj.ObjectType);
+            Assert.NotEmpty(obj.Properties);
+            Assert.NotSame(obj.Properties, obj.Properties);
+
+            List<MarkupProperty> properties = obj.Properties.ToList();
+            Assert.Equal(2, properties.Count);
+            Assert.Empty(properties[0].Attributes);
+            Assert.Same(properties[0].Attributes, properties[0].Attributes);
+            Assert.Null(properties[0].DependencyProperty);
+            Assert.False(properties[0].IsAttached);
+            Assert.False(properties[0].IsComposite);
+            Assert.True(properties[0].IsConstructorArgument);
+            Assert.False(properties[0].IsContent);
+            Assert.False(properties[0].IsKey);
+            Assert.False(properties[0].IsValueAsString);
+            Assert.Equal("Argument", properties[0].Name);
+            Assert.Null(properties[0].PropertyDescriptor);
+            Assert.Equal(typeof(int), properties[0].PropertyType);
+            Assert.Equal("1", properties[0].StringValue);
+            Assert.Empty(properties[0].TypeReferences);
+            Assert.Same(properties[0].TypeReferences, properties[0].TypeReferences);
+            Assert.NotSame(obj, Assert.Single(properties[0].Items));
+            Assert.NotSame(properties[0].Items, properties[0].Items);
+            Assert.Equal(1, properties[0].Value);
+
+            Assert.Empty(properties[1].Attributes);
+            Assert.Same(properties[1].Attributes, properties[1].Attributes);
+            Assert.Null(properties[1].DependencyProperty);
+            Assert.False(properties[1].IsAttached);
+            Assert.False(properties[1].IsComposite);
+            Assert.True(properties[1].IsConstructorArgument);
+            Assert.False(properties[1].IsContent);
+            Assert.False(properties[1].IsKey);
+            Assert.False(properties[1].IsValueAsString);
+            Assert.Equal("Argument", properties[1].Name);
+            Assert.Null(properties[1].PropertyDescriptor);
+            Assert.Equal(typeof(int), properties[1].PropertyType);
+            Assert.Equal("2", properties[1].StringValue);
+            Assert.Empty(properties[1].TypeReferences);
+            Assert.Same(properties[1].TypeReferences, properties[1].TypeReferences);
+            Assert.NotSame(obj, Assert.Single(properties[1].Items));
+            Assert.NotSame(properties[1].Items, properties[1].Items);
+            Assert.Equal(2, properties[1].Value);
+        }
+
+        [Fact]
+        public void Write_ConvertableToString_ReturnsExpected()
+        {
+            // Test the default implementation of VerifyOnlySerializableTypes.
+            // Don't test the output.
+            var instance = Rect.Empty;
+            Assert.NotEmpty(XamlWriter.Save(instance));
+        }
+
+        [Fact]
+        public void Write_Array_ReturnsExpected()
+        {
+            // Test the default implementation of VerifyOnlySerializableTypes.
+            // Don't test the output.
+            var instance = new int[] { 1, 2, 3 };
+            Assert.NotEmpty(XamlWriter.Save(instance));
+        }
+
+        [Fact]
+        public void Write_List_ThrowsInvalidOperationException()
+        {
+            // Test the default implementation of VerifyOnlySerializableTypes.
+            // Don't test the output.
+            var instance = new List<int> { 1, 2, 3 };
+            Assert.Throws<InvalidOperationException>(() => XamlWriter.Save(instance));
+        }
+
+        [Fact]
+        public void Write_Dictionary_ThrowsInvalidOperationException()
+        {
+            // Test the default implementation of VerifyOnlySerializableTypes.
+            // Don't test the output.
+            var instance = new Dictionary<int, string>
+            {
+                { 1, "value1" },
+                { 2, "value2" },
+                { 3, "value3" }
+            };
+            Assert.Throws<InvalidOperationException>(() => XamlWriter.Save(instance));
+        }
+
+        [Fact]
+        public void Write_Enumerable_ReturnsExpected()
+        {
+            // Test the default implementation of VerifyOnlySerializableTypes.
+            // Don't test the output.
+            var list = new List<int> { 1, 2, 3 };
+            var instance = new IEnumerableWrapper(list);
+            Assert.NotEmpty(XamlWriter.Save(instance));
+        }
+
+        [Fact]
+        public void Write_NormalProperty_ReturnsExpected()
+        {
+            // Test the default implementation of VerifyOnlySerializableTypes.
+            // Don't test the output.
+            var instance = new CustomClass
+            {
+                Property = 1
+            };
+            Assert.NotEmpty(XamlWriter.Save(instance));
+        }
+
+        [Fact]
+        public void Write_ArrayProperty_ReturnsExpected()
+        {
+            // Test the default implementation of VerifyOnlySerializableTypes.
+            // Don't test the output.
+            var array = new int[] { 1, 2, 3 };
+            var instance = new ArrayClass
+            {
+                Property = array
+            };
+            Assert.NotEmpty(XamlWriter.Save(instance));
+        }
+
+        [Fact]
+        public void Write_ListProperty_ThrowsInvalidOperationException()
+        {
+            // Test the default implementation of VerifyOnlySerializableTypes.
+            // Don't test the output.
+            var list = new List<int> { 1, 2, 3 };
+            var instance = new ListClass
+            {
+                Property = list
+            };
+            Assert.Throws<InvalidOperationException>(() => XamlWriter.Save(instance));
+        }
+
+        [Fact]
+        public void Write_DictionaryProperty_ThrowsInvalidOperationException()
+        {
+            // Test the default implementation of VerifyOnlySerializableTypes.
+            // Don't test the output.
+            var dictionary = new Dictionary<int, string>
+            {
+                { 1, "value1" },
+                { 2, "value2" },
+                { 3, "value3" }
+            };
+            var instance = new DictionaryClass
+            {
+                Property = dictionary
+            };
+            Assert.Throws<InvalidOperationException>(() => XamlWriter.Save(instance));
+        }
+
+        [Fact]
+        public void Write_MarkupExtensionWithTypeConverter_ReturnsExpected()
+        {
+            // Test the default implementation of VerifyOnlySerializableTypes.
+            // Don't test the output.
+            var instance = new MarkupExtensionWithTypeConverter();
+            Assert.NotEmpty(XamlWriter.Save(instance));
+        }
+    }
+}
+
+namespace System.Windows.Markup.Primitives.Tests.InternalClasses
+{
+    public class CustomTypeConverter : TypeConverter
+    {
+        public override bool CanConvertTo(ITypeDescriptorContext? context, Type? destinationType)
+        {
+            if (destinationType == typeof(InstanceDescriptor))
+            {
+                return true;
+            }
+
+            return base.CanConvertTo(context, destinationType);
+        }
+        
+        public override object? ConvertTo(ITypeDescriptorContext? context, CultureInfo? culture, object? value, Type destinationType)
+        {
+            if (destinationType == typeof(InstanceDescriptor))
+            {
+                var ctor = typeof(MarkupExtensionWithTypeConverter).GetConstructor(new[] { typeof(int), typeof(int) });
+                Assert.NotNull(ctor);
+                return new InstanceDescriptor(ctor, new object[] { 1, 2 });
+            }
+
+            return base.ConvertTo(context, culture, value, destinationType);
+        }
+    }
+
+    [TypeConverter(typeof(CustomTypeConverter))]
+    public class MarkupExtensionWithTypeConverter : MarkupExtension
+    {
+        public MarkupExtensionWithTypeConverter()
+        {
+        }
+
+        public MarkupExtensionWithTypeConverter(int property1, int property2)
+        {
+        }
+
+        public override object ProvideValue(IServiceProvider serviceProvider) => throw new NotImplementedException();
+    }
+
+    public class CustomClass
+    {
+        public int Property { get; set; }
+    }
+
+    public class ArrayClass
+    {
+        public int[]? Property { get; set; }
+    }
+
+    public class ListClass
+    {
+        public IList? Property { get; set; }
+    }
+
+    public class DictionaryClass
+    {
+        public IDictionary? Property { get; set; }
+    }
+
+    public class IEnumerableWrapper : IEnumerable
+    {
+        private IEnumerable _enumerable;
+
+        public IEnumerableWrapper(IEnumerable enumerable)
+        {
+            _enumerable = enumerable;
+        }
+
+        public IEnumerator GetEnumerator() => _enumerable.GetEnumerator();
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Markup/ServiceProvidersTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Markup/ServiceProvidersTests.cs
new file mode 100644
index 00000000000..a823bd1ceea
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Markup/ServiceProvidersTests.cs
@@ -0,0 +1,84 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Windows.Markup.Tests;
+
+public class ServiceProvidersTests
+{
+    [Fact]
+    public void AddService_Invoke_GetServiceReturnsExpected()
+    {
+        var serviceProviders = new ServiceProviders();
+
+        var service1 = new object();
+        serviceProviders.AddService(typeof(object), service1);
+        Assert.Same(service1, serviceProviders.GetService(typeof(object)));
+
+        // Add again.
+        serviceProviders.AddService(typeof(object), service1);
+        Assert.Same(service1, serviceProviders.GetService(typeof(object)));
+
+        // Add another.
+        var service2 = new object();
+        serviceProviders.AddService(typeof(string), service2);
+        Assert.Same(service1, serviceProviders.GetService(typeof(object)));
+        Assert.Same(service2, serviceProviders.GetService(typeof(string)));
+    }
+
+    [Fact]
+    public void AddService_NullServiceType_ThrowsArgumentNullException()
+    {
+        var serviceProviders = new ServiceProviders();
+        Assert.Throws<ArgumentNullException>("serviceType", () => serviceProviders.AddService(null, new object()));
+    }
+
+    [Fact]
+    public void AddService_NullService_ThrowsArgumentNullException()
+    {
+        var serviceProviders = new ServiceProviders();
+        Assert.Throws<ArgumentNullException>("service", () => serviceProviders.AddService(typeof(object), null));
+    }
+
+    [Fact]
+    public void AddService_ServiceTypeExists_ThrowsArgumentException()
+    {
+        var serviceProviders = new ServiceProviders();
+        serviceProviders.AddService(typeof(object), new object());
+        Assert.Throws<ArgumentException>("serviceType", () => serviceProviders.AddService(typeof(object), new object()));
+    }
+
+    [Fact]
+    public void GetService_NoSuchServiceTypeEmpty_ReturnsNull()
+    {
+        var serviceProviders = new ServiceProviders();
+        Assert.Null(serviceProviders.GetService(typeof(object)));
+    }
+
+    [Fact]
+    public void GetService_NoSuchServiceTypeNotEmpty_ReturnsNull()
+    {
+        var serviceProviders = new ServiceProviders();
+        serviceProviders.AddService(typeof(string), new object());
+
+        Assert.Null(serviceProviders.GetService(typeof(object)));
+    }
+
+    [Fact]
+    public void GetService_NullServiceTypeEmpty_ThrowsArgumentNullException()
+    {
+        var serviceProviders = new ServiceProviders();
+        // TODO: should have correct paramName
+        Assert.Throws<ArgumentNullException>("key", () => serviceProviders.GetService(null));
+    }
+
+    [Fact]
+    public void GetService_NullServiceTypeNotEmpty_ThrowsArgumentNullException()
+    {
+        var serviceProviders = new ServiceProviders();
+        serviceProviders.AddService(typeof(string), new object());
+
+        // TODO: should have correct paramName
+        Assert.Throws<ArgumentNullException>("key", () => serviceProviders.GetService(null));
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Media/Converters/MatrixValueSerializerTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Media/Converters/MatrixValueSerializerTests.cs
new file mode 100644
index 00000000000..d78c7b34020
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Media/Converters/MatrixValueSerializerTests.cs
@@ -0,0 +1,127 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.Windows.Markup;
+using System.Windows.Media.Tests;
+
+namespace System.Windows.Media.Converters.Tests;
+
+public class MatrixValueSerializerTests
+{
+    public static IEnumerable<object?[]> CanConvertToString_TestData()
+    {
+        yield return new object?[] { null, false };
+        yield return new object?[] { string.Empty, false };
+        yield return new object?[] { "value", false };
+        yield return new object?[] { new object(), false };
+        
+        yield return new object?[] { new Matrix(), true };
+    }
+
+    [Theory]
+    [MemberData(nameof(CanConvertToString_TestData))]
+    public void CanConvertToString_Invoke_ReturnsExpected(object value, bool expected)
+    {
+        var serializer = new MatrixValueSerializer();
+        Assert.Equal(expected, serializer.CanConvertToString(value, null));
+        Assert.Equal(expected, serializer.CanConvertToString(value, new CustomValueSerializerContext()));
+    }
+    
+    [Theory]
+    [MemberData(nameof(MatrixTests.ToString_TestData), MemberType = typeof(MatrixTests))]
+    public void ConvertToString_Invoke_ReturnsExpected(Matrix matrix, string expected)
+    {
+        var serializer = new MatrixValueSerializer();
+        Assert.Equal(expected, serializer.ConvertToString(matrix, null));
+        Assert.Equal(expected, serializer.ConvertToString(matrix, new CustomValueSerializerContext()));
+    }
+
+    public static IEnumerable<object?[]> ConvertToString_CantConvert_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { string.Empty };
+        yield return new object?[] { "value" };
+        yield return new object?[] { new object() };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertToString_CantConvert_TestData))]
+    public void ConvertToString_CantConvert_ThrowsNotSupportedException(object value)
+    {
+        var serializer = new MatrixValueSerializer();
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertToString(value, null));
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertToString(value, new CustomValueSerializerContext()));
+    }
+
+    public static IEnumerable<object?[]> CanConvertFromString_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { string.Empty };
+        yield return new object?[] { "value" };
+    }
+
+    [Theory]
+    [MemberData(nameof(CanConvertFromString_TestData))]
+    public void CanConvertFromString_Invoke_ReturnsTrue(string value)
+    {
+        var serializer = new MatrixValueSerializer();
+        Assert.True(serializer.CanConvertFromString(value, null));
+        Assert.True(serializer.CanConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [MemberData(nameof(MatrixTests.Parse_TestData), MemberType = typeof(MatrixTests))]
+    public void ConvertFromString_Invoke_ReturnsExpected(string value, Matrix expected)
+    {
+        var serializer = new MatrixValueSerializer();
+        Assert.Equal(expected, serializer.ConvertFromString(value, null));
+        Assert.Equal(expected, serializer.ConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    [Fact]
+    public void ConvertFromString_NullValue_ThrowsNotSupportedException()
+    {
+        var serializer = new MatrixValueSerializer();
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertFromString(null, null));
+        Assert.Throws<NotSupportedException>(() => serializer.ConvertFromString(null, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [MemberData(nameof(MatrixTests.Parse_InvalidSource_TestData), MemberType = typeof(MatrixTests))]
+    public void ConvertFromString_InvalidValue_ThrowsInvalidOperationException(string value)
+    {
+        var serializer = new MatrixValueSerializer();
+        Assert.Throws<InvalidOperationException>(() => serializer.ConvertFromString(value, null));
+        Assert.Throws<InvalidOperationException>(() => serializer.ConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    [Theory]
+    [MemberData(nameof(MatrixTests.Parse_NotDouble_TestData), MemberType = typeof(MatrixTests))]
+    public void ConvertFromString_NotDouble_ThrowsFormatException(string value)
+    {
+        var serializer = new MatrixValueSerializer();
+        Assert.Throws<FormatException>(() => serializer.ConvertFromString(value, null));
+        Assert.Throws<FormatException>(() => serializer.ConvertFromString(value, new CustomValueSerializerContext()));
+    }
+
+    private class CustomValueSerializerContext : IValueSerializerContext
+    {
+        public IContainer Container => throw new NotImplementedException();
+
+        public object Instance => throw new NotImplementedException();
+
+        public PropertyDescriptor PropertyDescriptor => throw new NotImplementedException();
+
+        public object? GetService(Type serviceType) => throw new NotImplementedException();
+
+        public ValueSerializer GetValueSerializerFor(PropertyDescriptor descriptor) => throw new NotImplementedException();
+
+        public ValueSerializer GetValueSerializerFor(Type type) => throw new NotImplementedException();
+
+        public void OnComponentChanged() => throw new NotImplementedException();
+
+        public bool OnComponentChanging() => throw new NotImplementedException();
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Media/DisableDpiAwarenessAttributeTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Media/DisableDpiAwarenessAttributeTests.cs
new file mode 100644
index 00000000000..be9c37b058d
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Media/DisableDpiAwarenessAttributeTests.cs
@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Windows.Media.Test;
+
+public class DisableDpiAwarenessAttributeTests
+{
+    [Fact]
+    public void Ctor_Default()
+    {
+        var attribute = new DisableDpiAwarenessAttribute();
+        Assert.Equal(typeof(DisableDpiAwarenessAttribute), attribute.TypeId);
+    }
+}
\ No newline at end of file
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Media/MatrixConverterTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Media/MatrixConverterTests.cs
new file mode 100644
index 00000000000..c0230180133
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Media/MatrixConverterTests.cs
@@ -0,0 +1,188 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.ComponentModel.Design.Serialization;
+using System.Globalization;
+
+namespace System.Windows.Media.Tests;
+
+public class MatrixConverterTests
+{
+    [Theory]
+    [InlineData(null, false)]
+    [InlineData(typeof(object), false)]
+    [InlineData(typeof(string), true)]
+    [InlineData(typeof(InstanceDescriptor), false)]
+    [InlineData(typeof(Matrix), false)]
+    public void CanConvertTo_Invoke_ReturnsExpected(Type? destinationType, bool expected)
+    {
+        var converter = new MatrixConverter();
+        Assert.Equal(expected, converter.CanConvertTo(null, destinationType));
+        Assert.Equal(expected, converter.CanConvertTo(new CustomTypeDescriptorContext(), destinationType));
+    }
+    
+    [Theory]
+    [MemberData(nameof(MatrixTests.ToString_TestData), MemberType = typeof(MatrixTests))]
+    public void ConvertTo_InvokeMatrixToString_ReturnsExpected(Matrix value, string expected)
+    {
+        var converter = new MatrixConverter();
+        Assert.Equal(expected, converter.ConvertTo(value, typeof(string)));
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), null, value, typeof(string)));
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value, typeof(string)));
+    }
+    
+    [Theory]
+    [MemberData(nameof(MatrixTests.ToString_IFormatProviderCustom_TestData), MemberType = typeof(MatrixTests))]
+    public void ConvertTo_InvokeMatrixToStringCustomCulture_ReturnsExpected(Matrix value, string numberDecimalSeparator, string expected)
+    {
+        var culture = new CultureInfo("en-US");
+        NumberFormatInfo formatInfo = culture.NumberFormat;
+        formatInfo.NumberDecimalSeparator = numberDecimalSeparator;
+
+        var converter = new MatrixConverter();
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), culture, value, typeof(string)));
+    }
+
+    [Theory]
+    [InlineData(null, "")]
+    [InlineData("", "")]
+    [InlineData("value", "value")]
+    [InlineData(1, "1")]
+    public void ConvertTo_InvokeNotMatrixToString_ReturnsExpected(object? value, string expected)
+    {
+        var converter = new MatrixConverter();
+        Assert.Equal(expected, converter.ConvertTo(value, typeof(string)));
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), null, value, typeof(string)));
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value, typeof(string)));
+    }
+
+    public static IEnumerable<object?[]> ConvertTo_CantConvert_TestData()
+    {
+        yield return new object?[] { null, typeof(object) };
+        yield return new object?[] { string.Empty, typeof(object) };
+        yield return new object?[] { "value", typeof(object) };
+        yield return new object?[] { new object(), typeof(object) };
+        yield return new object?[] { new Matrix(), typeof(object) };
+        
+        yield return new object?[] { null, typeof(Matrix) };
+        yield return new object?[] { string.Empty, typeof(Matrix) };
+        yield return new object?[] { "value", typeof(Matrix) };
+        yield return new object?[] { new object(), typeof(Matrix) };
+        yield return new object?[] { new Matrix(), typeof(Matrix) };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertTo_CantConvert_TestData))]
+    public void ConvertTo_CantConvert_ThrowsNotSupportedException(object value, Type destinationType)
+    {
+        var converter = new MatrixConverter();
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(value, destinationType));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(null, null, value, destinationType));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value, destinationType));
+    }
+
+    public static IEnumerable<object?[]> ConvertTo_NullDestinationType_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { string.Empty };
+        yield return new object?[] { "value" };
+        yield return new object?[] { new object() };
+        yield return new object?[] { new Matrix() };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertTo_NullDestinationType_TestData))]
+    public void ConvertTo_NullDestinationType_ThrowsArgumentNullException(object value)
+    {
+        var converter = new MatrixConverter();
+        Assert.Throws<ArgumentNullException>("destinationType", () => converter.ConvertTo(value, null!));
+        Assert.Throws<ArgumentNullException>("destinationType", () => converter.ConvertTo(null, null, new Matrix(), null!));
+        Assert.Throws<ArgumentNullException>("destinationType", () => converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, new Matrix(), null!));
+    }
+
+    [Theory]
+    [InlineData(null, false)]
+    [InlineData(typeof(object), false)]
+    [InlineData(typeof(string), true)]
+    [InlineData(typeof(InstanceDescriptor), true)]
+    [InlineData(typeof(Matrix), false)]
+    public void CanConvertFrom_Invoke_ReturnsExpected(Type? sourceType, bool expected)
+    {
+        var converter = new MatrixConverter();
+        Assert.Equal(expected, converter.CanConvertFrom(sourceType!));
+        Assert.Equal(expected, converter.CanConvertFrom(null, sourceType));
+        Assert.Equal(expected, converter.CanConvertFrom(new CustomTypeDescriptorContext(), sourceType));
+    }
+
+    [Theory]
+    [MemberData(nameof(MatrixTests.Parse_TestData), MemberType = typeof(MatrixTests))]
+    public void ConvertFrom_InvokeStringValue_ReturnsExpected(object value, Matrix expected)
+    {
+        var converter = new MatrixConverter();
+        Assert.Equal(expected, converter.ConvertFrom(value));
+        Assert.Equal(expected, converter.ConvertFrom(null, null, value));
+        Assert.Equal(expected, converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    [Fact]
+    public void ConvertFrom_NullValue_ThrowsNotSupportedException()
+    {
+        var converter = new MatrixConverter();
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(null!));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(null, null, null));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, null));
+    }
+
+    [Theory]
+    [MemberData(nameof(MatrixTests.Parse_InvalidSource_TestData), MemberType = typeof(MatrixTests))]
+    public void ConvertFrom_InvalidStringValue_ThrowsInvalidOperationException(object value)
+    {
+        var converter = new MatrixConverter();
+        Assert.Throws<InvalidOperationException>(() => converter.ConvertFrom(value));
+        Assert.Throws<InvalidOperationException>(() => converter.ConvertFrom(null, null, value));
+        Assert.Throws<InvalidOperationException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    [Theory]
+    [MemberData(nameof(MatrixTests.Parse_NotDouble_TestData), MemberType = typeof(MatrixTests))]
+    public void ConvertFrom_NotDoubleStringValue_ThrowsFormatException(object value)
+    {
+        var converter = new MatrixConverter();
+        Assert.Throws<FormatException>(() => converter.ConvertFrom(value));
+        Assert.Throws<FormatException>(() => converter.ConvertFrom(null, null, value));
+        Assert.Throws<FormatException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    public static IEnumerable<object[]> ConvertFrom_CantConvert_TestData()
+    {
+        yield return new object[] { new object() };
+        yield return new object[] { new Matrix() };
+    }
+    
+    [Theory]
+    [MemberData(nameof(ConvertFrom_CantConvert_TestData))]
+    public void ConvertFrom_CantConvert_ThrowsNotSupportedException(object value)
+    {
+        var converter = new MatrixConverter();
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(value));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(null, null, value));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    private class CustomTypeDescriptorContext : ITypeDescriptorContext
+    {
+        public IContainer Container => throw new NotImplementedException();
+
+        public object Instance => throw new NotImplementedException();
+
+        public PropertyDescriptor PropertyDescriptor => throw new NotImplementedException();
+
+        public object? GetService(Type serviceType) => throw new NotImplementedException();
+
+        public void OnComponentChanged() => throw new NotImplementedException();
+
+        public bool OnComponentChanging() => throw new NotImplementedException();
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Media/MatrixTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Media/MatrixTests.cs
new file mode 100644
index 00000000000..f7d1c6185b4
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Media/MatrixTests.cs
@@ -0,0 +1,5635 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.Globalization;
+using System.Windows.Markup;
+using System.Windows.Media.Converters;
+
+
+namespace System.Windows.Media.Tests;
+
+public class MatrixTests
+{
+    [Fact]
+    public void Ctor_Default()
+    {
+        var matrix = new Matrix();
+
+        Assert.Equal(1, matrix.M11);
+        Assert.Equal(0, matrix.M12);
+        Assert.Equal(0, matrix.M21);
+        Assert.Equal(1, matrix.M22);
+        Assert.Equal(0, matrix.OffsetX);
+        Assert.Equal(0, matrix.OffsetY);
+        Assert.True(matrix.HasInverse);
+        Assert.True(matrix.IsIdentity);
+        Assert.Equal(1, matrix.Determinant);
+        Assert.Equal(Matrix.Identity, matrix);
+    }
+
+    public static IEnumerable<object[]> Ctor_MatrixElements_TestData()
+    {
+        // Identity.
+        yield return new object[] { 1, 0, 0, 1, 0, 0, true, true, 1 };
+
+        // Scale.
+        yield return new object[] { 1, 0, 0, 2, 0, 0, true, false, 2 };
+        yield return new object[] { 2, 0, 0, 1, 0, 0, true, false, 2 };
+        yield return new object[] { 2, 0, 0, 3, 0, 0, true, false, 6 };
+
+        // Skew.
+        yield return new object[] { 1, 1, 0, 1, 0, 0, true, false, 1 };
+        yield return new object[] { 1, 0, 2, 1, 0, 0, true, false, 1 };
+        yield return new object[] { 1, 1, 2, 1, 0, 0, true, false, -1 };
+
+        // Translate.
+        yield return new object[] { 1, 0, 0, 1, 1, 0, true, false, 1 };
+        yield return new object[] { 1, 0, 0, 1, 0, 2, true, false, 1 };
+        yield return new object[] { 1, 0, 0, 1, 1, 2, true, false, 1 };
+
+        // Translate + Scale.
+        yield return new object[] { 2, 0, 0, 3, 4, 5, true, false, 6 };
+
+        // Translate + Skew.
+        yield return new object[] { 1, 2, 3, 1, 4, 5, true, false, -5 };
+
+        // Skew + Scale.
+        yield return new object[] { 1, 2, 3, 1, 0, 0, true, false, -5 };
+
+        // Complex.
+        yield return new object[] { 2, 3, 4, 5, 6, 7, true, false, -2 };
+        yield return new object[] { -1, -2, -3, -4, -5, -6, true, false, -2 };
+        yield return new object[] { 1.1, 2.2, 3.3, 4.4, 5.5, 6.6, true, false, -2.42 };
+
+        // Zero.
+        yield return new object[] { 0, 0, 0, 0, 0, 0, false, false, 0 };
+
+        // Infinity.
+        yield return new object[] { double.PositiveInfinity, 0, 0, 1, 0, 0, true, false, double.PositiveInfinity };
+        yield return new object[] { 1, double.PositiveInfinity, 0, 1, 0, 0, true, false, double.NaN };
+        yield return new object[] { 1, 0, double.PositiveInfinity, 1, 0, 0, true, false, double.NaN };
+        yield return new object[] { 1, 0, 0, double.PositiveInfinity, 0, 0, true, false, double.PositiveInfinity };
+        yield return new object[] { 1, 0, 0, 1, double.PositiveInfinity, 0, true, false, 1 };
+        yield return new object[] { 1, 0, 0, 1, 0, double.PositiveInfinity, true, false, 1 };
+        yield return new object[] { double.PositiveInfinity, double.PositiveInfinity, double.PositiveInfinity, double.PositiveInfinity, double.PositiveInfinity, double.PositiveInfinity, true, false, double.NaN };
+        yield return new object[] { double.NegativeInfinity, 0, 0, 1, 0, 0, true, false, double.NegativeInfinity };
+        yield return new object[] { 1, double.NegativeInfinity, 0, 1, 0, 0, true, false, double.NaN };
+        yield return new object[] { 1, 0, double.NegativeInfinity, 1, 0, 0, true, false, double.NaN };
+        yield return new object[] { 1, 0, 0, double.NegativeInfinity, 0, 0, true, false, double.NegativeInfinity };
+        yield return new object[] { 1, 0, 0, 1, double.NegativeInfinity, 0, true, false, 1 };
+        yield return new object[] { 1, 0, 0, 1, 0, double.NegativeInfinity, true, false, 1 };
+        yield return new object[] { double.NegativeInfinity, double.NegativeInfinity, double.NegativeInfinity, double.NegativeInfinity, double.NegativeInfinity, double.NegativeInfinity, true, false, double.NaN };
+
+        // NaN.
+        yield return new object[] { double.NaN, 0, 0, 1, 0, 0, true, false, double.NaN };
+        yield return new object[] { 1, double.NaN, 0, 1, 0, 0, true, false, double.NaN };
+        yield return new object[] { 1, 0, double.NaN, 1, 0, 0, true, false, double.NaN };
+        yield return new object[] { 1, 0, 0, double.NaN, 0, 0, true, false, double.NaN };
+        yield return new object[] { 1, 0, 0, 1, double.NaN, 0, true, false, 1 };
+        yield return new object[] { 1, 0, 0, 1, 0, double.NaN, true, false, 1 };
+        yield return new object[] { double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, true, false, double.NaN };
+    }
+
+    [Theory]
+    [MemberData(nameof(Ctor_MatrixElements_TestData))]
+    public void Ctor_MatrixElements(double m11, double m12, double m21, double m22, double offsetX, double offsetY, bool hasInverse, bool isIdentity, double expectedDeterminant)
+    {
+        var matrix = new Matrix(m11, m12, m21, m22, offsetX, offsetY);
+        Assert.Equal(m11, matrix.M11);
+        Assert.Equal(m12, matrix.M12);
+        Assert.Equal(m21, matrix.M21);
+        Assert.Equal(m22, matrix.M22);
+        Assert.Equal(offsetX, matrix.OffsetX);
+        Assert.Equal(offsetY, matrix.OffsetY);
+        Assert.Equal(hasInverse, matrix.HasInverse);
+        Assert.Equal(isIdentity, matrix.IsIdentity);
+        Assert.Equal(expectedDeterminant, matrix.Determinant, precision: 5);
+    }
+
+    [Fact]
+    public void Identity_Get_ReturnsExpected()
+    {
+        Matrix matrix = Matrix.Identity;
+        Assert.Equal(1, matrix.M11);
+        Assert.Equal(0, matrix.M12);
+        Assert.Equal(0, matrix.M21);
+        Assert.Equal(1, matrix.M22);
+        Assert.Equal(0, matrix.OffsetX);
+        Assert.Equal(0, matrix.OffsetY);
+        Assert.True(matrix.HasInverse);
+        Assert.True(matrix.IsIdentity);
+        Assert.Equal(1, matrix.Determinant);
+        Assert.Equal(Matrix.Identity, matrix);
+        Assert.Equal(new Matrix(), matrix);
+    }
+
+    public static IEnumerable<object[]> Determinant_Get_TestData()
+    {
+        // Identity
+        foreach (Matrix matrix in IdentityMatrices())
+        {
+            yield return new object[] { matrix, 1 };
+        }
+
+        // Scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 6 };
+
+        // Skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0.625 };
+
+        // Translated.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1 };
+
+        // Translated and scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 6 };
+
+        // Translated and skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0.625 };
+
+        // Skewed and scaled.
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 5.625 };
+
+        // Complex.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -2 };
+
+        // No inverse.
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0 };
+    }
+
+    [Theory]
+    [MemberData(nameof(Determinant_Get_TestData))]
+    public void Determinant_Get_ReturnsExpected(Matrix matrix, double expected)
+    {
+        Assert.Equal(expected, matrix.Determinant, precision: 5);
+    }
+    public static IEnumerable<object[]> HasInverse_Get_TestData()
+    {
+        // Identity
+        foreach (Matrix matrix in IdentityMatrices())
+        {
+            yield return new object[] { matrix, true };
+        }
+
+        // Scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), true };
+
+        // Skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), true };
+
+        // Translated.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), true };
+
+        // Translated and scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), true };
+
+        // Translated and skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), true };
+
+        // Skewed and scaled.
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), true };
+
+        // Complex.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), true };
+
+        // No inverse.
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), false };
+    }
+
+    [Theory]
+    [MemberData(nameof(HasInverse_Get_TestData))]
+    public void HasInverse_Get_ReturnsExpected(Matrix matrix, bool expected)
+    {
+        Assert.Equal(expected, matrix.HasInverse);
+    }
+
+    [Theory]
+    [MemberData(nameof(Multiply_TestData))]
+    public void Append_Invoke_ReturnsExpected(Matrix matrix1, Matrix matrix2, Matrix expected)
+    {
+        Matrix copy1 = matrix1;
+        Matrix copy2 = matrix2;
+
+        matrix1.Append(matrix2);
+        Assert.Equal(expected, matrix1);
+        Assert.Equal(copy2, matrix2);
+    }
+
+    public static IEnumerable<object?[]> Equals_TestData()
+    {
+        // Identity.
+        foreach (Matrix identity1 in IdentityMatrices())
+        {
+            // Identity + identity.
+            foreach (Matrix identity2 in IdentityMatrices())
+            {
+                yield return new object?[] { identity1, identity2, true, true };
+            }
+
+            // Identity + scaled.
+            yield return new object?[] { identity1, new Matrix(2, 0, 0, 1, 0, 0), false, false };
+            yield return new object?[] { identity1, new Matrix(1, 0, 0, 5, 0, 0), false, false };
+            yield return new object?[] { identity1, new Matrix(2, 0, 0, 5, 0, 0), false, false };
+
+            // Identity + skewed.
+            yield return new object?[] { identity1, new Matrix(1, 3, 0, 1, 0, 0), false, false };
+            yield return new object?[] { identity1, new Matrix(1, 0, 4, 1, 0, 0), false, false };
+            yield return new object?[] { identity1, new Matrix(1, 3, 4, 1, 0, 0), false, false };
+
+            // Identity + translated.
+            yield return new object?[] { identity1, new Matrix(1, 0, 0, 1, 6, 0), false, false };
+            yield return new object?[] { identity1, new Matrix(1, 0, 0, 1, 0, 7), false, false };
+            yield return new object?[] { identity1, new Matrix(1, 0, 0, 1, 6, 7), false, false };
+
+            // Identity + translated and scaled.
+            yield return new object?[] { identity1, new Matrix(2, 0, 0, 1, 6, 7), false, false };
+            yield return new object?[] { identity1, new Matrix(1, 0, 0, 5, 6, 7), false, false };
+            yield return new object?[] { identity1, new Matrix(2, 0, 0, 5, 6, 0), false, false };
+            yield return new object?[] { identity1, new Matrix(2, 0, 0, 5, 0, 7), false, false };
+            yield return new object?[] { identity1, new Matrix(2, 0, 0, 5, 6, 7), false, false };
+
+            // Identity + translate and skewed.
+            yield return new object?[] { identity1, new Matrix(1, 3, 0, 1, 6, 7), false, false };
+            yield return new object?[] { identity1, new Matrix(1, 0, 4, 1, 6, 7), false, false };
+            yield return new object?[] { identity1, new Matrix(1, 3, 4, 1, 6, 0), false, false };
+            yield return new object?[] { identity1, new Matrix(1, 3, 4, 1, 0, 7), false, false };
+            yield return new object?[] { identity1, new Matrix(1, 3, 4, 1, 6, 7), false, false };
+
+            // Identity + skewed and scaled.
+            yield return new object?[] { identity1, new Matrix(2, 3, 4, 5, 0, 0), false, false };
+            yield return new object?[] { identity1, new Matrix(1, 3, 4, 5, 0, 0), false, false };
+            yield return new object?[] { identity1, new Matrix(2, 3, 0, 5, 0, 0), false, false };
+            yield return new object?[] { identity1, new Matrix(2, 0, 4, 5, 0, 0), false, false };
+            yield return new object?[] { identity1, new Matrix(2, 3, 4, 5, 0, 0), false, false };
+
+            // Identity + complex.
+            yield return new object?[] { identity1, new Matrix(2, 3, 4, 5, 6, 7), false, false };
+            yield return new object?[] { identity1, new Matrix(0, 0, 0, 0, 0, 0), false, true };
+        }
+
+        // Scaled + identity.
+        foreach (Matrix identity in IdentityMatrices())
+        {
+            yield return new object?[] { new Matrix(2, 0, 0, 5, 0, 0), identity, false, false };
+        }
+
+        // Scaled + scaled.
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 0, 0, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 0, 0, 5, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 0, 0, 5, 0, 0), true, true };
+
+        // Scaled + skewed.
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 3, 0, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 0, 4, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 3, 4, 1, 0, 0), false, false };
+
+        // Scaled + translated.
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 0, 0, 1, 6, 0), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 0, 0, 1, 0, 7), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 0, 0, 1, 6, 7), false, false };
+
+        // Scaled + translated and scaled.
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 0, 0, 1, 6, 7), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 0, 0, 5, 6, 7), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 0, 0, 5, 0, 7), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 0, 0, 5, 6, 0), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 0, 0, 5, 6, 7), false, false };
+
+        // Scaled + translated and skewed.
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 3, 0, 1, 6, 7), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 4, 0, 1, 6, 7), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 3, 4, 1, 0, 7), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 3, 4, 1, 6, 0), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 3, 4, 1, 6, 7), false, false };
+
+        // Scaled + skewed and scaled.
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 3, 4, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 3, 4, 5, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 3, 0, 5, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 0, 4, 5, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 3, 4, 5, 0, 0), false, false };
+
+        // Scaled + complex.
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 3, 4, 5, 6, 7), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(0, 0, 0, 0, 0, 0), false, false };
+
+        // Skewed + identity.
+        foreach (Matrix identity in IdentityMatrices())
+        {
+            yield return new object?[] { new Matrix(1, 3, 4, 1, 0, 0), identity, false, false };
+        }
+
+        // Skewed + scaled.
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 0, 0, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 0, 0, 2, 0, 0), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 0, 0, 5, 0, 0), false, false };
+
+        // Skewed + skewed.
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 3, 0, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 0, 4, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 3, 4, 1, 0, 0), true, true };
+
+        // Skewed + translated.
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 0, 0, 1, 6, 0), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 0, 0, 1, 0, 7), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 0, 0, 1, 6, 7), false, false };
+
+        // Skewed + translated and scaled.
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 0, 0, 1, 6, 7), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 0, 0, 5, 6, 7), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 0, 0, 5, 6, 0), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 0, 0, 5, 0, 7), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 0, 0, 5, 6, 7), false, false };
+
+        // Skewed + translated and skewed.
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 3, 0, 1, 6, 7), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 0, 4, 1, 6, 7), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 3, 4, 1, 6, 0), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 3, 4, 1, 0, 7), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 3, 4, 1, 6, 7), false, false };
+
+        // Skewed + skewed and scaled.
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 3, 4, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 3, 4, 5, 0, 0), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 3, 0, 5, 0, 0), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 0, 4, 5, 0, 0), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 3, 4, 5, 0, 0), false, false };
+
+        // Skewed + complex.
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 3, 4, 5, 6, 7), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(0, 0, 0, 0, 0, 0), false, false };
+
+        // Translated + identity.
+        foreach (Matrix identity in IdentityMatrices())
+        {
+            yield return new object?[] { new Matrix(1, 0, 0, 1, 6, 7), identity, false, false };
+        }
+
+        // Translated + scaled.
+        yield return new object?[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 0, 0, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 0, 0, 2, 0, 0), false, false };
+        yield return new object?[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 0, 0, 5, 0, 0), false, false };
+
+        // Translated + skewed.
+        yield return new object?[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 3, 0, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 0, 4, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 3, 4, 1, 0, 0), false, false };
+
+        // Translated + translated.
+        yield return new object?[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 0, 0, 1, 6, 0), false, false };
+        yield return new object?[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 0, 0, 1, 0, 7), false, false };
+        yield return new object?[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 0, 0, 1, 6, 7), true, true };
+
+        // Translated + translated and scaled.
+        yield return new object?[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 0, 0, 1, 6, 7), false, false };
+        yield return new object?[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 0, 0, 5, 6, 7), false, false };
+        yield return new object?[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 0, 0, 5, 6, 0), false, false };
+        yield return new object?[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 0, 0, 5, 0, 7), false, false };
+        yield return new object?[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 0, 0, 5, 6, 7), false, false };
+
+        // Translated + translated and skewed.
+        yield return new object?[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 3, 0, 1, 6, 7), false, false };
+        yield return new object?[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 0, 4, 1, 6, 7), false, false };
+        yield return new object?[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 3, 4, 1, 6, 0), false, false };
+        yield return new object?[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 3, 4, 1, 0, 7), false, false };
+        yield return new object?[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 3, 4, 1, 6, 7), false, false };
+
+        // Translated + skewed and scaled.
+        yield return new object?[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 3, 4, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 3, 4, 5, 0, 0), false, false };
+        yield return new object?[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 3, 0, 5, 0, 0), false, false };
+        yield return new object?[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 0, 4, 5, 0, 0), false, false };
+        yield return new object?[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 3, 4, 5, 0, 0), false, false };
+
+        // Translated + complex.
+        yield return new object?[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 3, 4, 5, 6, 7), false, false };
+        yield return new object?[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(0, 0, 0, 0, 0, 0), false, false };
+
+        // Translated and scaled + identity.
+        foreach (Matrix identity in IdentityMatrices())
+        {
+            yield return new object?[] { new Matrix(2, 0, 0, 5, 6, 7), identity, false, false };
+        }
+
+        // Translated and scaled + scaled.
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 0, 0, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 0, 0, 2, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 0, 0, 5, 0, 0), false, false };
+
+        // Translated and scaled + skewed.
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 3, 0, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 0, 4, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 3, 4, 1, 0, 0), false, false };
+
+        // Translated and scaled + translated.
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 0, 0, 1, 6, 0), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 0, 0, 1, 0, 7), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 0, 0, 1, 6, 7), false, false };
+
+        // Translated and scaled + translated and scaled.
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 0, 0, 1, 6, 7), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 0, 0, 5, 6, 7), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 0, 0, 5, 6, 0), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 0, 0, 5, 0, 7), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 0, 0, 5, 6, 7), true, true };
+
+        // Translated and scaled + translated and skewed.
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 3, 0, 1, 6, 7), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 0, 4, 1, 6, 7), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 3, 4, 1, 6, 0), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 3, 4, 1, 0, 7), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 3, 4, 1, 6, 7), false, false };
+
+        // Translated and scaled + skewed and scaled.
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 3, 4, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 3, 4, 5, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 3, 0, 5, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 0, 4, 5, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 3, 4, 5, 0, 0), false, false };
+
+        // Translated and scaled + complex.
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 3, 4, 5, 6, 7), false, false };
+        yield return new object?[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(0, 0, 0, 0, 0, 0), false, false };
+
+        // Translated and skewed + identity.
+        foreach (Matrix identity in IdentityMatrices())
+        {
+            yield return new object?[] { new Matrix(1, 3, 4, 1, 6, 7), identity, false, false };
+        }
+
+        // Translated and skewed + scaled.
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 0, 0, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 0, 0, 2, 0, 0), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 0, 0, 5, 0, 0), false, false };
+
+        // Translated and skewed + skewed.
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 3, 0, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 0, 4, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 3, 4, 1, 0, 0), false, false };
+
+        // Translated and skewed + translated.
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 0, 0, 1, 6, 0), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 0, 0, 1, 0, 7), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 0, 0, 1, 6, 7), false, false };
+
+        // Translated and skewed + translated and scaled.
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 0, 0, 1, 6, 7), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 0, 0, 5, 6, 7), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 0, 0, 5, 6, 0), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 0, 0, 5, 0, 7), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 0, 0, 5, 6, 7), false, false };
+
+        // Translated and skewed + translated and skewed.
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 3, 0, 1, 6, 7), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 0, 4, 1, 6, 7), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 3, 4, 1, 6, 0), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 3, 4, 1, 0, 7), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 3, 4, 1, 6, 7), true, true };
+
+        // Translated and skewed + skewed and scaled.
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 3, 4, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 3, 4, 5, 0, 0), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 3, 0, 5, 0, 0), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 0, 4, 5, 0, 0), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 3, 4, 5, 0, 0), false, false };
+
+        // Translated and skewed + complex.
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 3, 4, 5, 6, 7), false, false };
+        yield return new object?[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(0, 0, 0, 0, 0, 0), false, false };
+
+        // Skewed and scaled + identity.
+        foreach (Matrix identity in IdentityMatrices())
+        {
+            yield return new object?[] { new Matrix(2, 3, 4, 5, 0, 0), identity, false, false };
+        }
+
+        // Skewed and scaled + scaled.
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 0, 0, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 0, 0, 2, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 0, 0, 5, 0, 0), false, false };
+
+        // Skewed and scaled + skewed.
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 3, 0, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 0, 4, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 3, 4, 1, 0, 0), false, false };
+
+        // Skewed and scaled + translated.
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 0, 0, 1, 6, 0), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 0, 0, 1, 0, 7), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 0, 0, 1, 6, 7), false, false };
+
+        // Skewed and scaled + translated and scaled.
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 0, 0, 1, 6, 7), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 0, 0, 5, 6, 7), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 0, 0, 5, 6, 0), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 0, 0, 5, 0, 7), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 0, 0, 5, 6, 7), false, false };
+
+        // Skewed and scaled + translated and skewed.
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 3, 0, 1, 6, 7), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 0, 4, 1, 6, 7), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 3, 4, 1, 6, 0), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 3, 4, 1, 0, 7), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 3, 4, 1, 6, 7), false, false };
+
+        // Skewed and scaled + skewed and scaled.
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 3, 4, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 3, 4, 5, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 3, 0, 5, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 0, 4, 5, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 3, 4, 5, 0, 0), true, true };
+
+        // Skewed and scaled + complex.
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 3, 4, 5, 6, 7), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(0, 0, 0, 0, 0, 0), false, false };
+
+        // Complex + identity.
+        foreach (Matrix identity in IdentityMatrices())
+        {
+            yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), identity, false, false };
+        }
+
+        // Complex + scaled.
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 0, 0, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 0, 0, 2, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 0, 0, 5, 0, 0), false, false };
+
+        // Complex + skewed.
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 3, 0, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 0, 4, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 3, 4, 1, 0, 0), false, false };
+
+        // Complex + translated.
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 0, 0, 1, 6, 0), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 0, 0, 1, 0, 7), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 0, 0, 1, 6, 7), false, false };
+
+        // Complex + translated and scaled.
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 0, 0, 1, 6, 7), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 0, 0, 5, 6, 7), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 0, 0, 5, 6, 0), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 0, 0, 5, 0, 7), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 0, 0, 5, 6, 7), false, false };
+
+        // Complex + translated and skewed.
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 3, 0, 1, 6, 7), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 0, 4, 1, 6, 7), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 3, 4, 1, 6, 0), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 3, 4, 1, 0, 7), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 3, 4, 1, 6, 7), false, false };
+
+        // Complex + skewed and scaled.
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 3, 4, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 3, 4, 5, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 3, 0, 5, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 0, 4, 5, 0, 0), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 3, 4, 5, 0, 0), false, false };
+
+        // Complex + complex.
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 3, 4, 5, 6, 7), true, true };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(0, 0, 0, 0, 0, 0), false, false };
+
+        // Zero + identity.
+        foreach (Matrix identity in IdentityMatrices())
+        {
+            yield return new object?[] { new Matrix(0, 0, 0, 0, 0, 0), identity, false, true };
+        }
+
+        // Zero + scaled.
+        yield return new object?[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 0, 0, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 0, 0, 2, 0, 0), false, false };
+        yield return new object?[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 0, 0, 5, 0, 0), false, false };
+
+        // Zero + skewed.
+        yield return new object?[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 3, 0, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 0, 4, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 3, 4, 1, 0, 0), false, false };
+
+        // Zero + translated.
+        yield return new object?[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 0, 0, 1, 6, 0), false, false };
+        yield return new object?[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 0, 0, 1, 0, 7), false, false };
+        yield return new object?[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 0, 0, 1, 6, 7), false, false };
+
+        // Zero + translated and scaled.
+        yield return new object?[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 0, 0, 1, 6, 7), false, false };
+        yield return new object?[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 0, 0, 5, 6, 7), false, false };
+        yield return new object?[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 0, 0, 5, 6, 0), false, false };
+        yield return new object?[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 0, 0, 5, 0, 7), false, false };
+        yield return new object?[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 0, 0, 5, 6, 7), false, false };
+
+        // Zero + translated and skewed.
+        yield return new object?[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 3, 0, 1, 6, 7), false, false };
+        yield return new object?[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 0, 4, 1, 6, 7), false, false };
+        yield return new object?[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 3, 4, 1, 6, 0), false, false };
+        yield return new object?[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 3, 4, 1, 0, 7), false, false };
+        yield return new object?[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 3, 4, 1, 6, 7), false, false };
+
+        // Zero + skewed and scaled.
+        yield return new object?[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 3, 4, 1, 0, 0), false, false };
+        yield return new object?[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 3, 4, 5, 0, 0), false, false };
+        yield return new object?[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 3, 0, 5, 0, 0), false, false };
+        yield return new object?[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 0, 4, 5, 0, 0), false, false };
+        yield return new object?[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 3, 4, 5, 0, 0), false, false };
+
+        // Zero + complex.
+        yield return new object?[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 3, 4, 5, 6, 7), false, false };
+        yield return new object?[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(0, 0, 0, 0, 0, 0), true, true };
+
+        // NaN.
+        yield return new object?[] { new Matrix(double.NaN, 3, 4, 5, 6, 7), new Matrix(double.NaN, 3, 4, 5, 6, 7), true, true };
+        yield return new object?[] { new Matrix(double.NaN, 3, 4, 5, 6, 7), new Matrix(2, 3, 4, 5, 6, 7), false, false };
+        yield return new object?[] { new Matrix(2, double.NaN, 4, 5, 6, 7), new Matrix(2, double.NaN, 4, 5, 6, 7), true, true };
+        yield return new object?[] { new Matrix(2, double.NaN, 4, 5, 6, 7), new Matrix(2, 3, 4, 5, 6, 7), false, false };
+        yield return new object?[] { new Matrix(2, 3, double.NaN, 5, 6, 7), new Matrix(2, 3, double.NaN, 5, 6, 7), true, true };
+        yield return new object?[] { new Matrix(2, 3, double.NaN, 5, 6, 7), new Matrix(2, 3, 4, 5, 6, 7), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, double.NaN, 6, 7), new Matrix(2, 3, 4, double.NaN, 6, 7), true, true };
+        yield return new object?[] { new Matrix(2, 3, 4, double.NaN, 6, 7), new Matrix(2, 3, 4, 5, 6, 7), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, double.NaN, 7), new Matrix(2, 3, 4, 5, double.NaN, 7), true, true };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, double.NaN, 7), new Matrix(2, 3, 4, 5, 6, 7), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, double.NaN), new Matrix(2, 3, 4, 5, 6, double.NaN), true, true };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, double.NaN), new Matrix(2, 3, 4, 5, 6, 7), false, false };
+        yield return new object?[] { new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), true, true };
+        yield return new object?[] { new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), new Matrix(2, 3, 4, 5, 6, 7), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(double.NaN, 3, 4, 5, 6, 7), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, double.NaN, 4, 5, 6, 7), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 3, double.NaN, 5, 6, 7), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 3, 4, double.NaN, 6, 7), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 3, 4, 5, double.NaN, 7), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 3, 4, 5, 6, double.NaN), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), false, false };
+
+        // Others.
+        foreach (Matrix identity in IdentityMatrices())
+        {
+            yield return new object?[] { identity, new object(), false, false };
+            yield return new object?[] { identity, null, false, false };
+        }
+
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), new object(), false, false };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), null, false, false };
+        yield return new object?[] { new Matrix(0, 0, 0, 0, 0, 0), new object(), false, false };
+        yield return new object?[] { new Matrix(0, 0, 0, 0, 0, 0), null, false, false };
+    }
+
+    [Theory]
+    [MemberData(nameof(Equals_TestData))]
+    public void Equals_Object_ReturnsExpected(Matrix matrix, object o, bool expected, bool expectedHashCode)
+    {
+        Assert.Equal(expected, matrix.Equals(o));
+        if (o is Matrix value)
+        {
+            Assert.Equal(expected, matrix.Equals(value));
+            Assert.Equal(expected, value.Equals(matrix));
+            Assert.Equal(expected, Matrix.Equals(matrix, value));
+            Assert.Equal(expected, Matrix.Equals(value, matrix));
+            Assert.Equal(expectedHashCode, matrix.GetHashCode().Equals(value.GetHashCode()));
+        }
+    }
+
+    public static IEnumerable<object[]> EqualityOperator_TestData()
+    {
+        // Identity.
+        foreach (Matrix identity1 in IdentityMatrices())
+        {
+            // Identity + identity.
+            foreach (Matrix identity2 in IdentityMatrices())
+            {
+                yield return new object[] { identity1, identity2, true };
+            }
+
+            // Identity + scaled.
+            yield return new object[] { identity1, new Matrix(2, 0, 0, 1, 0, 0), false };
+            yield return new object[] { identity1, new Matrix(1, 0, 0, 5, 0, 0), false };
+            yield return new object[] { identity1, new Matrix(2, 0, 0, 5, 0, 0), false };
+
+            // Identity + skewed.
+            yield return new object[] { identity1, new Matrix(1, 3, 0, 1, 0, 0), false };
+            yield return new object[] { identity1, new Matrix(1, 0, 4, 1, 0, 0), false };
+            yield return new object[] { identity1, new Matrix(1, 3, 4, 1, 0, 0), false };
+
+            // Identity + translated.
+            yield return new object[] { identity1, new Matrix(1, 0, 0, 1, 6, 0), false };
+            yield return new object[] { identity1, new Matrix(1, 0, 0, 1, 0, 7), false };
+            yield return new object[] { identity1, new Matrix(1, 0, 0, 1, 6, 7), false };
+
+            // Identity + translated and scaled.
+            yield return new object[] { identity1, new Matrix(2, 0, 0, 1, 6, 7), false };
+            yield return new object[] { identity1, new Matrix(1, 0, 0, 5, 6, 7), false };
+            yield return new object[] { identity1, new Matrix(2, 0, 0, 5, 6, 0), false };
+            yield return new object[] { identity1, new Matrix(2, 0, 0, 5, 0, 7), false };
+            yield return new object[] { identity1, new Matrix(2, 0, 0, 5, 6, 7), false };
+
+            // Identity + translate and skewed.
+            yield return new object[] { identity1, new Matrix(1, 3, 0, 1, 6, 7), false };
+            yield return new object[] { identity1, new Matrix(1, 0, 4, 1, 6, 7), false };
+            yield return new object[] { identity1, new Matrix(1, 3, 4, 1, 6, 0), false };
+            yield return new object[] { identity1, new Matrix(1, 3, 4, 1, 0, 7), false };
+            yield return new object[] { identity1, new Matrix(1, 3, 4, 1, 6, 7), false };
+
+            // Identity + skewed and scaled.
+            yield return new object[] { identity1, new Matrix(2, 3, 4, 5, 0, 0), false };
+            yield return new object[] { identity1, new Matrix(1, 3, 4, 5, 0, 0), false };
+            yield return new object[] { identity1, new Matrix(2, 3, 0, 5, 0, 0), false };
+            yield return new object[] { identity1, new Matrix(2, 0, 4, 5, 0, 0), false };
+            yield return new object[] { identity1, new Matrix(2, 3, 4, 5, 0, 0), false };
+
+            // Identity + complex.
+            yield return new object[] { identity1, new Matrix(2, 3, 4, 5, 6, 7), false };
+            yield return new object[] { identity1, new Matrix(0, 0, 0, 0, 0, 0), false };
+        }
+
+        // Scaled + identity.
+        foreach (Matrix identity in IdentityMatrices())
+        {
+            yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), identity, false };
+        }
+
+        // Scaled + scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 0, 0, 1, 0, 0), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 0, 0, 5, 0, 0), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 0, 0, 5, 0, 0), true };
+
+        // Scaled + skewed.
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 3, 0, 1, 0, 0), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 0, 4, 1, 0, 0), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 3, 4, 1, 0, 0), false };
+
+        // Scaled + translated.
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 0, 0, 1, 6, 0), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 0, 0, 1, 0, 7), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 0, 0, 1, 6, 7), false };
+
+        // Scaled + translated and scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 0, 0, 5, 0, 7), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 0, 0, 5, 6, 7), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 0, 0, 1, 6, 7), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 0, 0, 5, 6, 0), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 0, 0, 5, 6, 7), false };
+
+        // Scaled + translated and skewed.
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 3, 0, 1, 6, 7), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 4, 0, 1, 6, 7), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 3, 4, 1, 0, 7), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 3, 4, 1, 6, 0), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 3, 4, 1, 6, 7), false };
+
+        // Scaled + skewed and scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 3, 4, 1, 0, 0), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 3, 4, 5, 0, 0), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 3, 0, 5, 0, 0), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 0, 4, 5, 0, 0), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 3, 4, 5, 0, 0), false };
+
+        // Scaled + complex.
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 3, 4, 5, 6, 7), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(0, 0, 0, 0, 0, 0), false };
+
+        // Skewed + identity.
+        foreach (Matrix identity in IdentityMatrices())
+        {
+            yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), identity, false };
+        }
+
+        // Skewed + scaled.
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 0, 0, 1, 0, 0), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 0, 0, 2, 0, 0), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 0, 0, 5, 0, 0), false };
+
+        // Skewed + skewed.
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 3, 0, 1, 0, 0), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 0, 4, 1, 0, 0), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 3, 4, 1, 0, 0), true };
+
+        // Skewed + translated.
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 0, 0, 1, 6, 0), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 0, 0, 1, 0, 7), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 0, 0, 1, 6, 7), false };
+
+        // Skewed + translated and scaled.
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 0, 0, 1, 6, 7), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 0, 0, 5, 6, 7), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 0, 0, 5, 6, 0), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 0, 0, 5, 0, 7), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 0, 0, 5, 6, 7), false };
+
+        // Skewed + translated and skewed.
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 3, 0, 1, 6, 7), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 0, 4, 1, 6, 7), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 3, 4, 1, 6, 0), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 3, 4, 1, 0, 7), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 3, 4, 1, 6, 7), false };
+
+        // Skewed + skewed and scaled.
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 3, 4, 1, 0, 0), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 3, 4, 5, 0, 0), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 3, 0, 5, 0, 0), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 0, 4, 5, 0, 0), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 3, 4, 5, 0, 0), false };
+
+        // Skewed + complex.
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 3, 4, 5, 6, 7), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(0, 0, 0, 0, 0, 0), false };
+
+        // Translated + identity.
+        foreach (Matrix identity in IdentityMatrices())
+        {
+            yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), identity, false };
+        }
+
+        // Translated + scaled.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 0, 0, 1, 0, 0), false };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 0, 0, 2, 0, 0), false };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 0, 0, 5, 0, 0), false };
+
+        // Translated + skewed.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 3, 0, 1, 0, 0), false };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 0, 4, 1, 0, 0), false };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 3, 4, 1, 0, 0), false };
+
+        // Translated + translated.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 0, 0, 1, 6, 0), false };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 0, 0, 1, 0, 7), false };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 0, 0, 1, 6, 7), true };
+
+        // Translated + translated and scaled.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 0, 0, 1, 6, 7), false };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 0, 0, 5, 6, 7), false };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 0, 0, 5, 6, 0), false };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 0, 0, 5, 0, 7), false };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 0, 0, 5, 6, 7), false };
+
+        // Translated + translated and skewed.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 3, 0, 1, 6, 7), false };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 0, 4, 1, 6, 7), false };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 3, 4, 1, 6, 0), false };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 3, 4, 1, 0, 7), false };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 3, 4, 1, 6, 7), false };
+
+        // Translated + skewed and scaled.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 3, 4, 1, 0, 0), false };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 3, 4, 5, 0, 0), false };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 3, 0, 5, 0, 0), false };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 0, 4, 5, 0, 0), false };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 3, 4, 5, 0, 0), false };
+
+        // Translated + complex.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 3, 4, 5, 6, 7), false };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(0, 0, 0, 0, 0, 0), false };
+
+        // Translated and scaled + identity.
+        foreach (Matrix identity in IdentityMatrices())
+        {
+            yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), identity, false };
+        }
+
+        // Translated and scaled + scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 0, 0, 1, 0, 0), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 0, 0, 2, 0, 0), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 0, 0, 5, 0, 0), false };
+
+        // Translated and scaled + skewed.
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 3, 0, 1, 0, 0), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 0, 4, 1, 0, 0), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 3, 4, 1, 0, 0), false };
+
+        // Translated and scaled + translated.
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 0, 0, 1, 6, 0), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 0, 0, 1, 0, 7), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 0, 0, 1, 6, 7), false };
+
+        // Translated and scaled + translated and scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 0, 0, 1, 6, 7), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 0, 0, 5, 6, 7), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 0, 0, 5, 6, 0), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 0, 0, 5, 0, 7), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 0, 0, 5, 6, 7), true };
+
+        // Translated and scaled + translated and skewed.
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 3, 0, 1, 6, 7), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 0, 4, 1, 6, 7), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 3, 4, 1, 6, 0), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 3, 4, 1, 0, 7), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 3, 4, 1, 6, 7), false };
+
+        // Translated and scaled + skewed and scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 3, 4, 1, 0, 0), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 3, 4, 5, 0, 0), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 3, 0, 5, 0, 0), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 0, 4, 5, 0, 0), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 3, 4, 5, 0, 0), false };
+
+        // Translated and scaled + complex.
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 3, 4, 5, 6, 7), false };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(0, 0, 0, 0, 0, 0), false };
+
+        // Translated and skewed + identity.
+        foreach (Matrix identity in IdentityMatrices())
+        {
+            yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), identity, false };
+        }
+
+        // Translated and skewed + scaled.
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 0, 0, 1, 0, 0), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 0, 0, 2, 0, 0), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 0, 0, 5, 0, 0), false };
+
+        // Translated and skewed + skewed.
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 3, 0, 1, 0, 0), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 0, 4, 1, 0, 0), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 3, 4, 1, 0, 0), false };
+
+        // Translated and skewed + translated.
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 0, 0, 1, 6, 0), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 0, 0, 1, 0, 7), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 0, 0, 1, 6, 7), false };
+
+        // Translated and skewed + translated and scaled.
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 0, 0, 1, 6, 7), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 0, 0, 5, 6, 7), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 0, 0, 5, 6, 0), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 0, 0, 5, 0, 7), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 0, 0, 5, 6, 7), false };
+
+        // Translated and skewed + translated and skewed.
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 3, 0, 1, 6, 7), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 0, 4, 1, 6, 7), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 3, 4, 1, 6, 0), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 3, 4, 1, 0, 7), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 3, 4, 1, 6, 7), true };
+
+        // Translated and skewed + skewed and scaled.
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 3, 4, 1, 0, 0), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 3, 4, 5, 0, 0), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 3, 0, 5, 0, 0), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 0, 4, 5, 0, 0), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 3, 4, 5, 0, 0), false };
+
+        // Translated and skewed + complex.
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 3, 4, 5, 6, 7), false };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(0, 0, 0, 0, 0, 0), false };
+
+        // Skewed and scaled + identity.
+        foreach (Matrix identity in IdentityMatrices())
+        {
+            yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), identity, false };
+        }
+
+        // Skewed and scaled + scaled.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 0, 0, 1, 0, 0), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 0, 0, 2, 0, 0), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 0, 0, 5, 0, 0), false };
+
+        // Skewed and scaled + skewed.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 3, 0, 1, 0, 0), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 0, 4, 1, 0, 0), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 3, 4, 1, 0, 0), false };
+
+        // Skewed and scaled + translated.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 0, 0, 1, 6, 0), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 0, 0, 1, 0, 7), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 0, 0, 1, 6, 7), false };
+
+        // Skewed and scaled + translated and scaled.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 0, 0, 1, 6, 7), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 0, 0, 5, 6, 7), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 0, 0, 5, 6, 0), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 0, 0, 5, 0, 7), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 0, 0, 5, 6, 7), false };
+
+        // Skewed and scaled + translated and skewed.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 3, 0, 1, 6, 7), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 0, 4, 1, 6, 7), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 3, 4, 1, 6, 0), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 3, 4, 1, 0, 7), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 3, 4, 1, 6, 7), false };
+
+        // Skewed and scaled + skewed and scaled.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 3, 4, 1, 0, 0), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 3, 4, 5, 0, 0), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 3, 0, 5, 0, 0), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 0, 4, 5, 0, 0), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 3, 4, 5, 0, 0), true };
+
+        // Skewed and scaled + complex.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 3, 4, 5, 6, 7), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(0, 0, 0, 0, 0, 0), false };
+
+        // Complex + identity.
+        foreach (Matrix identity in IdentityMatrices())
+        {
+            yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), identity, false };
+        }
+
+        // Complex + scaled.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 0, 0, 1, 0, 0), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 0, 0, 2, 0, 0), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 0, 0, 5, 0, 0), false };
+
+        // Complex + skewed.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 3, 0, 1, 0, 0), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 0, 4, 1, 0, 0), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 3, 4, 1, 0, 0), false };
+
+        // Complex + translated.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 0, 0, 1, 6, 0), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 0, 0, 1, 0, 7), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 0, 0, 1, 6, 7), false };
+
+        // Complex + translated and scaled.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 0, 0, 1, 6, 7), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 0, 0, 5, 6, 7), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 0, 0, 5, 6, 0), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 0, 0, 5, 0, 7), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 0, 0, 5, 6, 7), false };
+
+        // Complex + translated and skewed.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 3, 0, 1, 6, 7), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 0, 4, 1, 6, 7), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 3, 4, 1, 6, 0), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 3, 4, 1, 0, 7), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 3, 4, 1, 6, 7), false };
+
+        // Complex + skewed and scaled.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 3, 4, 1, 0, 0), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 3, 4, 5, 0, 0), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 3, 0, 5, 0, 0), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 0, 4, 5, 0, 0), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 3, 4, 5, 0, 0), false };
+
+        // Complex + complex.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 3, 4, 5, 6, 7), true };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(0, 0, 0, 0, 0, 0), false };
+
+        // Zero + identity.
+        foreach (Matrix identity in IdentityMatrices())
+        {
+            yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), identity, false };
+        }
+
+        // Zero + scaled.
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 0, 0, 1, 0, 0), false };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 0, 0, 2, 0, 0), false };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 0, 0, 5, 0, 0), false };
+
+        // Zero + skewed.
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 3, 0, 1, 0, 0), false };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 0, 4, 1, 0, 0), false };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 3, 4, 1, 0, 0), false };
+
+        // Zero + translated.
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 0, 0, 1, 6, 0), false };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 0, 0, 1, 0, 7), false };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 0, 0, 1, 6, 7), false };
+
+        // Zero + translated and scaled.
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 0, 0, 1, 6, 7), false };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 0, 0, 5, 6, 7), false };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 0, 0, 5, 6, 0), false };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 0, 0, 5, 0, 7), false };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 0, 0, 5, 6, 7), false };
+
+        // Zero + translated and skewed.
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 3, 0, 1, 6, 7), false };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 0, 4, 1, 6, 7), false };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 3, 4, 1, 6, 0), false };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 3, 4, 1, 0, 7), false };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 3, 4, 1, 6, 7), false };
+
+        // Zero + skewed and scaled.
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 3, 4, 1, 0, 0), false };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 3, 4, 5, 0, 0), false };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 3, 0, 5, 0, 0), false };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 0, 4, 5, 0, 0), false };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 3, 4, 5, 0, 0), false };
+
+        // Zero + complex.
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 3, 4, 5, 6, 7), false };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(0, 0, 0, 0, 0, 0), true };
+
+        // NaN.
+        yield return new object[] { new Matrix(double.NaN, 3, 4, 5, 6, 7), new Matrix(double.NaN, 3, 4, 5, 6, 7), false };
+        yield return new object[] { new Matrix(double.NaN, 3, 4, 5, 6, 7), new Matrix(2, 3, 4, 5, 6, 7), false };
+        yield return new object[] { new Matrix(2, double.NaN, 4, 5, 6, 7), new Matrix(2, double.NaN, 4, 5, 6, 7), false };
+        yield return new object[] { new Matrix(2, double.NaN, 4, 5, 6, 7), new Matrix(2, 3, 4, 5, 6, 7), false };
+        yield return new object[] { new Matrix(2, 3, double.NaN, 5, 6, 7), new Matrix(2, 3, double.NaN, 5, 6, 7), false };
+        yield return new object[] { new Matrix(2, 3, double.NaN, 5, 6, 7), new Matrix(2, 3, 4, 5, 6, 7), false };
+        yield return new object[] { new Matrix(2, 3, 4, double.NaN, 6, 7), new Matrix(2, 3, 4, double.NaN, 6, 7), false };
+        yield return new object[] { new Matrix(2, 3, 4, double.NaN, 6, 7), new Matrix(2, 3, 4, 5, 6, 7), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, double.NaN, 7), new Matrix(2, 3, 4, 5, double.NaN, 7), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, double.NaN, 7), new Matrix(2, 3, 4, 5, 6, 7), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, double.NaN), new Matrix(2, 3, 4, 5, 6, double.NaN), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, double.NaN), new Matrix(2, 3, 4, 5, 6, 7), false };
+        yield return new object[] { new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), false };
+        yield return new object[] { new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), new Matrix(2, 3, 4, 5, 6, 7), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(double.NaN, 3, 4, 5, 6, 7), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, double.NaN, 4, 5, 6, 7), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 3, double.NaN, 5, 6, 7), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 3, 4, double.NaN, 6, 7), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 3, 4, 5, double.NaN, 7), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 3, 4, 5, 6, double.NaN), false };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), false };
+    }
+
+    [Theory]
+    [MemberData(nameof(EqualityOperator_TestData))]
+    public void EqualityOperator_Invoke_ReturnsExpected(Matrix matrix1, Matrix matrix2, bool expected)
+    {
+        Assert.Equal(expected, matrix1 == matrix2);
+        Assert.Equal(expected, matrix2 == matrix1);
+        Assert.Equal(expected, matrix2 == matrix1);
+        Assert.Equal(!expected, matrix2 != matrix1);
+    }
+
+    public static IEnumerable<object[]> GetHashCode_Identity_TestData()
+    {
+        foreach (Matrix identity in IdentityMatrices())
+        {
+            yield return new object[] { identity };
+        }
+    }
+
+    [Theory]
+    [MemberData(nameof(GetHashCode_Identity_TestData))]
+    public void GetHashCode_InvokeIdentity_ReturnsExpected(Matrix matrix)
+    {
+        Assert.Equal(0, matrix.GetHashCode());
+        Assert.Equal(matrix.GetHashCode(), matrix.GetHashCode());
+    }
+
+    public static IEnumerable<object[]> GetHashCode_NotIdentity_TestData()
+    {
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7) };
+    }
+
+    [Theory]
+    [MemberData(nameof(GetHashCode_NotIdentity_TestData))]
+    public void GetHashCode_InvokeNotIdentity_ReturnsExpected(Matrix matrix)
+    {
+        Assert.NotEqual(0, matrix.GetHashCode());
+        Assert.Equal(matrix.GetHashCode(), matrix.GetHashCode());
+    }
+
+    [Fact]
+    public void GetHashCode_InvokeZero_ReturnsExpected()
+    {
+        var matrix = new Matrix(0, 0, 0, 0, 0, 0);
+        Assert.Equal(0, matrix.GetHashCode());
+        Assert.Equal(matrix.GetHashCode(), matrix.GetHashCode());
+    }
+
+    public static IEnumerable<object[]> Invert_TestData()
+    {
+        // Identity
+        foreach (Matrix matrix in IdentityMatrices())
+        {
+            yield return new object[] { matrix, new Matrix(1, 0, 0, 1, 0, 0), 1 };
+        }
+
+        // Scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), new Matrix(0.5, 0, 0, 0.33333, 0, 0), 0.16667 };
+
+        // Skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), new Matrix(1.6, -0.8, -1.2, 1.6, 0, 0), 1.6 };
+
+        // Translated.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), new Matrix(1, 0, 0, 1, -2, -3), 1 };
+
+        // Translated and scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), new Matrix(0.5, 0, 0, 0.33333, -0.5, -0.66667), 0.16667 };
+
+        // Translated and skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), new Matrix(1.6, -0.8, -1.2, 1.6, 0.4, -3.2), 1.6 };
+
+        // Skewed and scaled.
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), new Matrix(0.53333, -0.08889, -0.13333, 0.35556, 0, 0), 0.17778 };
+
+        // Complex.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(-2.5, 1.5, 2, -1, 1, -2), -0.5 };
+    }
+
+    [Theory]
+    [MemberData(nameof(Invert_TestData))]
+    public void Invert_Invoke_Success(Matrix matrix, Matrix expected, double expectedDeterminant)
+    {
+        matrix.Invert();
+        Helpers.AssertEqualRounded(expected, matrix);
+        Assert.Equal(expected.IsIdentity, matrix.IsIdentity);
+        Assert.Equal(expected.HasInverse, matrix.HasInverse);
+        Assert.Equal(expectedDeterminant, matrix.Determinant, precision: 5);
+    }
+
+    [Fact]
+    public void Invert_NoInverse_ThrowsInvalidOperationException()
+    {
+        var matrix = new Matrix(0, 0, 0, 0, 0, 0);
+        Assert.Throws<InvalidOperationException>(() => matrix.Invert());
+    }
+
+    public static IEnumerable<object[]> Parse_TestData()
+    {
+        yield return new object[] { "Identity", Matrix.Identity };
+        yield return new object[] { "  Identity  ", Matrix.Identity };
+        yield return new object[] { "0,0,0,0,0,0", new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { "2,3,4,5,6,7", new Matrix(2, 3, 4, 5, 6, 7) };
+        yield return new object[] { "2.1,3.2,4.3,5.4,6.5,7.6", new Matrix(2.1, 3.2, 4.3, 5.4, 6.5, 7.6) };
+        yield return new object[] { "   2   ,   3  ,  4,  5  , 6  , 7  ", new Matrix(2, 3, 4, 5, 6, 7) };
+        yield return new object[] { "-1,-2,-3,-4,-5,-6", new Matrix(-1, -2, -3, -4, -5, -6) };
+    }
+
+    [Theory]
+    [MemberData(nameof(Parse_TestData))]
+    public void Parse_Invoke_Success(string source, Matrix expected)
+    {
+        Matrix result = Matrix.Parse(source);
+        Assert.Equal(expected.M11, result.M11, precision: 5);
+        Assert.Equal(expected.M12, result.M12, precision: 5);
+        Assert.Equal(expected.M21, result.M21, precision: 5);
+        Assert.Equal(expected.M22, result.M22, precision: 5);
+        Assert.Equal(expected.OffsetX, result.OffsetX, precision: 5);
+        Assert.Equal(expected.OffsetY, result.OffsetY, precision: 5);
+    }
+
+    [Fact]
+    public void Parse_NullSource_ThrowsNotSupportedException()
+    {
+        Assert.Throws<InvalidOperationException>(() => Matrix.Parse(null));
+    }
+
+    public static IEnumerable<object?[]> Parse_InvalidSource_TestData()
+    {
+        yield return new object?[] { "" };
+        yield return new object?[] { "  " };
+        yield return new object?[] { "2" };
+        yield return new object?[] { "2," };
+        yield return new object?[] { "2,3" };
+        yield return new object?[] { "2,3," };
+        yield return new object?[] { "2,3,4" };
+        yield return new object?[] { "2,3,4," };
+        yield return new object?[] { "2,3,4,5," };
+        yield return new object?[] { "2,3,4,5,6" };
+        yield return new object?[] { "2,3,4,5,6,7,8" };
+        yield return new object?[] { "2,3,4,5,6,7,test" };
+        yield return new object?[] { "Empty," };
+        yield return new object?[] { "Identity," };
+        yield return new object?[] { "Identity,3,4,5,6,7" };
+    }
+
+    [Theory]
+    [MemberData(nameof(Parse_InvalidSource_TestData))]
+    public void Parse_InvalidSource_ThrowsInvalidOperationException(string source)
+    {
+        Assert.Throws<InvalidOperationException>(() => Matrix.Parse(source));
+    }
+
+    public static IEnumerable<object?[]> Parse_NotDouble_TestData()
+    {
+        yield return new object[] { "Empty" };
+        yield return new object[] { " Empty " };
+        yield return new object[] { "Empty,2,3,4,5,6" };
+        yield return new object[] { "test" };
+        yield return new object[] { "test,2,3,4,5,6" };
+        yield return new object[] { "1,test,3,4,5,6" };
+        yield return new object[] { "1,2,test,4,5,6" };
+        yield return new object[] { "1,2,3,test,5,6" };
+        yield return new object[] { "1,2,3,4,test,6" };
+        yield return new object[] { "1,2,3,4,5,test" };
+        yield return new object[] { "1;2;3;4;5;6" };
+        yield return new object[] { """1"",""2"",""3"",""4"",""5"",""6""" };
+    }
+
+    [Theory]
+    [MemberData(nameof(Parse_NotDouble_TestData))]
+    public void Parse_NotDouble_ThrowsFormatException(string source)
+    {
+        Assert.Throws<FormatException>(() => Matrix.Parse(source));
+    }
+
+    public static IEnumerable<Matrix> IdentityMatrices()
+    {
+        yield return Matrix.Identity;
+        yield return new Matrix();
+        yield return new Matrix(1, 0, 0, 1, 0, 0);
+
+        var identitySetIdentity = Matrix.Identity;
+        identitySetIdentity.SetIdentity();
+        yield return identitySetIdentity;
+
+        var defaultSetIdentity = new Matrix();
+        defaultSetIdentity.SetIdentity();
+        yield return defaultSetIdentity;
+
+        var constructedSetIdentity = new Matrix(1, 0, 0, 1, 0, 0);
+        constructedSetIdentity.SetIdentity();
+        yield return constructedSetIdentity;
+
+        var scaleSetIdentity = new Matrix(2, 0, 0, 3, 0, 0);
+        scaleSetIdentity.SetIdentity();
+        yield return scaleSetIdentity;
+
+        var skewSetIdentity = new Matrix(1, 2, 3, 1, 0, 0);
+        skewSetIdentity.SetIdentity();
+        yield return skewSetIdentity;
+
+        var translateSetIdentity = new Matrix(1, 0, 0, 1, 1, 2);
+        translateSetIdentity.SetIdentity();
+        yield return translateSetIdentity;
+
+        var translateScaleSetIdentity = new Matrix(2, 0, 0, 3, 1, 2);
+        translateScaleSetIdentity.SetIdentity();
+        yield return translateScaleSetIdentity;
+
+        var translateSkewSetIdentity = new Matrix(1, 2, 3, 1, 1, 2);
+        translateSkewSetIdentity.SetIdentity();
+        yield return translateSkewSetIdentity;
+
+        var skewScaleSetIdentity = new Matrix(1, 2, 3, 1, 1, 2);
+        skewScaleSetIdentity.SetIdentity();
+        yield return skewScaleSetIdentity;
+
+        var complexSetIdentity = new Matrix(2, 3, 4, 5, 6, 7);
+        complexSetIdentity.SetIdentity();
+        yield return complexSetIdentity;
+
+        var noInverseSetIdentity = new Matrix(0, 0, 0, 0, 0, 0);
+        noInverseSetIdentity.SetIdentity();
+        yield return noInverseSetIdentity;
+    }
+
+    public static IEnumerable<object[]> Multiply_TestData()
+    {
+        // Identity.
+        foreach (Matrix identity1 in IdentityMatrices())
+        {
+            // Identity + identity.
+            foreach (Matrix identity2 in IdentityMatrices())
+            {
+                yield return new object[] { identity1, identity2, identity2 };
+            }
+
+            // Identity + scaled.
+            yield return new object[] { identity1, new Matrix(2, 0, 0, 1, 0, 0), new Matrix(2, 0, 0, 1, 0, 0) };
+            yield return new object[] { identity1, new Matrix(1, 0, 0, 5, 0, 0), new Matrix(1, 0, 0, 5, 0, 0) };
+            yield return new object[] { identity1, new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 0, 0, 5, 0, 0) };
+
+            // Identity + skewed.
+            yield return new object[] { identity1, new Matrix(1, 3, 0, 1, 0, 0), new Matrix(1, 3, 0, 1, 0, 0) };
+            yield return new object[] { identity1, new Matrix(1, 0, 4, 1, 0, 0), new Matrix(1, 0, 4, 1, 0, 0) };
+            yield return new object[] { identity1, new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 3, 4, 1, 0, 0) };
+
+            // Identity + translated.
+            yield return new object[] { identity1, new Matrix(1, 0, 0, 1, 6, 0), new Matrix(1, 0, 0, 1, 6, 0) };
+            yield return new object[] { identity1, new Matrix(1, 0, 0, 1, 0, 7), new Matrix(1, 0, 0, 1, 0, 7) };
+            yield return new object[] { identity1, new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 0, 0, 1, 6, 7) };
+
+            // Identity + translated and scaled.
+            yield return new object[] { identity1, new Matrix(2, 0, 0, 1, 6, 7), new Matrix(2, 0, 0, 1, 6, 7) };
+            yield return new object[] { identity1, new Matrix(1, 0, 0, 5, 6, 7), new Matrix(1, 0, 0, 5, 6, 7) };
+            yield return new object[] { identity1, new Matrix(2, 0, 0, 5, 6, 0), new Matrix(2, 0, 0, 5, 6, 0) };
+            yield return new object[] { identity1, new Matrix(2, 0, 0, 5, 0, 7), new Matrix(2, 0, 0, 5, 0, 7) };
+            yield return new object[] { identity1, new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 0, 0, 5, 6, 7) };
+
+            // Identity + translate and skewed.
+            yield return new object[] { identity1, new Matrix(1, 3, 0, 1, 6, 7), new Matrix(1, 3, 0, 1, 6, 7) };
+            yield return new object[] { identity1, new Matrix(1, 0, 4, 1, 6, 7), new Matrix(1, 0, 4, 1, 6, 7) };
+            yield return new object[] { identity1, new Matrix(1, 3, 4, 1, 6, 0), new Matrix(1, 3, 4, 1, 6, 0) };
+            yield return new object[] { identity1, new Matrix(1, 3, 4, 1, 0, 7), new Matrix(1, 3, 4, 1, 0, 7) };
+            yield return new object[] { identity1, new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 3, 4, 1, 6, 7) };
+
+            // Identity + skewed and scaled.
+            yield return new object[] { identity1, new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 3, 4, 5, 0, 0) };
+            yield return new object[] { identity1, new Matrix(1, 3, 4, 5, 0, 0), new Matrix(1, 3, 4, 5, 0, 0) };
+            yield return new object[] { identity1, new Matrix(2, 3, 0, 5, 0, 0), new Matrix(2, 3, 0, 5, 0, 0) };
+            yield return new object[] { identity1, new Matrix(2, 0, 4, 5, 0, 0), new Matrix(2, 0, 4, 5, 0, 0) };
+            yield return new object[] { identity1, new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 3, 4, 5, 0, 0) };
+
+            // Identity + complex.
+            yield return new object[] { identity1, new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 3, 4, 5, 6, 7) };
+            yield return new object[] { identity1, new Matrix(0, 0, 0, 0, 0, 0), new Matrix(0, 0, 0, 0, 0, 0) };
+        }
+
+
+        // Scaled + identity.
+        foreach (Matrix identity in IdentityMatrices())
+        {
+            yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), identity, new Matrix(2, 0, 0, 5, 0, 0) };
+        }
+
+        // Scaled + scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 0, 0, 1, 0, 0), new Matrix(4, 0, 0, 5, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 0, 0, 5, 0, 0), new Matrix(2, 0, 0, 25, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 0, 0, 5, 0, 0), new Matrix(4, 0, 0, 25, 0, 0) };
+
+        // Scaled + skewed.
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 3, 0, 1, 0, 0), new Matrix(2, 6, 0, 5, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 0, 4, 1, 0, 0), new Matrix(2, 0, 20, 5, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 6, 20, 5, 0, 0) };
+
+        // Scaled + translated.
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 0, 0, 1, 6, 0), new Matrix(2, 0, 0, 5, 6, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 0, 0, 1, 0, 7), new Matrix(2, 0, 0, 5, 0, 7) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 0, 0, 5, 6, 7) };
+
+        // Scaled + translated and scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 0, 0, 1, 6, 7), new Matrix(4, 0, 0, 5, 6, 7) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 0, 0, 5, 6, 7), new Matrix(2, 0, 0, 25, 6, 7) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 0, 0, 5, 0, 7), new Matrix(4, 0, 0, 25, 0, 7) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 0, 0, 5, 6, 0), new Matrix(4, 0, 0, 25, 6, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 0, 0, 5, 6, 7), new Matrix(4, 0, 0, 25, 6, 7) };
+
+        // Scaled + translated and skewed.
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 3, 0, 1, 6, 7), new Matrix(2, 6, 0, 5, 6, 7) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 4, 0, 1, 6, 7), new Matrix(2, 8, 0, 5, 6, 7) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 3, 4, 1, 0, 7), new Matrix(2, 6, 20, 5, 0, 7) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 3, 4, 1, 6, 0), new Matrix(2, 6, 20, 5, 6, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 6, 20, 5, 6, 7) };
+
+        // Scaled + skewed and scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 3, 4, 1, 0, 0), new Matrix(4, 6, 20, 5, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(1, 3, 4, 5, 0, 0), new Matrix(2, 6, 20, 25, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 3, 0, 5, 0, 0), new Matrix(4, 6, 0, 25, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 0, 4, 5, 0, 0), new Matrix(4, 0, 20, 25, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 3, 4, 5, 0, 0), new Matrix(4, 6, 20, 25, 0, 0) };
+
+        // Scaled + complex.
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 3, 4, 5, 6, 7), new Matrix(4, 6, 20, 25, 6, 7) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 0, 0), new Matrix(0, 0, 0, 0, 0, 0), new Matrix(0, 0, 0, 0, 0, 0) };
+
+        // Skewed + identity.
+        foreach (Matrix identity in IdentityMatrices())
+        {
+            yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), identity, new Matrix(1, 3, 4, 1, 0, 0) };
+        }
+
+        // Skewed + scaled.
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 0, 0, 1, 0, 0), new Matrix(2, 3, 8, 1, 0, 0) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 0, 0, 5, 0, 0), new Matrix(1, 15, 4, 5, 0, 0) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 15, 8, 5, 0, 0) };
+
+        // Skewed + skewed.
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 3, 0, 1, 0, 0), new Matrix(1, 6, 4, 13, 0, 0) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 0, 4, 1, 0, 0), new Matrix(13, 3, 8, 1, 0, 0) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 3, 4, 1, 0, 0), new Matrix(13, 6, 8, 13, 0, 0) };
+
+        // Skewed + translated.
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 0, 0, 1, 6, 0), new Matrix(1, 3, 4, 1, 6, 0) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 0, 0, 1, 0, 7), new Matrix(1, 3, 4, 1, 0, 7) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 3, 4, 1, 6, 7) };
+
+        // Skewed + translated and scaled.
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 0, 0, 1, 6, 7), new Matrix(2, 3, 8, 1, 6, 7) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 0, 0, 5, 6, 7), new Matrix(1, 15, 4, 5, 6, 7) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 0, 0, 5, 6, 0), new Matrix(2, 15, 8, 5, 6, 0) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 0, 0, 5, 0, 7), new Matrix(2, 15, 8, 5, 0, 7) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 15, 8, 5, 6, 7) };
+
+        // Skewed + translated and skewed.
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 3, 0, 1, 6, 7), new Matrix(1, 6, 4, 13, 6, 7) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 0, 4, 1, 6, 7), new Matrix(13, 3, 8, 1, 6, 7) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 3, 4, 1, 6, 0), new Matrix(13, 6, 8, 13, 6, 0) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 3, 4, 1, 0, 7), new Matrix(13, 6, 8, 13, 0, 7) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 3, 4, 1, 6, 7), new Matrix(13, 6, 8, 13, 6, 7) };
+
+        // Skewed + skewed and scaled.
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 3, 4, 1, 0, 0), new Matrix(14, 6, 12, 13, 0, 0) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 3, 4, 5, 0, 0), new Matrix(13, 18, 8, 17, 0, 0) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 3, 0, 5, 0, 0), new Matrix(2, 18, 8, 17, 0, 0) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 0, 4, 5, 0, 0), new Matrix(14, 15, 12, 5, 0, 0) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 3, 4, 5, 0, 0), new Matrix(14, 18, 12, 17, 0, 0) };
+
+        // Skewed + complex.
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 3, 4, 5, 6, 7), new Matrix(14, 18, 12, 17, 6, 7) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 0, 0), new Matrix(0, 0, 0, 0, 0, 0), new Matrix(0, 0, 0, 0, 0, 0) };
+
+        // Translated + identity.
+        foreach (Matrix identity in IdentityMatrices())
+        {
+            yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), identity, new Matrix(1, 0, 0, 1, 6, 7) };
+        }
+
+        // Translated + scaled.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 0, 0, 1, 0, 0), new Matrix(2, 0, 0, 1, 12, 7) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 0, 0, 5, 0, 0), new Matrix(1, 0, 0, 5, 6, 35) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 0, 0, 5, 12, 35) };
+
+        // Translated + skewed.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 3, 0, 1, 0, 0), new Matrix(1, 3, 0, 1, 6, 25) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 0, 4, 1, 0, 0), new Matrix(1, 0, 4, 1, 34, 7) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 3, 4, 1, 0, 0), new Matrix(1, 3, 4, 1, 34, 25) };
+
+        // Translated + translated.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 0, 0, 1, 6, 0), new Matrix(1, 0, 0, 1, 12, 7) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 0, 0, 1, 0, 7), new Matrix(1, 0, 0, 1, 6, 14) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 0, 0, 1, 12, 14) };
+
+        // Translated + translated and scaled.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 0, 0, 1, 6, 7), new Matrix(2, 0, 0, 1, 18, 14) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 0, 0, 5, 6, 7), new Matrix(1, 0, 0, 5, 12, 42) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 0, 0, 5, 6, 0), new Matrix(2, 0, 0, 5, 18, 35) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 0, 0, 5, 0, 7), new Matrix(2, 0, 0, 5, 12, 42) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 0, 0, 5, 18, 42) };
+
+        // Translated + translated and skewed.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 3, 0, 1, 6, 7), new Matrix(1, 3, 0, 1, 12, 32) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 0, 4, 1, 6, 7), new Matrix(1, 0, 4, 1, 40, 14) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 3, 4, 1, 6, 0), new Matrix(1, 3, 4, 1, 40, 25) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 3, 4, 1, 0, 7), new Matrix(1, 3, 4, 1, 34, 32) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 3, 4, 1, 40, 32) };
+
+        // Translated + skewed and scaled.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 3, 4, 1, 0, 0), new Matrix(2, 3, 4, 1, 40, 25) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 3, 4, 5, 0, 0), new Matrix(1, 3, 4, 5, 34, 53) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 3, 0, 5, 0, 0), new Matrix(2, 3, 0, 5, 12, 53) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 0, 4, 5, 0, 0), new Matrix(2, 0, 4, 5, 40, 35) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 3, 4, 5, 40, 53) };
+
+        // Translated + complex.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 3, 4, 5, 46, 60) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 6, 7), new Matrix(0, 0, 0, 0, 0, 0), new Matrix(0, 0, 0, 0, 0, 0) };
+
+        // Translated and scaled + identity.
+        foreach (Matrix identity in IdentityMatrices())
+        {
+            yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), identity, new Matrix(2, 0, 0, 5, 6, 7) };
+        }
+
+        // Translated and scaled + scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 0, 0, 1, 0, 0), new Matrix(4, 0, 0, 5, 12, 7) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 0, 0, 5, 0, 0), new Matrix(2, 0, 0, 25, 6, 35) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 0, 0, 5, 0, 0), new Matrix(4, 0, 0, 25, 12, 35) };
+
+        // Translated and scaled + skewed.
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 3, 0, 1, 0, 0), new Matrix(2, 6, 0, 5, 6, 25) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 0, 4, 1, 0, 0), new Matrix(2, 0, 20, 5, 34, 7) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 3, 4, 1, 0, 0), new Matrix(2, 6, 20, 5, 34, 25) };
+
+        // Translated and scaled + translated.
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 0, 0, 1, 6, 0), new Matrix(2, 0, 0, 5, 12, 7) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 0, 0, 1, 0, 7), new Matrix(2, 0, 0, 5, 6, 14) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 0, 0, 5, 12, 14) };
+
+        // Translated and scaled + translated and scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 0, 0, 1, 6, 7), new Matrix(4, 0, 0, 5, 18, 14) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 0, 0, 5, 6, 7), new Matrix(2, 0, 0, 25, 12, 42) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 0, 0, 5, 6, 0), new Matrix(4, 0, 0, 25, 18, 35) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 0, 0, 5, 0, 7), new Matrix(4, 0, 0, 25, 12, 42) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 0, 0, 5, 6, 7), new Matrix(4, 0, 0, 25, 18, 42) };
+
+        // Translated and scaled + translated and skewed.
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 3, 0, 1, 6, 7), new Matrix(2, 6, 0, 5, 12, 32) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 0, 4, 1, 6, 7), new Matrix(2, 0, 20, 5, 40, 14) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 3, 4, 1, 6, 0), new Matrix(2, 6, 20, 5, 40, 25) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 3, 4, 1, 0, 7), new Matrix(2, 6, 20, 5, 34, 32) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 6, 20, 5, 40, 32) };
+
+        // Translated and scaled + skewed and scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 3, 4, 1, 0, 0), new Matrix(4, 6, 20, 5, 40, 25) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(1, 3, 4, 5, 0, 0), new Matrix(2, 6, 20, 25, 34, 53) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 3, 0, 5, 0, 0), new Matrix(4, 6, 0, 25, 12, 53) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 0, 4, 5, 0, 0), new Matrix(4, 0, 20, 25, 40, 35) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 3, 4, 5, 0, 0), new Matrix(4, 6, 20, 25, 40, 53) };
+
+        // Translated and scaled + complex.
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 3, 4, 5, 6, 7), new Matrix(4, 6, 20, 25, 46, 60) };
+        yield return new object[] { new Matrix(2, 0, 0, 5, 6, 7), new Matrix(0, 0, 0, 0, 0, 0), new Matrix(0, 0, 0, 0, 0, 0) };
+
+        // Translated and skewed + identity.
+        foreach (Matrix identity in IdentityMatrices())
+        {
+            yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), identity, new Matrix(1, 3, 4, 1, 6, 7) };
+        }
+
+        // Translated and skewed + scaled.
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 0, 0, 1, 0, 0), new Matrix(2, 3, 8, 1, 12, 7) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 0, 0, 5, 0, 0), new Matrix(1, 15, 4, 5, 6, 35) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 0, 0, 5, 0, 0), new Matrix(2, 15, 8, 5, 12, 35) };
+
+        // Translated and skewed + skewed.
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 3, 0, 1, 0, 0), new Matrix(1, 6, 4, 13, 6, 25) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 0, 4, 1, 0, 0), new Matrix(13, 3, 8, 1, 34, 7) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 3, 4, 1, 0, 0), new Matrix(13, 6, 8, 13, 34, 25) };
+
+        // Translated and skewed + translated.
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 0, 0, 1, 6, 0), new Matrix(1, 3, 4, 1, 12, 7) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 0, 0, 1, 0, 7), new Matrix(1, 3, 4, 1, 6, 14) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 0, 0, 1, 6, 7), new Matrix(1, 3, 4, 1, 12, 14) };
+
+        // Translated and skewed + translated and scaled.
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 0, 0, 1, 6, 7), new Matrix(2, 3, 8, 1, 18, 14) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 0, 0, 5, 6, 7), new Matrix(1, 15, 4, 5, 12, 42) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 0, 0, 5, 6, 0), new Matrix(2, 15, 8, 5, 18, 35) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 0, 0, 5, 0, 7), new Matrix(2, 15, 8, 5, 12, 42) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 0, 0, 5, 6, 7), new Matrix(2, 15, 8, 5, 18, 42) };
+
+        // Translated and skewed + translated and skewed.
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 3, 0, 1, 6, 7), new Matrix(1, 6, 4, 13, 12, 32) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 0, 4, 1, 6, 7), new Matrix(13, 3, 8, 1, 40, 14) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 3, 4, 1, 6, 0), new Matrix(13, 6, 8, 13, 40, 25) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 3, 4, 1, 0, 7), new Matrix(13, 6, 8, 13, 34, 32) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 3, 4, 1, 6, 7), new Matrix(13, 6, 8, 13, 40, 32) };
+
+        // Translated and skewed + skewed and scaled.
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 3, 4, 1, 0, 0), new Matrix(14, 6, 12, 13, 40, 25) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(1, 3, 4, 5, 0, 0), new Matrix(13, 18, 8, 17, 34, 53) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 3, 0, 5, 0, 0), new Matrix(2, 18, 8, 17, 12, 53) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 0, 4, 5, 0, 0), new Matrix(14, 15, 12, 5, 40, 35) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 3, 4, 5, 0, 0), new Matrix(14, 18, 12, 17, 40, 53) };
+
+        // Translated and skewed + complex.
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(2, 3, 4, 5, 6, 7), new Matrix(14, 18, 12, 17, 46, 60) };
+        yield return new object[] { new Matrix(1, 3, 4, 1, 6, 7), new Matrix(0, 0, 0, 0, 0, 0), new Matrix(0, 0, 0, 0, 0, 0) };
+
+        // Skewed and scaled + identity.
+        foreach (Matrix identity in IdentityMatrices())
+        {
+            yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), identity, new Matrix(2, 3, 4, 5, 0, 0) };
+        }
+
+        // Skewed and scaled + scaled.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 0, 0, 1, 0, 0), new Matrix(4, 3, 8, 5, 0, 0) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 0, 0, 5, 0, 0), new Matrix(2, 15, 4, 25, 0, 0) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 0, 0, 5, 0, 0), new Matrix(4, 15, 8, 25, 0, 0) };
+
+        // Skewed and scaled + skewed.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 3, 0, 1, 0, 0), new Matrix(2, 9, 4, 17, 0, 0) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 0, 4, 1, 0, 0), new Matrix(14, 3, 24, 5, 0, 0) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 3, 4, 1, 0, 0), new Matrix(14, 9, 24, 17, 0, 0) };
+
+        // Skewed and scaled + translated.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 0, 0, 1, 6, 0), new Matrix(2, 3, 4, 5, 6, 0) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 0, 0, 1, 0, 7), new Matrix(2, 3, 4, 5, 0, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 3, 4, 5, 6, 7) };
+
+        // Skewed and scaled + translated and scaled.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 0, 0, 1, 6, 7), new Matrix(4, 3, 8, 5, 6, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 0, 0, 5, 6, 7), new Matrix(2, 15, 4, 25, 6, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 0, 0, 5, 6, 0), new Matrix(4, 15, 8, 25, 6, 0) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 0, 0, 5, 0, 7), new Matrix(4, 15, 8, 25, 0, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 0, 0, 5, 6, 7), new Matrix(4, 15, 8, 25, 6, 7) };
+
+        // Skewed and scaled + translated and skewed.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 3, 0, 1, 6, 7), new Matrix(2, 9, 4, 17, 6, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 0, 4, 1, 6, 7), new Matrix(14, 3, 24, 5, 6, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 3, 4, 1, 6, 0), new Matrix(14, 9, 24, 17, 6, 0) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 3, 4, 1, 0, 7), new Matrix(14, 9, 24, 17, 0, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 3, 4, 1, 6, 7), new Matrix(14, 9, 24, 17, 6, 7) };
+
+        // Skewed and scaled + skewed and scaled.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 3, 4, 1, 0, 0), new Matrix(16, 9, 28, 17, 0, 0) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(1, 3, 4, 5, 0, 0), new Matrix(14, 21, 24, 37, 0, 0) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 3, 0, 5, 0, 0), new Matrix(4, 21, 8, 37, 0, 0) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 0, 4, 5, 0, 0), new Matrix(16, 15, 28, 25, 0, 0) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 3, 4, 5, 0, 0), new Matrix(16, 21, 28, 37, 0, 0) };
+
+        // Skewed and scaled + complex.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(2, 3, 4, 5, 6, 7), new Matrix(16, 21, 28, 37, 6, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Matrix(0, 0, 0, 0, 0, 0), new Matrix(0, 0, 0, 0, 0, 0) };
+
+        // Complex + identity.
+        foreach (Matrix identity in IdentityMatrices())
+        {
+            yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), identity, new Matrix(2, 3, 4, 5, 6, 7) };
+        }
+
+        // Complex + scaled.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 0, 0, 1, 0, 0), new Matrix(4, 3, 8, 5, 12, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 0, 0, 5, 0, 0), new Matrix(2, 15, 4, 25, 6, 35) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 0, 0, 5, 0, 0), new Matrix(4, 15, 8, 25, 12, 35) };
+
+        // Complex + skewed.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 3, 0, 1, 0, 0), new Matrix(2, 9, 4, 17, 6, 25) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 0, 4, 1, 0, 0), new Matrix(14, 3, 24, 5, 34, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 3, 4, 1, 0, 0), new Matrix(14, 9, 24, 17, 34, 25) };
+
+        // Complex + translated.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 0, 0, 1, 6, 0), new Matrix(2, 3, 4, 5, 12, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 0, 0, 1, 0, 7), new Matrix(2, 3, 4, 5, 6, 14) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 0, 0, 1, 6, 7), new Matrix(2, 3, 4, 5, 12, 14) };
+
+        // Complex + translated and scaled.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 0, 0, 1, 6, 7), new Matrix(4, 3, 8, 5, 18, 14) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 0, 0, 5, 6, 7), new Matrix(2, 15, 4, 25, 12, 42) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 0, 0, 5, 6, 0), new Matrix(4, 15, 8, 25, 18, 35) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 0, 0, 5, 0, 7), new Matrix(4, 15, 8, 25, 12, 42) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 0, 0, 5, 6, 7), new Matrix(4, 15, 8, 25, 18, 42) };
+
+        // Complex + translated and skewed.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 3, 0, 1, 6, 7), new Matrix(2, 9, 4, 17, 12, 32) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 0, 4, 1, 6, 7), new Matrix(14, 3, 24, 5, 40, 14) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 3, 4, 1, 6, 0), new Matrix(14, 9, 24, 17, 40, 25) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 3, 4, 1, 0, 7), new Matrix(14, 9, 24, 17, 34, 32) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 3, 4, 1, 6, 7), new Matrix(14, 9, 24, 17, 40, 32) };
+
+        // Complex + skewed and scaled.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 3, 4, 1, 0, 0), new Matrix(16, 9, 28, 17, 40, 25) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(1, 3, 4, 5, 0, 0), new Matrix(14, 21, 24, 37, 34, 53) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 3, 0, 5, 0, 0), new Matrix(4, 21, 8, 37, 12, 53) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 0, 4, 5, 0, 0), new Matrix(16, 15, 28, 25, 40, 35) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 3, 4, 5, 0, 0), new Matrix(16, 21, 28, 37, 40, 53) };
+
+        // Complex + complex.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 3, 4, 5, 6, 7), new Matrix(16, 21, 28, 37, 46, 60) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(0, 0, 0, 0, 0, 0), new Matrix(0, 0, 0, 0, 0, 0) };
+
+        // Zero + identity.
+        foreach (Matrix identity in IdentityMatrices())
+        {
+            yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), identity, new Matrix(0, 0, 0, 0, 0, 0) };
+        }
+
+        // Zero + scaled.
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 0, 0, 1, 0, 0), new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 0, 0, 5, 0, 0), new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 0, 0, 5, 0, 0), new Matrix(0, 0, 0, 0, 0, 0) };
+
+        // Zero + skewed.
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 3, 0, 1, 0, 0), new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 0, 4, 1, 0, 0), new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 3, 4, 1, 0, 0), new Matrix(0, 0, 0, 0, 0, 0) };
+
+        // Zero + translated.
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 0, 0, 1, 6, 0), new Matrix(0, 0, 0, 0, 6, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 0, 0, 1, 0, 7), new Matrix(0, 0, 0, 0, 0, 7) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 0, 0, 1, 6, 7), new Matrix(0, 0, 0, 0, 6, 7) };
+
+        // Zero + translated and scaled.
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 0, 0, 1, 6, 7), new Matrix(0, 0, 0, 0, 6, 7) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 0, 0, 5, 6, 7), new Matrix(0, 0, 0, 0, 6, 7) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 0, 0, 5, 6, 0), new Matrix(0, 0, 0, 0, 6, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 0, 0, 5, 0, 7), new Matrix(0, 0, 0, 0, 0, 7) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 0, 0, 5, 6, 7), new Matrix(0, 0, 0, 0, 6, 7) };
+
+        // Zero + translated and skewed.
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 3, 0, 1, 6, 7), new Matrix(0, 0, 0, 0, 6, 7) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 0, 4, 1, 6, 7), new Matrix(0, 0, 0, 0, 6, 7) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 3, 4, 1, 6, 0), new Matrix(0, 0, 0, 0, 6, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 3, 4, 1, 0, 7), new Matrix(0, 0, 0, 0, 0, 7) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 3, 4, 1, 6, 7), new Matrix(0, 0, 0, 0, 6, 7) };
+
+        // Zero + skewed and scaled.
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 3, 4, 1, 0, 0), new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(1, 3, 4, 5, 0, 0), new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 3, 0, 5, 0, 0), new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 0, 4, 5, 0, 0), new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 3, 4, 5, 0, 0), new Matrix(0, 0, 0, 0, 0, 0) };
+
+        // Zero + complex.
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(2, 3, 4, 5, 6, 7), new Matrix(0, 0, 0, 0, 6, 7) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Matrix(0, 0, 0, 0, 0, 0), new Matrix(0, 0, 0, 0, 0, 0) };
+
+        // NaN.
+        yield return new object[] { new Matrix(double.NaN, 3, 4, 5, 6, 7), new Matrix(double.NaN, 3, 4, 5, 6, 7), new Matrix(double.NaN, double.NaN, double.NaN, 37, double.NaN, 60) };
+        yield return new object[] { new Matrix(double.NaN, 3, 4, 5, 6, 7), new Matrix(2, 3, 4, 5, 6, 7), new Matrix(double.NaN, double.NaN, 28, 37, 46, 60) };
+        yield return new object[] { new Matrix(2, double.NaN, 4, 5, 6, 7), new Matrix(2, double.NaN, 4, 5, 6, 7), new Matrix(double.NaN, double.NaN, 28, double.NaN, 46, double.NaN) };
+        yield return new object[] { new Matrix(2, double.NaN, 4, 5, 6, 7), new Matrix(2, 3, 4, 5, 6, 7), new Matrix(double.NaN, double.NaN, 28, 37, 46, 60) };
+        yield return new object[] { new Matrix(2, 3, double.NaN, 5, 6, 7), new Matrix(2, 3, double.NaN, 5, 6, 7), new Matrix(double.NaN, 21, double.NaN, double.NaN, double.NaN, 60) };
+        yield return new object[] { new Matrix(2, 3, double.NaN, 5, 6, 7), new Matrix(2, 3, 4, 5, 6, 7), new Matrix(16, 21, double.NaN, double.NaN, 46, 60) };
+        yield return new object[] { new Matrix(2, 3, 4, double.NaN, 6, 7), new Matrix(2, 3, 4, double.NaN, 6, 7), new Matrix(16, double.NaN, double.NaN, double.NaN, 46, double.NaN) };
+        yield return new object[] { new Matrix(2, 3, 4, double.NaN, 6, 7), new Matrix(2, 3, 4, 5, 6, 7), new Matrix(16, 21, double.NaN, double.NaN, 46, 60) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, double.NaN, 7), new Matrix(2, 3, 4, 5, double.NaN, 7), new Matrix(16, 21, 28, 37, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, double.NaN, 7), new Matrix(2, 3, 4, 5, 6, 7), new Matrix(16, 21, 28, 37, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, double.NaN), new Matrix(2, 3, 4, 5, 6, double.NaN), new Matrix(16, 21, 28, 37, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, double.NaN), new Matrix(2, 3, 4, 5, 6, 7), new Matrix(16, 21, 28, 37, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), new Matrix(2, 3, 4, 5, 6, 7), new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(double.NaN, 3, 4, 5, 6, 7), new Matrix(double.NaN, 21, double.NaN, 37, double.NaN, 60) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, double.NaN, 4, 5, 6, 7), new Matrix(16, double.NaN, 28, double.NaN, 46, double.NaN) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 3, double.NaN, 5, 6, 7), new Matrix(double.NaN, 21, double.NaN, 37, double.NaN, 60) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 3, 4, double.NaN, 6, 7), new Matrix(16, double.NaN, 28, double.NaN, 46, double.NaN) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 3, 4, 5, double.NaN, 7), new Matrix(16, 21, 28, 37, double.NaN, 60) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(2, 3, 4, 5, 6, double.NaN), new Matrix(16, 21, 28, 37, 46, double.NaN) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+    }
+
+    [Theory]
+    [MemberData(nameof(Multiply_TestData))]
+    public void Multiply_Invoke_ReturnsExpected(Matrix matrix1, Matrix matrix2, Matrix expected)
+    {
+        Matrix copy1 = matrix1;
+        Matrix copy2 = matrix2;
+
+        Matrix result = Matrix.Multiply(matrix1, matrix2);
+        Assert.Equal(expected, result);
+        Assert.Equal(copy1, matrix1);
+        Assert.Equal(copy2, matrix2);
+    }
+
+    [Theory]
+    [MemberData(nameof(Multiply_TestData))]
+    public void OperatorMultiply_Invoke_ReturnsExpected(Matrix matrix1, Matrix matrix2, Matrix expected)
+    {
+        Matrix copy1 = matrix1;
+        Matrix copy2 = matrix2;
+
+        Matrix result = matrix1 * matrix2;
+        Assert.Equal(expected, result);
+        Assert.Equal(copy1, matrix1);
+        Assert.Equal(copy2, matrix2);
+    }
+
+    [Theory]
+    [MemberData(nameof(Multiply_TestData))]
+    public void Prepend_Invoke_ReturnsExpected(Matrix matrix1, Matrix matrix2, Matrix expected)
+    {
+        Matrix copy1 = matrix1;
+        Matrix copy2 = matrix2;
+
+        matrix2.Prepend(matrix1);
+        Assert.Equal(expected, matrix2);
+        Assert.Equal(copy1, matrix1);
+    }
+
+    public static IEnumerable<object[]> Rotate_TestData()
+    {
+        // Identity
+        foreach (Matrix matrix in IdentityMatrices())
+        {
+            yield return new object[] { matrix, -360, new Matrix(1, -0, 0, 1, 0, 0), 1 };
+            yield return new object[] { matrix, -270, new Matrix(-0, 1, -1, -0, 0, 0), 1 };
+            yield return new object[] { matrix, -180, new Matrix(-1, -0, 0, -1, 0, 0), 1 };
+            yield return new object[] { matrix, -90, new Matrix(0, -1, 1, 0, 0, 0), 1 };
+            yield return new object[] { matrix, -45, new Matrix(0.70711, -0.70711, 0.70711, 0.70711, 0, 0), 1 };
+            yield return new object[] { matrix, 45, new Matrix(0.70711, 0.70711, -0.70711, 0.70711, 0, 0), 1 };
+            yield return new object[] { matrix, 0, new Matrix(1, 0, -0, 1, 0, 0), 1 };
+            yield return new object[] { matrix, 90, new Matrix(0, 1, -1, 0, 0, 0), 1 };
+            yield return new object[] { matrix, 30, new Matrix(0.86603, 0.5, -0.5, 0.86603, 0, 0), 1 };
+            yield return new object[] { matrix, 180, new Matrix(-1, 0, -0, -1, 0, 0), 1 };
+            yield return new object[] { matrix, 270, new Matrix(-0, -1, 1, -0, 0, 0), 1 };
+            yield return new object[] { matrix, 360, new Matrix(1, 0, -0, 1, 0, 0), 1 };
+            yield return new object[] { matrix, 720, new Matrix(1, 0, -0, 1, 0, 0), 1 };
+            yield return new object[] { matrix, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        }
+
+        // Scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -360, new Matrix(2, 0, 0, 3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -270, new Matrix(-0, 2, -3, -0, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -180, new Matrix(-2, -0, 0, -3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -90, new Matrix(0, -2, 3, 0, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -45, new Matrix(1.41421, -1.41421, 2.12132, 2.12132, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 45, new Matrix(1.41421, 1.41421, -2.12132, 2.12132, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, new Matrix(2, 0, 0, 3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 90, new Matrix(0, 2, -3, 0, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 30, new Matrix(1.73205, 1, -1.5, 2.59808, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 180, new Matrix(-2, 0, -0, -3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 270, new Matrix(-0, -2, 3, -0, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 360, new Matrix(2, 0, 0, 3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 720, new Matrix(2, 0, 0, 3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+
+        // Skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -360, new Matrix(1, 0.5, 0.75, 1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -270, new Matrix(-0.5, 1, -1, 0.75, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -180, new Matrix(-1, -0.5, -0.75, -1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -90, new Matrix(0.5, -1, 1, -0.75, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -45, new Matrix(1.06066, -0.35355, 1.23744, 0.17678, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 45, new Matrix(0.35355, 1.06066, -0.17678, 1.23744, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, new Matrix(1, 0.5, 0.75, 1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 90, new Matrix(-0.5, 1, -1, 0.75, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 30, new Matrix(0.61603, 0.93301, 0.14951, 1.24103, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 180, new Matrix(-1, -0.5, -0.75, -1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 270, new Matrix(0.5, -1, 1, -0.75, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 360, new Matrix(1, 0.5, 0.75, 1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 720, new Matrix(1, 0.5, 0.75, 1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+
+        // Translated.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -360, new Matrix(1, -0, 0, 1, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -270, new Matrix(-0, 1, -1, -0, -3, 2), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -180, new Matrix(-1, -0, 0, -1, -2, -3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -90, new Matrix(0, -1, 1, 0, 3, -2), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -45, new Matrix(0.70711, -0.70711, 0.70711, 0.70711, 3.53553, 0.70711), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 45, new Matrix(0.70711, 0.70711, -0.70711, 0.70711, -0.70711, 3.53553), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, new Matrix(1, 0, -0, 1, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 90, new Matrix(0, 1, -1, 0, -3, 2), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 30, new Matrix(0.86603, 0.5, -0.5, 0.86603, 0.23205, 3.59808), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 180, new Matrix(-1, 0, -0, -1, -2, -3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 270, new Matrix(-0, -1, 1, -0, 3, -2), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 360, new Matrix(1, 0, -0, 1, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 720, new Matrix(1, 0, -0, 1, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+
+        // Translated and scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -360, new Matrix(2, 0, 0, 3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -270, new Matrix(-0, 2, -3, -0, -2, 1), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -180, new Matrix(-2, -0, 0, -3, -1, -2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -90, new Matrix(0, -2, 3, 0, 2, -1), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -45, new Matrix(1.41421, -1.41421, 2.12132, 2.12132, 2.12132, 0.70711), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 45, new Matrix(1.41421, 1.41421, -2.12132, 2.12132, -0.70711, 2.12132), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, new Matrix(2, 0, 0, 3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 90, new Matrix(0, 2, -3, 0, -2, 1), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 30, new Matrix(1.73205, 1, -1.5, 2.59808, -0.13397, 2.23205), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 180, new Matrix(-2, 0, -0, -3, -1, -2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 270, new Matrix(-0, -2, 3, -0, 2, -1), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 360, new Matrix(2, 0, 0, 3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 720, new Matrix(2, 0, 0, 3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+
+        // Translated and skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -360, new Matrix(1, 0.5, 0.75, 1, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -270, new Matrix(-0.5, 1, -1, 0.75, -3, 2), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -180, new Matrix(-1, -0.5, -0.75, -1, -2, -3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -90, new Matrix(0.5, -1, 1, -0.75, 3, -2), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -45, new Matrix(1.06066, -0.35355, 1.23744, 0.17678, 3.53553, 0.70711), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 45, new Matrix(0.35355, 1.06066, -0.17678, 1.23744, -0.70711, 3.53553), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, new Matrix(1, 0.5, 0.75, 1, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 90, new Matrix(-0.5, 1, -1, 0.75, -3, 2), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 30, new Matrix(0.61603, 0.93301, 0.14951, 1.24103, 0.23205, 3.59808), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 180, new Matrix(-1, -0.5, -0.75, -1, -2, -3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 270, new Matrix(0.5, -1, 1, -0.75, 3, -2), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 360, new Matrix(1, 0.5, 0.75, 1, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 720, new Matrix(1, 0.5, 0.75, 1, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+
+        // Skewed and scaled.
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -360, new Matrix(2, 0.5, 0.75, 3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -270, new Matrix(-0.5, 2, -3, 0.75, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -180, new Matrix(-2, -0.5, -0.75, -3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -90, new Matrix(0.5, -2, 3, -0.75, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -45, new Matrix(1.76777, -1.06066, 2.65165, 1.59099, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 45, new Matrix(1.06066, 1.76777, -1.59099, 2.65165, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, new Matrix(2, 0.5, 0.75, 3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 90, new Matrix(-0.5, 2, -3, 0.75, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 30, new Matrix(1.48205, 1.43301, -0.85048, 2.97308, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 180, new Matrix(-2, -0.5, -0.75, -3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 270, new Matrix(0.5, -2, 3, -0.75, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 360, new Matrix(2, 0.5, 0.75, 3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 720, new Matrix(2, 0.5, 0.75, 3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+
+        // Complex.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -360, new Matrix(2, 3, 4, 5, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -270, new Matrix(-3, 2, -5, 4, -7, 6), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -180, new Matrix(-2, -3, -4, -5, -6, -7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -90, new Matrix(3, -2, 5, -4, 7, -6), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -45, new Matrix(3.53553, 0.70711, 6.36396, 0.70711, 9.19239, 0.70711), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 45, new Matrix(-0.70711, 3.53553, -0.70711, 6.36396, -0.70711, 9.19239), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, new Matrix(2, 3, 4, 5, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 90, new Matrix(-3, 2, -5, 4, -7, 6), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 30, new Matrix(0.23205, 3.59808, 0.9641, 6.33013, 1.69615, 9.06218), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 180, new Matrix(-2, -3, -4, -5, -6, -7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 270, new Matrix(3, -2, 5, -4, 7, -6), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 360, new Matrix(2, 3, 4, 5, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 720, new Matrix(2, 3, 4, 5, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+
+        // No inverse.
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -360, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -270, new Matrix(-0, 0, -0, 0, 0, 0), -0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -180, new Matrix(0, -0, 0, -0, 0, 0), -0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -90, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -45, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 45, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 90, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 30, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 180, new Matrix(-0, 0, -0, 0, 0, 0), -0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 270, new Matrix(0, -0, 0, -0, 0, 0), -0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 360, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 720, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+    }
+
+    [Theory]
+    [MemberData(nameof(Rotate_TestData))]
+    
+    public void Rotate_Invoke_Success(Matrix matrix, double angle, Matrix expected, double expectedDeterminant)
+    {
+        matrix.Rotate(angle);
+        Helpers.AssertEqualRounded(expected, matrix);
+        Assert.Equal(expected.IsIdentity, matrix.IsIdentity);
+        Assert.Equal(expected.HasInverse, matrix.HasInverse);
+        Assert.Equal(expectedDeterminant, matrix.Determinant, precision: 5);
+    }
+
+    public static IEnumerable<object[]> RotatePrepend_TestData()
+    {
+        // Identity
+        foreach (Matrix matrix in IdentityMatrices())
+        {
+            yield return new object[] { matrix, -360, new Matrix(1, -0, 0, 1, 0, 0), 1 };
+            yield return new object[] { matrix, -270, new Matrix(-0, 1, -1, -0, 0, 0), 1 };
+            yield return new object[] { matrix, -180, new Matrix(-1, -0, 0, -1, 0, 0), 1 };
+            yield return new object[] { matrix, -90, new Matrix(0, -1, 1, 0, 0, 0), 1 };
+            yield return new object[] { matrix, -45, new Matrix(0.70711, -0.70711, 0.70711, 0.70711, 0, 0), 1 };
+            yield return new object[] { matrix, 45, new Matrix(0.70711, 0.70711, -0.70711, 0.70711, 0, 0), 1 };
+            yield return new object[] { matrix, 0, new Matrix(1, 0, -0, 1, 0, 0), 1 };
+            yield return new object[] { matrix, 90, new Matrix(0, 1, -1, 0, 0, 0), 1 };
+            yield return new object[] { matrix, 30, new Matrix(0.86603, 0.5, -0.5, 0.86603, 0, 0), 1 };
+            yield return new object[] { matrix, 180, new Matrix(-1, 0, -0, -1, 0, 0), 1 };
+            yield return new object[] { matrix, 270, new Matrix(-0, -1, 1, -0, 0, 0), 1 };
+            yield return new object[] { matrix, 360, new Matrix(1, 0, -0, 1, 0, 0), 1 };
+            yield return new object[] { matrix, 720, new Matrix(1, 0, -0, 1, 0, 0), 1 };
+            yield return new object[] { matrix, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        }
+
+        // Scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -360, new Matrix(2, 0, 0, 3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -270, new Matrix(-0, 3, -2, -0, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -180, new Matrix(-2, -0, 0, -3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -90, new Matrix(0, -3, 2, 0, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -45, new Matrix(1.41421, -2.12132, 1.41421, 2.12132, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 45, new Matrix(1.41421, 2.12132, -1.41421, 2.12132, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, new Matrix(2, 0, 0, 3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 90, new Matrix(0, 3, -2, 0, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 30, new Matrix(1.73205, 1.5, -1, 2.59808, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 180, new Matrix(-2, 0, -0, -3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 270, new Matrix(-0, -3, 2, -0, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 360, new Matrix(2, 0, 0, 3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 720, new Matrix(2, 0, 0, 3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+
+        // Skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -360, new Matrix(1, 0.5, 0.75, 1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -270, new Matrix(0.75, 1, -1, -0.5, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -180, new Matrix(-1, -0.5, -0.75, -1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -90, new Matrix(-0.75, -1, 1, 0.5, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -45, new Matrix(0.17678, -0.35355, 1.23744, 1.06066, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 45, new Matrix(1.23744, 1.06066, -0.17678, 0.35355, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, new Matrix(1, 0.5, 0.75, 1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 90, new Matrix(0.75, 1, -1, -0.5, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 30, new Matrix(1.24103, 0.93301, 0.14951, 0.61603, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 180, new Matrix(-1, -0.5, -0.75, -1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 270, new Matrix(-0.75, -1, 1, 0.5, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 360, new Matrix(1, 0.5, 0.75, 1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 720, new Matrix(1, 0.5, 0.75, 1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+
+        // Translated.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -360, new Matrix(1, -0, 0, 1, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -270, new Matrix(-0, 1, -1, -0, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -180, new Matrix(-1, -0, 0, -1, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -90, new Matrix(0, -1, 1, 0, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -45, new Matrix(0.70711, -0.70711, 0.70711, 0.70711, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 45, new Matrix(0.70711, 0.70711, -0.70711, 0.70711, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, new Matrix(1, 0, -0, 1, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 90, new Matrix(0, 1, -1, 0, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 30, new Matrix(0.86603, 0.5, -0.5, 0.86603, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 180, new Matrix(-1, 0, -0, -1, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 270, new Matrix(-0, -1, 1, -0, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 360, new Matrix(1, 0, -0, 1, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 720, new Matrix(1, 0, -0, 1, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+
+        // Translated and scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -360, new Matrix(2, 0, 0, 3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -270, new Matrix(-0, 3, -2, -0, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -180, new Matrix(-2, -0, 0, -3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -90, new Matrix(0, -3, 2, 0, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -45, new Matrix(1.41421, -2.12132, 1.41421, 2.12132, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 45, new Matrix(1.41421, 2.12132, -1.41421, 2.12132, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, new Matrix(2, 0, 0, 3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 90, new Matrix(0, 3, -2, 0, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 30, new Matrix(1.73205, 1.5, -1, 2.59808, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 180, new Matrix(-2, 0, -0, -3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 270, new Matrix(-0, -3, 2, -0, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 360, new Matrix(2, 0, 0, 3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 720, new Matrix(2, 0, 0, 3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+
+        // Translated and skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -360, new Matrix(1, 0.5, 0.75, 1, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -270, new Matrix(0.75, 1, -1, -0.5, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -180, new Matrix(-1, -0.5, -0.75, -1, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -90, new Matrix(-0.75, -1, 1, 0.5, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -45, new Matrix(0.17678, -0.35355, 1.23744, 1.06066, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 45, new Matrix(1.23744, 1.06066, -0.17678, 0.35355, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, new Matrix(1, 0.5, 0.75, 1, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 90, new Matrix(0.75, 1, -1, -0.5, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 30, new Matrix(1.24103, 0.93301, 0.14951, 0.61603, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 180, new Matrix(-1, -0.5, -0.75, -1, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 270, new Matrix(-0.75, -1, 1, 0.5, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 360, new Matrix(1, 0.5, 0.75, 1, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 720, new Matrix(1, 0.5, 0.75, 1, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+
+        // Skewed and scaled.
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -360, new Matrix(2, 0.5, 0.75, 3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -270, new Matrix(0.75, 3, -2, -0.5, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -180, new Matrix(-2, -0.5, -0.75, -3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -90, new Matrix(-0.75, -3, 2, 0.5, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -45, new Matrix(0.88388, -1.76777, 1.94454, 2.47487, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 45, new Matrix(1.94454, 2.47487, -0.88388, 1.76777, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, new Matrix(2, 0.5, 0.75, 3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 90, new Matrix(0.75, 3, -2, -0.5, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 30, new Matrix(2.10705, 1.93301, -0.35048, 2.34808, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 180, new Matrix(-2, -0.5, -0.75, -3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 270, new Matrix(-0.75, -3, 2, 0.5, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 360, new Matrix(2, 0.5, 0.75, 3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 720, new Matrix(2, 0.5, 0.75, 3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+
+        // Complex.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -360, new Matrix(2, 3, 4, 5, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -270, new Matrix(4, 5, -2, -3, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -180, new Matrix(-2, -3, -4, -5, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -90, new Matrix(-4, -5, 2, 3, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -45, new Matrix(-1.41421, -1.41421, 4.24264, 5.65685, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 45, new Matrix(4.24264, 5.65685, 1.41421, 1.41421, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, new Matrix(2, 3, 4, 5, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 90, new Matrix(4, 5, -2, -3, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 30, new Matrix(3.73205, 5.09808, 2.4641, 2.83013, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 180, new Matrix(-2, -3, -4, -5, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 270, new Matrix(-4, -5, 2, 3, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 360, new Matrix(2, 3, 4, 5, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 720, new Matrix(2, 3, 4, 5, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+
+        // No inverse.
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -360, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -270, new Matrix(0, 0, -0, -0, 0, 0), -0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -180, new Matrix(-0, -0, 0, 0, 0, 0), -0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -90, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -45, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 45, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 90, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 30, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 180, new Matrix(0, 0, -0, -0, 0, 0), -0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 270, new Matrix(-0, -0, 0, 0, 0, 0), -0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 360, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 720, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+    }
+
+    [Theory]
+    [MemberData(nameof(RotatePrepend_TestData))]
+    public void RotatePrepend_Invoke_Success(Matrix matrix, double angle, Matrix expected, double expectedDeterminant)
+    {
+        matrix.RotatePrepend(angle);
+        Helpers.AssertEqualRounded(expected, matrix);
+        Assert.Equal(expected.IsIdentity, matrix.IsIdentity);
+        Assert.Equal(expected.HasInverse, matrix.HasInverse);
+        Assert.Equal(expectedDeterminant, matrix.Determinant, precision: 5);
+    }
+
+    public static IEnumerable<object[]> RotateAt_TestData()
+    {
+        // Identity
+        foreach (Matrix matrix in IdentityMatrices())
+        {
+            yield return new object[] { matrix, -360, 0, 0, new Matrix(1, -0, 0, 1, 0, 0), 1 };
+            yield return new object[] { matrix, -270, 0, 0, new Matrix(-0, 1, -1, -0, 0, 0), 1 };
+            yield return new object[] { matrix, -180, 0, 0, new Matrix(-1, -0, 0, -1, 0, 0), 1 };
+            yield return new object[] { matrix, -90, 0, 0, new Matrix(0, -1, 1, 0, 0, 0), 1 };
+            yield return new object[] { matrix, -45, 0, 0, new Matrix(0.70711, -0.70711, 0.70711, 0.70711, 0, 0), 1 };
+            yield return new object[] { matrix, 45, 0, 0, new Matrix(0.70711, 0.70711, -0.70711, 0.70711, 0, 0), 1 };
+            yield return new object[] { matrix, 0, 0, 0, new Matrix(1, 0, -0, 1, 0, 0), 1 };
+            yield return new object[] { matrix, 90, 0, 0, new Matrix(0, 1, -1, 0, 0, 0), 1 };
+            yield return new object[] { matrix, 30, 0, 0, new Matrix(0.86603, 0.5, -0.5, 0.86603, 0, 0), 1 };
+            yield return new object[] { matrix, 180, 0, 0, new Matrix(-1, 0, -0, -1, 0, 0), 1 };
+            yield return new object[] { matrix, 270, 0, 0, new Matrix(-0, -1, 1, -0, 0, 0), 1 };
+            yield return new object[] { matrix, 360, 0, 0, new Matrix(1, 0, -0, 1, 0, 0), 1 };
+            yield return new object[] { matrix, 720, 0, 0, new Matrix(1, 0, -0, 1, 0, 0), 1 };
+            yield return new object[] { matrix, double.NaN, 0, 0, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+            yield return new object[] { matrix, -360, 1, 2, new Matrix(1, -0, 0, 1, 0, 0), 1 };
+            yield return new object[] { matrix, -270, 1, 2, new Matrix(-0, 1, -1, -0, 3, 1), 1 };
+            yield return new object[] { matrix, -180, 1, 2, new Matrix(-1, -0, 0, -1, 2, 4), 1 };
+            yield return new object[] { matrix, -90, 1, 2, new Matrix(0, -1, 1, 0, -1, 3), 1 };
+            yield return new object[] { matrix, -45, 1, 2, new Matrix(0.70711, -0.70711, 0.70711, 0.70711, -1.12132, 1.29289), 1 };
+            yield return new object[] { matrix, 45, 1, 2, new Matrix(0.70711, 0.70711, -0.70711, 0.70711, 1.70711, -0.12132), 1 };
+            yield return new object[] { matrix, 0, 1, 2, new Matrix(1, 0, -0, 1, 0, 0), 1 };
+            yield return new object[] { matrix, 90, 1, 2, new Matrix(0, 1, -1, 0, 3, 1), 1 };
+            yield return new object[] { matrix, 30, 1, 2, new Matrix(0.86603, 0.5, -0.5, 0.86603, 1.13396, -0.23205), 1 };
+            yield return new object[] { matrix, 180, 1, 2, new Matrix(-1, 0, -0, -1, 2, 4), 1 };
+            yield return new object[] { matrix, 270, 1, 2, new Matrix(-0, -1, 1, -0, -1, 3), 1 };
+            yield return new object[] { matrix, 360, 1, 2, new Matrix(1, 0, -0, 1, 0, 0), 1 };
+            yield return new object[] { matrix, 720, 1, 2, new Matrix(1, 0, -0, 1, 0, 0), 1 };
+            yield return new object[] { matrix, double.NaN, 1, 2, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+            yield return new object[] { matrix, 20, double.NaN, double.NaN, new Matrix(0.93969, 0.34202, -0.34202, 0.93969, double.NaN, double.NaN), 1 };
+        }
+
+        // Scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -360, 0, 0, new Matrix(2, 0, 0, 3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -270, 0, 0, new Matrix(-0, 2, -3, -0, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -180, 0, 0, new Matrix(-2, -0, 0, -3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -90, 0, 0, new Matrix(0, -2, 3, 0, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -45, 0, 0, new Matrix(1.41421, -1.41421, 2.12132, 2.12132, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 45, 0, 0, new Matrix(1.41421, 1.41421, -2.12132, 2.12132, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, 0, 0, new Matrix(2, 0, 0, 3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 90, 0, 0, new Matrix(0, 2, -3, 0, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 30, 0, 0, new Matrix(1.73205, 1, -1.5, 2.59808, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 180, 0, 0, new Matrix(-2, 0, -0, -3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 270, 0, 0, new Matrix(-0, -2, 3, -0, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 360, 0, 0, new Matrix(2, 0, 0, 3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 720, 0, 0, new Matrix(2, 0, 0, 3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), double.NaN, 0, 0, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -360, 1, 2, new Matrix(2, 0, 0, 3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -270, 1, 2, new Matrix(-0, 2, -3, -0, 3, 1), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -180, 1, 2, new Matrix(-2, -0, 0, -3, 2, 4), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -90, 1, 2, new Matrix(0, -2, 3, 0, -1, 3), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -45, 1, 2, new Matrix(1.41421, -1.41421, 2.12132, 2.12132, -1.12132, 1.29289), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 45, 1, 2, new Matrix(1.41421, 1.41421, -2.12132, 2.12132, 1.70711, -0.12132), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, 1, 2, new Matrix(2, 0, 0, 3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 90, 1, 2, new Matrix(0, 2, -3, 0, 3, 1), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 30, 1, 2, new Matrix(1.73205, 1, -1.5, 2.59808, 1.13396, -0.23205), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 180, 1, 2, new Matrix(-2, 0, -0, -3, 2, 4), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 270, 1, 2, new Matrix(-0, -2, 3, -0, -1, 3), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 360, 1, 2, new Matrix(2, 0, 0, 3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 720, 1, 2, new Matrix(2, 0, 0, 3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), double.NaN, 1, 2, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 20, double.NaN, double.NaN, new Matrix(1.87939, 0.68404, -1.02606, 2.81908, double.NaN, double.NaN), 6 };
+
+        // Skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -360, 0, 0, new Matrix(1, 0.5, 0.75, 1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -270, 0, 0, new Matrix(-0.5, 1, -1, 0.75, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -180, 0, 0, new Matrix(-1, -0.5, -0.75, -1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -90, 0, 0, new Matrix(0.5, -1, 1, -0.75, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -45, 0, 0, new Matrix(1.06066, -0.35355, 1.23744, 0.17678, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 45, 0, 0, new Matrix(0.35355, 1.06066, -0.17678, 1.23744, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, 0, 0, new Matrix(1, 0.5, 0.75, 1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 90, 0, 0, new Matrix(-0.5, 1, -1, 0.75, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 30, 0, 0, new Matrix(0.61603, 0.93301, 0.14951, 1.24103, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 180, 0, 0, new Matrix(-1, -0.5, -0.75, -1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 270, 0, 0, new Matrix(0.5, -1, 1, -0.75, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 360, 0, 0, new Matrix(1, 0.5, 0.75, 1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 720, 0, 0, new Matrix(1, 0.5, 0.75, 1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), double.NaN, 0, 0, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -360, 1, 2, new Matrix(1, 0.5, 0.75, 1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -270, 1, 2, new Matrix(-0.5, 1, -1, 0.75, 3, 1), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -180, 1, 2, new Matrix(-1, -0.5, -0.75, -1, 2, 4), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -90, 1, 2, new Matrix(0.5, -1, 1, -0.75, -1, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -45, 1, 2, new Matrix(1.06066, -0.35355, 1.23744, 0.17678, -1.12132, 1.29289), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 45, 1, 2, new Matrix(0.35355, 1.06066, -0.17678, 1.23744, 1.70711, -0.12132), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, 1, 2, new Matrix(1, 0.5, 0.75, 1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 90, 1, 2, new Matrix(-0.5, 1, -1, 0.75, 3, 1), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 30, 1, 2, new Matrix(0.61603, 0.93301, 0.14951, 1.24103, 1.13396, -0.23205), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 180, 1, 2, new Matrix(-1, -0.5, -0.75, -1, 2, 4), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 270, 1, 2, new Matrix(0.5, -1, 1, -0.75, -1, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 360, 1, 2, new Matrix(1, 0.5, 0.75, 1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 720, 1, 2, new Matrix(1, 0.5, 0.75, 1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), double.NaN, 1, 2, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 20, double.NaN, double.NaN, new Matrix(0.76868, 0.81187, 0.36275, 1.19621, double.NaN, double.NaN), 0.625 };
+
+        // Translated.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -360, 0, 0, new Matrix(1, -0, 0, 1, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -270, 0, 0, new Matrix(-0, 1, -1, -0, -3, 2), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -180, 0, 0, new Matrix(-1, -0, 0, -1, -2, -3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -90, 0, 0, new Matrix(0, -1, 1, 0, 3, -2), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -45, 0, 0, new Matrix(0.70711, -0.70711, 0.70711, 0.70711, 3.53553, 0.70711), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 45, 0, 0, new Matrix(0.70711, 0.70711, -0.70711, 0.70711, -0.70711, 3.53553), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, 0, 0, new Matrix(1, 0, -0, 1, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 90, 0, 0, new Matrix(0, 1, -1, 0, -3, 2), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 30, 0, 0, new Matrix(0.86603, 0.5, -0.5, 0.86603, 0.23205, 3.59808), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 180, 0, 0, new Matrix(-1, 0, -0, -1, -2, -3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 270, 0, 0, new Matrix(-0, -1, 1, -0, 3, -2), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 360, 0, 0, new Matrix(1, 0, -0, 1, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 720, 0, 0, new Matrix(1, 0, -0, 1, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), double.NaN, 0, 0, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -360, 1, 2, new Matrix(1, -0, 0, 1, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -270, 1, 2, new Matrix(-0, 1, -1, -0, -0, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -180, 1, 2, new Matrix(-1, -0, 0, -1, 0, 1), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -90, 1, 2, new Matrix(0, -1, 1, 0, 2, 1), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -45, 1, 2, new Matrix(0.70711, -0.70711, 0.70711, 0.70711, 2.41421, 2), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 45, 1, 2, new Matrix(0.70711, 0.70711, -0.70711, 0.70711, 1, 3.41421), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, 1, 2, new Matrix(1, 0, -0, 1, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 90, 1, 2, new Matrix(0, 1, -1, 0, 0, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 30, 1, 2, new Matrix(0.86603, 0.5, -0.5, 0.86603, 1.36603, 3.36603), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 180, 1, 2, new Matrix(-1, 0, -0, -1, 0, 1), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 270, 1, 2, new Matrix(-0, -1, 1, -0, 2, 1), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 360, 1, 2, new Matrix(1, 0, -0, 1, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 720, 1, 2, new Matrix(1, 0, -0, 1, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), double.NaN, 1, 2, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 20, double.NaN, double.NaN, new Matrix(0.93969, 0.34202, -0.34202, 0.93969, double.NaN, double.NaN), 1 };
+
+        // Translated and scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -360, 0, 0, new Matrix(2, 0, 0, 3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -270, 0, 0, new Matrix(-0, 2, -3, -0, -2, 1), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -180, 0, 0, new Matrix(-2, -0, 0, -3, -1, -2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -90, 0, 0, new Matrix(0, -2, 3, 0, 2, -1), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -45, 0, 0, new Matrix(1.41421, -1.41421, 2.12132, 2.12132, 2.12132, 0.70711), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 45, 0, 0, new Matrix(1.41421, 1.41421, -2.12132, 2.12132, -0.70711, 2.12132), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, 0, 0, new Matrix(2, 0, 0, 3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 90, 0, 0, new Matrix(0, 2, -3, 0, -2, 1), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 30, 0, 0, new Matrix(1.73205, 1, -1.5, 2.59808, -0.13397, 2.23205), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 180, 0, 0, new Matrix(-2, 0, -0, -3, -1, -2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 270, 0, 0, new Matrix(-0, -2, 3, -0, 2, -1), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 360, 0, 0, new Matrix(2, 0, 0, 3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 720, 0, 0, new Matrix(2, 0, 0, 3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), double.NaN, 0, 0, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -360, 1, 2, new Matrix(2, 0, 0, 3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -270, 1, 2, new Matrix(-0, 2, -3, -0, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -180, 1, 2, new Matrix(-2, -0, 0, -3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -90, 1, 2, new Matrix(0, -2, 3, 0, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -45, 1, 2, new Matrix(1.41421, -1.41421, 2.12132, 2.12132, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 45, 1, 2, new Matrix(1.41421, 1.41421, -2.12132, 2.12132, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, 1, 2, new Matrix(2, 0, 0, 3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 90, 1, 2, new Matrix(0, 2, -3, 0, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 30, 1, 2, new Matrix(1.73205, 1, -1.5, 2.59808, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 180, 1, 2, new Matrix(-2, 0, -0, -3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 270, 1, 2, new Matrix(-0, -2, 3, -0, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 360, 1, 2, new Matrix(2, 0, 0, 3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 720, 1, 2, new Matrix(2, 0, 0, 3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), double.NaN, 1, 2, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 20, double.NaN, double.NaN, new Matrix(1.87939, 0.68404, -1.02606, 2.81908, double.NaN, double.NaN), 6 };
+
+        // Translated and skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -360, 0, 0, new Matrix(1, 0.5, 0.75, 1, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -270, 0, 0, new Matrix(-0.5, 1, -1, 0.75, -3, 2), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -180, 0, 0, new Matrix(-1, -0.5, -0.75, -1, -2, -3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -90, 0, 0, new Matrix(0.5, -1, 1, -0.75, 3, -2), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -45, 0, 0, new Matrix(1.06066, -0.35355, 1.23744, 0.17678, 3.53553, 0.70711), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 45, 0, 0, new Matrix(0.35355, 1.06066, -0.17678, 1.23744, -0.70711, 3.53553), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, 0, 0, new Matrix(1, 0.5, 0.75, 1, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 90, 0, 0, new Matrix(-0.5, 1, -1, 0.75, -3, 2), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 30, 0, 0, new Matrix(0.61603, 0.93301, 0.14951, 1.24103, 0.23205, 3.59808), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 180, 0, 0, new Matrix(-1, -0.5, -0.75, -1, -2, -3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 270, 0, 0, new Matrix(0.5, -1, 1, -0.75, 3, -2), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 360, 0, 0, new Matrix(1, 0.5, 0.75, 1, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 720, 0, 0, new Matrix(1, 0.5, 0.75, 1, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), double.NaN, 0, 0, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -360, 1, 2, new Matrix(1, 0.5, 0.75, 1, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -270, 1, 2, new Matrix(-0.5, 1, -1, 0.75, -0, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -180, 1, 2, new Matrix(-1, -0.5, -0.75, -1, 0, 1), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -90, 1, 2, new Matrix(0.5, -1, 1, -0.75, 2, 1), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -45, 1, 2, new Matrix(1.06066, -0.35355, 1.23744, 0.17678, 2.41421, 2), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 45, 1, 2, new Matrix(0.35355, 1.06066, -0.17678, 1.23744, 1, 3.41421), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, 1, 2, new Matrix(1, 0.5, 0.75, 1, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 90, 1, 2, new Matrix(-0.5, 1, -1, 0.75, 0, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 30, 1, 2, new Matrix(0.61603, 0.93301, 0.14951, 1.24103, 1.36603, 3.36603), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 180, 1, 2, new Matrix(-1, -0.5, -0.75, -1, 0, 1), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 270, 1, 2, new Matrix(0.5, -1, 1, -0.75, 2, 1), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 360, 1, 2, new Matrix(1, 0.5, 0.75, 1, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 720, 1, 2, new Matrix(1, 0.5, 0.75, 1, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), double.NaN, 1, 2, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 20, double.NaN, double.NaN, new Matrix(0.76868, 0.81187, 0.36275, 1.19621, double.NaN, double.NaN), 0.625 };
+
+        // Skewed and scaled.
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -360, 0, 0, new Matrix(2, 0.5, 0.75, 3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -270, 0, 0, new Matrix(-0.5, 2, -3, 0.75, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -180, 0, 0, new Matrix(-2, -0.5, -0.75, -3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -90, 0, 0, new Matrix(0.5, -2, 3, -0.75, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -45, 0, 0, new Matrix(1.76777, -1.06066, 2.65165, 1.59099, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 45, 0, 0, new Matrix(1.06066, 1.76777, -1.59099, 2.65165, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, 0, 0, new Matrix(2, 0.5, 0.75, 3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 90, 0, 0, new Matrix(-0.5, 2, -3, 0.75, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 30, 0, 0, new Matrix(1.48205, 1.43301, -0.85048, 2.97308, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 180, 0, 0, new Matrix(-2, -0.5, -0.75, -3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 270, 0, 0, new Matrix(0.5, -2, 3, -0.75, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 360, 0, 0, new Matrix(2, 0.5, 0.75, 3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 720, 0, 0, new Matrix(2, 0.5, 0.75, 3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), double.NaN, 0, 0, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -360, 1, 2, new Matrix(2, 0.5, 0.75, 3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -270, 1, 2, new Matrix(-0.5, 2, -3, 0.75, 3, 1), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -180, 1, 2, new Matrix(-2, -0.5, -0.75, -3, 2, 4), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -90, 1, 2, new Matrix(0.5, -2, 3, -0.75, -1, 3), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -45, 1, 2, new Matrix(1.76777, -1.06066, 2.65165, 1.59099, -1.12132, 1.29289), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 45, 1, 2, new Matrix(1.06066, 1.76777, -1.59099, 2.65165, 1.70711, -0.12132), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, 1, 2, new Matrix(2, 0.5, 0.75, 3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 90, 1, 2, new Matrix(-0.5, 2, -3, 0.75, 3, 1), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 30, 1, 2, new Matrix(1.48205, 1.43301, -0.85048, 2.97308, 1.13396, -0.23205), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 180, 1, 2, new Matrix(-2, -0.5, -0.75, -3, 2, 4), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 270, 1, 2, new Matrix(0.5, -2, 3, -0.75, -1, 3), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 360, 1, 2, new Matrix(2, 0.5, 0.75, 3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 720, 1, 2, new Matrix(2, 0.5, 0.75, 3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), double.NaN, 1, 2, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 20, double.NaN, double.NaN, new Matrix(1.70838, 1.15389, -0.32129, 3.07559, double.NaN, double.NaN), 5.625 };
+
+        // Complex.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -360, 0, 0, new Matrix(2, 3, 4, 5, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -270, 0, 0, new Matrix(-3, 2, -5, 4, -7, 6), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -180, 0, 0, new Matrix(-2, -3, -4, -5, -6, -7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -90, 0, 0, new Matrix(3, -2, 5, -4, 7, -6), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -45, 0, 0, new Matrix(3.53553, 0.70711, 6.36396, 0.70711, 9.19239, 0.70711), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 45, 0, 0, new Matrix(-0.70711, 3.53553, -0.70711, 6.36396, -0.70711, 9.19239), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, 0, 0, new Matrix(2, 3, 4, 5, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 90, 0, 0, new Matrix(-3, 2, -5, 4, -7, 6), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 30, 0, 0, new Matrix(0.23205, 3.59808, 0.9641, 6.33013, 1.69615, 9.06218), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 180, 0, 0, new Matrix(-2, -3, -4, -5, -6, -7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 270, 0, 0, new Matrix(3, -2, 5, -4, 7, -6), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 360, 0, 0, new Matrix(2, 3, 4, 5, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 720, 0, 0, new Matrix(2, 3, 4, 5, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), double.NaN, 0, 0, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -360, 1, 2, new Matrix(2, 3, 4, 5, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -270, 1, 2, new Matrix(-3, 2, -5, 4, -4, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -180, 1, 2, new Matrix(-2, -3, -4, -5, -4, -3), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -90, 1, 2, new Matrix(3, -2, 5, -4, 6, -3), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -45, 1, 2, new Matrix(3.53553, 0.70711, 6.36396, 0.70711, 8.07107, 2), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 45, 1, 2, new Matrix(-0.70711, 3.53553, -0.70711, 6.36396, 1, 9.07107), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, 1, 2, new Matrix(2, 3, 4, 5, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 90, 1, 2, new Matrix(-3, 2, -5, 4, -4, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 30, 1, 2, new Matrix(0.23205, 3.59808, 0.9641, 6.33013, 2.83013, 8.83013), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 180, 1, 2, new Matrix(-2, -3, -4, -5, -4, -3), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 270, 1, 2, new Matrix(3, -2, 5, -4, 6, -3), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 360, 1, 2, new Matrix(2, 3, 4, 5, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 720, 1, 2, new Matrix(2, 3, 4, 5, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), double.NaN, 1, 2, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 20, double.NaN, double.NaN, new Matrix(0.85332, 3.50312, 2.04867, 6.06654, double.NaN, double.NaN), -2 };
+
+        // No inverse.
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -360, 0, 0, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -270, 0, 0, new Matrix(-0, 0, -0, 0, 0, 0), -0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -180, 0, 0, new Matrix(0, -0, 0, -0, 0, 0), -0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -90, 0, 0, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -45, 0, 0, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 45, 0, 0, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, 0, 0, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 90, 0, 0, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 30, 0, 0, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 180, 0, 0, new Matrix(-0, 0, -0, 0, 0, 0), -0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 270, 0, 0, new Matrix(0, -0, 0, -0, 0, 0), -0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 360, 0, 0, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 720, 0, 0, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), double.NaN, 0, 0, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -360, 1, 2, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -270, 1, 2, new Matrix(-0, 0, -0, 0, 3, 1), -0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -180, 1, 2, new Matrix(0, -0, 0, -0, 2, 4), -0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -90, 1, 2, new Matrix(0, 0, 0, 0, -1, 3), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -45, 1, 2, new Matrix(0, 0, 0, 0, -1.12132, 1.29289), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 45, 1, 2, new Matrix(0, 0, 0, 0, 1.70711, -0.12132), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, 1, 2, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 90, 1, 2, new Matrix(0, 0, 0, 0, 3, 1), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 30, 1, 2, new Matrix(0, 0, 0, 0, 1.13396, -0.23205), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 180, 1, 2, new Matrix(-0, 0, -0, 0, 2, 4), -0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 270, 1, 2, new Matrix(0, -0, 0, -0, -1, 3), -0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 360, 1, 2, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 720, 1, 2, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), double.NaN, 1, 2, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 20, double.NaN, double.NaN, new Matrix(0, 0, 0, 0, double.NaN, double.NaN), 0 };
+    }
+    
+    [Theory]
+    [MemberData(nameof(RotateAt_TestData))]
+    public void RotateAt_Invoke_Success(Matrix matrix, double angle, double centerX, double centerY, Matrix expected, double expectedDeterminant)
+    {
+        matrix.RotateAt(angle, centerX, centerY);
+        Helpers.AssertEqualRounded(expected, matrix);
+        Assert.Equal(expected.IsIdentity, matrix.IsIdentity);
+        Assert.Equal(expected.HasInverse, matrix.HasInverse);
+        Assert.Equal(expectedDeterminant, matrix.Determinant, precision: 5);
+    }
+
+    public static IEnumerable<object[]> RotateAtPrepend_TestData()
+    {
+        // Identity
+        foreach (Matrix matrix in IdentityMatrices())
+        {
+            yield return new object[] { matrix, -360, 0, 0, new Matrix(1, -0, 0, 1, 0, 0), 1 };
+            yield return new object[] { matrix, -270, 0, 0, new Matrix(-0, 1, -1, -0, 0, 0), 1 };
+            yield return new object[] { matrix, -180, 0, 0, new Matrix(-1, -0, 0, -1, 0, 0), 1 };
+            yield return new object[] { matrix, -90, 0, 0, new Matrix(0, -1, 1, 0, 0, 0), 1 };
+            yield return new object[] { matrix, -45, 0, 0, new Matrix(0.70711, -0.70711, 0.70711, 0.70711, 0, 0), 1 };
+            yield return new object[] { matrix, 45, 0, 0, new Matrix(0.70711, 0.70711, -0.70711, 0.70711, 0, 0), 1 };
+            yield return new object[] { matrix, 0, 0, 0, new Matrix(1, 0, -0, 1, 0, 0), 1 };
+            yield return new object[] { matrix, 90, 0, 0, new Matrix(0, 1, -1, 0, 0, 0), 1 };
+            yield return new object[] { matrix, 30, 0, 0, new Matrix(0.86603, 0.5, -0.5, 0.86603, 0, 0), 1 };
+            yield return new object[] { matrix, 180, 0, 0, new Matrix(-1, 0, -0, -1, 0, 0), 1 };
+            yield return new object[] { matrix, 270, 0, 0, new Matrix(-0, -1, 1, -0, 0, 0), 1 };
+            yield return new object[] { matrix, 360, 0, 0, new Matrix(1, 0, -0, 1, 0, 0), 1 };
+            yield return new object[] { matrix, 720, 0, 0, new Matrix(1, 0, -0, 1, 0, 0), 1 };
+            yield return new object[] { matrix, double.NaN, 0, 0, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+            yield return new object[] { matrix, -360, 1, 2, new Matrix(1, -0, 0, 1, 0, 0), 1 };
+            yield return new object[] { matrix, -270, 1, 2, new Matrix(-0, 1, -1, -0, 3, 1), 1 };
+            yield return new object[] { matrix, -180, 1, 2, new Matrix(-1, -0, 0, -1, 2, 4), 1 };
+            yield return new object[] { matrix, -90, 1, 2, new Matrix(0, -1, 1, 0, -1, 3), 1 };
+            yield return new object[] { matrix, -45, 1, 2, new Matrix(0.70711, -0.70711, 0.70711, 0.70711, -1.12132, 1.29289), 1 };
+            yield return new object[] { matrix, 45, 1, 2, new Matrix(0.70711, 0.70711, -0.70711, 0.70711, 1.70711, -0.12132), 1 };
+            yield return new object[] { matrix, 0, 1, 2, new Matrix(1, 0, -0, 1, 0, 0), 1 };
+            yield return new object[] { matrix, 90, 1, 2, new Matrix(0, 1, -1, 0, 3, 1), 1 };
+            yield return new object[] { matrix, 30, 1, 2, new Matrix(0.86603, 0.5, -0.5, 0.86603, 1.13396, -0.23205), 1 };
+            yield return new object[] { matrix, 180, 1, 2, new Matrix(-1, 0, -0, -1, 2, 4), 1 };
+            yield return new object[] { matrix, 270, 1, 2, new Matrix(-0, -1, 1, -0, -1, 3), 1 };
+            yield return new object[] { matrix, 360, 1, 2, new Matrix(1, 0, -0, 1, 0, 0), 1 };
+            yield return new object[] { matrix, 720, 1, 2, new Matrix(1, 0, -0, 1, 0, 0), 1 };
+            yield return new object[] { matrix, double.NaN, 1, 2, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+            yield return new object[] { matrix, 20, double.NaN, double.NaN, new Matrix(0.93969, 0.34202, -0.34202, 0.93969, double.NaN, double.NaN), 1 };
+        }
+
+        // Scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -360, 0, 0, new Matrix(2, 0, 0, 3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -270, 0, 0, new Matrix(-0, 3, -2, -0, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -180, 0, 0, new Matrix(-2, -0, 0, -3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -90, 0, 0, new Matrix(0, -3, 2, 0, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -45, 0, 0, new Matrix(1.41421, -2.12132, 1.41421, 2.12132, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 45, 0, 0, new Matrix(1.41421, 2.12132, -1.41421, 2.12132, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, 0, 0, new Matrix(2, 0, 0, 3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 90, 0, 0, new Matrix(0, 3, -2, 0, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 30, 0, 0, new Matrix(1.73205, 1.5, -1, 2.59808, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 180, 0, 0, new Matrix(-2, 0, -0, -3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 270, 0, 0, new Matrix(-0, -3, 2, -0, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 360, 0, 0, new Matrix(2, 0, 0, 3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 720, 0, 0, new Matrix(2, 0, 0, 3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), double.NaN, 0, 0, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -360, 1, 2, new Matrix(2, 0, 0, 3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -270, 1, 2, new Matrix(-0, 3, -2, -0, 6, 3), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -180, 1, 2, new Matrix(-2, -0, 0, -3, 4, 12), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -90, 1, 2, new Matrix(0, -3, 2, 0, -2, 9), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -45, 1, 2, new Matrix(1.41421, -2.12132, 1.41421, 2.12132, -2.24264, 3.87868), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 45, 1, 2, new Matrix(1.41421, 2.12132, -1.41421, 2.12132, 3.41421, -0.36396), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, 1, 2, new Matrix(2, 0, 0, 3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 90, 1, 2, new Matrix(0, 3, -2, 0, 6, 3), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 30, 1, 2, new Matrix(1.73205, 1.5, -1, 2.59808, 2.26795, -0.69615), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 180, 1, 2, new Matrix(-2, 0, -0, -3, 4, 12), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 270, 1, 2, new Matrix(-0, -3, 2, -0, -2, 9), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 360, 1, 2, new Matrix(2, 0, 0, 3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 720, 1, 2, new Matrix(2, 0, 0, 3, 0, 0), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), double.NaN, 1, 2, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 20, double.NaN, double.NaN, new Matrix(1.87939, 1.02606, -0.68404, 2.81908, double.NaN, double.NaN), 6 };
+
+        // Skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -360, 0, 0, new Matrix(1, 0.5, 0.75, 1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -270, 0, 0, new Matrix(0.75, 1, -1, -0.5, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -180, 0, 0, new Matrix(-1, -0.5, -0.75, -1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -90, 0, 0, new Matrix(-0.75, -1, 1, 0.5, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -45, 0, 0, new Matrix(0.17678, -0.35355, 1.23744, 1.06066, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 45, 0, 0, new Matrix(1.23744, 1.06066, -0.17678, 0.35355, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, 0, 0, new Matrix(1, 0.5, 0.75, 1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 90, 0, 0, new Matrix(0.75, 1, -1, -0.5, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 30, 0, 0, new Matrix(1.24103, 0.93301, 0.14951, 0.61603, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 180, 0, 0, new Matrix(-1, -0.5, -0.75, -1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 270, 0, 0, new Matrix(-0.75, -1, 1, 0.5, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 360, 0, 0, new Matrix(1, 0.5, 0.75, 1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 720, 0, 0, new Matrix(1, 0.5, 0.75, 1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), double.NaN, 0, 0, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -360, 1, 2, new Matrix(1, 0.5, 0.75, 1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -270, 1, 2, new Matrix(0.75, 1, -1, -0.5, 3.75, 2.5), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -180, 1, 2, new Matrix(-1, -0.5, -0.75, -1, 5, 5), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -90, 1, 2, new Matrix(-0.75, -1, 1, 0.5, 1.25, 2.5), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -45, 1, 2, new Matrix(0.17678, -0.35355, 1.23744, 1.06066, -0.15165, 0.73223), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 45, 1, 2, new Matrix(1.23744, 1.06066, -0.17678, 0.35355, 1.61612, 0.73223), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, 1, 2, new Matrix(1, 0.5, 0.75, 1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 90, 1, 2, new Matrix(0.75, 1, -1, -0.5, 3.75, 2.5), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 30, 1, 2, new Matrix(1.24103, 0.93301, 0.14951, 0.61603, 0.95994, 0.33494), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 180, 1, 2, new Matrix(-1, -0.5, -0.75, -1, 5, 5), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 270, 1, 2, new Matrix(-0.75, -1, 1, 0.5, 1.25, 2.5), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 360, 1, 2, new Matrix(1, 0.5, 0.75, 1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 720, 1, 2, new Matrix(1, 0.5, 0.75, 1, 0, 0), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), double.NaN, 1, 2, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 20, double.NaN, double.NaN, new Matrix(1.19621, 0.81187, 0.36275, 0.76868, double.NaN, double.NaN), 0.625 };
+
+        // Translated.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -360, 0, 0, new Matrix(1, -0, 0, 1, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -270, 0, 0, new Matrix(-0, 1, -1, -0, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -180, 0, 0, new Matrix(-1, -0, 0, -1, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -90, 0, 0, new Matrix(0, -1, 1, 0, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -45, 0, 0, new Matrix(0.70711, -0.70711, 0.70711, 0.70711, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 45, 0, 0, new Matrix(0.70711, 0.70711, -0.70711, 0.70711, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, 0, 0, new Matrix(1, 0, -0, 1, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 90, 0, 0, new Matrix(0, 1, -1, 0, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 30, 0, 0, new Matrix(0.86603, 0.5, -0.5, 0.86603, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 180, 0, 0, new Matrix(-1, 0, -0, -1, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 270, 0, 0, new Matrix(-0, -1, 1, -0, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 360, 0, 0, new Matrix(1, 0, -0, 1, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 720, 0, 0, new Matrix(1, 0, -0, 1, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), double.NaN, 0, 0, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -360, 1, 2, new Matrix(1, -0, 0, 1, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -270, 1, 2, new Matrix(-0, 1, -1, -0, 5, 4), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -180, 1, 2, new Matrix(-1, -0, 0, -1, 4, 7), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -90, 1, 2, new Matrix(0, -1, 1, 0, 1, 6), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -45, 1, 2, new Matrix(0.70711, -0.70711, 0.70711, 0.70711, 0.87868, 4.29289), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 45, 1, 2, new Matrix(0.70711, 0.70711, -0.70711, 0.70711, 3.70711, 2.87868), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, 1, 2, new Matrix(1, 0, -0, 1, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 90, 1, 2, new Matrix(0, 1, -1, 0, 5, 4), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 30, 1, 2, new Matrix(0.86603, 0.5, -0.5, 0.86603, 3.13397, 2.76795), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 180, 1, 2, new Matrix(-1, 0, -0, -1, 4, 7), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 270, 1, 2, new Matrix(-0, -1, 1, -0, 1, 6), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 360, 1, 2, new Matrix(1, 0, -0, 1, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 720, 1, 2, new Matrix(1, 0, -0, 1, 2, 3), 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), double.NaN, 1, 2, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 20, double.NaN, double.NaN, new Matrix(0.93969, 0.34202, -0.34202, 0.93969, double.NaN, double.NaN), 1 };
+
+        // Translated and scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -360, 0, 0, new Matrix(2, 0, 0, 3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -270, 0, 0, new Matrix(-0, 3, -2, -0, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -180, 0, 0, new Matrix(-2, -0, 0, -3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -90, 0, 0, new Matrix(0, -3, 2, 0, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -45, 0, 0, new Matrix(1.41421, -2.12132, 1.41421, 2.12132, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 45, 0, 0, new Matrix(1.41421, 2.12132, -1.41421, 2.12132, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, 0, 0, new Matrix(2, 0, 0, 3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 90, 0, 0, new Matrix(0, 3, -2, 0, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 30, 0, 0, new Matrix(1.73205, 1.5, -1, 2.59808, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 180, 0, 0, new Matrix(-2, 0, -0, -3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 270, 0, 0, new Matrix(-0, -3, 2, -0, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 360, 0, 0, new Matrix(2, 0, 0, 3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 720, 0, 0, new Matrix(2, 0, 0, 3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), double.NaN, 0, 0, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -360, 1, 2, new Matrix(2, 0, 0, 3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -270, 1, 2, new Matrix(-0, 3, -2, -0, 7, 5), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -180, 1, 2, new Matrix(-2, -0, 0, -3, 5, 14), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -90, 1, 2, new Matrix(0, -3, 2, 0, -1, 11), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -45, 1, 2, new Matrix(1.41421, -2.12132, 1.41421, 2.12132, -1.24264, 5.87868), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 45, 1, 2, new Matrix(1.41421, 2.12132, -1.41421, 2.12132, 4.41421, 1.63604), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, 1, 2, new Matrix(2, 0, 0, 3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 90, 1, 2, new Matrix(0, 3, -2, 0, 7, 5), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 30, 1, 2, new Matrix(1.73205, 1.5, -1, 2.59808, 3.26795, 1.30385), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 180, 1, 2, new Matrix(-2, 0, -0, -3, 5, 14), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 270, 1, 2, new Matrix(-0, -3, 2, -0, -1, 11), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 360, 1, 2, new Matrix(2, 0, 0, 3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 720, 1, 2, new Matrix(2, 0, 0, 3, 1, 2), 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), double.NaN, 1, 2, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 20, double.NaN, double.NaN, new Matrix(1.87939, 1.02606, -0.68404, 2.81908, double.NaN, double.NaN), 6 };
+
+        // Translated and skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -360, 0, 0, new Matrix(1, 0.5, 0.75, 1, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -270, 0, 0, new Matrix(0.75, 1, -1, -0.5, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -180, 0, 0, new Matrix(-1, -0.5, -0.75, -1, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -90, 0, 0, new Matrix(-0.75, -1, 1, 0.5, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -45, 0, 0, new Matrix(0.17678, -0.35355, 1.23744, 1.06066, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 45, 0, 0, new Matrix(1.23744, 1.06066, -0.17678, 0.35355, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, 0, 0, new Matrix(1, 0.5, 0.75, 1, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 90, 0, 0, new Matrix(0.75, 1, -1, -0.5, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 30, 0, 0, new Matrix(1.24103, 0.93301, 0.14951, 0.61603, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 180, 0, 0, new Matrix(-1, -0.5, -0.75, -1, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 270, 0, 0, new Matrix(-0.75, -1, 1, 0.5, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 360, 0, 0, new Matrix(1, 0.5, 0.75, 1, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 720, 0, 0, new Matrix(1, 0.5, 0.75, 1, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), double.NaN, 0, 0, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -360, 1, 2, new Matrix(1, 0.5, 0.75, 1, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -270, 1, 2, new Matrix(0.75, 1, -1, -0.5, 5.75, 5.5), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -180, 1, 2, new Matrix(-1, -0.5, -0.75, -1, 7, 8), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -90, 1, 2, new Matrix(-0.75, -1, 1, 0.5, 3.25, 5.5), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -45, 1, 2, new Matrix(0.17678, -0.35355, 1.23744, 1.06066, 1.84835, 3.73223), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 45, 1, 2, new Matrix(1.23744, 1.06066, -0.17678, 0.35355, 3.61612, 3.73223), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, 1, 2, new Matrix(1, 0.5, 0.75, 1, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 90, 1, 2, new Matrix(0.75, 1, -1, -0.5, 5.75, 5.5), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 30, 1, 2, new Matrix(1.24103, 0.93301, 0.14951, 0.61603, 2.95994, 3.33494), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 180, 1, 2, new Matrix(-1, -0.5, -0.75, -1, 7, 8), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 270, 1, 2, new Matrix(-0.75, -1, 1, 0.5, 3.25, 5.5), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 360, 1, 2, new Matrix(1, 0.5, 0.75, 1, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 720, 1, 2, new Matrix(1, 0.5, 0.75, 1, 2, 3), 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), double.NaN, 1, 2, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 20, double.NaN, double.NaN, new Matrix(1.19621, 0.81187, 0.36275, 0.76868, double.NaN, double.NaN), 0.625 };
+
+        // Skewed and scaled.
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -360, 0, 0, new Matrix(2, 0.5, 0.75, 3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -270, 0, 0, new Matrix(0.75, 3, -2, -0.5, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -180, 0, 0, new Matrix(-2, -0.5, -0.75, -3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -90, 0, 0, new Matrix(-0.75, -3, 2, 0.5, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -45, 0, 0, new Matrix(0.88388, -1.76777, 1.94454, 2.47487, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 45, 0, 0, new Matrix(1.94454, 2.47487, -0.88388, 1.76777, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, 0, 0, new Matrix(2, 0.5, 0.75, 3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 90, 0, 0, new Matrix(0.75, 3, -2, -0.5, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 30, 0, 0, new Matrix(2.10705, 1.93301, -0.35048, 2.34808, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 180, 0, 0, new Matrix(-2, -0.5, -0.75, -3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 270, 0, 0, new Matrix(-0.75, -3, 2, 0.5, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 360, 0, 0, new Matrix(2, 0.5, 0.75, 3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 720, 0, 0, new Matrix(2, 0.5, 0.75, 3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), double.NaN, 0, 0, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -360, 1, 2, new Matrix(2, 0.5, 0.75, 3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -270, 1, 2, new Matrix(0.75, 3, -2, -0.5, 6.75, 4.5), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -180, 1, 2, new Matrix(-2, -0.5, -0.75, -3, 7, 13), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -90, 1, 2, new Matrix(-0.75, -3, 2, 0.5, 0.25, 8.5), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -45, 1, 2, new Matrix(0.88388, -1.76777, 1.94454, 2.47487, -1.27297, 3.31802), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 45, 1, 2, new Matrix(1.94454, 2.47487, -0.88388, 1.76777, 3.32322, 0.48959), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, 1, 2, new Matrix(2, 0.5, 0.75, 3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 90, 1, 2, new Matrix(0.75, 3, -2, -0.5, 6.75, 4.5), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 30, 1, 2, new Matrix(2.10705, 1.93301, -0.35048, 2.34808, 2.09391, -0.12917), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 180, 1, 2, new Matrix(-2, -0.5, -0.75, -3, 7, 13), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 270, 1, 2, new Matrix(-0.75, -3, 2, 0.5, 0.25, 8.5), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 360, 1, 2, new Matrix(2, 0.5, 0.75, 3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 720, 1, 2, new Matrix(2, 0.5, 0.75, 3, 0, 0), 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), double.NaN, 1, 2, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 20, double.NaN, double.NaN, new Matrix(2.1359, 1.49591, 0.02073, 2.64807, double.NaN, double.NaN), 5.625 };
+
+        // Complex.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -360, 0, 0, new Matrix(2, 3, 4, 5, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -270, 0, 0, new Matrix(4, 5, -2, -3, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -180, 0, 0, new Matrix(-2, -3, -4, -5, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -90, 0, 0, new Matrix(-4, -5, 2, 3, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -45, 0, 0, new Matrix(-1.41421, -1.41421, 4.24264, 5.65685, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 45, 0, 0, new Matrix(4.24264, 5.65685, 1.41421, 1.41421, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, 0, 0, new Matrix(2, 3, 4, 5, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 90, 0, 0, new Matrix(4, 5, -2, -3, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 30, 0, 0, new Matrix(3.73205, 5.09808, 2.4641, 2.83013, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 180, 0, 0, new Matrix(-2, -3, -4, -5, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 270, 0, 0, new Matrix(-4, -5, 2, 3, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 360, 0, 0, new Matrix(2, 3, 4, 5, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 720, 0, 0, new Matrix(2, 3, 4, 5, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), double.NaN, 0, 0, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -360, 1, 2, new Matrix(2, 3, 4, 5, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -270, 1, 2, new Matrix(4, 5, -2, -3, 16, 21), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -180, 1, 2, new Matrix(-2, -3, -4, -5, 26, 33), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -90, 1, 2, new Matrix(-4, -5, 2, 3, 16, 19), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -45, 1, 2, new Matrix(-1.41421, -1.41421, 4.24264, 5.65685, 8.92892, 10.10051), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 45, 1, 2, new Matrix(4.24264, 5.65685, 1.41421, 1.41421, 8.92892, 11.51472), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, 1, 2, new Matrix(2, 3, 4, 5, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 90, 1, 2, new Matrix(4, 5, -2, -3, 16, 21), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 30, 1, 2, new Matrix(3.73205, 5.09808, 2.4641, 2.83013, 7.33975, 9.24166), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 180, 1, 2, new Matrix(-2, -3, -4, -5, 26, 33), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 270, 1, 2, new Matrix(-4, -5, 2, 3, 16, 19), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 360, 1, 2, new Matrix(2, 3, 4, 5, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 720, 1, 2, new Matrix(2, 3, 4, 5, 6, 7), -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), double.NaN, 1, 2, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 20, double.NaN, double.NaN, new Matrix(3.24747, 4.52918, 3.07473, 3.6724, double.NaN, double.NaN), -2 };
+
+        // No inverse.
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -360, 0, 0, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -270, 0, 0, new Matrix(0, 0, -0, -0, 0, 0), -0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -180, 0, 0, new Matrix(-0, -0, 0, 0, 0, 0), -0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -90, 0, 0, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -45, 0, 0, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 45, 0, 0, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, 0, 0, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 90, 0, 0, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 30, 0, 0, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 180, 0, 0, new Matrix(0, 0, -0, -0, 0, 0), -0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 270, 0, 0, new Matrix(-0, -0, 0, 0, 0, 0), -0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 360, 0, 0, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 720, 0, 0, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), double.NaN, 0, 0, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -360, 1, 2, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -270, 1, 2, new Matrix(0, 0, -0, -0, 0, 0), -0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -180, 1, 2, new Matrix(-0, -0, 0, 0, 0, 0), -0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -90, 1, 2, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -45, 1, 2, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 45, 1, 2, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, 1, 2, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 90, 1, 2, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 30, 1, 2, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 180, 1, 2, new Matrix(0, 0, -0, -0, 0, 0), -0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 270, 1, 2, new Matrix(-0, -0, 0, 0, 0, 0), -0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 360, 1, 2, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 720, 1, 2, new Matrix(0, 0, 0, 0, 0, 0), 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), double.NaN, 1, 2, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 20, double.NaN, double.NaN, new Matrix(0, 0, 0, 0, double.NaN, double.NaN), 0 };
+    }
+    
+    [Theory]
+    [MemberData(nameof(RotateAt_TestData))]
+    public void RotateAtPrepend_Invoke_Success(Matrix matrix, double angle, double centerX, double centerY, Matrix expected, double expectedDeterminant)
+    {
+        matrix.RotateAtPrepend(angle, centerX, centerY);
+        Helpers.AssertEqualRounded(expected, matrix);
+        Assert.Equal(expected.IsIdentity, matrix.IsIdentity);
+        Assert.Equal(expected.HasInverse, matrix.HasInverse);
+        Assert.Equal(expectedDeterminant, matrix.Determinant, precision: 5);
+    }
+
+
+    public static IEnumerable<object[]> Scale_TestData()
+    {        
+        // Identity
+        foreach (Matrix matrix in IdentityMatrices())
+        {
+            yield return new object[] { matrix, -2, -3, new Matrix(-2, 0, 0, -3, 0, 0) };
+            yield return new object[] { matrix, -2, 3, new Matrix(-2, 0, 0, 3, 0, 0) };
+            yield return new object[] { matrix, 2, -3, new Matrix(2, 0, 0, -3, 0, 0) };
+            yield return new object[] { matrix, -1, -2, new Matrix(-1, 0, 0, -2, 0, 0) };
+            yield return new object[] { matrix, -1, 0, new Matrix(-1, 0, 0, 0, 0, 0) };
+            yield return new object[] { matrix, 0, -2, new Matrix(0, 0, 0, -2, 0, 0) };
+            yield return new object[] { matrix, 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+            yield return new object[] { matrix, 1, 1, new Matrix(1, 0, 0, 1, 0, 0) };
+            yield return new object[] { matrix, 1, 0, new Matrix(1, 0, 0, 0, 0, 0) };
+            yield return new object[] { matrix, 0, 2, new Matrix(0, 0, 0, 2, 0, 0) };
+            yield return new object[] { matrix, 1, 2, new Matrix(1, 0, 0, 2, 0, 0) };
+            yield return new object[] { matrix, 1.1, 2.2, new Matrix(1.1, 0, 0, 2.2, 0, 0) };
+            yield return new object[] { matrix, 2, 3, new Matrix(2, 0, 0, 3, 0, 0) };
+            yield return new object[] { matrix, double.NaN, 3, new Matrix(double.NaN, 0, 0, 3, 0, 0) };
+            yield return new object[] { matrix, 2, double.NaN, new Matrix(2, 0, 0, double.NaN, 0, 0) };
+            yield return new object[] { matrix, double.NaN, double.NaN, new Matrix(double.NaN, 0, 0, double.NaN, 0, 0) };
+        }
+
+        // Scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -2, -3, new Matrix(-4, 0, 0, -9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -2, 3, new Matrix(-4, 0, 0, 9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 2, -3, new Matrix(4, 0, 0, -9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -1, -2, new Matrix(-2, 0, 0, -6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -1, 0, new Matrix(-2, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, -2, new Matrix(0, 0, 0, -6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1, 1, new Matrix(2, 0, 0, 3, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1, 0, new Matrix(2, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, 2, new Matrix(0, 0, 0, 6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1, 2, new Matrix(2, 0, 0, 6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1.1, 2.2, new Matrix(2.2, 0, 0, 6.6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 2, 3, new Matrix(4, 0, 0, 9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), double.NaN, 3, new Matrix(double.NaN, 0, 0, 9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 2, double.NaN, new Matrix(4, 0, 0, double.NaN, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), double.NaN, double.NaN, new Matrix(double.NaN, 0, 0, double.NaN, 0, 0) };
+
+        // Skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -2, -3, new Matrix(-2, -1.5, -1.5, -3, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -2, 3, new Matrix(-2, 1.5, -1.5, 3, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 2, -3, new Matrix(2, -1.5, 1.5, -3, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -1, -2, new Matrix(-1, -1, -0.75, -2, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -1, 0, new Matrix(-1, 0, -0.75, 0, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, -2, new Matrix(0, -1, 0, -2, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1, 1, new Matrix(1, 0.5, 0.75, 1, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1, 0, new Matrix(1, 0, 0.75, 0, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, 2, new Matrix(0, 1, 0, 2, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1, 2, new Matrix(1, 1, 0.75, 2, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1.1, 2.2, new Matrix(1.1, 1.1, 0.825, 2.2, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 2, 3, new Matrix(2, 1.5, 1.5, 3, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), double.NaN, 3, new Matrix(double.NaN, 1.5, double.NaN, 3, double.NaN, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 2, double.NaN, new Matrix(2, double.NaN, 1.5, double.NaN, 0, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+
+        // Translated.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -2, -3, new Matrix(-2, 0, 0, -3, -4, -9) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -2, 3, new Matrix(-2, 0, 0, 3, -4, 9) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 2, -3, new Matrix(2, 0, 0, -3, 4, -9) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -1, -2, new Matrix(-1, 0, 0, -2, -2, -6) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -1, 0, new Matrix(-1, 0, 0, 0, -2, 0) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, -2, new Matrix(0, 0, 0, -2, 0, -6) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1, 1, new Matrix(1, 0, 0, 1, 2, 3) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1, 0, new Matrix(1, 0, 0, 0, 2, 0) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, 2, new Matrix(0, 0, 0, 2, 0, 6) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1, 2, new Matrix(1, 0, 0, 2, 2, 6) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1.1, 2.2, new Matrix(1.1, 0, 0, 2.2, 2.2, 6.6) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 2, 3, new Matrix(2, 0, 0, 3, 4, 9) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), double.NaN, 3, new Matrix(double.NaN, 0, 0, 3, double.NaN, 9) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 2, double.NaN, new Matrix(2, 0, 0, double.NaN, 4, double.NaN) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), double.NaN, double.NaN, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+
+        // Translated and scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -2, -3, new Matrix(-4, 0, 0, -9, -2, -6) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -2, 3, new Matrix(-4, 0, 0, 9, -2, 6) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 2, -3, new Matrix(4, 0, 0, -9, 2, -6) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -1, -2, new Matrix(-2, 0, 0, -6, -1, -4) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -1, 0, new Matrix(-2, 0, 0, 0, -1, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, -2, new Matrix(0, 0, 0, -6, 0, -4) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1, 1, new Matrix(2, 0, 0, 3, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1, 0, new Matrix(2, 0, 0, 0, 1, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, 2, new Matrix(0, 0, 0, 6, 0, 4) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1, 2, new Matrix(2, 0, 0, 6, 1, 4) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1.1, 2.2, new Matrix(2.2, 0, 0, 6.6, 1.1, 4.4) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 2, 3, new Matrix(4, 0, 0, 9, 2, 6) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), double.NaN, 3, new Matrix(double.NaN, 0, 0, 9, double.NaN, 6) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 2, double.NaN, new Matrix(4, 0, 0, double.NaN, 2, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), double.NaN, double.NaN, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+
+        // Translated and skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -2, -3, new Matrix(-2, -1.5, -1.5, -3, -4, -9) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -2, 3, new Matrix(-2, 1.5, -1.5, 3, -4, 9) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 2, -3, new Matrix(2, -1.5, 1.5, -3, 4, -9) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -1, -2, new Matrix(-1, -1, -0.75, -2, -2, -6) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -1, 0, new Matrix(-1, 0, -0.75, 0, -2, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, -2, new Matrix(0, -1, 0, -2, 0, -6) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1, 1, new Matrix(1, 0.5, 0.75, 1, 2, 3) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1, 0, new Matrix(1, 0, 0.75, 0, 2, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, 2, new Matrix(0, 1, 0, 2, 0, 6) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1, 2, new Matrix(1, 1, 0.75, 2, 2, 6) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1.1, 2.2, new Matrix(1.1, 1.1, 0.825, 2.2, 2.2, 6.6) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 2, 3, new Matrix(2, 1.5, 1.5, 3, 4, 9) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), double.NaN, 3, new Matrix(double.NaN, 1.5, double.NaN, 3, double.NaN, 9) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 2, double.NaN, new Matrix(2, double.NaN, 1.5, double.NaN, 4, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+
+        // Skewed and scaled.
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -2, -3, new Matrix(-4, -1.5, -1.5, -9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -2, 3, new Matrix(-4, 1.5, -1.5, 9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 2, -3, new Matrix(4, -1.5, 1.5, -9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -1, -2, new Matrix(-2, -1, -0.75, -6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -1, 0, new Matrix(-2, 0, -0.75, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, -2, new Matrix(0, -1, 0, -6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1, 1, new Matrix(2, 0.5, 0.75, 3, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1, 0, new Matrix(2, 0, 0.75, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, 2, new Matrix(0, 1, 0, 6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1, 2, new Matrix(2, 1, 0.75, 6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1.1, 2.2, new Matrix(2.2, 1.1, 0.825, 6.6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 2, 3, new Matrix(4, 1.5, 1.5, 9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), double.NaN, 3, new Matrix(double.NaN, 1.5, double.NaN, 9, double.NaN, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 2, double.NaN, new Matrix(4, double.NaN, 1.5, double.NaN, 0, double.NaN) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+
+        // Complex.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -2, -3, new Matrix(-4, -9, -8, -15, -12, -21) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -2, 3, new Matrix(-4, 9, -8, 15, -12, 21) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 2, -3, new Matrix(4, -9, 8, -15, 12, -21) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -1, -2, new Matrix(-2, -6, -4, -10, -6, -14) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -1, 0, new Matrix(-2, 0, -4, 0, -6, 0) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, -2, new Matrix(0, -6, 0, -10, 0, -14) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1, 1, new Matrix(2, 3, 4, 5, 6, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1, 0, new Matrix(2, 0, 4, 0, 6, 0) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, 2, new Matrix(0, 6, 0, 10, 0, 14) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1, 2, new Matrix(2, 6, 4, 10, 6, 14) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1.1, 2.2, new Matrix(2.2, 6.6, 4.4, 11, 6.6, 15.4) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 2, 3, new Matrix(4, 9, 8, 15, 12, 21) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), double.NaN, 3, new Matrix(double.NaN, 9, double.NaN, 15, double.NaN, 21) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 2, double.NaN, new Matrix(4, double.NaN, 8, double.NaN, 12, double.NaN) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+
+        // No inverse.
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -2, -3, new Matrix(-0, 0, 0, -0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -2, 3, new Matrix(-0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 2, -3, new Matrix(0, 0, 0, -0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -1, -2, new Matrix(-0, 0, 0, -0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -1, 0, new Matrix(-0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, -2, new Matrix(0, 0, 0, -0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1, 1, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, 2, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1, 2, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1.1, 2.2, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 2, 3, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), double.NaN, 3, new Matrix(double.NaN, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 2, double.NaN, new Matrix(0, 0, 0, double.NaN, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), double.NaN, double.NaN, new Matrix(double.NaN, 0, 0, double.NaN, 0, 0) };
+    }
+
+    [Theory]
+    [MemberData(nameof(Scale_TestData))]
+    public void Scale_Invoke_Success(Matrix matrix, double scaleX, double scaleY, Matrix expected)
+    {
+        matrix.Scale(scaleX, scaleY);
+        Helpers.AssertEqualRounded(expected, matrix);
+        Assert.Equal(expected.IsIdentity, matrix.IsIdentity);
+        Assert.Equal(expected.HasInverse, matrix.HasInverse);
+        Assert.Equal(expected.Determinant, matrix.Determinant, precision: 5);
+    }
+
+    public static IEnumerable<object[]> ScalePrepend_TestData()
+    {
+        // Identity
+        foreach (Matrix matrix in IdentityMatrices())
+        {
+            yield return new object[] { matrix, -2, -3, new Matrix(-2, 0, 0, -3, 0, 0) };
+            yield return new object[] { matrix, -2, 3, new Matrix(-2, 0, 0, 3, 0, 0) };
+            yield return new object[] { matrix, 2, -3, new Matrix(2, 0, 0, -3, 0, 0) };
+            yield return new object[] { matrix, -1, -2, new Matrix(-1, 0, 0, -2, 0, 0) };
+            yield return new object[] { matrix, -1, 0, new Matrix(-1, 0, 0, 0, 0, 0) };
+            yield return new object[] { matrix, 0, -2, new Matrix(0, 0, 0, -2, 0, 0) };
+            yield return new object[] { matrix, 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+            yield return new object[] { matrix, 1, 1, new Matrix(1, 0, 0, 1, 0, 0) };
+            yield return new object[] { matrix, 1, 0, new Matrix(1, 0, 0, 0, 0, 0) };
+            yield return new object[] { matrix, 0, 2, new Matrix(0, 0, 0, 2, 0, 0) };
+            yield return new object[] { matrix, 1, 2, new Matrix(1, 0, 0, 2, 0, 0) };
+            yield return new object[] { matrix, 1.1, 2.2, new Matrix(1.1, 0, 0, 2.2, 0, 0) };
+            yield return new object[] { matrix, 2, 3, new Matrix(2, 0, 0, 3, 0, 0) };
+            yield return new object[] { matrix, double.NaN, 3, new Matrix(double.NaN, 0, 0, 3, 0, 0) };
+            yield return new object[] { matrix, 2, double.NaN, new Matrix(2, 0, 0, double.NaN, 0, 0) };
+            yield return new object[] { matrix, double.NaN, double.NaN, new Matrix(double.NaN, 0, 0, double.NaN, 0, 0) };
+        }
+
+        // Scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -2, -3, new Matrix(-4, 0, 0, -9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -2, 3, new Matrix(-4, 0, 0, 9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 2, -3, new Matrix(4, 0, 0, -9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -1, -2, new Matrix(-2, 0, 0, -6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -1, 0, new Matrix(-2, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, -2, new Matrix(0, 0, 0, -6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1, 1, new Matrix(2, 0, 0, 3, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1, 0, new Matrix(2, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, 2, new Matrix(0, 0, 0, 6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1, 2, new Matrix(2, 0, 0, 6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1.1, 2.2, new Matrix(2.2, 0, 0, 6.6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 2, 3, new Matrix(4, 0, 0, 9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), double.NaN, 3, new Matrix(double.NaN, 0, 0, 9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 2, double.NaN, new Matrix(4, 0, 0, double.NaN, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), double.NaN, double.NaN, new Matrix(double.NaN, 0, 0, double.NaN, 0, 0) };
+
+        // Skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -2, -3, new Matrix(-2, -1.5, -1.5, -3, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -2, 3, new Matrix(-2, 1.5, -1.5, 3, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 2, -3, new Matrix(2, -1.5, 1.5, -3, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -1, -2, new Matrix(-1, -1, -0.75, -2, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -1, 0, new Matrix(-1, 0, -0.75, 0, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, -2, new Matrix(0, -1, 0, -2, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1, 1, new Matrix(1, 0.5, 0.75, 1, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1, 0, new Matrix(1, 0, 0.75, 0, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, 2, new Matrix(0, 1, 0, 2, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1, 2, new Matrix(1, 1, 0.75, 2, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1.1, 2.2, new Matrix(1.1, 1.1, 0.825, 2.2, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 2, 3, new Matrix(2, 1.5, 1.5, 3, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), double.NaN, 3, new Matrix(double.NaN, 1.5, double.NaN, 3, double.NaN, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 2, double.NaN, new Matrix(2, double.NaN, 1.5, double.NaN, 0, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+
+        // Translated.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -2, -3, new Matrix(-2, 0, 0, -3, -4, -9) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -2, 3, new Matrix(-2, 0, 0, 3, -4, 9) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 2, -3, new Matrix(2, 0, 0, -3, 4, -9) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -1, -2, new Matrix(-1, 0, 0, -2, -2, -6) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -1, 0, new Matrix(-1, 0, 0, 0, -2, 0) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, -2, new Matrix(0, 0, 0, -2, 0, -6) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1, 1, new Matrix(1, 0, 0, 1, 2, 3) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1, 0, new Matrix(1, 0, 0, 0, 2, 0) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, 2, new Matrix(0, 0, 0, 2, 0, 6) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1, 2, new Matrix(1, 0, 0, 2, 2, 6) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1.1, 2.2, new Matrix(1.1, 0, 0, 2.2, 2.2, 6.6) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 2, 3, new Matrix(2, 0, 0, 3, 4, 9) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), double.NaN, 3, new Matrix(double.NaN, 0, 0, 3, double.NaN, 9) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 2, double.NaN, new Matrix(2, 0, 0, double.NaN, 4, double.NaN) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), double.NaN, double.NaN, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+
+        // Translated and scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -2, -3, new Matrix(-4, 0, 0, -9, -2, -6) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -2, 3, new Matrix(-4, 0, 0, 9, -2, 6) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 2, -3, new Matrix(4, 0, 0, -9, 2, -6) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -1, -2, new Matrix(-2, 0, 0, -6, -1, -4) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -1, 0, new Matrix(-2, 0, 0, 0, -1, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, -2, new Matrix(0, 0, 0, -6, 0, -4) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1, 1, new Matrix(2, 0, 0, 3, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1, 0, new Matrix(2, 0, 0, 0, 1, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, 2, new Matrix(0, 0, 0, 6, 0, 4) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1, 2, new Matrix(2, 0, 0, 6, 1, 4) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1.1, 2.2, new Matrix(2.2, 0, 0, 6.6, 1.1, 4.4) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 2, 3, new Matrix(4, 0, 0, 9, 2, 6) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), double.NaN, 3, new Matrix(double.NaN, 0, 0, 9, double.NaN, 6) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 2, double.NaN, new Matrix(4, 0, 0, double.NaN, 2, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), double.NaN, double.NaN, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+
+        // Translated and skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -2, -3, new Matrix(-2, -1.5, -1.5, -3, -4, -9) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -2, 3, new Matrix(-2, 1.5, -1.5, 3, -4, 9) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 2, -3, new Matrix(2, -1.5, 1.5, -3, 4, -9) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -1, -2, new Matrix(-1, -1, -0.75, -2, -2, -6) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -1, 0, new Matrix(-1, 0, -0.75, 0, -2, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, -2, new Matrix(0, -1, 0, -2, 0, -6) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1, 1, new Matrix(1, 0.5, 0.75, 1, 2, 3) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1, 0, new Matrix(1, 0, 0.75, 0, 2, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, 2, new Matrix(0, 1, 0, 2, 0, 6) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1, 2, new Matrix(1, 1, 0.75, 2, 2, 6) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1.1, 2.2, new Matrix(1.1, 1.1, 0.825, 2.2, 2.2, 6.6) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 2, 3, new Matrix(2, 1.5, 1.5, 3, 4, 9) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), double.NaN, 3, new Matrix(double.NaN, 1.5, double.NaN, 3, double.NaN, 9) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 2, double.NaN, new Matrix(2, double.NaN, 1.5, double.NaN, 4, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+
+        // Skewed and scaled.
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -2, -3, new Matrix(-4, -1.5, -1.5, -9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -2, 3, new Matrix(-4, 1.5, -1.5, 9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 2, -3, new Matrix(4, -1.5, 1.5, -9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -1, -2, new Matrix(-2, -1, -0.75, -6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -1, 0, new Matrix(-2, 0, -0.75, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, -2, new Matrix(0, -1, 0, -6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1, 1, new Matrix(2, 0.5, 0.75, 3, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1, 0, new Matrix(2, 0, 0.75, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, 2, new Matrix(0, 1, 0, 6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1, 2, new Matrix(2, 1, 0.75, 6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1.1, 2.2, new Matrix(2.2, 1.1, 0.825, 6.6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 2, 3, new Matrix(4, 1.5, 1.5, 9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), double.NaN, 3, new Matrix(double.NaN, 1.5, double.NaN, 9, double.NaN, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 2, double.NaN, new Matrix(4, double.NaN, 1.5, double.NaN, 0, double.NaN) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+
+        // Complex.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -2, -3, new Matrix(-4, -9, -8, -15, -12, -21) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -2, 3, new Matrix(-4, 9, -8, 15, -12, 21) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 2, -3, new Matrix(4, -9, 8, -15, 12, -21) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -1, -2, new Matrix(-2, -6, -4, -10, -6, -14) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -1, 0, new Matrix(-2, 0, -4, 0, -6, 0) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, -2, new Matrix(0, -6, 0, -10, 0, -14) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1, 1, new Matrix(2, 3, 4, 5, 6, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1, 0, new Matrix(2, 0, 4, 0, 6, 0) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, 2, new Matrix(0, 6, 0, 10, 0, 14) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1, 2, new Matrix(2, 6, 4, 10, 6, 14) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1.1, 2.2, new Matrix(2.2, 6.6, 4.4, 11, 6.6, 15.4) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 2, 3, new Matrix(4, 9, 8, 15, 12, 21) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), double.NaN, 3, new Matrix(double.NaN, 9, double.NaN, 15, double.NaN, 21) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 2, double.NaN, new Matrix(4, double.NaN, 8, double.NaN, 12, double.NaN) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+
+        // No inverse.
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -2, -3, new Matrix(-0, 0, 0, -0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -2, 3, new Matrix(-0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 2, -3, new Matrix(0, 0, 0, -0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -1, -2, new Matrix(-0, 0, 0, -0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -1, 0, new Matrix(-0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, -2, new Matrix(0, 0, 0, -0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1, 1, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, 2, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1, 2, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1.1, 2.2, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 2, 3, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), double.NaN, 3, new Matrix(double.NaN, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 2, double.NaN, new Matrix(0, 0, 0, double.NaN, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), double.NaN, double.NaN, new Matrix(double.NaN, 0, 0, double.NaN, 0, 0) };
+    }
+
+    [Theory]
+    [MemberData(nameof(ScalePrepend_TestData))]
+    public void ScalePrepend_Invoke_Success(Matrix matrix, double scaleX, double scaleY, Matrix expected)
+    {
+        matrix.Scale(scaleX, scaleY);
+        Helpers.AssertEqualRounded(expected, matrix);
+        Assert.Equal(expected.IsIdentity, matrix.IsIdentity);
+        Assert.Equal(expected.HasInverse, matrix.HasInverse);
+        Assert.Equal(expected.Determinant, matrix.Determinant, precision: 5);
+    }
+
+    public static IEnumerable<object[]> ScaleAt_TestData()
+    {
+        // Identity
+        foreach (Matrix matrix in IdentityMatrices())
+        {
+            yield return new object[] { matrix, -2, -3, 0, 0, new Matrix(-2, 0, 0, -3, 0, 0) };
+            yield return new object[] { matrix, -2, 3, 0, 0, new Matrix(-2, 0, 0, 3, 0, 0) };
+            yield return new object[] { matrix, 2, -3, 0, 0, new Matrix(2, 0, 0, -3, 0, 0) };
+            yield return new object[] { matrix, -1, -2, 0, 0, new Matrix(-1, 0, 0, -2, 0, 0) };
+            yield return new object[] { matrix, -1, 0, 0, 0, new Matrix(-1, 0, 0, 0, 0, 0) };
+            yield return new object[] { matrix, 0, -2, 0, 0, new Matrix(0, 0, 0, -2, 0, 0) };
+            yield return new object[] { matrix, 0, 0, 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+            yield return new object[] { matrix, 1, 1, 0, 0, new Matrix(1, 0, 0, 1, 0, 0) };
+            yield return new object[] { matrix, 1, 0, 0, 0, new Matrix(1, 0, 0, 0, 0, 0) };
+            yield return new object[] { matrix, 0, 2, 0, 0, new Matrix(0, 0, 0, 2, 0, 0) };
+            yield return new object[] { matrix, 1, 2, 0, 0, new Matrix(1, 0, 0, 2, 0, 0) };
+            yield return new object[] { matrix, 1.1, 2.2, 0, 0, new Matrix(1.1, 0, 0, 2.2, 0, 0) };
+            yield return new object[] { matrix, 2, 3, 0, 0, new Matrix(2, 0, 0, 3, 0, 0) };
+            yield return new object[] { matrix, double.NaN, 3, 0, 0, new Matrix(double.NaN, 0, 0, 3, double.NaN, 0) };
+            yield return new object[] { matrix, 2, double.NaN, 0, 0, new Matrix(2, 0, 0, double.NaN, 0, double.NaN) };
+            yield return new object[] { matrix, double.NaN, double.NaN, 0, 0, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+            yield return new object[] { matrix, -2, -3, 1, 2, new Matrix(-2, 0, 0, -3, 3, 8) };
+            yield return new object[] { matrix, -2, 3, 1, 2, new Matrix(-2, 0, 0, 3, 3, -4) };
+            yield return new object[] { matrix, 2, -3, 1, 2, new Matrix(2, 0, 0, -3, -1, 8) };
+            yield return new object[] { matrix, -1, -2, 1, 2, new Matrix(-1, 0, 0, -2, 2, 6) };
+            yield return new object[] { matrix, -1, 0, 1, 2, new Matrix(-1, 0, 0, 0, 2, 2) };
+            yield return new object[] { matrix, 0, -2, 1, 2, new Matrix(0, 0, 0, -2, 1, 6) };
+            yield return new object[] { matrix, 0, 0, 1, 2, new Matrix(0, 0, 0, 0, 1, 2) };
+            yield return new object[] { matrix, 1, 1, 1, 2, new Matrix(1, 0, 0, 1, 0, 0) };
+            yield return new object[] { matrix, 1, 0, 1, 2, new Matrix(1, 0, 0, 0, 0, 2) };
+            yield return new object[] { matrix, 0, 2, 1, 2, new Matrix(0, 0, 0, 2, 1, -2) };
+            yield return new object[] { matrix, 1, 2, 1, 2, new Matrix(1, 0, 0, 2, 0, -2) };
+            yield return new object[] { matrix, 1.1, 2.2, 1, 2, new Matrix(1.1, 0, 0, 2.2, -0.1, -2.4) };
+            yield return new object[] { matrix, 2, 3, 1, 2, new Matrix(2, 0, 0, 3, -1, -4) };
+            yield return new object[] { matrix, double.NaN, 3, 1, 2, new Matrix(double.NaN, 0, 0, 3, double.NaN, -4) };
+            yield return new object[] { matrix, 2, double.NaN, 1, 2, new Matrix(2, 0, 0, double.NaN, -1, double.NaN) };
+            yield return new object[] { matrix, double.NaN, double.NaN, 1, 2, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+            yield return new object[] { matrix, 2, 3, double.NaN, 2, new Matrix(2, 0, 0, 3, double.NaN, -4) };
+            yield return new object[] { matrix, 2, 3, 1, double.NaN, new Matrix(2, 0, 0, 3, -1, double.NaN) };
+            yield return new object[] { matrix, 2, 3, double.NaN, double.NaN, new Matrix(2, 0, 0, 3, double.NaN, double.NaN) };
+            yield return new object[] { matrix, double.NaN, double.NaN, double.NaN, double.NaN, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+        }
+
+        // Scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -2, -3, 0, 0, new Matrix(-4, 0, 0, -9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -2, 3, 0, 0, new Matrix(-4, 0, 0, 9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 2, -3, 0, 0, new Matrix(4, 0, 0, -9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -1, -2, 0, 0, new Matrix(-2, 0, 0, -6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -1, 0, 0, 0, new Matrix(-2, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, -2, 0, 0, new Matrix(0, 0, 0, -6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, 0, 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1, 1, 0, 0, new Matrix(2, 0, 0, 3, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1, 0, 0, 0, new Matrix(2, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, 2, 0, 0, new Matrix(0, 0, 0, 6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1, 2, 0, 0, new Matrix(2, 0, 0, 6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1.1, 2.2, 0, 0, new Matrix(2.2, 0, 0, 6.6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 2, 3, 0, 0, new Matrix(4, 0, 0, 9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), double.NaN, 3, 0, 0, new Matrix(double.NaN, 0, 0, 9, double.NaN, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 2, double.NaN, 0, 0, new Matrix(4, 0, 0, double.NaN, 0, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), double.NaN, double.NaN, 0, 0, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -2, -3, 1, 2, new Matrix(-4, 0, 0, -9, 3, 8) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -2, 3, 1, 2, new Matrix(-4, 0, 0, 9, 3, -4) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 2, -3, 1, 2, new Matrix(4, 0, 0, -9, -1, 8) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -1, -2, 1, 2, new Matrix(-2, 0, 0, -6, 2, 6) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -1, 0, 1, 2, new Matrix(-2, 0, 0, 0, 2, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, -2, 1, 2, new Matrix(0, 0, 0, -6, 1, 6) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, 0, 1, 2, new Matrix(0, 0, 0, 0, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1, 1, 1, 2, new Matrix(2, 0, 0, 3, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1, 0, 1, 2, new Matrix(2, 0, 0, 0, 0, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, 2, 1, 2, new Matrix(0, 0, 0, 6, 1, -2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1, 2, 1, 2, new Matrix(2, 0, 0, 6, 0, -2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1.1, 2.2, 1, 2, new Matrix(2.2, 0, 0, 6.6, -0.1, -2.4) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 2, 3, 1, 2, new Matrix(4, 0, 0, 9, -1, -4) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), double.NaN, 3, 1, 2, new Matrix(double.NaN, 0, 0, 9, double.NaN, -4) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 2, double.NaN, 1, 2, new Matrix(4, 0, 0, double.NaN, -1, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), double.NaN, double.NaN, 1, 2, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 2, 3, double.NaN, 2, new Matrix(4, 0, 0, 9, double.NaN, -4) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 2, 3, 1, double.NaN, new Matrix(4, 0, 0, 9, -1, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 2, 3, double.NaN, double.NaN, new Matrix(4, 0, 0, 9, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), double.NaN, double.NaN, double.NaN, double.NaN, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+
+        // Skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -2, -3, 0, 0, new Matrix(-2, -1.5, -1.5, -3, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -2, 3, 0, 0, new Matrix(-2, 1.5, -1.5, 3, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 2, -3, 0, 0, new Matrix(2, -1.5, 1.5, -3, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -1, -2, 0, 0, new Matrix(-1, -1, -0.75, -2, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -1, 0, 0, 0, new Matrix(-1, 0, -0.75, 0, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, -2, 0, 0, new Matrix(0, -1, 0, -2, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, 0, 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1, 1, 0, 0, new Matrix(1, 0.5, 0.75, 1, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1, 0, 0, 0, new Matrix(1, 0, 0.75, 0, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, 2, 0, 0, new Matrix(0, 1, 0, 2, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1, 2, 0, 0, new Matrix(1, 1, 0.75, 2, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1.1, 2.2, 0, 0, new Matrix(1.1, 1.1, 0.825, 2.2, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 2, 3, 0, 0, new Matrix(2, 1.5, 1.5, 3, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), double.NaN, 3, 0, 0, new Matrix(double.NaN, 1.5, double.NaN, 3, double.NaN, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 2, double.NaN, 0, 0, new Matrix(2, double.NaN, 1.5, double.NaN, 0, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), double.NaN, double.NaN, 0, 0, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -2, -3, 1, 2, new Matrix(-2, -1.5, -1.5, -3, 3, 8) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -2, 3, 1, 2, new Matrix(-2, 1.5, -1.5, 3, 3, -4) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 2, -3, 1, 2, new Matrix(2, -1.5, 1.5, -3, -1, 8) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -1, -2, 1, 2, new Matrix(-1, -1, -0.75, -2, 2, 6) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -1, 0, 1, 2, new Matrix(-1, 0, -0.75, 0, 2, 2) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, -2, 1, 2, new Matrix(0, -1, 0, -2, 1, 6) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, 0, 1, 2, new Matrix(0, 0, 0, 0, 1, 2) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1, 1, 1, 2, new Matrix(1, 0.5, 0.75, 1, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1, 0, 1, 2, new Matrix(1, 0, 0.75, 0, 0, 2) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, 2, 1, 2, new Matrix(0, 1, 0, 2, 1, -2) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1, 2, 1, 2, new Matrix(1, 1, 0.75, 2, 0, -2) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1.1, 2.2, 1, 2, new Matrix(1.1, 1.1, 0.825, 2.2, -0.1, -2.4) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 2, 3, 1, 2, new Matrix(2, 1.5, 1.5, 3, -1, -4) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), double.NaN, 3, 1, 2, new Matrix(double.NaN, 1.5, double.NaN, 3, double.NaN, -4) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 2, double.NaN, 1, 2, new Matrix(2, double.NaN, 1.5, double.NaN, -1, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), double.NaN, double.NaN, 1, 2, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 2, 3, double.NaN, 2, new Matrix(2, 1.5, 1.5, 3, double.NaN, -4) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 2, 3, 1, double.NaN, new Matrix(2, 1.5, 1.5, 3, -1, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 2, 3, double.NaN, double.NaN, new Matrix(2, 1.5, 1.5, 3, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), double.NaN, double.NaN, double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+
+        // Translated.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -2, -3, 0, 0, new Matrix(-2, 0, 0, -3, -4, -9) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -2, 3, 0, 0, new Matrix(-2, 0, 0, 3, -4, 9) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 2, -3, 0, 0, new Matrix(2, 0, 0, -3, 4, -9) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -1, -2, 0, 0, new Matrix(-1, 0, 0, -2, -2, -6) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -1, 0, 0, 0, new Matrix(-1, 0, 0, 0, -2, 0) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, -2, 0, 0, new Matrix(0, 0, 0, -2, 0, -6) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, 0, 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1, 1, 0, 0, new Matrix(1, 0, 0, 1, 2, 3) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1, 0, 0, 0, new Matrix(1, 0, 0, 0, 2, 0) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, 2, 0, 0, new Matrix(0, 0, 0, 2, 0, 6) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1, 2, 0, 0, new Matrix(1, 0, 0, 2, 2, 6) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1.1, 2.2, 0, 0, new Matrix(1.1, 0, 0, 2.2, 2.2, 6.6) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 2, 3, 0, 0, new Matrix(2, 0, 0, 3, 4, 9) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), double.NaN, 3, 0, 0, new Matrix(double.NaN, 0, 0, 3, double.NaN, 9) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 2, double.NaN, 0, 0, new Matrix(2, 0, 0, double.NaN, 4, double.NaN) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), double.NaN, double.NaN, 0, 0, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -2, -3, 1, 2, new Matrix(-2, 0, 0, -3, -1, -1) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -2, 3, 1, 2, new Matrix(-2, 0, 0, 3, -1, 5) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 2, -3, 1, 2, new Matrix(2, 0, 0, -3, 3, -1) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -1, -2, 1, 2, new Matrix(-1, 0, 0, -2, 0, 0) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -1, 0, 1, 2, new Matrix(-1, 0, 0, 0, 0, 2) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, -2, 1, 2, new Matrix(0, 0, 0, -2, 1, 0) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, 0, 1, 2, new Matrix(0, 0, 0, 0, 1, 2) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1, 1, 1, 2, new Matrix(1, 0, 0, 1, 2, 3) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1, 0, 1, 2, new Matrix(1, 0, 0, 0, 2, 2) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, 2, 1, 2, new Matrix(0, 0, 0, 2, 1, 4) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1, 2, 1, 2, new Matrix(1, 0, 0, 2, 2, 4) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1.1, 2.2, 1, 2, new Matrix(1.1, 0, 0, 2.2, 2.1, 4.2) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 2, 3, 1, 2, new Matrix(2, 0, 0, 3, 3, 5) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), double.NaN, 3, 1, 2, new Matrix(double.NaN, 0, 0, 3, double.NaN, 5) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 2, double.NaN, 1, 2, new Matrix(2, 0, 0, double.NaN, 3, double.NaN) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), double.NaN, double.NaN, 1, 2, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 2, 3, double.NaN, 2, new Matrix(2, 0, 0, 3, double.NaN, 5) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 2, 3, 1, double.NaN, new Matrix(2, 0, 0, 3, 3, double.NaN) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 2, 3, double.NaN, double.NaN, new Matrix(2, 0, 0, 3, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), double.NaN, double.NaN, double.NaN, double.NaN, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+
+        // Translated and scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -2, -3, 0, 0, new Matrix(-4, 0, 0, -9, -2, -6) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -2, 3, 0, 0, new Matrix(-4, 0, 0, 9, -2, 6) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 2, -3, 0, 0, new Matrix(4, 0, 0, -9, 2, -6) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -1, -2, 0, 0, new Matrix(-2, 0, 0, -6, -1, -4) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -1, 0, 0, 0, new Matrix(-2, 0, 0, 0, -1, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, -2, 0, 0, new Matrix(0, 0, 0, -6, 0, -4) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, 0, 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1, 1, 0, 0, new Matrix(2, 0, 0, 3, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1, 0, 0, 0, new Matrix(2, 0, 0, 0, 1, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, 2, 0, 0, new Matrix(0, 0, 0, 6, 0, 4) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1, 2, 0, 0, new Matrix(2, 0, 0, 6, 1, 4) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1.1, 2.2, 0, 0, new Matrix(2.2, 0, 0, 6.6, 1.1, 4.4) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 2, 3, 0, 0, new Matrix(4, 0, 0, 9, 2, 6) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), double.NaN, 3, 0, 0, new Matrix(double.NaN, 0, 0, 9, double.NaN, 6) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 2, double.NaN, 0, 0, new Matrix(4, 0, 0, double.NaN, 2, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), double.NaN, double.NaN, 0, 0, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -2, -3, 1, 2, new Matrix(-4, 0, 0, -9, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -2, 3, 1, 2, new Matrix(-4, 0, 0, 9, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 2, -3, 1, 2, new Matrix(4, 0, 0, -9, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -1, -2, 1, 2, new Matrix(-2, 0, 0, -6, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -1, 0, 1, 2, new Matrix(-2, 0, 0, 0, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, -2, 1, 2, new Matrix(0, 0, 0, -6, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, 0, 1, 2, new Matrix(0, 0, 0, 0, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1, 1, 1, 2, new Matrix(2, 0, 0, 3, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1, 0, 1, 2, new Matrix(2, 0, 0, 0, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, 2, 1, 2, new Matrix(0, 0, 0, 6, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1, 2, 1, 2, new Matrix(2, 0, 0, 6, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1.1, 2.2, 1, 2, new Matrix(2.2, 0, 0, 6.6, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 2, 3, 1, 2, new Matrix(4, 0, 0, 9, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), double.NaN, 3, 1, 2, new Matrix(double.NaN, 0, 0, 9, double.NaN, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 2, double.NaN, 1, 2, new Matrix(4, 0, 0, double.NaN, 1, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), double.NaN, double.NaN, 1, 2, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 2, 3, double.NaN, 2, new Matrix(4, 0, 0, 9, double.NaN, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 2, 3, 1, double.NaN, new Matrix(4, 0, 0, 9, 1, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 2, 3, double.NaN, double.NaN, new Matrix(4, 0, 0, 9, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), double.NaN, double.NaN, double.NaN, double.NaN, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+
+        // Translated and skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -2, -3, 0, 0, new Matrix(-2, -1.5, -1.5, -3, -4, -9) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -2, 3, 0, 0, new Matrix(-2, 1.5, -1.5, 3, -4, 9) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 2, -3, 0, 0, new Matrix(2, -1.5, 1.5, -3, 4, -9) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -1, -2, 0, 0, new Matrix(-1, -1, -0.75, -2, -2, -6) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -1, 0, 0, 0, new Matrix(-1, 0, -0.75, 0, -2, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, -2, 0, 0, new Matrix(0, -1, 0, -2, 0, -6) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, 0, 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1, 1, 0, 0, new Matrix(1, 0.5, 0.75, 1, 2, 3) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1, 0, 0, 0, new Matrix(1, 0, 0.75, 0, 2, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, 2, 0, 0, new Matrix(0, 1, 0, 2, 0, 6) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1, 2, 0, 0, new Matrix(1, 1, 0.75, 2, 2, 6) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1.1, 2.2, 0, 0, new Matrix(1.1, 1.1, 0.825, 2.2, 2.2, 6.6) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 2, 3, 0, 0, new Matrix(2, 1.5, 1.5, 3, 4, 9) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), double.NaN, 3, 0, 0, new Matrix(double.NaN, 1.5, double.NaN, 3, double.NaN, 9) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 2, double.NaN, 0, 0, new Matrix(2, double.NaN, 1.5, double.NaN, 4, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), double.NaN, double.NaN, 0, 0, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -2, -3, 1, 2, new Matrix(-2, -1.5, -1.5, -3, -1, -1) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -2, 3, 1, 2, new Matrix(-2, 1.5, -1.5, 3, -1, 5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 2, -3, 1, 2, new Matrix(2, -1.5, 1.5, -3, 3, -1) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -1, -2, 1, 2, new Matrix(-1, -1, -0.75, -2, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -1, 0, 1, 2, new Matrix(-1, 0, -0.75, 0, 0, 2) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, -2, 1, 2, new Matrix(0, -1, 0, -2, 1, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, 0, 1, 2, new Matrix(0, 0, 0, 0, 1, 2) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1, 1, 1, 2, new Matrix(1, 0.5, 0.75, 1, 2, 3) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1, 0, 1, 2, new Matrix(1, 0, 0.75, 0, 2, 2) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, 2, 1, 2, new Matrix(0, 1, 0, 2, 1, 4) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1, 2, 1, 2, new Matrix(1, 1, 0.75, 2, 2, 4) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1.1, 2.2, 1, 2, new Matrix(1.1, 1.1, 0.825, 2.2, 2.1, 4.2) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 2, 3, 1, 2, new Matrix(2, 1.5, 1.5, 3, 3, 5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), double.NaN, 3, 1, 2, new Matrix(double.NaN, 1.5, double.NaN, 3, double.NaN, 5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 2, double.NaN, 1, 2, new Matrix(2, double.NaN, 1.5, double.NaN, 3, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), double.NaN, double.NaN, 1, 2, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 2, 3, double.NaN, 2, new Matrix(2, 1.5, 1.5, 3, double.NaN, 5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 2, 3, 1, double.NaN, new Matrix(2, 1.5, 1.5, 3, 3, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 2, 3, double.NaN, double.NaN, new Matrix(2, 1.5, 1.5, 3, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), double.NaN, double.NaN, double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+
+        // Skewed and scaled.
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -2, -3, 0, 0, new Matrix(-4, -1.5, -1.5, -9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -2, 3, 0, 0, new Matrix(-4, 1.5, -1.5, 9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 2, -3, 0, 0, new Matrix(4, -1.5, 1.5, -9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -1, -2, 0, 0, new Matrix(-2, -1, -0.75, -6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -1, 0, 0, 0, new Matrix(-2, 0, -0.75, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, -2, 0, 0, new Matrix(0, -1, 0, -6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, 0, 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1, 1, 0, 0, new Matrix(2, 0.5, 0.75, 3, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1, 0, 0, 0, new Matrix(2, 0, 0.75, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, 2, 0, 0, new Matrix(0, 1, 0, 6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1, 2, 0, 0, new Matrix(2, 1, 0.75, 6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1.1, 2.2, 0, 0, new Matrix(2.2, 1.1, 0.825, 6.6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 2, 3, 0, 0, new Matrix(4, 1.5, 1.5, 9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), double.NaN, 3, 0, 0, new Matrix(double.NaN, 1.5, double.NaN, 9, double.NaN, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 2, double.NaN, 0, 0, new Matrix(4, double.NaN, 1.5, double.NaN, 0, double.NaN) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), double.NaN, double.NaN, 0, 0, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -2, -3, 1, 2, new Matrix(-4, -1.5, -1.5, -9, 3, 8) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -2, 3, 1, 2, new Matrix(-4, 1.5, -1.5, 9, 3, -4) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 2, -3, 1, 2, new Matrix(4, -1.5, 1.5, -9, -1, 8) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -1, -2, 1, 2, new Matrix(-2, -1, -0.75, -6, 2, 6) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -1, 0, 1, 2, new Matrix(-2, 0, -0.75, 0, 2, 2) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, -2, 1, 2, new Matrix(0, -1, 0, -6, 1, 6) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, 0, 1, 2, new Matrix(0, 0, 0, 0, 1, 2) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1, 1, 1, 2, new Matrix(2, 0.5, 0.75, 3, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1, 0, 1, 2, new Matrix(2, 0, 0.75, 0, 0, 2) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, 2, 1, 2, new Matrix(0, 1, 0, 6, 1, -2) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1, 2, 1, 2, new Matrix(2, 1, 0.75, 6, 0, -2) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1.1, 2.2, 1, 2, new Matrix(2.2, 1.1, 0.825, 6.6, -0.1, -2.4) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 2, 3, 1, 2, new Matrix(4, 1.5, 1.5, 9, -1, -4) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), double.NaN, 3, 1, 2, new Matrix(double.NaN, 1.5, double.NaN, 9, double.NaN, -4) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 2, double.NaN, 1, 2, new Matrix(4, double.NaN, 1.5, double.NaN, -1, double.NaN) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), double.NaN, double.NaN, 1, 2, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 2, 3, double.NaN, 2, new Matrix(4, 1.5, 1.5, 9, double.NaN, -4) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 2, 3, 1, double.NaN, new Matrix(4, 1.5, 1.5, 9, -1, double.NaN) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 2, 3, double.NaN, double.NaN, new Matrix(4, 1.5, 1.5, 9, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), double.NaN, double.NaN, double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+
+        // Complex.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -2, -3, 0, 0, new Matrix(-4, -9, -8, -15, -12, -21) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -2, 3, 0, 0, new Matrix(-4, 9, -8, 15, -12, 21) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 2, -3, 0, 0, new Matrix(4, -9, 8, -15, 12, -21) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -1, -2, 0, 0, new Matrix(-2, -6, -4, -10, -6, -14) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -1, 0, 0, 0, new Matrix(-2, 0, -4, 0, -6, 0) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, -2, 0, 0, new Matrix(0, -6, 0, -10, 0, -14) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, 0, 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1, 1, 0, 0, new Matrix(2, 3, 4, 5, 6, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1, 0, 0, 0, new Matrix(2, 0, 4, 0, 6, 0) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, 2, 0, 0, new Matrix(0, 6, 0, 10, 0, 14) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1, 2, 0, 0, new Matrix(2, 6, 4, 10, 6, 14) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1.1, 2.2, 0, 0, new Matrix(2.2, 6.6, 4.4, 11, 6.6, 15.4) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 2, 3, 0, 0, new Matrix(4, 9, 8, 15, 12, 21) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), double.NaN, 3, 0, 0, new Matrix(double.NaN, 9, double.NaN, 15, double.NaN, 21) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 2, double.NaN, 0, 0, new Matrix(4, double.NaN, 8, double.NaN, 12, double.NaN) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), double.NaN, double.NaN, 0, 0, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -2, -3, 1, 2, new Matrix(-4, -9, -8, -15, -9, -13) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -2, 3, 1, 2, new Matrix(-4, 9, -8, 15, -9, 17) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 2, -3, 1, 2, new Matrix(4, -9, 8, -15, 11, -13) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -1, -2, 1, 2, new Matrix(-2, -6, -4, -10, -4, -8) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -1, 0, 1, 2, new Matrix(-2, 0, -4, 0, -4, 2) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, -2, 1, 2, new Matrix(0, -6, 0, -10, 1, -8) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, 0, 1, 2, new Matrix(0, 0, 0, 0, 1, 2) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1, 1, 1, 2, new Matrix(2, 3, 4, 5, 6, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1, 0, 1, 2, new Matrix(2, 0, 4, 0, 6, 2) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, 2, 1, 2, new Matrix(0, 6, 0, 10, 1, 12) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1, 2, 1, 2, new Matrix(2, 6, 4, 10, 6, 12) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1.1, 2.2, 1, 2, new Matrix(2.2, 6.6, 4.4, 11, 6.5, 13) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 2, 3, 1, 2, new Matrix(4, 9, 8, 15, 11, 17) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), double.NaN, 3, 1, 2, new Matrix(double.NaN, 9, double.NaN, 15, double.NaN, 17) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 2, double.NaN, 1, 2, new Matrix(4, double.NaN, 8, double.NaN, 11, double.NaN) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), double.NaN, double.NaN, 1, 2, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 2, 3, double.NaN, 2, new Matrix(4, 9, 8, 15, double.NaN, 17) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 2, 3, 1, double.NaN, new Matrix(4, 9, 8, 15, 11, double.NaN) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 2, 3, double.NaN, double.NaN, new Matrix(4, 9, 8, 15, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), double.NaN, double.NaN, double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+
+        // No inverse.
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -2, -3, 0, 0, new Matrix(-0, 0, 0, -0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -2, 3, 0, 0, new Matrix(-0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 2, -3, 0, 0, new Matrix(0, 0, 0, -0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -1, -2, 0, 0, new Matrix(-0, 0, 0, -0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -1, 0, 0, 0, new Matrix(-0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, -2, 0, 0, new Matrix(0, 0, 0, -0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, 0, 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1, 1, 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1, 0, 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, 2, 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1, 2, 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1.1, 2.2, 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 2, 3, 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), double.NaN, 3, 0, 0, new Matrix(double.NaN, 0, 0, 0, double.NaN, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 2, double.NaN, 0, 0, new Matrix(0, 0, 0, double.NaN, 0, double.NaN) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), double.NaN, double.NaN, 0, 0, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -2, -3, 1, 2, new Matrix(-0, 0, 0, -0, 3, 8) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -2, 3, 1, 2, new Matrix(-0, 0, 0, 0, 3, -4) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 2, -3, 1, 2, new Matrix(0, 0, 0, -0, -1, 8) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -1, -2, 1, 2, new Matrix(-0, 0, 0, -0, 2, 6) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -1, 0, 1, 2, new Matrix(-0, 0, 0, 0, 2, 2) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, -2, 1, 2, new Matrix(0, 0, 0, -0, 1, 6) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, 0, 1, 2, new Matrix(0, 0, 0, 0, 1, 2) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1, 1, 1, 2, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1, 0, 1, 2, new Matrix(0, 0, 0, 0, 0, 2) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, 2, 1, 2, new Matrix(0, 0, 0, 0, 1, -2) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1, 2, 1, 2, new Matrix(0, 0, 0, 0, 0, -2) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1.1, 2.2, 1, 2, new Matrix(0, 0, 0, 0, -0.1, -2.4) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 2, 3, 1, 2, new Matrix(0, 0, 0, 0, -1, -4) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), double.NaN, 3, 1, 2, new Matrix(double.NaN, 0, 0, 0, double.NaN, -4) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 2, double.NaN, 1, 2, new Matrix(0, 0, 0, double.NaN, -1, double.NaN) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), double.NaN, double.NaN, 1, 2, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 2, 3, double.NaN, 2, new Matrix(0, 0, 0, 0, double.NaN, -4) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 2, 3, 1, double.NaN, new Matrix(0, 0, 0, 0, -1, double.NaN) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 2, 3, double.NaN, double.NaN, new Matrix(0, 0, 0, 0, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), double.NaN, double.NaN, double.NaN, double.NaN, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+    }
+
+    [Theory]
+    [MemberData(nameof(ScaleAt_TestData))]
+    public void ScaleAt_Invoke_Success(Matrix matrix, double scaleX, double scaleY, double centerX, double centerY, Matrix expected)
+    {
+        matrix.ScaleAt(scaleX, scaleY, centerX, centerY);
+        Helpers.AssertEqualRounded(expected, matrix);
+        Assert.Equal(expected.IsIdentity, matrix.IsIdentity);
+        Assert.Equal(expected.HasInverse, matrix.HasInverse);
+        Assert.Equal(expected.Determinant, matrix.Determinant, precision: 5);
+    }
+
+    public static IEnumerable<object[]> ScaleAtPrepend_TestData()
+    {
+        // Identity
+        foreach (Matrix matrix in IdentityMatrices())
+        {
+            yield return new object[] { matrix, -2, -3, 0, 0, new Matrix(-2, 0, 0, -3, 0, 0) };
+            yield return new object[] { matrix, -2, 3, 0, 0, new Matrix(-2, 0, 0, 3, 0, 0) };
+            yield return new object[] { matrix, 2, -3, 0, 0, new Matrix(2, 0, 0, -3, 0, 0) };
+            yield return new object[] { matrix, -1, -2, 0, 0, new Matrix(-1, 0, 0, -2, 0, 0) };
+            yield return new object[] { matrix, -1, 0, 0, 0, new Matrix(-1, 0, 0, 0, 0, 0) };
+            yield return new object[] { matrix, 0, -2, 0, 0, new Matrix(0, 0, 0, -2, 0, 0) };
+            yield return new object[] { matrix, 0, 0, 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+            yield return new object[] { matrix, 1, 1, 0, 0, new Matrix(1, 0, 0, 1, 0, 0) };
+            yield return new object[] { matrix, 1, 0, 0, 0, new Matrix(1, 0, 0, 0, 0, 0) };
+            yield return new object[] { matrix, 0, 2, 0, 0, new Matrix(0, 0, 0, 2, 0, 0) };
+            yield return new object[] { matrix, 1, 2, 0, 0, new Matrix(1, 0, 0, 2, 0, 0) };
+            yield return new object[] { matrix, 1.1, 2.2, 0, 0, new Matrix(1.1, 0, 0, 2.2, 0, 0) };
+            yield return new object[] { matrix, 2, 3, 0, 0, new Matrix(2, 0, 0, 3, 0, 0) };
+            yield return new object[] { matrix, double.NaN, 3, 0, 0, new Matrix(double.NaN, 0, 0, 3, double.NaN, 0) };
+            yield return new object[] { matrix, 2, double.NaN, 0, 0, new Matrix(2, 0, 0, double.NaN, 0, double.NaN) };
+            yield return new object[] { matrix, double.NaN, double.NaN, 0, 0, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+            yield return new object[] { matrix, -2, -3, 1, 2, new Matrix(-2, 0, 0, -3, 3, 8) };
+            yield return new object[] { matrix, -2, 3, 1, 2, new Matrix(-2, 0, 0, 3, 3, -4) };
+            yield return new object[] { matrix, 2, -3, 1, 2, new Matrix(2, 0, 0, -3, -1, 8) };
+            yield return new object[] { matrix, -1, -2, 1, 2, new Matrix(-1, 0, 0, -2, 2, 6) };
+            yield return new object[] { matrix, -1, 0, 1, 2, new Matrix(-1, 0, 0, 0, 2, 2) };
+            yield return new object[] { matrix, 0, -2, 1, 2, new Matrix(0, 0, 0, -2, 1, 6) };
+            yield return new object[] { matrix, 0, 0, 1, 2, new Matrix(0, 0, 0, 0, 1, 2) };
+            yield return new object[] { matrix, 1, 1, 1, 2, new Matrix(1, 0, 0, 1, 0, 0) };
+            yield return new object[] { matrix, 1, 0, 1, 2, new Matrix(1, 0, 0, 0, 0, 2) };
+            yield return new object[] { matrix, 0, 2, 1, 2, new Matrix(0, 0, 0, 2, 1, -2) };
+            yield return new object[] { matrix, 1, 2, 1, 2, new Matrix(1, 0, 0, 2, 0, -2) };
+            yield return new object[] { matrix, 1.1, 2.2, 1, 2, new Matrix(1.1, 0, 0, 2.2, -0.1, -2.4) };
+            yield return new object[] { matrix, 2, 3, 1, 2, new Matrix(2, 0, 0, 3, -1, -4) };
+            yield return new object[] { matrix, double.NaN, 3, 1, 2, new Matrix(double.NaN, 0, 0, 3, double.NaN, -4) };
+            yield return new object[] { matrix, 2, double.NaN, 1, 2, new Matrix(2, 0, 0, double.NaN, -1, double.NaN) };
+            yield return new object[] { matrix, double.NaN, double.NaN, 1, 2, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+            yield return new object[] { matrix, 2, 3, double.NaN, 2, new Matrix(2, 0, 0, 3, double.NaN, -4) };
+            yield return new object[] { matrix, 2, 3, 1, double.NaN, new Matrix(2, 0, 0, 3, -1, double.NaN) };
+            yield return new object[] { matrix, 2, 3, double.NaN, double.NaN, new Matrix(2, 0, 0, 3, double.NaN, double.NaN) };
+            yield return new object[] { matrix, double.NaN, double.NaN, double.NaN, double.NaN, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+        }
+
+        // Scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -2, -3, 0, 0, new Matrix(-4, 0, 0, -9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -2, 3, 0, 0, new Matrix(-4, 0, 0, 9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 2, -3, 0, 0, new Matrix(4, 0, 0, -9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -1, -2, 0, 0, new Matrix(-2, 0, 0, -6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -1, 0, 0, 0, new Matrix(-2, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, -2, 0, 0, new Matrix(0, 0, 0, -6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, 0, 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1, 1, 0, 0, new Matrix(2, 0, 0, 3, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1, 0, 0, 0, new Matrix(2, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, 2, 0, 0, new Matrix(0, 0, 0, 6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1, 2, 0, 0, new Matrix(2, 0, 0, 6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1.1, 2.2, 0, 0, new Matrix(2.2, 0, 0, 6.6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 2, 3, 0, 0, new Matrix(4, 0, 0, 9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), double.NaN, 3, 0, 0, new Matrix(double.NaN, 0, 0, 9, double.NaN, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 2, double.NaN, 0, 0, new Matrix(4, 0, 0, double.NaN, 0, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), double.NaN, double.NaN, 0, 0, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -2, -3, 1, 2, new Matrix(-4, 0, 0, -9, 6, 24) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -2, 3, 1, 2, new Matrix(-4, 0, 0, 9, 6, -12) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 2, -3, 1, 2, new Matrix(4, 0, 0, -9, -2, 24) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -1, -2, 1, 2, new Matrix(-2, 0, 0, -6, 4, 18) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -1, 0, 1, 2, new Matrix(-2, 0, 0, 0, 4, 6) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, -2, 1, 2, new Matrix(0, 0, 0, -6, 2, 18) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, 0, 1, 2, new Matrix(0, 0, 0, 0, 2, 6) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1, 1, 1, 2, new Matrix(2, 0, 0, 3, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1, 0, 1, 2, new Matrix(2, 0, 0, 0, 0, 6) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, 2, 1, 2, new Matrix(0, 0, 0, 6, 2, -6) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1, 2, 1, 2, new Matrix(2, 0, 0, 6, 0, -6) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1.1, 2.2, 1, 2, new Matrix(2.2, 0, 0, 6.6, -0.2, -7.2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 2, 3, 1, 2, new Matrix(4, 0, 0, 9, -2, -12) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), double.NaN, 3, 1, 2, new Matrix(double.NaN, 0, 0, 9, double.NaN, -12) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 2, double.NaN, 1, 2, new Matrix(4, 0, 0, double.NaN, -2, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), double.NaN, double.NaN, 1, 2, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 2, 3, double.NaN, 2, new Matrix(4, 0, 0, 9, double.NaN, -12) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 2, 3, 1, double.NaN, new Matrix(4, 0, 0, 9, -2, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 2, 3, double.NaN, double.NaN, new Matrix(4, 0, 0, 9, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), double.NaN, double.NaN, double.NaN, double.NaN, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+
+        // Skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -2, -3, 0, 0, new Matrix(-2, -1, -2.25, -3, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -2, 3, 0, 0, new Matrix(-2, -1, 2.25, 3, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 2, -3, 0, 0, new Matrix(2, 1, -2.25, -3, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -1, -2, 0, 0, new Matrix(-1, -0.5, -1.5, -2, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -1, 0, 0, 0, new Matrix(-1, -0.5, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, -2, 0, 0, new Matrix(0, 0, -1.5, -2, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, 0, 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1, 1, 0, 0, new Matrix(1, 0.5, 0.75, 1, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1, 0, 0, 0, new Matrix(1, 0.5, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, 2, 0, 0, new Matrix(0, 0, 1.5, 2, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1, 2, 0, 0, new Matrix(1, 0.5, 1.5, 2, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1.1, 2.2, 0, 0, new Matrix(1.1, 0.55, 1.65, 2.2, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 2, 3, 0, 0, new Matrix(2, 1, 2.25, 3, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), double.NaN, 3, 0, 0, new Matrix(double.NaN, double.NaN, 2.25, 3, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 2, double.NaN, 0, 0, new Matrix(2, 1, double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), double.NaN, double.NaN, 0, 0, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -2, -3, 1, 2, new Matrix(-2, -1, -2.25, -3, 9, 9.5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -2, 3, 1, 2, new Matrix(-2, -1, 2.25, 3, 0, -2.5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 2, -3, 1, 2, new Matrix(2, 1, -2.25, -3, 5, 7.5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -1, -2, 1, 2, new Matrix(-1, -0.5, -1.5, -2, 6.5, 7) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -1, 0, 1, 2, new Matrix(-1, -0.5, 0, 0, 3.5, 3) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, -2, 1, 2, new Matrix(0, 0, -1.5, -2, 5.5, 6.5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, 0, 1, 2, new Matrix(0, 0, 0, 0, 2.5, 2.5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1, 1, 1, 2, new Matrix(1, 0.5, 0.75, 1, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1, 0, 1, 2, new Matrix(1, 0.5, 0, 0, 1.5, 2) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, 2, 1, 2, new Matrix(0, 0, 1.5, 2, -0.5, -1.5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1, 2, 1, 2, new Matrix(1, 0.5, 1.5, 2, -1.5, -2) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1.1, 2.2, 1, 2, new Matrix(1.1, 0.55, 1.65, 2.2, -1.9, -2.45) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 2, 3, 1, 2, new Matrix(2, 1, 2.25, 3, -4, -4.5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), double.NaN, 3, 1, 2, new Matrix(double.NaN, double.NaN, 2.25, 3, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 2, double.NaN, 1, 2, new Matrix(2, 1, double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), double.NaN, double.NaN, 1, 2, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 2, 3, double.NaN, 2, new Matrix(2, 1, 2.25, 3, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 2, 3, 1, double.NaN, new Matrix(2, 1, 2.25, 3, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 2, 3, double.NaN, double.NaN, new Matrix(2, 1, 2.25, 3, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), double.NaN, double.NaN, double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+
+        // Translated.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -2, -3, 0, 0, new Matrix(-2, 0, 0, -3, 2, 3) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -2, 3, 0, 0, new Matrix(-2, 0, 0, 3, 2, 3) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 2, -3, 0, 0, new Matrix(2, 0, 0, -3, 2, 3) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -1, -2, 0, 0, new Matrix(-1, 0, 0, -2, 2, 3) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -1, 0, 0, 0, new Matrix(-1, 0, 0, 0, 2, 3) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, -2, 0, 0, new Matrix(0, 0, 0, -2, 2, 3) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, 0, 0, 0, new Matrix(0, 0, 0, 0, 2, 3) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1, 1, 0, 0, new Matrix(1, 0, 0, 1, 2, 3) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1, 0, 0, 0, new Matrix(1, 0, 0, 0, 2, 3) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, 2, 0, 0, new Matrix(0, 0, 0, 2, 2, 3) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1, 2, 0, 0, new Matrix(1, 0, 0, 2, 2, 3) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1.1, 2.2, 0, 0, new Matrix(1.1, 0, 0, 2.2, 2, 3) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 2, 3, 0, 0, new Matrix(2, 0, 0, 3, 2, 3) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), double.NaN, 3, 0, 0, new Matrix(double.NaN, 0, 0, 3, double.NaN, 3) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 2, double.NaN, 0, 0, new Matrix(2, 0, 0, double.NaN, 2, double.NaN) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), double.NaN, double.NaN, 0, 0, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -2, -3, 1, 2, new Matrix(-2, 0, 0, -3, 5, 11) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -2, 3, 1, 2, new Matrix(-2, 0, 0, 3, 5, -1) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 2, -3, 1, 2, new Matrix(2, 0, 0, -3, 1, 11) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -1, -2, 1, 2, new Matrix(-1, 0, 0, -2, 4, 9) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -1, 0, 1, 2, new Matrix(-1, 0, 0, 0, 4, 5) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, -2, 1, 2, new Matrix(0, 0, 0, -2, 3, 9) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, 0, 1, 2, new Matrix(0, 0, 0, 0, 3, 5) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1, 1, 1, 2, new Matrix(1, 0, 0, 1, 2, 3) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1, 0, 1, 2, new Matrix(1, 0, 0, 0, 2, 5) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, 2, 1, 2, new Matrix(0, 0, 0, 2, 3, 1) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1, 2, 1, 2, new Matrix(1, 0, 0, 2, 2, 1) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1.1, 2.2, 1, 2, new Matrix(1.1, 0, 0, 2.2, 1.9, 0.6) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 2, 3, 1, 2, new Matrix(2, 0, 0, 3, 1, -1) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), double.NaN, 3, 1, 2, new Matrix(double.NaN, 0, 0, 3, double.NaN, -1) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 2, double.NaN, 1, 2, new Matrix(2, 0, 0, double.NaN, 1, double.NaN) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), double.NaN, double.NaN, 1, 2, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 2, 3, double.NaN, 2, new Matrix(2, 0, 0, 3, double.NaN, -1) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 2, 3, 1, double.NaN, new Matrix(2, 0, 0, 3, 1, double.NaN) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 2, 3, double.NaN, double.NaN, new Matrix(2, 0, 0, 3, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), double.NaN, double.NaN, double.NaN, double.NaN, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+
+        // Translated and scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -2, -3, 0, 0, new Matrix(-4, 0, 0, -9, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -2, 3, 0, 0, new Matrix(-4, 0, 0, 9, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 2, -3, 0, 0, new Matrix(4, 0, 0, -9, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -1, -2, 0, 0, new Matrix(-2, 0, 0, -6, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -1, 0, 0, 0, new Matrix(-2, 0, 0, 0, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, -2, 0, 0, new Matrix(0, 0, 0, -6, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, 0, 0, 0, new Matrix(0, 0, 0, 0, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1, 1, 0, 0, new Matrix(2, 0, 0, 3, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1, 0, 0, 0, new Matrix(2, 0, 0, 0, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, 2, 0, 0, new Matrix(0, 0, 0, 6, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1, 2, 0, 0, new Matrix(2, 0, 0, 6, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1.1, 2.2, 0, 0, new Matrix(2.2, 0, 0, 6.6, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 2, 3, 0, 0, new Matrix(4, 0, 0, 9, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), double.NaN, 3, 0, 0, new Matrix(double.NaN, 0, 0, 9, double.NaN, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 2, double.NaN, 0, 0, new Matrix(4, 0, 0, double.NaN, 1, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), double.NaN, double.NaN, 0, 0, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -2, -3, 1, 2, new Matrix(-4, 0, 0, -9, 7, 26) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -2, 3, 1, 2, new Matrix(-4, 0, 0, 9, 7, -10) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 2, -3, 1, 2, new Matrix(4, 0, 0, -9, -1, 26) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -1, -2, 1, 2, new Matrix(-2, 0, 0, -6, 5, 20) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -1, 0, 1, 2, new Matrix(-2, 0, 0, 0, 5, 8) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, -2, 1, 2, new Matrix(0, 0, 0, -6, 3, 20) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, 0, 1, 2, new Matrix(0, 0, 0, 0, 3, 8) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1, 1, 1, 2, new Matrix(2, 0, 0, 3, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1, 0, 1, 2, new Matrix(2, 0, 0, 0, 1, 8) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, 2, 1, 2, new Matrix(0, 0, 0, 6, 3, -4) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1, 2, 1, 2, new Matrix(2, 0, 0, 6, 1, -4) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1.1, 2.2, 1, 2, new Matrix(2.2, 0, 0, 6.6, 0.8, -5.2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 2, 3, 1, 2, new Matrix(4, 0, 0, 9, -1, -10) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), double.NaN, 3, 1, 2, new Matrix(double.NaN, 0, 0, 9, double.NaN, -10) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 2, double.NaN, 1, 2, new Matrix(4, 0, 0, double.NaN, -1, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), double.NaN, double.NaN, 1, 2, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 2, 3, double.NaN, 2, new Matrix(4, 0, 0, 9, double.NaN, -10) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 2, 3, 1, double.NaN, new Matrix(4, 0, 0, 9, -1, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 2, 3, double.NaN, double.NaN, new Matrix(4, 0, 0, 9, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), double.NaN, double.NaN, double.NaN, double.NaN, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+
+        // Translated and skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -2, -3, 0, 0, new Matrix(-2, -1, -2.25, -3, 2, 3) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -2, 3, 0, 0, new Matrix(-2, -1, 2.25, 3, 2, 3) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 2, -3, 0, 0, new Matrix(2, 1, -2.25, -3, 2, 3) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -1, -2, 0, 0, new Matrix(-1, -0.5, -1.5, -2, 2, 3) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -1, 0, 0, 0, new Matrix(-1, -0.5, 0, 0, 2, 3) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, -2, 0, 0, new Matrix(0, 0, -1.5, -2, 2, 3) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, 0, 0, 0, new Matrix(0, 0, 0, 0, 2, 3) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1, 1, 0, 0, new Matrix(1, 0.5, 0.75, 1, 2, 3) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1, 0, 0, 0, new Matrix(1, 0.5, 0, 0, 2, 3) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, 2, 0, 0, new Matrix(0, 0, 1.5, 2, 2, 3) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1, 2, 0, 0, new Matrix(1, 0.5, 1.5, 2, 2, 3) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1.1, 2.2, 0, 0, new Matrix(1.1, 0.55, 1.65, 2.2, 2, 3) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 2, 3, 0, 0, new Matrix(2, 1, 2.25, 3, 2, 3) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), double.NaN, 3, 0, 0, new Matrix(double.NaN, double.NaN, 2.25, 3, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 2, double.NaN, 0, 0, new Matrix(2, 1, double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), double.NaN, double.NaN, 0, 0, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -2, -3, 1, 2, new Matrix(-2, -1, -2.25, -3, 11, 12.5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -2, 3, 1, 2, new Matrix(-2, -1, 2.25, 3, 2, 0.5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 2, -3, 1, 2, new Matrix(2, 1, -2.25, -3, 7, 10.5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -1, -2, 1, 2, new Matrix(-1, -0.5, -1.5, -2, 8.5, 10) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -1, 0, 1, 2, new Matrix(-1, -0.5, 0, 0, 5.5, 6) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, -2, 1, 2, new Matrix(0, 0, -1.5, -2, 7.5, 9.5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, 0, 1, 2, new Matrix(0, 0, 0, 0, 4.5, 5.5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1, 1, 1, 2, new Matrix(1, 0.5, 0.75, 1, 2, 3) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1, 0, 1, 2, new Matrix(1, 0.5, 0, 0, 3.5, 5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, 2, 1, 2, new Matrix(0, 0, 1.5, 2, 1.5, 1.5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1, 2, 1, 2, new Matrix(1, 0.5, 1.5, 2, 0.5, 1) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1.1, 2.2, 1, 2, new Matrix(1.1, 0.55, 1.65, 2.2, 0.1, 0.55) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 2, 3, 1, 2, new Matrix(2, 1, 2.25, 3, -2, -1.5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), double.NaN, 3, 1, 2, new Matrix(double.NaN, double.NaN, 2.25, 3, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 2, double.NaN, 1, 2, new Matrix(2, 1, double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), double.NaN, double.NaN, 1, 2, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 2, 3, double.NaN, 2, new Matrix(2, 1, 2.25, 3, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 2, 3, 1, double.NaN, new Matrix(2, 1, 2.25, 3, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 2, 3, double.NaN, double.NaN, new Matrix(2, 1, 2.25, 3, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), double.NaN, double.NaN, double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+
+        // Skewed and scaled.
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -2, -3, 0, 0, new Matrix(-4, -1, -2.25, -9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -2, 3, 0, 0, new Matrix(-4, -1, 2.25, 9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 2, -3, 0, 0, new Matrix(4, 1, -2.25, -9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -1, -2, 0, 0, new Matrix(-2, -0.5, -1.5, -6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -1, 0, 0, 0, new Matrix(-2, -0.5, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, -2, 0, 0, new Matrix(0, 0, -1.5, -6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, 0, 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1, 1, 0, 0, new Matrix(2, 0.5, 0.75, 3, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1, 0, 0, 0, new Matrix(2, 0.5, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, 2, 0, 0, new Matrix(0, 0, 1.5, 6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1, 2, 0, 0, new Matrix(2, 0.5, 1.5, 6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1.1, 2.2, 0, 0, new Matrix(2.2, 0.55, 1.65, 6.6, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 2, 3, 0, 0, new Matrix(4, 1, 2.25, 9, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), double.NaN, 3, 0, 0, new Matrix(double.NaN, double.NaN, 2.25, 9, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 2, double.NaN, 0, 0, new Matrix(4, 1, double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), double.NaN, double.NaN, 0, 0, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -2, -3, 1, 2, new Matrix(-4, -1, -2.25, -9, 12, 25.5) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -2, 3, 1, 2, new Matrix(-4, -1, 2.25, 9, 3, -10.5) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 2, -3, 1, 2, new Matrix(4, 1, -2.25, -9, 4, 23.5) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -1, -2, 1, 2, new Matrix(-2, -0.5, -1.5, -6, 8.5, 19) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -1, 0, 1, 2, new Matrix(-2, -0.5, 0, 0, 5.5, 7) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, -2, 1, 2, new Matrix(0, 0, -1.5, -6, 6.5, 18.5) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, 0, 1, 2, new Matrix(0, 0, 0, 0, 3.5, 6.5) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1, 1, 1, 2, new Matrix(2, 0.5, 0.75, 3, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1, 0, 1, 2, new Matrix(2, 0.5, 0, 0, 1.5, 6) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, 2, 1, 2, new Matrix(0, 0, 1.5, 6, 0.5, -5.5) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1, 2, 1, 2, new Matrix(2, 0.5, 1.5, 6, -1.5, -6) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1.1, 2.2, 1, 2, new Matrix(2.2, 0.55, 1.65, 6.6, -2, -7.25) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 2, 3, 1, 2, new Matrix(4, 1, 2.25, 9, -5, -12.5) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), double.NaN, 3, 1, 2, new Matrix(double.NaN, double.NaN, 2.25, 9, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 2, double.NaN, 1, 2, new Matrix(4, 1, double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), double.NaN, double.NaN, 1, 2, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 2, 3, double.NaN, 2, new Matrix(4, 1, 2.25, 9, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 2, 3, 1, double.NaN, new Matrix(4, 1, 2.25, 9, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 2, 3, double.NaN, double.NaN, new Matrix(4, 1, 2.25, 9, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), double.NaN, double.NaN, double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+
+        // Complex.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -2, -3, 0, 0, new Matrix(-4, -6, -12, -15, 6, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -2, 3, 0, 0, new Matrix(-4, -6, 12, 15, 6, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 2, -3, 0, 0, new Matrix(4, 6, -12, -15, 6, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -1, -2, 0, 0, new Matrix(-2, -3, -8, -10, 6, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -1, 0, 0, 0, new Matrix(-2, -3, 0, 0, 6, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, -2, 0, 0, new Matrix(0, 0, -8, -10, 6, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, 0, 0, 0, new Matrix(0, 0, 0, 0, 6, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1, 1, 0, 0, new Matrix(2, 3, 4, 5, 6, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1, 0, 0, 0, new Matrix(2, 3, 0, 0, 6, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, 2, 0, 0, new Matrix(0, 0, 8, 10, 6, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1, 2, 0, 0, new Matrix(2, 3, 8, 10, 6, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1.1, 2.2, 0, 0, new Matrix(2.2, 3.3, 8.8, 11, 6, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 2, 3, 0, 0, new Matrix(4, 6, 12, 15, 6, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), double.NaN, 3, 0, 0, new Matrix(double.NaN, double.NaN, 12, 15, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 2, double.NaN, 0, 0, new Matrix(4, 6, double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), double.NaN, double.NaN, 0, 0, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -2, -3, 1, 2, new Matrix(-4, -6, -12, -15, 44, 56) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -2, 3, 1, 2, new Matrix(-4, -6, 12, 15, -4, -4) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 2, -3, 1, 2, new Matrix(4, 6, -12, -15, 36, 44) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -1, -2, 1, 2, new Matrix(-2, -3, -8, -10, 34, 43) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -1, 0, 1, 2, new Matrix(-2, -3, 0, 0, 18, 23) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, -2, 1, 2, new Matrix(0, 0, -8, -10, 32, 40) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, 0, 1, 2, new Matrix(0, 0, 0, 0, 16, 20) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1, 1, 1, 2, new Matrix(2, 3, 4, 5, 6, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1, 0, 1, 2, new Matrix(2, 3, 0, 0, 14, 17) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, 2, 1, 2, new Matrix(0, 0, 8, 10, 0, 0) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1, 2, 1, 2, new Matrix(2, 3, 8, 10, -2, -3) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1.1, 2.2, 1, 2, new Matrix(2.2, 3.3, 8.8, 11, -3.8, -5.3) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 2, 3, 1, 2, new Matrix(4, 6, 12, 15, -12, -16) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), double.NaN, 3, 1, 2, new Matrix(double.NaN, double.NaN, 12, 15, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 2, double.NaN, 1, 2, new Matrix(4, 6, double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), double.NaN, double.NaN, 1, 2, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 2, 3, double.NaN, 2, new Matrix(4, 6, 12, 15, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 2, 3, 1, double.NaN, new Matrix(4, 6, 12, 15, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 2, 3, double.NaN, double.NaN, new Matrix(4, 6, 12, 15, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), double.NaN, double.NaN, double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN) };
+
+        // No inverse.
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -2, -3, 0, 0, new Matrix(-0, 0, 0, -0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -2, 3, 0, 0, new Matrix(-0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 2, -3, 0, 0, new Matrix(0, 0, 0, -0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -1, -2, 0, 0, new Matrix(-0, 0, 0, -0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -1, 0, 0, 0, new Matrix(-0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, -2, 0, 0, new Matrix(0, 0, 0, -0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, 0, 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1, 1, 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1, 0, 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, 2, 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1, 2, 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1.1, 2.2, 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 2, 3, 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), double.NaN, 3, 0, 0, new Matrix(double.NaN, 0, 0, 0, double.NaN, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 2, double.NaN, 0, 0, new Matrix(0, 0, 0, double.NaN, 0, double.NaN) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), double.NaN, double.NaN, 0, 0, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -2, -3, 1, 2, new Matrix(-0, 0, 0, -0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -2, 3, 1, 2, new Matrix(-0, 0, 0, 0, 0, -0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 2, -3, 1, 2, new Matrix(0, 0, 0, -0, -0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -1, -2, 1, 2, new Matrix(-0, 0, 0, -0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -1, 0, 1, 2, new Matrix(-0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, -2, 1, 2, new Matrix(0, 0, 0, -0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, 0, 1, 2, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1, 1, 1, 2, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1, 0, 1, 2, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, 2, 1, 2, new Matrix(0, 0, 0, 0, 0, -0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1, 2, 1, 2, new Matrix(0, 0, 0, 0, 0, -0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1.1, 2.2, 1, 2, new Matrix(0, 0, 0, 0, -0, -0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 2, 3, 1, 2, new Matrix(0, 0, 0, 0, -0, -0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), double.NaN, 3, 1, 2, new Matrix(double.NaN, 0, 0, 0, double.NaN, -0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 2, double.NaN, 1, 2, new Matrix(0, 0, 0, double.NaN, -0, double.NaN) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), double.NaN, double.NaN, 1, 2, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 2, 3, double.NaN, 2, new Matrix(0, 0, 0, 0, double.NaN, -0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 2, 3, 1, double.NaN, new Matrix(0, 0, 0, 0, -0, double.NaN) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 2, 3, double.NaN, double.NaN, new Matrix(0, 0, 0, 0, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), double.NaN, double.NaN, double.NaN, double.NaN, new Matrix(double.NaN, 0, 0, double.NaN, double.NaN, double.NaN) };
+    }
+    
+    [Theory]
+    [MemberData(nameof(ScaleAtPrepend_TestData))]
+    public void ScaleAtPrepend_Invoke_Success(Matrix matrix, double scaleX, double scaleY, double centerX, double centerY, Matrix expected)
+    {
+        matrix.ScaleAtPrepend(scaleX, scaleY, centerX, centerY);
+        Helpers.AssertEqualRounded(expected, matrix);
+        Assert.Equal(expected.IsIdentity, matrix.IsIdentity);
+        Assert.Equal(expected.HasInverse, matrix.HasInverse);
+        Assert.Equal(expected.Determinant, matrix.Determinant, precision: 5);
+    }
+
+    public static IEnumerable<object[]> SetIdentity_TestData()
+    {
+        // Identity
+        foreach (Matrix matrix in IdentityMatrices())
+        {
+            yield return new object[] { matrix };
+        }
+
+        // Scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0) };
+
+        // Skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0) };
+
+        // Translated.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3) };
+
+        // Translated and scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2) };
+
+        // Translated and skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3) };
+
+        // Skewed and scaled.
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0) };
+
+        // Complex.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7) };
+
+        // No inverse.
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0) };
+    }
+
+    [Theory]
+    [MemberData(nameof(SetIdentity_TestData))]
+    public void SetIdentity_Invoke_Success(Matrix matrix)
+    {
+        matrix.SetIdentity();
+        Assert.Equal(Matrix.Identity, matrix);
+        Assert.Equal(1, matrix.M11);
+        Assert.Equal(0, matrix.M12);
+        Assert.Equal(0, matrix.M21);
+        Assert.Equal(1, matrix.M22);
+        Assert.Equal(0, matrix.OffsetX);
+        Assert.Equal(0, matrix.OffsetY);
+        Assert.True(matrix.HasInverse);
+        Assert.True(matrix.IsIdentity);
+        Assert.Equal(1, matrix.Determinant);
+        Assert.Equal(new Matrix(), matrix);
+    }
+
+    public static IEnumerable<object[]> Skew_TestData()
+    {
+        // Identity
+        foreach (Matrix matrix in IdentityMatrices())
+        {
+            yield return new object[] { matrix, -90, -180, new Matrix(1, 0, -16331239353195370, 1, 0, 0), false, true, 3 };
+            yield return new object[] { matrix, -90, 180, new Matrix(1, -0, -16331239353195370, 1, 0, 0), false, true, -1 };
+            yield return new object[] { matrix, 90, -180, new Matrix(1, 0, 16331239353195370, 1, 0, 0), false, true, -1 };
+            yield return new object[] { matrix, -90, 0, new Matrix(1, 0, -16331239353195370, 1, 0, 0), false, true, 1 };
+            yield return new object[] { matrix, 0, -180, new Matrix(1, 0, 0, 1, 0, 0), false, true, 1 };
+            yield return new object[] { matrix, 0, 0, new Matrix(1, 0, 0, 1, 0, 0), true, true, 1 };
+            yield return new object[] { matrix, 90, 180, new Matrix(1, -0, 16331239353195370, 1, 0, 0), false, true, 3 };
+            yield return new object[] { matrix, 90, 0, new Matrix(1, 0, 16331239353195370, 1, 0, 0), false, true, 1 };
+            yield return new object[] { matrix, 180, 0, new Matrix(1, 0, -0, 1, 0, 0), false, true, 1 };
+            yield return new object[] { matrix, 0, 180, new Matrix(1, -0, 0, 1, 0, 0), false, true, 1 };
+            yield return new object[] { matrix, 180, 180, new Matrix(1, -0, -0, 1, 0, 0), false, true, 1 };
+            yield return new object[] { matrix, 270, 270, new Matrix(1, 5443746451065123, 5443746451065123, 1, 0, 0), false, true, -2.963437542348412E+31 };
+            yield return new object[] { matrix, 180, 270, new Matrix(1, 5443746451065123, -0, 1, 0, 0), false, true, 1.66667 };
+            yield return new object[] { matrix, 270, 270, new Matrix(1, 5443746451065123, 5443746451065123, 1, 0, 0), false, true, -2.963437542348412E+31 };
+            yield return new object[] { matrix, -20, -30, new Matrix(1, -0.57735, -0.36397, 1, 0, 0), false, true, 0.78986 };
+            yield return new object[] { matrix, 20, 30, new Matrix(1, 0.57735, 0.36397, 1, 0, 0), false, true, 0.78986 };
+            yield return new object[] { matrix, -380, -390, new Matrix(1, -0.57735, -0.36397, 1, 0, 0), false, true, 0.78986 };
+            yield return new object[] { matrix, 380, 390, new Matrix(1, 0.57735, 0.36397, 1, 0, 0), false, true, 0.78986 };
+            yield return new object[] { matrix, -740, -750, new Matrix(1, -0.57735, -0.36397, 1, 0, 0), false, true, 0.78986 };
+            yield return new object[] { matrix, 740, 750, new Matrix(1, 0.57735, 0.36397, 1, 0, 0), false, true, 0.78986 };
+            yield return new object[] { matrix, 35, 0, new Matrix(1, 0, 0.70021, 1, 0, 0), false, true, 1 };
+            yield return new object[] { matrix, 0, 35, new Matrix(1, 0.70021, 0, 1, 0, 0), false, true, 1 };
+            yield return new object[] { matrix, -720, -720, new Matrix(1, -0, -0, 1, 0, 0), true, true, 1 };
+            yield return new object[] { matrix, -360, -360, new Matrix(1, -0, -0, 1, 0, 0), true, true, 1 };
+            yield return new object[] { matrix, 360, 360, new Matrix(1, 0, 0, 1, 0, 0), true, true, 1 };
+            yield return new object[] { matrix, 720, 720, new Matrix(1, 0, 0, 1, 0, 0), true, true, 1 };
+            yield return new object[] { matrix, 720, 720, new Matrix(1, 0, 0, 1, 0, 0), true, true, 1 };
+            yield return new object[] { matrix, 20, double.NaN, new Matrix(1, double.NaN, 0.36397, 1, 0, 0), false, true, double.NaN };
+            yield return new object[] { matrix, double.NaN, 30, new Matrix(1, 0.57735, double.NaN, 1, 0, 0), false, true, double.NaN };
+            yield return new object[] { matrix, double.NaN, double.NaN, new Matrix(1, double.NaN, double.NaN, 1, 0, 0), false, true, double.NaN };
+        }
+
+        // Scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -90, -180, new Matrix(2, 0, -48993718059586110, 3, 0, 0), false, true, 18 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -90, 180, new Matrix(2, -0, -48993718059586110, 3, 0, 0), false, true, -6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 90, -180, new Matrix(2, 0, 48993718059586110, 3, 0, 0), false, true, -6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -90, 0, new Matrix(2, 0, -48993718059586110, 3, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, -180, new Matrix(2, 0, 0, 3, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, 0, new Matrix(2, 0, 0, 3, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 90, 180, new Matrix(2, -0, 48993718059586110, 3, 0, 0), false, true, 18 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 90, 0, new Matrix(2, 0, 48993718059586110, 3, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 180, 0, new Matrix(2, 0, -0, 3, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, 180, new Matrix(2, -0, 0, 3, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 180, 180, new Matrix(2, -0, -0, 3, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 270, 270, new Matrix(2, 10887492902130246, 16331239353195366, 3, 0, 0), false, true, -1.7780625254090473E+32 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 180, 270, new Matrix(2, 10887492902130246, -0, 3, 0, 0), false, true, 10 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 270, 270, new Matrix(2, 10887492902130246, 16331239353195366, 3, 0, 0), false, true, -1.7780625254090473E+32 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -20, -30, new Matrix(2, -1.1547, -1.09191, 3, 0, 0), false, true, 4.73917 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 20, 30, new Matrix(2, 1.1547, 1.09191, 3, 0, 0), false, true, 4.73917 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -380, -390, new Matrix(2, -1.1547, -1.09191, 3, 0, 0), false, true, 4.73917 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 380, 390, new Matrix(2, 1.1547, 1.09191, 3, 0, 0), false, true, 4.73917 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -740, -750, new Matrix(2, -1.1547, -1.09191, 3, 0, 0), false, true, 4.73917 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 740, 750, new Matrix(2, 1.1547, 1.09191, 3, 0, 0), false, true, 4.73917 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 35, 0, new Matrix(2, 0, 2.10062, 3, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, 35, new Matrix(2, 1.40042, 0, 3, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -720, -720, new Matrix(2, 0, 0, 3, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -360, -360, new Matrix(2, 0, 0, 3, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 360, 360, new Matrix(2, 0, 0, 3, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 720, 720, new Matrix(2, 0, 0, 3, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 720, 720, new Matrix(2, 0, 0, 3, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 20, double.NaN, new Matrix(2, double.NaN, 1.09191, double.NaN, 0, double.NaN), false, true, double.NaN };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), double.NaN, 30, new Matrix(double.NaN, 1.1547, double.NaN, 3, double.NaN, 0), false, true, double.NaN };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), false, true, double.NaN };
+
+        // Skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -90, -180, new Matrix(-8165619676597683, 0.5, -16331239353195370, 1, 0, 0), false, true, 3 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -90, 180, new Matrix(-8165619676597683, 0.5, -16331239353195370, 1, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 90, -180, new Matrix(8165619676597686, 0.5, 16331239353195370, 1, 0, 0), false, true, -1 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -90, 0, new Matrix(-8165619676597683, 0.5, -16331239353195370, 1, 0, 0), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, -180, new Matrix(1, 0.5, 0.75, 1, 0, 0), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, 0, new Matrix(1, 0.5, 0.75, 1, 0, 0), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 90, 180, new Matrix(8165619676597686, 0.5, 16331239353195370, 1, 0, 0), false, true, 2 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 90, 0, new Matrix(8165619676597686, 0.5, 16331239353195370, 1, 0, 0), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 180, 0, new Matrix(1, 0.5, 0.75, 1, 0, 0), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, 180, new Matrix(1, 0.5, 0.75, 1, 0, 0), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 180, 180, new Matrix(1, 0.5, 0.75, 1, 0, 0), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 270, 270, new Matrix(2721873225532562.5, 5443746451065124, 5443746451065124, 4082809838298843, 0, 0), false, true, -1.8521484639677582E+31 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 180, 270, new Matrix(1, 5443746451065124, 0.75, 4082809838298843, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 270, 270, new Matrix(2721873225532562.5, 5443746451065124, 5443746451065124, 4082809838298843, 0, 0), false, true, -1.8521484639677582E+31 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -20, -30, new Matrix(0.81801, -0.07735, 0.38603, 0.56699, 0, 0), false, true, 0.49366 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 20, 30, new Matrix(1.18199, 1.07735, 1.11396, 1.43301, 0, 0), false, true, 0.49366 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -380, -390, new Matrix(0.81801, -0.07735, 0.38603, 0.56699, 0, 0), false, true, 0.49366 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 380, 390, new Matrix(1.18199, 1.07735, 1.11396, 1.43301, 0, 0), false, true, 0.49366 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -740, -750, new Matrix(0.81801, -0.07735, 0.38603, 0.56699, 0, 0), false, true, 0.49366 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 740, 750, new Matrix(1.18199, 1.07735, 1.11396, 1.43301, 0, 0), false, true, 0.49366 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 35, 0, new Matrix(1.3501, 0.5, 1.45021, 1, 0, 0), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, 35, new Matrix(1, 1.20021, 0.75, 1.52516, 0, 0), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -720, -720, new Matrix(1, 0.5, 0.75, 1, 0, 0), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -360, -360, new Matrix(1, 0.5, 0.75, 1, 0, 0), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 360, 360, new Matrix(1, 0.5, 0.75, 1, 0, 0), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 720, 720, new Matrix(1, 0.5, 0.75, 1, 0, 0), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 720, 720, new Matrix(1, 0.5, 0.75, 1, 0, 0), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 20, double.NaN, new Matrix(1.18199, double.NaN, 1.11396, double.NaN, 0, double.NaN), false, true, double.NaN };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), double.NaN, 30, new Matrix(double.NaN, 1.07735, double.NaN, 1.43301, double.NaN, 0), false, true, double.NaN };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), false, true, double.NaN };
+
+        // Translated.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -90, -180, new Matrix(1, 0, -16331239353195370, 1, -48993718059586110, 3), false, true, 3 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -90, 180, new Matrix(1, -0, -16331239353195370, 1, -48993718059586110, 3), false, true, -1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 90, -180, new Matrix(1, 0, 16331239353195370, 1, 48993718059586110, 3), false, true, -1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -90, 0, new Matrix(1, 0, -16331239353195370, 1, -48993718059586110, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, -180, new Matrix(1, 0, 0, 1, 2, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, 0, new Matrix(1, 0, 0, 1, 2, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 90, 180, new Matrix(1, -0, 16331239353195370, 1, 48993718059586110, 3), false, true, 3 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 90, 0, new Matrix(1, 0, 16331239353195370, 1, 48993718059586110, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 180, 0, new Matrix(1, 0, -0, 1, 2, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, 180, new Matrix(1, -0, 0, 1, 2, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 180, 180, new Matrix(1, -0, -0, 1, 2, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 270, 270, new Matrix(1, 5443746451065123, 5443746451065123, 1, 16331239353195370, 10887492902130248), false, true, -2.963437542348412E+31 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 180, 270, new Matrix(1, 5443746451065123, -0, 1, 2, 10887492902130248), false, true, 1.66667 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 270, 270, new Matrix(1, 5443746451065123, 5443746451065123, 1, 16331239353195370, 10887492902130248), false, true, -2.963437542348412E+31 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -20, -30, new Matrix(1, -0.57735, -0.36397, 1, 0.90809, 1.8453), false, true, 0.78986 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 20, 30, new Matrix(1, 0.57735, 0.36397, 1, 3.09191, 4.1547), false, true, 0.78986 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -380, -390, new Matrix(1, -0.57735, -0.36397, 1, 0.90809, 1.8453), false, true, 0.78986 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 380, 390, new Matrix(1, 0.57735, 0.36397, 1, 3.09191, 4.1547), false, true, 0.78986 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -740, -750, new Matrix(1, -0.57735, -0.36397, 1, 0.90809, 1.8453), false, true, 0.78986 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 740, 750, new Matrix(1, 0.57735, 0.36397, 1, 3.09191, 4.1547), false, true, 0.78986 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 35, 0, new Matrix(1, 0, 0.70021, 1, 4.10062, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, 35, new Matrix(1, 0.70021, 0, 1, 2, 4.40042), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -720, -720, new Matrix(1, -0, -0, 1, 2, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -360, -360, new Matrix(1, -0, -0, 1, 2, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 360, 360, new Matrix(1, 0, 0, 1, 2, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 720, 720, new Matrix(1, 0, 0, 1, 2, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 720, 720, new Matrix(1, 0, 0, 1, 2, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 20, double.NaN, new Matrix(1, double.NaN, 0.36397, 1, 3.09191, double.NaN), false, true, double.NaN };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), double.NaN, 30, new Matrix(1, 0.57735, double.NaN, 1, double.NaN, 4.1547), false, true, double.NaN };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), double.NaN, double.NaN, new Matrix(1, double.NaN, double.NaN, 1, double.NaN, double.NaN), false, true, double.NaN };
+
+        // Translated and scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -90, -180, new Matrix(2, 0, -48993718059586110, 3, -32662478706390740, 2), false, true, 18 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -90, 180, new Matrix(2, -0, -48993718059586110, 3, -32662478706390740, 2), false, true, -6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 90, -180, new Matrix(2, 0, 48993718059586110, 3, 32662478706390740, 2), false, true, -6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -90, 0, new Matrix(2, 0, -48993718059586110, 3, -32662478706390740, 2), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, -180, new Matrix(2, 0, 0, 3, 1, 2), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, 0, new Matrix(2, 0, 0, 3, 1, 2), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 90, 180, new Matrix(2, -0, 48993718059586110, 3, 32662478706390740, 2), false, true, 18 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 90, 0, new Matrix(2, 0, 48993718059586110, 3, 32662478706390740, 2), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 180, 0, new Matrix(2, 0, -0, 3, 1, 2), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, 180, new Matrix(2, -0, 0, 3, 1, 2), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 180, 180, new Matrix(2, -0, -0, 3, 1, 2), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 270, 270, new Matrix(2, 10887492902130246, 16331239353195366, 3, 10887492902130248, 5443746451065125), false, true, -1.7780625254090473E+32 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 180, 270, new Matrix(2, 10887492902130246, -0, 3, 1, 5443746451065125), false, true, 10 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 270, 270, new Matrix(2, 10887492902130246, 16331239353195366, 3, 10887492902130248, 5443746451065125), false, true, -1.7780625254090473E+32 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -20, -30, new Matrix(2, -1.1547, -1.09191, 3, 0.27206, 1.42265), false, true, 4.73917 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 20, 30, new Matrix(2, 1.1547, 1.09191, 3, 1.72794, 2.57735), false, true, 4.73917 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -380, -390, new Matrix(2, -1.1547, -1.09191, 3, 0.27206, 1.42265), false, true, 4.73917 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 380, 390, new Matrix(2, 1.1547, 1.09191, 3, 1.72794, 2.57735), false, true, 4.73917 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -740, -750, new Matrix(2, -1.1547, -1.09191, 3, 0.27206, 1.42265), false, true, 4.73917 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 740, 750, new Matrix(2, 1.1547, 1.09191, 3, 1.72794, 2.57735), false, true, 4.73917 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 35, 0, new Matrix(2, 0, 2.10062, 3, 2.40042, 2), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, 35, new Matrix(2, 1.40042, 0, 3, 1, 2.70021), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -720, -720, new Matrix(2, 0, 0, 3, 1, 2), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -360, -360, new Matrix(2, 0, 0, 3, 1, 2), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 360, 360, new Matrix(2, 0, 0, 3, 1, 2), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 720, 720, new Matrix(2, 0, 0, 3, 1, 2), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 720, 720, new Matrix(2, 0, 0, 3, 1, 2), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 20, double.NaN, new Matrix(2, double.NaN, 1.09191, double.NaN, 1.72794, double.NaN), false, true, double.NaN };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), double.NaN, 30, new Matrix(double.NaN, 1.1547, double.NaN, 3, double.NaN, 2.57735), false, true, double.NaN };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), false, true, double.NaN };
+
+        // Translated and skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -90, -180, new Matrix(-8165619676597683, 0.5, -16331239353195370, 1, -48993718059586110, 3), false, true, 3 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -90, 180, new Matrix(-8165619676597683, 0.5, -16331239353195370, 1, -48993718059586110, 3), false, false, 0 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 90, -180, new Matrix(8165619676597686, 0.5, 16331239353195370, 1, 48993718059586110, 3), false, true, -1 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -90, 0, new Matrix(-8165619676597683, 0.5, -16331239353195370, 1, -48993718059586110, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, -180, new Matrix(1, 0.5, 0.75, 1, 2, 3), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, 0, new Matrix(1, 0.5, 0.75, 1, 2, 3), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 90, 180, new Matrix(8165619676597686, 0.5, 16331239353195370, 1, 48993718059586110, 3), false, true, 2 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 90, 0, new Matrix(8165619676597686, 0.5, 16331239353195370, 1, 48993718059586110, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 180, 0, new Matrix(1, 0.5, 0.75, 1, 2, 3), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, 180, new Matrix(1, 0.5, 0.75, 1, 2, 3), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 180, 180, new Matrix(1, 0.5, 0.75, 1, 2, 3), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 270, 270, new Matrix(2721873225532562.5, 5443746451065124, 5443746451065124, 4082809838298843, 16331239353195370, 10887492902130248), false, true, -1.8521484639677582E+31 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 180, 270, new Matrix(1, 5443746451065124, 0.75, 4082809838298843, 2, 10887492902130248), false, false, 0 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 270, 270, new Matrix(2721873225532562.5, 5443746451065124, 5443746451065124, 4082809838298843, 16331239353195370, 10887492902130248), false, true, -1.8521484639677582E+31 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -20, -30, new Matrix(0.81801, -0.07735, 0.38603, 0.56699, 0.90809, 1.8453), false, true, 0.49366 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 20, 30, new Matrix(1.18199, 1.07735, 1.11396, 1.43301, 3.09191, 4.1547), false, true, 0.49366 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -380, -390, new Matrix(0.81801, -0.07735, 0.38603, 0.56699, 0.90809, 1.8453), false, true, 0.49366 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 380, 390, new Matrix(1.18199, 1.07735, 1.11396, 1.43301, 3.09191, 4.1547), false, true, 0.49366 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -740, -750, new Matrix(0.81801, -0.07735, 0.38603, 0.56699, 0.90809, 1.8453), false, true, 0.49366 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 740, 750, new Matrix(1.18199, 1.07735, 1.11396, 1.43301, 3.09191, 4.1547), false, true, 0.49366 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 35, 0, new Matrix(1.3501, 0.5, 1.45021, 1, 4.10062, 3), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, 35, new Matrix(1, 1.20021, 0.75, 1.52516, 2, 4.40042), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -720, -720, new Matrix(1, 0.5, 0.75, 1, 2, 3), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -360, -360, new Matrix(1, 0.5, 0.75, 1, 2, 3), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 360, 360, new Matrix(1, 0.5, 0.75, 1, 2, 3), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 720, 720, new Matrix(1, 0.5, 0.75, 1, 2, 3), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 720, 720, new Matrix(1, 0.5, 0.75, 1, 2, 3), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 20, double.NaN, new Matrix(1.18199, double.NaN, 1.11396, double.NaN, 3.09191, double.NaN), false, true, double.NaN };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), double.NaN, 30, new Matrix(double.NaN, 1.07735, double.NaN, 1.43301, double.NaN, 4.1547), false, true, double.NaN };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), false, true, double.NaN };
+
+        // Skewed and scaled.
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -90, -180, new Matrix(-8165619676597683, 0.5, -48993718059586110, 3, 0, 0), false, true, 20 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -90, 180, new Matrix(-8165619676597683, 0.5, -48993718059586110, 3, 0, 0), false, true, -4 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 90, -180, new Matrix(8165619676597687, 0.5, 48993718059586110, 3, 0, 0), false, true, -8 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -90, 0, new Matrix(-8165619676597683, 0.5, -48993718059586110, 3, 0, 0), false, true, 8 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, -180, new Matrix(2, 0.5, 0.75, 3, 0, 0), false, true, 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, 0, new Matrix(2, 0.5, 0.75, 3, 0, 0), false, true, 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 90, 180, new Matrix(8165619676597687, 0.5, 48993718059586110, 3, 0, 0), false, true, 16 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 90, 0, new Matrix(8165619676597687, 0.5, 48993718059586110, 3, 0, 0), false, true, 4 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 180, 0, new Matrix(2, 0.5, 0.75, 3, 0, 0), false, true, 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, 180, new Matrix(2, 0.5, 0.75, 3, 0, 0), false, true, 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 180, 180, new Matrix(2, 0.5, 0.75, 3, 0, 0), false, true, 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 270, 270, new Matrix(2721873225532563.5, 10887492902130246, 16331239353195366, 4082809838298845, 0, 0), false, true, -1.6669336175709816E+32 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 180, 270, new Matrix(2, 10887492902130246, 0.75, 4082809838298845, 0, 0), false, true, 9 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 270, 270, new Matrix(2721873225532563.5, 10887492902130246, 16331239353195366, 4082809838298845, 0, 0), false, true, -1.6669336175709816E+32 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -20, -30, new Matrix(1.81801, -0.65469, -0.34191, 2.56699, 0, 0), false, true, 4.44297 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 20, 30, new Matrix(2.18199, 1.6547, 1.84191, 3.43301, 0, 0), false, true, 4.44297 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -380, -390, new Matrix(1.81801, -0.65469, -0.34191, 2.56699, 0, 0), false, true, 4.44297 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 380, 390, new Matrix(2.18199, 1.6547, 1.84191, 3.43301, 0, 0), false, true, 4.44297 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -740, -750, new Matrix(1.81801, -0.65469, -0.34191, 2.56699, 0, 0), false, true, 4.44297 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 740, 750, new Matrix(2.18199, 1.6547, 1.84191, 3.43301, 0, 0), false, true, 4.44297 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 35, 0, new Matrix(2.3501, 0.5, 2.85062, 3, 0, 0), false, true, 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, 35, new Matrix(2, 1.90042, 0.75, 3.52516, 0, 0), false, true, 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -720, -720, new Matrix(2, 0.5, 0.75, 3, 0, 0), false, true, 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -360, -360, new Matrix(2, 0.5, 0.75, 3, 0, 0), false, true, 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 360, 360, new Matrix(2, 0.5, 0.75, 3, 0, 0), false, true, 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 720, 720, new Matrix(2, 0.5, 0.75, 3, 0, 0), false, true, 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 720, 720, new Matrix(2, 0.5, 0.75, 3, 0, 0), false, true, 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 20, double.NaN, new Matrix(2.18199, double.NaN, 1.84191, double.NaN, 0, double.NaN), false, true, double.NaN };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), double.NaN, 30, new Matrix(double.NaN, 1.6547, double.NaN, 3.43301, double.NaN, 0), false, true, double.NaN };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), false, true, double.NaN };
+
+        // Complex.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -90, -180, new Matrix(-48993718059586110, 3, -81656196765976850, 5, -1.1431867547236758E+17, 7), false, false, 0 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -90, 180, new Matrix(-48993718059586110, 3, -81656196765976850, 5, -1.1431867547236758E+17, 7), false, true, -32 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 90, -180, new Matrix(48993718059586110, 3, 81656196765976850, 5, 1.1431867547236758E+17, 7), false, false, 0 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -90, 0, new Matrix(-48993718059586110, 3, -81656196765976850, 5, -1.1431867547236758E+17, 7), false, false, 0 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, -180, new Matrix(2, 3, 4, 5, 6, 7), false, true, -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, 0, new Matrix(2, 3, 4, 5, 6, 7), false, true, -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 90, 180, new Matrix(48993718059586110, 3, 81656196765976850, 5, 1.1431867547236758E+17, 7), false, true, 32 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 90, 0, new Matrix(48993718059586110, 3, 81656196765976850, 5, 1.1431867547236758E+17, 7), false, false, 0 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 180, 0, new Matrix(2, 3, 4, 5, 6, 7), false, true, -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, 180, new Matrix(2, 3, 4, 5, 6, 7), false, true, -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 180, 180, new Matrix(2, 3, 4, 5, 6, 7), false, true, -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 270, 270, new Matrix(16331239353195370, 10887492902130248, 27218732255325624, 21774985804260496, 38106225157455870, 32662478706390744), false, true, 5.926875084696823E+31 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 180, 270, new Matrix(2, 10887492902130248, 4, 21774985804260496, 6, 32662478706390744), false, false, 0 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 270, 270, new Matrix(16331239353195370, 10887492902130248, 27218732255325624, 21774985804260496, 38106225157455870, 32662478706390744), false, true, 5.926875084696823E+31 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -20, -30, new Matrix(0.90809, 1.8453, 2.18014, 2.6906, 3.45221, 3.5359), false, true, -1.57972 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 20, 30, new Matrix(3.09191, 4.1547, 5.81985, 7.3094, 8.54779, 10.4641), false, true, -1.57972 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -380, -390, new Matrix(0.90809, 1.8453, 2.18014, 2.6906, 3.45221, 3.5359), false, true, -1.57972 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 380, 390, new Matrix(3.09191, 4.1547, 5.81985, 7.3094, 8.54779, 10.4641), false, true, -1.57972 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -740, -750, new Matrix(0.90809, 1.8453, 2.18014, 2.6906, 3.45221, 3.5359), false, true, -1.57972 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 740, 750, new Matrix(3.09191, 4.1547, 5.81985, 7.3094, 8.54779, 10.4641), false, true, -1.57972 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 35, 0, new Matrix(4.10062, 3, 7.50104, 5, 10.90145, 7), false, true, -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, 35, new Matrix(2, 4.40042, 4, 7.80083, 6, 11.20125), false, true, -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -720, -720, new Matrix(2, 3, 4, 5, 6, 7), false, true, -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -360, -360, new Matrix(2, 3, 4, 5, 6, 7), false, true, -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 360, 360, new Matrix(2, 3, 4, 5, 6, 7), false, true, -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 720, 720, new Matrix(2, 3, 4, 5, 6, 7), false, true, -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 720, 720, new Matrix(2, 3, 4, 5, 6, 7), false, true, -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 20, double.NaN, new Matrix(3.09191, double.NaN, 5.81985, double.NaN, 8.54779, double.NaN), false, true, double.NaN };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), double.NaN, 30, new Matrix(double.NaN, 4.1547, double.NaN, 7.3094, double.NaN, 10.4641), false, true, double.NaN };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), false, true, double.NaN };
+
+        // No inverse.
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -90, -180, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -90, 180, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 90, -180, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -90, 0, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, -180, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, 0, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 90, 180, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 90, 0, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 180, 0, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, 180, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 180, 180, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 270, 270, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 180, 270, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 270, 270, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -20, -30, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 20, 30, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -380, -390, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 380, 390, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -740, -750, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 740, 750, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 35, 0, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, 35, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -720, -720, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -360, -360, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 360, 360, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 720, 720, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 720, 720, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 20, double.NaN, new Matrix(0, double.NaN, 0, double.NaN, 0, double.NaN), false, true, double.NaN };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), double.NaN, 30, new Matrix(double.NaN, 0, double.NaN, 0, double.NaN, 0), false, true, double.NaN };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, double.NaN, double.NaN), false, true, double.NaN };
+
+    }
+
+    [Theory]
+    [MemberData(nameof(Skew_TestData))]
+    public void Skew_Invoke_Success(Matrix matrix, double skewX, double skewY, Matrix expected, bool expectedIsIdentity, bool expectedHasInverse, double expectedDeterminant)
+    {
+        matrix.Skew(skewX, skewY);
+        Helpers.AssertEqualRounded(expected, matrix);
+        Assert.Equal(expectedIsIdentity, matrix.IsIdentity);
+        Assert.Equal(expectedHasInverse, matrix.HasInverse);
+        Assert.Equal(expectedDeterminant, matrix.Determinant, precision: 5);
+    }
+
+    public static IEnumerable<object[]> SkewPrepend_TestData()
+    {
+        // Identity
+        foreach (Matrix matrix in IdentityMatrices())
+        {
+            yield return new object[] { matrix, -90, -180, new Matrix(1, 0, -16331239353195370, 1, 0, 0), false, true, 3 };
+            yield return new object[] { matrix, -90, 180, new Matrix(1, -0, -16331239353195370, 1, 0, 0), false, true, -1 };
+            yield return new object[] { matrix, 90, -180, new Matrix(1, 0, 16331239353195370, 1, 0, 0), false, true, -1 };
+            yield return new object[] { matrix, -90, 0, new Matrix(1, 0, -16331239353195370, 1, 0, 0), false, true, 1 };
+            yield return new object[] { matrix, 0, -180, new Matrix(1, 0, 0, 1, 0, 0), false, true, 1 };
+            yield return new object[] { matrix, 0, 0, new Matrix(1, 0, 0, 1, 0, 0), true, true, 1 };
+            yield return new object[] { matrix, 90, 180, new Matrix(1, -0, 16331239353195370, 1, 0, 0), false, true, 3 };
+            yield return new object[] { matrix, 90, 0, new Matrix(1, 0, 16331239353195370, 1, 0, 0), false, true, 1 };
+            yield return new object[] { matrix, 180, 0, new Matrix(1, 0, -0, 1, 0, 0), false, true, 1 };
+            yield return new object[] { matrix, 0, 180, new Matrix(1, -0, 0, 1, 0, 0), false, true, 1 };
+            yield return new object[] { matrix, 180, 180, new Matrix(1, -0, -0, 1, 0, 0), false, true, 1 };
+            yield return new object[] { matrix, 270, 270, new Matrix(1, 5443746451065123, 5443746451065123, 1, 0, 0), false, true, -2.963437542348412E+31 };
+            yield return new object[] { matrix, 180, 270, new Matrix(1, 5443746451065123, -0, 1, 0, 0), false, true, 1.66667 };
+            yield return new object[] { matrix, 270, 270, new Matrix(1, 5443746451065123, 5443746451065123, 1, 0, 0), false, true, -2.963437542348412E+31 };
+            yield return new object[] { matrix, -20, -30, new Matrix(1, -0.57735, -0.36397, 1, 0, 0), false, true, 0.78986 };
+            yield return new object[] { matrix, 20, 30, new Matrix(1, 0.57735, 0.36397, 1, 0, 0), false, true, 0.78986 };
+            yield return new object[] { matrix, -380, -390, new Matrix(1, -0.57735, -0.36397, 1, 0, 0), false, true, 0.78986 };
+            yield return new object[] { matrix, 380, 390, new Matrix(1, 0.57735, 0.36397, 1, 0, 0), false, true, 0.78986 };
+            yield return new object[] { matrix, -740, -750, new Matrix(1, -0.57735, -0.36397, 1, 0, 0), false, true, 0.78986 };
+            yield return new object[] { matrix, 740, 750, new Matrix(1, 0.57735, 0.36397, 1, 0, 0), false, true, 0.78986 };
+            yield return new object[] { matrix, 35, 0, new Matrix(1, 0, 0.70021, 1, 0, 0), false, true, 1 };
+            yield return new object[] { matrix, 0, 35, new Matrix(1, 0.70021, 0, 1, 0, 0), false, true, 1 };
+            yield return new object[] { matrix, -720, -720, new Matrix(1, -0, -0, 1, 0, 0), true, true, 1 };
+            yield return new object[] { matrix, -360, -360, new Matrix(1, -0, -0, 1, 0, 0), true, true, 1 };
+            yield return new object[] { matrix, 360, 360, new Matrix(1, 0, 0, 1, 0, 0), true, true, 1 };
+            yield return new object[] { matrix, 720, 720, new Matrix(1, 0, 0, 1, 0, 0), true, true, 1 };
+            yield return new object[] { matrix, 720, 720, new Matrix(1, 0, 0, 1, 0, 0), true, true, 1 };
+            yield return new object[] { matrix, 20, double.NaN, new Matrix(1, double.NaN, 0.36397, 1, 0, 0), false, true, double.NaN };
+            yield return new object[] { matrix, double.NaN, 30, new Matrix(1, 0.57735, double.NaN, 1, 0, 0), false, true, double.NaN };
+            yield return new object[] { matrix, double.NaN, double.NaN, new Matrix(1, double.NaN, double.NaN, 1, 0, 0), false, true, double.NaN };
+        }
+
+        // Scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -90, -180, new Matrix(2, 0, -32662478706390740, 3, 0, 0), false, true, 18 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -90, 180, new Matrix(2, -0, -32662478706390740, 3, 0, 0), false, true, -6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 90, -180, new Matrix(2, 0, 32662478706390740, 3, 0, 0), false, true, -6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -90, 0, new Matrix(2, 0, -32662478706390740, 3, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, -180, new Matrix(2, 0, 0, 3, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, 0, new Matrix(2, 0, 0, 3, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 90, 180, new Matrix(2, -0, 32662478706390740, 3, 0, 0), false, true, 18 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 90, 0, new Matrix(2, 0, 32662478706390740, 3, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 180, 0, new Matrix(2, 0, -0, 3, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, 180, new Matrix(2, -0, 0, 3, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 180, 180, new Matrix(2, -0, -0, 3, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 270, 270, new Matrix(2, 16331239353195366, 10887492902130246, 3, 0, 0), false, true, -1.7780625254090473E+32 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 180, 270, new Matrix(2, 16331239353195366, -0, 3, 0, 0), false, true, 10 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 270, 270, new Matrix(2, 16331239353195366, 10887492902130246, 3, 0, 0), false, true, -1.7780625254090473E+32 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -20, -30, new Matrix(2, -1.73205, -0.72794, 3, 0, 0), false, true, 4.73917 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 20, 30, new Matrix(2, 1.73205, 0.72794, 3, 0, 0), false, true, 4.73917 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -380, -390, new Matrix(2, -1.73205, -0.72794, 3, 0, 0), false, true, 4.73917 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 380, 390, new Matrix(2, 1.73205, 0.72794, 3, 0, 0), false, true, 4.73917 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -740, -750, new Matrix(2, -1.73205, -0.72794, 3, 0, 0), false, true, 4.73917 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 740, 750, new Matrix(2, 1.73205, 0.72794, 3, 0, 0), false, true, 4.73917 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 35, 0, new Matrix(2, 0, 1.40042, 3, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, 35, new Matrix(2, 2.10062, 0, 3, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -720, -720, new Matrix(2, 0, 0, 3, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -360, -360, new Matrix(2, 0, 0, 3, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 360, 360, new Matrix(2, 0, 0, 3, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 720, 720, new Matrix(2, 0, 0, 3, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 720, 720, new Matrix(2, 0, 0, 3, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 20, double.NaN, new Matrix(double.NaN, double.NaN, 0.72794, 3, 0, 0), false, true, double.NaN };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), double.NaN, 30, new Matrix(2, 1.73205, double.NaN, double.NaN, 0, 0), false, true, double.NaN };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, 0, 0), false, true, double.NaN };
+
+        // Skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -90, -180, new Matrix(1, 0.5, -16331239353195370, -8165619676597683, 0, 0), false, true, 3 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -90, 180, new Matrix(1, 0.5, -16331239353195370, -8165619676597683, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 90, -180, new Matrix(1, 0.5, 16331239353195370, 8165619676597686, 0, 0), false, true, -1 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -90, 0, new Matrix(1, 0.5, -16331239353195370, -8165619676597683, 0, 0), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, -180, new Matrix(1, 0.5, 0.75, 1, 0, 0), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, 0, new Matrix(1, 0.5, 0.75, 1, 0, 0), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 90, 180, new Matrix(1, 0.5, 16331239353195370, 8165619676597686, 0, 0), false, true, 2 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 90, 0, new Matrix(1, 0.5, 16331239353195370, 8165619676597686, 0, 0), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 180, 0, new Matrix(1, 0.5, 0.75, 1, 0, 0), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, 180, new Matrix(1, 0.5, 0.75, 1, 0, 0), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 180, 180, new Matrix(1, 0.5, 0.75, 1, 0, 0), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 270, 270, new Matrix(4082809838298843, 5443746451065124, 5443746451065124, 2721873225532562.5, 0, 0), false, true, -1.8521484639677582E+31 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 180, 270, new Matrix(4082809838298843, 5443746451065124, 0.75, 1, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 270, 270, new Matrix(4082809838298843, 5443746451065124, 5443746451065124, 2721873225532562.5, 0, 0), false, true, -1.8521484639677582E+31 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -20, -30, new Matrix(0.56699, -0.07735, 0.38603, 0.81801, 0, 0), false, true, 0.49366 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 20, 30, new Matrix(1.43301, 1.07735, 1.11396, 1.18199, 0, 0), false, true, 0.49366 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -380, -390, new Matrix(0.56699, -0.07735, 0.38603, 0.81801, 0, 0), false, true, 0.49366 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 380, 390, new Matrix(1.43301, 1.07735, 1.11396, 1.18199, 0, 0), false, true, 0.49366 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -740, -750, new Matrix(0.56699, -0.07735, 0.38603, 0.81801, 0, 0), false, true, 0.49366 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 740, 750, new Matrix(1.43301, 1.07735, 1.11396, 1.18199, 0, 0), false, true, 0.49366 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 35, 0, new Matrix(1, 0.5, 1.45021, 1.3501, 0, 0), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, 35, new Matrix(1.52516, 1.20021, 0.75, 1, 0, 0), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -720, -720, new Matrix(1, 0.5, 0.75, 1, 0, 0), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -360, -360, new Matrix(1, 0.5, 0.75, 1, 0, 0), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 360, 360, new Matrix(1, 0.5, 0.75, 1, 0, 0), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 720, 720, new Matrix(1, 0.5, 0.75, 1, 0, 0), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 720, 720, new Matrix(1, 0.5, 0.75, 1, 0, 0), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 20, double.NaN, new Matrix(double.NaN, double.NaN, 1.11396, 1.18199, 0, 0), false, true, double.NaN };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), double.NaN, 30, new Matrix(1.43301, 1.07735, double.NaN, double.NaN, 0, 0), false, true, double.NaN };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, 0, 0), false, true, double.NaN };
+
+        // Translated.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -90, -180, new Matrix(1, 0, -16331239353195370, 1, 2, 3), false, true, 3 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -90, 180, new Matrix(1, -0, -16331239353195370, 1, 2, 3), false, true, -1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 90, -180, new Matrix(1, 0, 16331239353195370, 1, 2, 3), false, true, -1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -90, 0, new Matrix(1, 0, -16331239353195370, 1, 2, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, -180, new Matrix(1, 0, 0, 1, 2, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, 0, new Matrix(1, 0, 0, 1, 2, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 90, 180, new Matrix(1, -0, 16331239353195370, 1, 2, 3), false, true, 3 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 90, 0, new Matrix(1, 0, 16331239353195370, 1, 2, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 180, 0, new Matrix(1, 0, -0, 1, 2, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, 180, new Matrix(1, -0, 0, 1, 2, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 180, 180, new Matrix(1, -0, -0, 1, 2, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 270, 270, new Matrix(1, 5443746451065123, 5443746451065123, 1, 2, 3), false, true, -2.963437542348412E+31 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 180, 270, new Matrix(1, 5443746451065123, -0, 1, 2, 3), false, true, 1.66667 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 270, 270, new Matrix(1, 5443746451065123, 5443746451065123, 1, 2, 3), false, true, -2.963437542348412E+31 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -20, -30, new Matrix(1, -0.57735, -0.36397, 1, 2, 3), false, true, 0.78986 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 20, 30, new Matrix(1, 0.57735, 0.36397, 1, 2, 3), false, true, 0.78986 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -380, -390, new Matrix(1, -0.57735, -0.36397, 1, 2, 3), false, true, 0.78986 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 380, 390, new Matrix(1, 0.57735, 0.36397, 1, 2, 3), false, true, 0.78986 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -740, -750, new Matrix(1, -0.57735, -0.36397, 1, 2, 3), false, true, 0.78986 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 740, 750, new Matrix(1, 0.57735, 0.36397, 1, 2, 3), false, true, 0.78986 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 35, 0, new Matrix(1, 0, 0.70021, 1, 2, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, 35, new Matrix(1, 0.70021, 0, 1, 2, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -720, -720, new Matrix(1, -0, -0, 1, 2, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -360, -360, new Matrix(1, -0, -0, 1, 2, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 360, 360, new Matrix(1, 0, 0, 1, 2, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 720, 720, new Matrix(1, 0, 0, 1, 2, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 720, 720, new Matrix(1, 0, 0, 1, 2, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 20, double.NaN, new Matrix(1, double.NaN, 0.36397, 1, 2, 3), false, true, double.NaN };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), double.NaN, 30, new Matrix(1, 0.57735, double.NaN, 1, 2, 3), false, true, double.NaN };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), double.NaN, double.NaN, new Matrix(1, double.NaN, double.NaN, 1, 2, 3), false, true, double.NaN };
+
+        // Translated and scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -90, -180, new Matrix(2, 0, -32662478706390740, 3, 1, 2), false, true, 18 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -90, 180, new Matrix(2, -0, -32662478706390740, 3, 1, 2), false, true, -6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 90, -180, new Matrix(2, 0, 32662478706390740, 3, 1, 2), false, true, -6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -90, 0, new Matrix(2, 0, -32662478706390740, 3, 1, 2), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, -180, new Matrix(2, 0, 0, 3, 1, 2), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, 0, new Matrix(2, 0, 0, 3, 1, 2), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 90, 180, new Matrix(2, -0, 32662478706390740, 3, 1, 2), false, true, 18 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 90, 0, new Matrix(2, 0, 32662478706390740, 3, 1, 2), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 180, 0, new Matrix(2, 0, -0, 3, 1, 2), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, 180, new Matrix(2, -0, 0, 3, 1, 2), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 180, 180, new Matrix(2, -0, -0, 3, 1, 2), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 270, 270, new Matrix(2, 16331239353195366, 10887492902130246, 3, 1, 2), false, true, -1.7780625254090473E+32 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 180, 270, new Matrix(2, 16331239353195366, -0, 3, 1, 2), false, true, 10 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 270, 270, new Matrix(2, 16331239353195366, 10887492902130246, 3, 1, 2), false, true, -1.7780625254090473E+32 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -20, -30, new Matrix(2, -1.73205, -0.72794, 3, 1, 2), false, true, 4.73917 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 20, 30, new Matrix(2, 1.73205, 0.72794, 3, 1, 2), false, true, 4.73917 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -380, -390, new Matrix(2, -1.73205, -0.72794, 3, 1, 2), false, true, 4.73917 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 380, 390, new Matrix(2, 1.73205, 0.72794, 3, 1, 2), false, true, 4.73917 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -740, -750, new Matrix(2, -1.73205, -0.72794, 3, 1, 2), false, true, 4.73917 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 740, 750, new Matrix(2, 1.73205, 0.72794, 3, 1, 2), false, true, 4.73917 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 35, 0, new Matrix(2, 0, 1.40042, 3, 1, 2), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, 35, new Matrix(2, 2.10062, 0, 3, 1, 2), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -720, -720, new Matrix(2, 0, 0, 3, 1, 2), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -360, -360, new Matrix(2, 0, 0, 3, 1, 2), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 360, 360, new Matrix(2, 0, 0, 3, 1, 2), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 720, 720, new Matrix(2, 0, 0, 3, 1, 2), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 720, 720, new Matrix(2, 0, 0, 3, 1, 2), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 20, double.NaN, new Matrix(double.NaN, double.NaN, 0.72794, 3, 1, 2), false, true, double.NaN };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), double.NaN, 30, new Matrix(2, 1.73205, double.NaN, double.NaN, 1, 2), false, true, double.NaN };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, 1, 2), false, true, double.NaN };
+
+        // Translated and skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -90, -180, new Matrix(1, 0.5, -16331239353195370, -8165619676597683, 2, 3), false, true, 3 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -90, 180, new Matrix(1, 0.5, -16331239353195370, -8165619676597683, 2, 3), false, false, 0 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 90, -180, new Matrix(1, 0.5, 16331239353195370, 8165619676597686, 2, 3), false, true, -1 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -90, 0, new Matrix(1, 0.5, -16331239353195370, -8165619676597683, 2, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, -180, new Matrix(1, 0.5, 0.75, 1, 2, 3), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, 0, new Matrix(1, 0.5, 0.75, 1, 2, 3), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 90, 180, new Matrix(1, 0.5, 16331239353195370, 8165619676597686, 2, 3), false, true, 2 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 90, 0, new Matrix(1, 0.5, 16331239353195370, 8165619676597686, 2, 3), false, true, 1 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 180, 0, new Matrix(1, 0.5, 0.75, 1, 2, 3), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, 180, new Matrix(1, 0.5, 0.75, 1, 2, 3), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 180, 180, new Matrix(1, 0.5, 0.75, 1, 2, 3), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 270, 270, new Matrix(4082809838298843, 5443746451065124, 5443746451065124, 2721873225532562.5, 2, 3), false, true, -1.8521484639677582E+31 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 180, 270, new Matrix(4082809838298843, 5443746451065124, 0.75, 1, 2, 3), false, false, 0 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 270, 270, new Matrix(4082809838298843, 5443746451065124, 5443746451065124, 2721873225532562.5, 2, 3), false, true, -1.8521484639677582E+31 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -20, -30, new Matrix(0.56699, -0.07735, 0.38603, 0.81801, 2, 3), false, true, 0.49366 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 20, 30, new Matrix(1.43301, 1.07735, 1.11396, 1.18199, 2, 3), false, true, 0.49366 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -380, -390, new Matrix(0.56699, -0.07735, 0.38603, 0.81801, 2, 3), false, true, 0.49366 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 380, 390, new Matrix(1.43301, 1.07735, 1.11396, 1.18199, 2, 3), false, true, 0.49366 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -740, -750, new Matrix(0.56699, -0.07735, 0.38603, 0.81801, 2, 3), false, true, 0.49366 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 740, 750, new Matrix(1.43301, 1.07735, 1.11396, 1.18199, 2, 3), false, true, 0.49366 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 35, 0, new Matrix(1, 0.5, 1.45021, 1.3501, 2, 3), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, 35, new Matrix(1.52516, 1.20021, 0.75, 1, 2, 3), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -720, -720, new Matrix(1, 0.5, 0.75, 1, 2, 3), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -360, -360, new Matrix(1, 0.5, 0.75, 1, 2, 3), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 360, 360, new Matrix(1, 0.5, 0.75, 1, 2, 3), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 720, 720, new Matrix(1, 0.5, 0.75, 1, 2, 3), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 720, 720, new Matrix(1, 0.5, 0.75, 1, 2, 3), false, true, 0.625 };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 20, double.NaN, new Matrix(double.NaN, double.NaN, 1.11396, 1.18199, 2, 3), false, true, double.NaN };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), double.NaN, 30, new Matrix(1.43301, 1.07735, double.NaN, double.NaN, 2, 3), false, true, double.NaN };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, 2, 3), false, true, double.NaN };
+
+        // Skewed and scaled.
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -90, -180, new Matrix(2, 0.5, -32662478706390740, -8165619676597682, 0, 0), false, true, 16 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -90, 180, new Matrix(2, 0.5, -32662478706390740, -8165619676597682, 0, 0), false, true, -6 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 90, -180, new Matrix(2, 0.5, 32662478706390740, 8165619676597687, 0, 0), false, true, -4 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -90, 0, new Matrix(2, 0.5, -32662478706390740, -8165619676597682, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, -180, new Matrix(2, 0.5, 0.75, 3, 0, 0), false, true, 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, 0, new Matrix(2, 0.5, 0.75, 3, 0, 0), false, true, 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 90, 180, new Matrix(2, 0.5, 32662478706390740, 8165619676597687, 0, 0), false, true, 18 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 90, 0, new Matrix(2, 0.5, 32662478706390740, 8165619676597687, 0, 0), false, true, 6 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 180, 0, new Matrix(2, 0.5, 0.75, 3, 0, 0), false, true, 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, 180, new Matrix(2, 0.5, 0.75, 3, 0, 0), false, true, 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 180, 180, new Matrix(2, 0.5, 0.75, 3, 0, 0), false, true, 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 270, 270, new Matrix(4082809838298843.5, 16331239353195366, 10887492902130246, 2721873225532564.5, 0, 0), false, true, -1.6669336175709816E+32 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 180, 270, new Matrix(4082809838298843.5, 16331239353195366, 0.75, 3, 0, 0), false, true, 10 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 270, 270, new Matrix(4082809838298843.5, 16331239353195366, 10887492902130246, 2721873225532564.5, 0, 0), false, true, -1.6669336175709816E+32 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -20, -30, new Matrix(1.56699, -1.23205, 0.02206, 2.81801, 0, 0), false, true, 4.44297 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 20, 30, new Matrix(2.43301, 2.23205, 1.47794, 3.18199, 0, 0), false, true, 4.44297 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -380, -390, new Matrix(1.56699, -1.23205, 0.02206, 2.81801, 0, 0), false, true, 4.44297 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 380, 390, new Matrix(2.43301, 2.23205, 1.47794, 3.18199, 0, 0), false, true, 4.44297 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -740, -750, new Matrix(1.56699, -1.23205, 0.02206, 2.81801, 0, 0), false, true, 4.44297 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 740, 750, new Matrix(2.43301, 2.23205, 1.47794, 3.18199, 0, 0), false, true, 4.44297 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 35, 0, new Matrix(2, 0.5, 2.15042, 3.3501, 0, 0), false, true, 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, 35, new Matrix(2.52516, 2.60062, 0.75, 3, 0, 0), false, true, 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -720, -720, new Matrix(2, 0.5, 0.75, 3, 0, 0), false, true, 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -360, -360, new Matrix(2, 0.5, 0.75, 3, 0, 0), false, true, 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 360, 360, new Matrix(2, 0.5, 0.75, 3, 0, 0), false, true, 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 720, 720, new Matrix(2, 0.5, 0.75, 3, 0, 0), false, true, 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 720, 720, new Matrix(2, 0.5, 0.75, 3, 0, 0), false, true, 5.625 };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 20, double.NaN, new Matrix(double.NaN, double.NaN, 1.47794, 3.18199, 0, 0), false, true, double.NaN };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), double.NaN, 30, new Matrix(2.43301, 2.23205, double.NaN, double.NaN, 0, 0), false, true, double.NaN };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, 0, 0), false, true, double.NaN };
+
+        // Complex.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -90, -180, new Matrix(2, 3, -32662478706390732, -48993718059586104, 6, 7), false, false, 0 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -90, 180, new Matrix(2, 3, -32662478706390732, -48993718059586104, 6, 7), false, false, 0 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 90, -180, new Matrix(2, 3, 32662478706390744, 48993718059586120, 6, 7), false, true, 16 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -90, 0, new Matrix(2, 3, -32662478706390732, -48993718059586104, 6, 7), false, false, 0 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, -180, new Matrix(2, 3, 4, 5, 6, 7), false, true, -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, 0, new Matrix(2, 3, 4, 5, 6, 7), false, true, -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 90, 180, new Matrix(2, 3, 32662478706390744, 48993718059586120, 6, 7), false, false, 0 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 90, 0, new Matrix(2, 3, 32662478706390744, 48993718059586120, 6, 7), false, true, 16 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 180, 0, new Matrix(2, 3, 4, 5, 6, 7), false, true, -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, 180, new Matrix(2, 3, 4, 5, 6, 7), false, true, -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 180, 180, new Matrix(2, 3, 4, 5, 6, 7), false, true, -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 270, 270, new Matrix(21774985804260496, 27218732255325624, 10887492902130250, 16331239353195372, 6, 7), false, true, 5.926875084696823E+31 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 180, 270, new Matrix(21774985804260496, 27218732255325624, 4, 5, 6, 7), false, true, 16 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 270, 270, new Matrix(21774985804260496, 27218732255325624, 10887492902130250, 16331239353195372, 6, 7), false, true, 5.926875084696823E+31 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -20, -30, new Matrix(-0.3094, 0.11325, 3.27206, 3.90809, 6, 7), false, true, -1.57972 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 20, 30, new Matrix(4.3094, 5.88675, 4.72794, 6.09191, 6, 7), false, true, -1.57972 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -380, -390, new Matrix(-0.3094, 0.11325, 3.27206, 3.90809, 6, 7), false, true, -1.57972 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 380, 390, new Matrix(4.3094, 5.88675, 4.72794, 6.09191, 6, 7), false, true, -1.57972 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -740, -750, new Matrix(-0.3094, 0.11325, 3.27206, 3.90809, 6, 7), false, true, -1.57972 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 740, 750, new Matrix(4.3094, 5.88675, 4.72794, 6.09191, 6, 7), false, true, -1.57972 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 35, 0, new Matrix(2, 3, 5.40042, 7.10062, 6, 7), false, true, -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, 35, new Matrix(4.80083, 6.50104, 4, 5, 6, 7), false, true, -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -720, -720, new Matrix(2, 3, 4, 5, 6, 7), false, true, -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -360, -360, new Matrix(2, 3, 4, 5, 6, 7), false, true, -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 360, 360, new Matrix(2, 3, 4, 5, 6, 7), false, true, -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 720, 720, new Matrix(2, 3, 4, 5, 6, 7), false, true, -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 720, 720, new Matrix(2, 3, 4, 5, 6, 7), false, true, -2 };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 20, double.NaN, new Matrix(double.NaN, double.NaN, 4.72794, 6.09191, 6, 7), false, true, double.NaN };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), double.NaN, 30, new Matrix(4.3094, 5.88675, double.NaN, double.NaN, 6, 7), false, true, double.NaN };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, 6, 7), false, true, double.NaN };
+
+        // No inverse.
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -90, -180, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -90, 180, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 90, -180, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -90, 0, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, -180, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, 0, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 90, 180, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 90, 0, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 180, 0, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, 180, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 180, 180, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 270, 270, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 180, 270, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 270, 270, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -20, -30, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 20, 30, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -380, -390, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 380, 390, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -740, -750, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 740, 750, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 35, 0, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, 35, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -720, -720, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -360, -360, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 360, 360, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 720, 720, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 720, 720, new Matrix(0, 0, 0, 0, 0, 0), false, false, 0 };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 20, double.NaN, new Matrix(double.NaN, double.NaN, 0, 0, 0, 0), false, true, double.NaN };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), double.NaN, 30, new Matrix(0, 0, double.NaN, double.NaN, 0, 0), false, true, double.NaN };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), double.NaN, double.NaN, new Matrix(double.NaN, double.NaN, double.NaN, double.NaN, 0, 0), false, true, double.NaN };
+    }
+    
+    [Theory]
+    [MemberData(nameof(SkewPrepend_TestData))]
+    public void SkewPrepend_Invoke_Success(Matrix matrix, double skewX, double skewY, Matrix expected, bool expectedIsIdentity, bool expectedHasInverse, double expectedDeterminant)
+    {
+        matrix.SkewPrepend(skewX, skewY);
+        Helpers.AssertEqualRounded(expected, matrix);
+        Assert.Equal(expectedIsIdentity, matrix.IsIdentity);
+        Assert.Equal(expectedHasInverse, matrix.HasInverse);
+        Assert.Equal(expectedDeterminant, matrix.Determinant, precision: 5);
+    }
+
+    public static IEnumerable<object[]> ToString_TestData()
+    {
+        foreach (Matrix matrix in IdentityMatrices())
+        {
+            yield return new object[] { matrix, "Identity" };
+        }
+
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), "0,0,0,0,0,0" };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), "2,3,4,5,6,7" };
+        yield return new object[] { new Matrix(2.2, 3.3, 4.4, 5.5, 6.6, 7.7), "2.2,3.3,4.4,5.5,6.6,7.7" };
+        yield return new object[] { new Matrix(-1, -2, -3, -4, -5, -6), "-1,-2,-3,-4,-5,-6" };
+    }
+
+    [Theory]
+    [MemberData(nameof(ToString_TestData))]
+    public void ToString_Invoke_ReturnsExpected(Matrix matrix, string expected)
+    {
+        Assert.Equal(expected, matrix.ToString());
+    }
+
+    [Theory]
+    [MemberData(nameof(ToString_TestData))]
+    public void ToString_InvokeIFormatProviderInvariantCulture_ReturnsExpected(Matrix matrix, string expected)
+    {
+        Assert.Equal(expected, matrix.ToString(CultureInfo.InvariantCulture));
+    }
+
+    public static IEnumerable<object[]> ToString_IFormatProviderCustom_TestData()
+    {
+        foreach (Matrix matrix in IdentityMatrices())
+        {
+            yield return new object[] { matrix, "|", "Identity" };
+            yield return new object[] { matrix, "|_", "Identity" };
+            yield return new object[] { matrix, ",_", "Identity" };
+            yield return new object[] { matrix, ",", "Identity" };
+            yield return new object[] { matrix, ";", "Identity" };
+            yield return new object[] { matrix, " ", "Identity" };
+        }
+
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), "|", "0,0,0,0,0,0"  };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), "|_", "0,0,0,0,0,0" };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), ",_", "0;0;0;0;0;0" };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), ",", "0;0;0;0;0;0" };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), ";", "0,0,0,0,0,0" };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), " ", "0,0,0,0,0,0" };
+        
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), "|", "2,3,4,5,6,7" };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), "|_", "2,3,4,5,6,7" };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), ",_", "2;3;4;5;6;7" };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), ",", "2;3;4;5;6;7" };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6,  7), ";", "2,3,4,5,6,7" };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6,  7), " ", "2,3,4,5,6,7" };
+
+        yield return new object[] { new Matrix(2.2, 3.3, 4.4, 5.5, 6.6, 7.7), "|", "2|2,3|3,4|4,5|5,6|6,7|7" };
+        yield return new object[] { new Matrix(2.2, 3.3, 4.4, 5.5, 6.6, 7.7), "|_", "2|_2,3|_3,4|_4,5|_5,6|_6,7|_7" };
+        yield return new object[] { new Matrix(2.2, 3.3, 4.4, 5.5, 6.6, 7.7), ",_", "2,_2;3,_3;4,_4;5,_5;6,_6;7,_7" };
+        yield return new object[] { new Matrix(2.2, 3.3, 4.4, 5.5, 6.6, 7.7), ",", "2,2;3,3;4,4;5,5;6,6;7,7" };
+        yield return new object[] { new Matrix(2.2, 3.3, 4.4, 5.5, 6.6, 7.7), ";", "2;2,3;3,4;4,5;5,6;6,7;7" };
+        yield return new object[] { new Matrix(2.2, 3.3, 4.4, 5.5, 6.6, 7.7), " ", "2 2,3 3,4 4,5 5,6 6,7 7" };
+
+        yield return new object[] { new Matrix(-1, -2, -3, -4, -5, -6), "|", "-1,-2,-3,-4,-5,-6" };
+        yield return new object[] { new Matrix(-1, -2, -3, -4, -5, -6), "|_", "-1,-2,-3,-4,-5,-6" };
+        yield return new object[] { new Matrix(-1, -2, -3, -4, -5, -6), ",_", "-1;-2;-3;-4;-5;-6" };
+        yield return new object[] { new Matrix(-1, -2, -3, -4, -5, -6), ",", "-1;-2;-3;-4;-5;-6" };
+        yield return new object[] { new Matrix(-1, -2, -3, -4, -5, -6), ";", "-1,-2,-3,-4,-5,-6" };
+        yield return new object[] { new Matrix(-1, -2, -3, -4, -5, -6), " ", "-1,-2,-3,-4,-5,-6" };
+    }
+
+    [Theory]
+    [MemberData(nameof(ToString_IFormatProviderCustom_TestData))]
+    public void ToString_InvokeIFormatProviderCustom_ReturnsExpected(Matrix matrix, string numberDecimalSeparator, string expected)
+    {
+        var culture = new CultureInfo("en-US");
+        NumberFormatInfo formatInfo = culture.NumberFormat;
+        formatInfo.NumberDecimalSeparator = numberDecimalSeparator;
+
+        Assert.Equal(expected, matrix.ToString(formatInfo));
+    }
+
+    [Theory]
+    [MemberData(nameof(ToString_TestData))]
+    public void ToString_InvokeIFormattableInvariantCulture_ReturnsExpected(Matrix matrix, string expected)
+    {
+        IFormattable formattable = matrix;
+
+        Assert.Equal(expected, formattable.ToString(null, null));
+        Assert.Equal(expected, formattable.ToString(null, CultureInfo.InvariantCulture));
+    }
+
+    public static IEnumerable<object[]> ToString_IFormattableCustomFormat_TestData()
+    {
+        yield return new object[] { "|", "1|23,2|35,3|00,4|00,5|00,6|00" };
+        yield return new object[] { "|_", "1|_23,2|_35,3|_00,4|_00,5|_00,6|_00" };
+        yield return new object[] { ",_", "1,_23;2,_35;3,_00;4,_00;5,_00;6,_00" };
+        yield return new object[] { ",", "1,23;2,35;3,00;4,00;5,00;6,00" };
+        yield return new object[] { ";", "1;23,2;35,3;00,4;00,5;00,6;00" };
+        yield return new object[] { " ", "1 23,2 35,3 00,4 00,5 00,6 00" };
+    }
+
+    [Theory]
+    [MemberData(nameof(ToString_IFormattableCustomFormat_TestData))]
+    public void ToString_InvokeIFormattableCustomFormat_ReturnsExpected(string numberDecimalSeparator, string expected)
+    {
+        var matrix = new Matrix(1.23456, 2.34567, 3, 4, 5, 6);
+        IFormattable formattable = matrix;
+
+        var culture = new CultureInfo("en-US");
+        NumberFormatInfo formatInfo = culture.NumberFormat;
+        formatInfo.NumberDecimalSeparator = numberDecimalSeparator;
+
+        Assert.Equal(expected, formattable.ToString("F2", formatInfo));
+    }
+
+    public static IEnumerable<object[]> Transform_Point_TestData()
+    {
+        // Identity.
+        foreach (Matrix matrix in MatrixTests.IdentityMatrices())
+        {
+            yield return new object[] { matrix, new Point(1, 2), new Point(1, 2) };
+        }
+
+        // Scale.
+        yield return new object[] { new Matrix(2, 0, 0, 1, 0, 0), new Point(1, 2), new Point(2, 2) };
+        yield return new object[] { new Matrix(1, 0, 0, 2, 0, 0), new Point(1, 2), new Point(1, 4) };
+        yield return new object[] { new Matrix(0, 0, 0, 3, 0, 0), new Point(1, 2), new Point(0, 6) };
+        yield return new object[] { new Matrix(2, 0, 0, 0, 0, 0), new Point(1, 2), new Point(2, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Point(1, 2), new Point(0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), new Point(1, 2), new Point(2, 6) };
+        yield return new object[] { new Matrix(-2, 0, 0, 3, 0, 0), new Point(1, 2), new Point(-2, 6) };
+        yield return new object[] { new Matrix(2, 0, 0, -3, 0, 0), new Point(1, 2), new Point(2, -6) };
+        yield return new object[] { new Matrix(-2, 0, 0, -3, 0, 0), new Point(1, 2), new Point(-2, -6) };
+
+        // Skew.
+        yield return new object[] { new Matrix(1, 2, 0, 1, 0, 0), new Point(1, 2), new Point(1, 4) };
+        yield return new object[] { new Matrix(1, 0, 3, 1, 0, 0), new Point(1, 2), new Point(7, 2) };
+        yield return new object[] { new Matrix(1, 2, 3, 1, 0, 0), new Point(1, 2), new Point(7, 4) };
+
+        // Translate.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 0), new Point(1, 2), new Point(3, 2) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 0, 3), new Point(1, 2), new Point(1, 5) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), new Point(1, 2), new Point(3, 5) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, -2, 0), new Point(1, 2), new Point(-1, 2) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 0, -3), new Point(1, 2), new Point(1, -1) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, -2, -3), new Point(1, 2), new Point(-1, -1) };
+
+        // Translate + Scale.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 4, 5), new Point(1, 2), new Point(6, 11) };
+
+        // Translate + Skew.
+        yield return new object[] { new Matrix(1, 2, 3, 1, 4, 5), new Point(1, 2), new Point(11, 9) };
+
+        // Skew + Scale.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Point(1, 2), new Point(10, 13) };
+
+        // Complex.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Point(1, 2), new Point(16, 20) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Point(1, 2), new Point(0, 0) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Point(1.1, 2.2), new Point(17, 21.3) };
+
+        // Other cases.
+        yield return new object[] { Matrix.Identity, new Point(-1, -2), new Point(-1, -2) };
+        yield return new object[] { new Matrix(), new Point(-1, -2), new Point(-1, -2) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 0, 0), new Point(-1, -2), new Point(-1, -2) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Point(-1, -2), new Point(-4, -6) };
+
+        yield return new object[] { Matrix.Identity, new Point(), new Point() };
+        yield return new object[] { new Matrix(), new Point(), new Point() };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 0, 0), new Point(), new Point() };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Point(), new Point(6, 7) };
+    }
+
+    [Theory]
+    [MemberData(nameof(Transform_Point_TestData))]
+    public void Transform_InvokePoint_ReturnsExpected(Matrix matrix, Point point, Point expected)
+    {
+        Assert.Equal(expected, matrix.Transform(point));
+    }
+
+    public static IEnumerable<object?[]> Transform_PointArray_TestData()
+    {
+        foreach (object[] testData in Transform_Point_TestData())
+        {
+            yield return new object[] { (Matrix)testData[0], new Point[] { (Point)testData[1] }, new Point[] { (Point)testData[2] } };
+        }
+
+        // Other cases.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Point[0], new Point[0] };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Point[] { new Point(1, 2), new Point(2, 3) }, new Point[] { new Point(16, 20), new Point(22, 28) } };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), null, null };
+    }
+
+    [Theory]
+    [MemberData(nameof(Transform_PointArray_TestData))]
+    public void Transform_InvokePointArray_ReturnsExpected(Matrix matrix, Point[] points, Point[] expected)
+    {
+        matrix.Transform(points);
+        Assert.Equal(expected, points);
+    }
+
+    public static IEnumerable<object[]> Transform_Vector_TestData()
+    {
+        // Identity.
+        foreach (Matrix matrix in MatrixTests.IdentityMatrices())
+        {
+            yield return new object[] { matrix, new Vector(1, 2), new Vector(1, 2) };
+        }
+
+        // Scale.
+        yield return new object[] { new Matrix(2, 0, 0, 1, 0, 0), new Vector(1, 2), new Vector(2, 2) };
+        yield return new object[] { new Matrix(1, 0, 0, 2, 0, 0), new Vector(1, 2), new Vector(1, 4) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), new Vector(1, 2), new Vector(2, 6) };
+        yield return new object[] { new Matrix(0, 0, 0, 3, 0, 0), new Vector(1, 2), new Vector(0, 6) };
+        yield return new object[] { new Matrix(2, 0, 0, 0, 0, 0), new Vector(1, 2), new Vector(2, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Vector(1, 2), new Vector(0, 0) };
+        yield return new object[] { new Matrix(-2, 0, 0, 3, 0, 0), new Vector(1, 2), new Vector(-2, 6) };
+        yield return new object[] { new Matrix(2, 0, 0, -3, 0, 0), new Vector(1, 2), new Vector(2, -6) };
+        yield return new object[] { new Matrix(-2, 0, 0, -3, 0, 0), new Vector(1, 2), new Vector(-2, -6) };
+
+        // Skew.
+        yield return new object[] { new Matrix(1, 2, 0, 1, 0, 0), new Vector(1, 2), new Vector(1, 4) };
+        yield return new object[] { new Matrix(1, 0, 3, 1, 0, 0), new Vector(1, 2), new Vector(7, 2) };
+        yield return new object[] { new Matrix(1, 2, 3, 1, 0, 0), new Vector(1, 2), new Vector(7, 4) };
+
+        // Translate.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 0), new Vector(1, 2), new Vector(1, 2) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 0, 3), new Vector(1, 2), new Vector(1, 2) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), new Vector(1, 2), new Vector(1, 2) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, -2, 0), new Vector(1, 2), new Vector(1, 2) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 0, -3), new Vector(1, 2), new Vector(1, 2) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, -2, -3), new Vector(1, 2), new Vector(1, 2) };
+
+        // Translate + Scale.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 4, 5), new Vector(1, 2), new Vector(2, 6) };
+
+        // Translate + Skew.
+        yield return new object[] { new Matrix(1, 2, 3, 1, 4, 5), new Vector(1, 2), new Vector(7, 4) };
+
+        // Skew + Scale.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 0, 0), new Vector(1, 2), new Vector(10, 13) };
+
+        // Complex.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Vector(1, 2), new Vector(10, 13) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), new Vector(1, 2), new Vector(0, 0) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Vector(1.1, 2.2), new Vector(11, 14.3) };
+
+        // Other cases.
+        yield return new object[] { Matrix.Identity, new Vector(-1, -2), new Vector(-1, -2) };
+        yield return new object[] { new Matrix(), new Vector(-1, -2), new Vector(-1, -2) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 0, 0), new Vector(-1, -2), new Vector(-1, -2) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Vector(-1, -2), new Vector(-10, -13) };
+
+        // Zero.
+        yield return new object[] { Matrix.Identity, new Vector(0, 0), new Vector() };
+        yield return new object[] { new Matrix(), new Vector(0, 0), new Vector() };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 0, 0), new Vector(0, 0), new Vector() };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Vector(0, 0), new Vector() };
+
+        // Default.
+        yield return new object[] { Matrix.Identity, new Vector(), new Vector() };
+        yield return new object[] { new Matrix(), new Vector(), new Vector() };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 0, 0), new Vector(), new Vector() };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Vector(), new Vector() };
+    }
+
+    [Theory]
+    [MemberData(nameof(Transform_Vector_TestData))]
+    public void Transform_InvokeVector_ReturnsExpected(Matrix matrix, Vector vector, Vector expected)
+    {
+        Assert.Equal(expected, matrix.Transform(vector));
+    }
+
+    public static IEnumerable<object?[]> Transform_VectorArray_TestData()
+    {
+        foreach (object[] testData in Transform_Vector_TestData())
+        {
+            yield return new object[] { (Matrix)testData[0], new Vector[] { (Vector)testData[1] }, new Vector[] { (Vector)testData[2] } };
+        }
+
+        // Other cases.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Vector[0], new Vector[0] };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), new Vector[] { new Vector(1, 2), new Vector(2, 3) }, new Vector[] { new Vector(10, 13), new Vector(16, 21) } };
+        yield return new object?[] { new Matrix(2, 3, 4, 5, 6, 7), null, null };
+    }
+
+    [Theory]
+    [MemberData(nameof(Transform_VectorArray_TestData))]
+    public void Transform_InvokeVectorArray_ReturnsExpected(Matrix matrix, Vector[] vectors, Vector[] expected)
+    {
+        matrix.Transform(vectors);
+        Assert.Equal(expected, vectors);
+    }
+
+    public static IEnumerable<object[]> Translate_TestData()
+    {        // Identity
+        foreach (Matrix matrix in IdentityMatrices())
+        {
+            yield return new object[] { matrix, -1, -2, new Matrix(1, 0, 0, 1, -1, -2) };
+            yield return new object[] { matrix, -1, 0, new Matrix(1, 0, 0, 1, -1, 0) };
+            yield return new object[] { matrix, 0, -2, new Matrix(1, 0, 0, 1, 0, -2) };
+            yield return new object[] { matrix, 0, 0, new Matrix(1, 0, 0, 1, 0, 0) };
+            yield return new object[] { matrix, 1, 0, new Matrix(1, 0, 0, 1, 1, 0) };
+            yield return new object[] { matrix, 0, 2, new Matrix(1, 0, 0, 1, 0, 2) };
+            yield return new object[] { matrix, 1, 2, new Matrix(1, 0, 0, 1, 1, 2) };
+            yield return new object[] { matrix, 1.1, 2.2, new Matrix(1, 0, 0, 1, 1.1, 2.2) };
+            yield return new object[] { matrix, -2, -3, new Matrix(1, 0, 0, 1, -2, -3) };
+            yield return new object[] { matrix, double.NaN, 2, new Matrix(1, 0, 0, 1, double.NaN, 2) };
+            yield return new object[] { matrix, 1, double.NaN, new Matrix(1, 0, 0, 1, 1, double.NaN) };
+            yield return new object[] { matrix, double.NaN, double.NaN, new Matrix(1, 0, 0, 1, double.NaN, double.NaN) };
+        }
+
+        // Scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -1, -2, new Matrix(2, 0, 0, 3, -1, -2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -1, 0, new Matrix(2, 0, 0, 3, -1, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, -2, new Matrix(2, 0, 0, 3, 0, -2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, 0, new Matrix(2, 0, 0, 3, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1, 0, new Matrix(2, 0, 0, 3, 1, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, 2, new Matrix(2, 0, 0, 3, 0, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1, 2, new Matrix(2, 0, 0, 3, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1.1, 2.2, new Matrix(2, 0, 0, 3, 1.1, 2.2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -2, -3, new Matrix(2, 0, 0, 3, -2, -3) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), double.NaN, 2, new Matrix(2, 0, 0, 3, double.NaN, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1, double.NaN, new Matrix(2, 0, 0, 3, 1, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), double.NaN, double.NaN, new Matrix(2, 0, 0, 3, double.NaN, double.NaN) };
+
+        // Skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -1, -2, new Matrix(1, 0.5, 0.75, 1, -1, -2) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -1, 0, new Matrix(1, 0.5, 0.75, 1, -1, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, -2, new Matrix(1, 0.5, 0.75, 1, 0, -2) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, 0, new Matrix(1, 0.5, 0.75, 1, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1, 0, new Matrix(1, 0.5, 0.75, 1, 1, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, 2, new Matrix(1, 0.5, 0.75, 1, 0, 2) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1, 2, new Matrix(1, 0.5, 0.75, 1, 1, 2) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1.1, 2.2, new Matrix(1, 0.5, 0.75, 1, 1.1, 2.2) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -2, -3, new Matrix(1, 0.5, 0.75, 1, -2, -3) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), double.NaN, 2, new Matrix(1, 0.5, 0.75, 1, double.NaN, 2) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1, double.NaN, new Matrix(1, 0.5, 0.75, 1, 1, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), double.NaN, double.NaN, new Matrix(1, 0.5, 0.75, 1, double.NaN, double.NaN) };
+
+        // Translated.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -1, -2, new Matrix(1, 0, 0, 1, 1, 1) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -1, 0, new Matrix(1, 0, 0, 1, 1, 3) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, -2, new Matrix(1, 0, 0, 1, 2, 1) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, 0, new Matrix(1, 0, 0, 1, 2, 3) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1, 0, new Matrix(1, 0, 0, 1, 3, 3) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, 2, new Matrix(1, 0, 0, 1, 2, 5) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1, 2, new Matrix(1, 0, 0, 1, 3, 5) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1.1, 2.2, new Matrix(1, 0, 0, 1, 3.1, 5.2) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -2, -3, new Matrix(1, 0, 0, 1, 0, 0) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), double.NaN, 2, new Matrix(1, 0, 0, 1, double.NaN, 5) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1, double.NaN, new Matrix(1, 0, 0, 1, 3, double.NaN) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), double.NaN, double.NaN, new Matrix(1, 0, 0, 1, double.NaN, double.NaN) };
+
+        // Translated and scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -1, -2, new Matrix(2, 0, 0, 3, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -1, 0, new Matrix(2, 0, 0, 3, 0, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, -2, new Matrix(2, 0, 0, 3, 1, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, 0, new Matrix(2, 0, 0, 3, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1, 0, new Matrix(2, 0, 0, 3, 2, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, 2, new Matrix(2, 0, 0, 3, 1, 4) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1, 2, new Matrix(2, 0, 0, 3, 2, 4) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1.1, 2.2, new Matrix(2, 0, 0, 3, 2.1, 4.2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -2, -3, new Matrix(2, 0, 0, 3, -1, -1) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), double.NaN, 2, new Matrix(2, 0, 0, 3, double.NaN, 4) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1, double.NaN, new Matrix(2, 0, 0, 3, 2, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), double.NaN, double.NaN, new Matrix(2, 0, 0, 3, double.NaN, double.NaN) };
+
+        // Translated and skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -1, -2, new Matrix(1, 0.5, 0.75, 1, 1, 1) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -1, 0, new Matrix(1, 0.5, 0.75, 1, 1, 3) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, -2, new Matrix(1, 0.5, 0.75, 1, 2, 1) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, 0, new Matrix(1, 0.5, 0.75, 1, 2, 3) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1, 0, new Matrix(1, 0.5, 0.75, 1, 3, 3) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, 2, new Matrix(1, 0.5, 0.75, 1, 2, 5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1, 2, new Matrix(1, 0.5, 0.75, 1, 3, 5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1.1, 2.2, new Matrix(1, 0.5, 0.75, 1, 3.1, 5.2) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -2, -3, new Matrix(1, 0.5, 0.75, 1, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), double.NaN, 2, new Matrix(1, 0.5, 0.75, 1, double.NaN, 5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1, double.NaN, new Matrix(1, 0.5, 0.75, 1, 3, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), double.NaN, double.NaN, new Matrix(1, 0.5, 0.75, 1, double.NaN, double.NaN) };
+
+        // Skewed and scaled.
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -1, -2, new Matrix(2, 0.5, 0.75, 3, -1, -2) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -1, 0, new Matrix(2, 0.5, 0.75, 3, -1, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, -2, new Matrix(2, 0.5, 0.75, 3, 0, -2) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, 0, new Matrix(2, 0.5, 0.75, 3, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1, 0, new Matrix(2, 0.5, 0.75, 3, 1, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, 2, new Matrix(2, 0.5, 0.75, 3, 0, 2) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1, 2, new Matrix(2, 0.5, 0.75, 3, 1, 2) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1.1, 2.2, new Matrix(2, 0.5, 0.75, 3, 1.1, 2.2) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -2, -3, new Matrix(2, 0.5, 0.75, 3, -2, -3) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), double.NaN, 2, new Matrix(2, 0.5, 0.75, 3, double.NaN, 2) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1, double.NaN, new Matrix(2, 0.5, 0.75, 3, 1, double.NaN) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), double.NaN, double.NaN, new Matrix(2, 0.5, 0.75, 3, double.NaN, double.NaN) };
+
+        // Complex.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -1, -2, new Matrix(2, 3, 4, 5, 5, 5) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -1, 0, new Matrix(2, 3, 4, 5, 5, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, -2, new Matrix(2, 3, 4, 5, 6, 5) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, 0, new Matrix(2, 3, 4, 5, 6, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1, 0, new Matrix(2, 3, 4, 5, 7, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, 2, new Matrix(2, 3, 4, 5, 6, 9) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1, 2, new Matrix(2, 3, 4, 5, 7, 9) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1.1, 2.2, new Matrix(2, 3, 4, 5, 7.1, 9.2) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -2, -3, new Matrix(2, 3, 4, 5, 4, 4) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), double.NaN, 2, new Matrix(2, 3, 4, 5, double.NaN, 9) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1, double.NaN, new Matrix(2, 3, 4, 5, 7, double.NaN) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), double.NaN, double.NaN, new Matrix(2, 3, 4, 5, double.NaN, double.NaN) };
+
+        // No inverse.
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -1, -2, new Matrix(0, 0, 0, 0, -1, -2) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -1, 0, new Matrix(0, 0, 0, 0, -1, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, -2, new Matrix(0, 0, 0, 0, 0, -2) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1, 0, new Matrix(0, 0, 0, 0, 1, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, 2, new Matrix(0, 0, 0, 0, 0, 2) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1, 2, new Matrix(0, 0, 0, 0, 1, 2) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1.1, 2.2, new Matrix(0, 0, 0, 0, 1.1, 2.2) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -2, -3, new Matrix(0, 0, 0, 0, -2, -3) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), double.NaN, 2, new Matrix(0, 0, 0, 0, double.NaN, 2) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1, double.NaN, new Matrix(0, 0, 0, 0, 1, double.NaN) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), double.NaN, double.NaN, new Matrix(0, 0, 0, 0, double.NaN, double.NaN) };
+    }
+
+    [Theory]
+    [MemberData(nameof(Translate_TestData))]
+    public void Translate_Invoke_Success(Matrix matrix, double offsetX, double offsetY, Matrix expected)
+    {
+        matrix.Translate(offsetX, offsetY);
+        Helpers.AssertEqualRounded(expected, matrix);
+        Assert.Equal(expected.IsIdentity, matrix.IsIdentity);
+        Assert.Equal(expected.HasInverse, matrix.HasInverse);
+        Assert.Equal(expected.Determinant, matrix.Determinant, precision: 5);
+    }
+
+    public static IEnumerable<object[]> TranslatePrepend_TestData()
+    {        
+        // Identity
+        foreach (Matrix matrix in IdentityMatrices())
+        {
+            yield return new object[] { matrix, -1, -2, new Matrix(1, 0, 0, 1, -1, -2) };
+            yield return new object[] { matrix, -1, 0, new Matrix(1, 0, 0, 1, -1, 0) };
+            yield return new object[] { matrix, 0, -2, new Matrix(1, 0, 0, 1, 0, -2) };
+            yield return new object[] { matrix, 0, 0, new Matrix(1, 0, 0, 1, 0, 0) };
+            yield return new object[] { matrix, 1, 0, new Matrix(1, 0, 0, 1, 1, 0) };
+            yield return new object[] { matrix, 0, 2, new Matrix(1, 0, 0, 1, 0, 2) };
+            yield return new object[] { matrix, 1, 2, new Matrix(1, 0, 0, 1, 1, 2) };
+            yield return new object[] { matrix, 1.1, 2.2, new Matrix(1, 0, 0, 1, 1.1, 2.2) };
+            yield return new object[] { matrix, -2, -3, new Matrix(1, 0, 0, 1, -2, -3) };
+            yield return new object[] { matrix, double.NaN, 2, new Matrix(1, 0, 0, 1, double.NaN, 2) };
+            yield return new object[] { matrix, 1, double.NaN, new Matrix(1, 0, 0, 1, 1, double.NaN) };
+            yield return new object[] { matrix, double.NaN, double.NaN, new Matrix(1, 0, 0, 1, double.NaN, double.NaN) };
+        }
+
+        // Scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -1, -2, new Matrix(2, 0, 0, 3, -2, -6) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -1, 0, new Matrix(2, 0, 0, 3, -2, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, -2, new Matrix(2, 0, 0, 3, 0, -6) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, 0, new Matrix(2, 0, 0, 3, 0, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1, 0, new Matrix(2, 0, 0, 3, 2, 0) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 0, 2, new Matrix(2, 0, 0, 3, 0, 6) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1, 2, new Matrix(2, 0, 0, 3, 2, 6) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1.1, 2.2, new Matrix(2, 0, 0, 3, 2.2, 6.6) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), -2, -3, new Matrix(2, 0, 0, 3, -4, -9) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), double.NaN, 2, new Matrix(2, 0, 0, 3, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), 1, double.NaN, new Matrix(2, 0, 0, 3, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 0, 0), double.NaN, double.NaN, new Matrix(2, 0, 0, 3, double.NaN, double.NaN) };
+
+        // Skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -1, -2, new Matrix(1, 0.5, 0.75, 1, -2.5, -2.5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -1, 0, new Matrix(1, 0.5, 0.75, 1, -1, -0.5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, -2, new Matrix(1, 0.5, 0.75, 1, -1.5, -2) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, 0, new Matrix(1, 0.5, 0.75, 1, 0, 0) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1, 0, new Matrix(1, 0.5, 0.75, 1, 1, 0.5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 0, 2, new Matrix(1, 0.5, 0.75, 1, 1.5, 2) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1, 2, new Matrix(1, 0.5, 0.75, 1, 2.5, 2.5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1.1, 2.2, new Matrix(1, 0.5, 0.75, 1, 2.75, 2.75) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), -2, -3, new Matrix(1, 0.5, 0.75, 1, -4.25, -4) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), double.NaN, 2, new Matrix(1, 0.5, 0.75, 1, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), 1, double.NaN, new Matrix(1, 0.5, 0.75, 1, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 0, 0), double.NaN, double.NaN, new Matrix(1, 0.5, 0.75, 1, double.NaN, double.NaN) };
+
+        // Translated.
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -1, -2, new Matrix(1, 0, 0, 1, 1, 1) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -1, 0, new Matrix(1, 0, 0, 1, 1, 3) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, -2, new Matrix(1, 0, 0, 1, 2, 1) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, 0, new Matrix(1, 0, 0, 1, 2, 3) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1, 0, new Matrix(1, 0, 0, 1, 3, 3) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 0, 2, new Matrix(1, 0, 0, 1, 2, 5) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1, 2, new Matrix(1, 0, 0, 1, 3, 5) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1.1, 2.2, new Matrix(1, 0, 0, 1, 3.1, 5.2) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), -2, -3, new Matrix(1, 0, 0, 1, 0, 0) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), double.NaN, 2, new Matrix(1, 0, 0, 1, double.NaN, 5) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), 1, double.NaN, new Matrix(1, 0, 0, 1, 3, double.NaN) };
+        yield return new object[] { new Matrix(1, 0, 0, 1, 2, 3), double.NaN, double.NaN, new Matrix(1, 0, 0, 1, double.NaN, double.NaN) };
+
+        // Translated and scaled.
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -1, -2, new Matrix(2, 0, 0, 3, -1, -4) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -1, 0, new Matrix(2, 0, 0, 3, -1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, -2, new Matrix(2, 0, 0, 3, 1, -4) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, 0, new Matrix(2, 0, 0, 3, 1, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1, 0, new Matrix(2, 0, 0, 3, 3, 2) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 0, 2, new Matrix(2, 0, 0, 3, 1, 8) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1, 2, new Matrix(2, 0, 0, 3, 3, 8) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1.1, 2.2, new Matrix(2, 0, 0, 3, 3.2, 8.6) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), -2, -3, new Matrix(2, 0, 0, 3, -3, -7) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), double.NaN, 2, new Matrix(2, 0, 0, 3, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), 1, double.NaN, new Matrix(2, 0, 0, 3, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0, 0, 3, 1, 2), double.NaN, double.NaN, new Matrix(2, 0, 0, 3, double.NaN, double.NaN) };
+
+        // Translated and skewed.
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -1, -2, new Matrix(1, 0.5, 0.75, 1, -0.5, 0.5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -1, 0, new Matrix(1, 0.5, 0.75, 1, 1, 2.5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, -2, new Matrix(1, 0.5, 0.75, 1, 0.5, 1) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, 0, new Matrix(1, 0.5, 0.75, 1, 2, 3) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1, 0, new Matrix(1, 0.5, 0.75, 1, 3, 3.5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 0, 2, new Matrix(1, 0.5, 0.75, 1, 3.5, 5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1, 2, new Matrix(1, 0.5, 0.75, 1, 4.5, 5.5) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1.1, 2.2, new Matrix(1, 0.5, 0.75, 1, 4.75, 5.75) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), -2, -3, new Matrix(1, 0.5, 0.75, 1, -2.25, -1) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), double.NaN, 2, new Matrix(1, 0.5, 0.75, 1, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), 1, double.NaN, new Matrix(1, 0.5, 0.75, 1, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(1, 0.5, 0.75, 1, 2, 3), double.NaN, double.NaN, new Matrix(1, 0.5, 0.75, 1, double.NaN, double.NaN) };
+
+        // Skewed and scaled.
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -1, -2, new Matrix(2, 0.5, 0.75, 3, -3.5, -6.5) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -1, 0, new Matrix(2, 0.5, 0.75, 3, -2, -0.5) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, -2, new Matrix(2, 0.5, 0.75, 3, -1.5, -6) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, 0, new Matrix(2, 0.5, 0.75, 3, 0, 0) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1, 0, new Matrix(2, 0.5, 0.75, 3, 2, 0.5) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 0, 2, new Matrix(2, 0.5, 0.75, 3, 1.5, 6) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1, 2, new Matrix(2, 0.5, 0.75, 3, 3.5, 6.5) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1.1, 2.2, new Matrix(2, 0.5, 0.75, 3, 3.85, 7.15) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), -2, -3, new Matrix(2, 0.5, 0.75, 3, -6.25, -10) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), double.NaN, 2, new Matrix(2, 0.5, 0.75, 3, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), 1, double.NaN, new Matrix(2, 0.5, 0.75, 3, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 0.5, 0.75, 3, 0, 0), double.NaN, double.NaN, new Matrix(2, 0.5, 0.75, 3, double.NaN, double.NaN) };
+
+        // Complex.
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -1, -2, new Matrix(2, 3, 4, 5, -4, -6) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -1, 0, new Matrix(2, 3, 4, 5, 4, 4) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, -2, new Matrix(2, 3, 4, 5, -2, -3) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, 0, new Matrix(2, 3, 4, 5, 6, 7) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1, 0, new Matrix(2, 3, 4, 5, 8, 10) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 0, 2, new Matrix(2, 3, 4, 5, 14, 17) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1, 2, new Matrix(2, 3, 4, 5, 16, 20) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1.1, 2.2, new Matrix(2, 3, 4, 5, 17, 21.3) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), -2, -3, new Matrix(2, 3, 4, 5, -10, -14) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), double.NaN, 2, new Matrix(2, 3, 4, 5, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), 1, double.NaN, new Matrix(2, 3, 4, 5, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(2, 3, 4, 5, 6, 7), double.NaN, double.NaN, new Matrix(2, 3, 4, 5, double.NaN, double.NaN) };
+
+        // No inverse.
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -1, -2, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -1, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, -2, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1, 0, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 0, 2, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1, 2, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1.1, 2.2, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), -2, -3, new Matrix(0, 0, 0, 0, 0, 0) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), double.NaN, 2, new Matrix(0, 0, 0, 0, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), 1, double.NaN, new Matrix(0, 0, 0, 0, double.NaN, double.NaN) };
+        yield return new object[] { new Matrix(0, 0, 0, 0, 0, 0), double.NaN, double.NaN, new Matrix(0, 0, 0, 0, double.NaN, double.NaN) };
+    }
+
+    [Theory]
+    [MemberData(nameof(TranslatePrepend_TestData))]
+    public void TranslatePrepend_Invoke_Success(Matrix matrix, double offsetX, double offsetY, Matrix expected)
+    {
+        matrix.TranslatePrepend(offsetX, offsetY);
+        Helpers.AssertEqualRounded(expected, matrix);
+        Assert.Equal(expected.IsIdentity, matrix.IsIdentity);
+        Assert.Equal(expected.HasInverse, matrix.HasInverse);
+        Assert.Equal(expected.Determinant, matrix.Determinant, precision: 5);
+    }
+
+    public static IEnumerable<object[]> Scale_SetIdentity_TestData()
+    {
+        foreach (Matrix matrix in IdentityMatrices())
+        {
+            yield return new object[] { matrix, double.NegativeInfinity, false };
+            yield return new object[] { matrix, double.MinValue, false };
+            yield return new object[] { matrix, -1, false };
+            yield return new object[] { matrix, double.NegativeZero, false };
+            yield return new object[] { matrix, 0, false };
+            yield return new object[] { matrix, 1, true };
+            yield return new object[] { matrix, double.MaxValue, false };
+            yield return new object[] { matrix, double.PositiveInfinity, false };
+            yield return new object[] { matrix, double.NaN, false };
+        }
+    }
+
+    [Theory]
+    [MemberData(nameof(Scale_SetIdentity_TestData))]
+    public void M11_SetIdentity_GetReturnsExpected(Matrix matrix, double value, bool expectedIsIdentity)
+    {
+        // Set.
+        matrix.M11 = value;
+        Assert.Equal(value, matrix.M11);
+        Assert.Equal(0, matrix.M12);
+        Assert.Equal(0, matrix.M21);
+        Assert.Equal(1, matrix.M22);
+        Assert.Equal(0, matrix.OffsetX);
+        Assert.Equal(0, matrix.OffsetY);
+        Assert.Equal(expectedIsIdentity, matrix.IsIdentity);
+
+        // Set again.
+        matrix.M11 = value;
+        Assert.Equal(value, matrix.M11);
+        Assert.Equal(0, matrix.M12);
+        Assert.Equal(0, matrix.M21);
+        Assert.Equal(1, matrix.M22);
+        Assert.Equal(0, matrix.OffsetX);
+        Assert.Equal(0, matrix.OffsetY);
+        Assert.Equal(expectedIsIdentity, matrix.IsIdentity);
+    }
+
+    public static IEnumerable<object[]> Scale_SetToIdentity_TestData()
+    {
+        yield return new object[] { double.NegativeInfinity, false };
+        yield return new object[] { double.MinValue, false };
+        yield return new object[] { -1, false };
+        yield return new object[] { double.NegativeZero, false };
+        yield return new object[] { 0, false };
+        yield return new object[] { 1, true };
+        yield return new object[] { double.MaxValue, false };
+        yield return new object[] { double.PositiveInfinity, false };
+        yield return new object[] { double.NaN, false };
+    }
+
+    [Theory]
+    [MemberData(nameof(Scale_SetToIdentity_TestData))]
+    public void M11_SetScaleToIdentity_GetReturnsExpected(double value, bool expectedIsIdentity)
+    {
+        var matrix = new Matrix(2, 0, 0, 1, 0, 0);
+
+        // Set.
+        matrix.M11 = value;
+        Assert.Equal(value, matrix.M11);
+        Assert.Equal(0, matrix.M12);
+        Assert.Equal(0, matrix.M21);
+        Assert.Equal(1, matrix.M22);
+        Assert.Equal(0, matrix.OffsetX);
+        Assert.Equal(0, matrix.OffsetY);
+        Assert.Equal(expectedIsIdentity, matrix.IsIdentity);
+
+        // Set again.
+        matrix.M11 = value;
+        Assert.Equal(value, matrix.M11);
+        Assert.Equal(0, matrix.M12);
+        Assert.Equal(0, matrix.M21);
+        Assert.Equal(1, matrix.M22);
+        Assert.Equal(0, matrix.OffsetX);
+        Assert.Equal(0, matrix.OffsetY);
+        Assert.Equal(expectedIsIdentity, matrix.IsIdentity);
+    }
+
+    public static IEnumerable<object[]> MatrixElement_Set_TestData()
+    {
+        yield return new object[] { double.NegativeInfinity };
+        yield return new object[] { double.MinValue };
+        yield return new object[] { -1 };
+        yield return new object[] { double.NegativeZero };
+        yield return new object[] { 0 };
+        yield return new object[] { 1 };
+        yield return new object[] { double.MaxValue };
+        yield return new object[] { double.PositiveInfinity };
+        yield return new object[] { double.NaN };
+    }
+
+    [Theory]
+    [MemberData(nameof(MatrixElement_Set_TestData))]
+    public void M11_Set_GetReturnsExpected(double value)
+    {
+        var matrix = new Matrix(2, 3, 4, 5, 6, 7);
+
+        // Set.
+        matrix.M11 = value;
+        Assert.Equal(value, matrix.M11);
+        Assert.Equal(3, matrix.M12);
+        Assert.Equal(4, matrix.M21);
+        Assert.Equal(5, matrix.M22);
+        Assert.Equal(6, matrix.OffsetX);
+        Assert.Equal(7, matrix.OffsetY);
+        Assert.False(matrix.IsIdentity);
+
+        // Set again.
+        matrix.M11 = value;
+        Assert.Equal(value, matrix.M11);
+        Assert.Equal(3, matrix.M12);
+        Assert.Equal(4, matrix.M21);
+        Assert.Equal(5, matrix.M22);
+        Assert.Equal(6, matrix.OffsetX);
+        Assert.Equal(7, matrix.OffsetY);
+        Assert.False(matrix.IsIdentity);
+    }
+
+    public static IEnumerable<object[]> NonScale_SetIdentity_TestData()
+    {
+        foreach (Matrix matrix in IdentityMatrices())
+        {
+            yield return new object[] { matrix, double.NegativeInfinity, false };
+            yield return new object[] { matrix, double.MinValue, false };
+            yield return new object[] { matrix, -1, false };
+            yield return new object[] { matrix, double.NegativeZero, true };
+            yield return new object[] { matrix, 0, true };
+            yield return new object[] { matrix, 1, false };
+            yield return new object[] { matrix, double.MaxValue, false };
+            yield return new object[] { matrix, double.PositiveInfinity, false };
+            yield return new object[] { matrix, double.NaN, false };
+        }
+    }
+
+    [Theory]
+    [MemberData(nameof(NonScale_SetIdentity_TestData))]
+    public void M12_SetIdentity_GetReturnsExpected(Matrix matrix, double value, bool expectedIsIdentity)
+    {
+        // Set.
+        matrix.M12 = value;
+        Assert.Equal(1, matrix.M11);
+        Assert.Equal(value, matrix.M12);
+        Assert.Equal(0, matrix.M21);
+        Assert.Equal(1, matrix.M22);
+        Assert.Equal(0, matrix.OffsetX);
+        Assert.Equal(0, matrix.OffsetY);
+        Assert.Equal(expectedIsIdentity, matrix.IsIdentity);
+
+        // Set again.
+        matrix.M12 = value;
+        Assert.Equal(1, matrix.M11);
+        Assert.Equal(value, matrix.M12);
+        Assert.Equal(0, matrix.M21);
+        Assert.Equal(1, matrix.M22);
+        Assert.Equal(0, matrix.OffsetX);
+        Assert.Equal(0, matrix.OffsetY);
+        Assert.Equal(expectedIsIdentity, matrix.IsIdentity);
+    }
+
+    public static IEnumerable<object[]> NonScale_SetToIdentity_TestData()
+    {
+        yield return new object[] { double.NegativeInfinity, false };
+        yield return new object[] { double.MinValue, false };
+        yield return new object[] { -1, false };
+        yield return new object[] { double.NegativeZero, true };
+        yield return new object[] { 0, true };
+        yield return new object[] { 1, false };
+        yield return new object[] { double.MaxValue, false };
+        yield return new object[] { double.PositiveInfinity, false };
+        yield return new object[] { double.NaN, false };
+    }
+
+    [Theory]
+    [MemberData(nameof(NonScale_SetToIdentity_TestData))]
+    public void M12_SetScaleToIdentity_GetReturnsExpected(double value, bool expectedIsIdentity)
+    {
+        var matrix = new Matrix(1, 1, 0, 1, 0, 0);
+
+        // Set.
+        matrix.M12 = value;
+        Assert.Equal(1, matrix.M11);
+        Assert.Equal(value, matrix.M12);
+        Assert.Equal(0, matrix.M21);
+        Assert.Equal(1, matrix.M22);
+        Assert.Equal(0, matrix.OffsetX);
+        Assert.Equal(0, matrix.OffsetY);
+        Assert.Equal(expectedIsIdentity, matrix.IsIdentity);
+
+        // Set again.
+        matrix.M12 = value;
+        Assert.Equal(1, matrix.M11);
+        Assert.Equal(value, matrix.M12);
+        Assert.Equal(0, matrix.M21);
+        Assert.Equal(1, matrix.M22);
+        Assert.Equal(0, matrix.OffsetX);
+        Assert.Equal(0, matrix.OffsetY);
+        Assert.Equal(expectedIsIdentity, matrix.IsIdentity);
+    }
+
+    [Theory]
+    [MemberData(nameof(MatrixElement_Set_TestData))]
+    public void M12_Set_GetReturnsExpected(double value)
+    {
+        var matrix = new Matrix(2, 3, 4, 5, 6, 7);
+
+        // Set.
+        matrix.M12 = value;
+        Assert.Equal(2, matrix.M11);
+        Assert.Equal(value, matrix.M12);
+        Assert.Equal(4, matrix.M21);
+        Assert.Equal(5, matrix.M22);
+        Assert.Equal(6, matrix.OffsetX);
+        Assert.Equal(7, matrix.OffsetY);
+        Assert.False(matrix.IsIdentity);
+
+        // Set again.
+        matrix.M12 = value;
+        Assert.Equal(2, matrix.M11);
+        Assert.Equal(value, matrix.M12);
+        Assert.Equal(4, matrix.M21);
+        Assert.Equal(5, matrix.M22);
+        Assert.Equal(6, matrix.OffsetX);
+        Assert.Equal(7, matrix.OffsetY);
+        Assert.False(matrix.IsIdentity);
+    }
+
+    [Theory]
+    [MemberData(nameof(NonScale_SetIdentity_TestData))]
+    public void M21_SetIdentity_GetReturnsExpected(Matrix matrix, double value, bool expectedIsIdentity)
+    {
+        // Set.
+        matrix.M21 = value;
+        Assert.Equal(1, matrix.M11);
+        Assert.Equal(0, matrix.M12);
+        Assert.Equal(value, matrix.M21);
+        Assert.Equal(1, matrix.M22);
+        Assert.Equal(0, matrix.OffsetX);
+        Assert.Equal(0, matrix.OffsetY);
+        Assert.Equal(expectedIsIdentity, matrix.IsIdentity);
+
+        // Set again.
+        matrix.M21 = value;
+        Assert.Equal(1, matrix.M11);
+        Assert.Equal(0, matrix.M12);
+        Assert.Equal(value, matrix.M21);
+        Assert.Equal(1, matrix.M22);
+        Assert.Equal(0, matrix.OffsetX);
+        Assert.Equal(0, matrix.OffsetY);
+        Assert.Equal(expectedIsIdentity, matrix.IsIdentity);
+    }
+
+    [Theory]
+    [MemberData(nameof(NonScale_SetToIdentity_TestData))]
+    public void M21_SetScaleToIdentity_GetReturnsExpected(double value, bool expectedIsIdentity)
+    {
+        var matrix = new Matrix(1, 0, 1, 1, 0, 0);
+
+        // Set.
+        matrix.M21 = value;
+        Assert.Equal(1, matrix.M11);
+        Assert.Equal(0, matrix.M12);
+        Assert.Equal(value, matrix.M21);
+        Assert.Equal(1, matrix.M22);
+        Assert.Equal(0, matrix.OffsetX);
+        Assert.Equal(0, matrix.OffsetY);
+        Assert.Equal(expectedIsIdentity, matrix.IsIdentity);
+
+        // Set again.
+        matrix.M21 = value;
+        Assert.Equal(1, matrix.M11);
+        Assert.Equal(0, matrix.M12);
+        Assert.Equal(value, matrix.M21);
+        Assert.Equal(1, matrix.M22);
+        Assert.Equal(0, matrix.OffsetX);
+        Assert.Equal(0, matrix.OffsetY);
+        Assert.Equal(expectedIsIdentity, matrix.IsIdentity);
+    }
+
+    [Theory]
+    [MemberData(nameof(MatrixElement_Set_TestData))]
+    public void M21_Set_GetReturnsExpected(double value)
+    {
+        var matrix = new Matrix(2, 3, 4, 5, 6, 7);
+
+        // Set.
+        matrix.M21 = value;
+        Assert.Equal(2, matrix.M11);
+        Assert.Equal(3, matrix.M12);
+        Assert.Equal(value, matrix.M21);
+        Assert.Equal(5, matrix.M22);
+        Assert.Equal(6, matrix.OffsetX);
+        Assert.Equal(7, matrix.OffsetY);
+        Assert.False(matrix.IsIdentity);
+
+        // Set again.
+        matrix.M21 = value;
+        Assert.Equal(2, matrix.M11);
+        Assert.Equal(3, matrix.M12);
+        Assert.Equal(value, matrix.M21);
+        Assert.Equal(5, matrix.M22);
+        Assert.Equal(6, matrix.OffsetX);
+        Assert.Equal(7, matrix.OffsetY);
+        Assert.False(matrix.IsIdentity);
+    }
+
+    [Theory]
+    [MemberData(nameof(Scale_SetIdentity_TestData))]
+    public void M22_SetIdentity_GetReturnsExpected(Matrix matrix, double value, bool expectedIsIdentity)
+    {
+        // Set.
+        matrix.M22 = value;
+        Assert.Equal(1, matrix.M11);
+        Assert.Equal(0, matrix.M12);
+        Assert.Equal(0, matrix.M21);
+        Assert.Equal(value, matrix.M22);
+        Assert.Equal(0, matrix.OffsetX);
+        Assert.Equal(0, matrix.OffsetY);
+        Assert.Equal(expectedIsIdentity, matrix.IsIdentity);
+
+        // Set again.
+        matrix.M22 = value;
+        Assert.Equal(1, matrix.M11);
+        Assert.Equal(0, matrix.M12);
+        Assert.Equal(0, matrix.M21);
+        Assert.Equal(value, matrix.M22);
+        Assert.Equal(0, matrix.OffsetX);
+        Assert.Equal(0, matrix.OffsetY);
+        Assert.Equal(expectedIsIdentity, matrix.IsIdentity);
+    }
+
+    [Theory]
+    [MemberData(nameof(Scale_SetToIdentity_TestData))]
+    public void M22_SetScaleToIdentity_GetReturnsExpected(double value, bool expectedIsIdentity)
+    {
+        var matrix = new Matrix(1, 0, 0, 2, 0, 0);
+
+        // Set.
+        matrix.M22 = value;
+        Assert.Equal(1, matrix.M11);
+        Assert.Equal(0, matrix.M12);
+        Assert.Equal(0, matrix.M21);
+        Assert.Equal(value, matrix.M22);
+        Assert.Equal(0, matrix.OffsetX);
+        Assert.Equal(0, matrix.OffsetY);
+        Assert.Equal(expectedIsIdentity, matrix.IsIdentity);
+
+        // Set again.
+        matrix.M22 = value;
+        Assert.Equal(1, matrix.M11);
+        Assert.Equal(0, matrix.M12);
+        Assert.Equal(0, matrix.M21);
+        Assert.Equal(value, matrix.M22);
+        Assert.Equal(0, matrix.OffsetX);
+        Assert.Equal(0, matrix.OffsetY);
+        Assert.Equal(expectedIsIdentity, matrix.IsIdentity);
+    }
+
+    [Theory]
+    [MemberData(nameof(MatrixElement_Set_TestData))]
+    public void M22_Set_GetReturnsExpected(double value)
+    {
+        var matrix = new Matrix(2, 3, 4, 5, 6, 7);
+
+        // Set.
+        matrix.M22 = value;
+        Assert.Equal(2, matrix.M11);
+        Assert.Equal(3, matrix.M12);
+        Assert.Equal(4, matrix.M21);
+        Assert.Equal(value, matrix.M22);
+        Assert.Equal(6, matrix.OffsetX);
+        Assert.Equal(7, matrix.OffsetY);
+        Assert.False(matrix.IsIdentity);
+
+        // Set again.
+        matrix.M22 = value;
+        Assert.Equal(2, matrix.M11);
+        Assert.Equal(3, matrix.M12);
+        Assert.Equal(4, matrix.M21);
+        Assert.Equal(value, matrix.M22);
+        Assert.Equal(6, matrix.OffsetX);
+        Assert.Equal(7, matrix.OffsetY);
+        Assert.False(matrix.IsIdentity);
+    }
+
+    [Theory]
+    [MemberData(nameof(NonScale_SetIdentity_TestData))]
+    public void OffsetX_SetIdentity_GetReturnsExpected(Matrix matrix, double value, bool expectedIsIdentity)
+    {
+        // Set.
+        matrix.OffsetX = value;
+        Assert.Equal(1, matrix.M11);
+        Assert.Equal(0, matrix.M12);
+        Assert.Equal(0, matrix.M21);
+        Assert.Equal(1, matrix.M22);
+        Assert.Equal(value, matrix.OffsetX);
+        Assert.Equal(0, matrix.OffsetY);
+        Assert.Equal(expectedIsIdentity, matrix.IsIdentity);
+
+        // Set again.
+        matrix.OffsetX = value;
+        Assert.Equal(1, matrix.M11);
+        Assert.Equal(0, matrix.M12);
+        Assert.Equal(0, matrix.M21);
+        Assert.Equal(1, matrix.M22);
+        Assert.Equal(value, matrix.OffsetX);
+        Assert.Equal(0, matrix.OffsetY);
+        Assert.Equal(expectedIsIdentity, matrix.IsIdentity);
+    }
+
+    [Theory]
+    [MemberData(nameof(NonScale_SetToIdentity_TestData))]
+    public void OffsetX_SetScaleToIdentity_GetReturnsExpected(double value, bool expectedIsIdentity)
+    {
+        var matrix = new Matrix(1, 0, 0, 1, 1, 0);
+
+        // Set.
+        matrix.OffsetX = value;
+        Assert.Equal(1, matrix.M11);
+        Assert.Equal(0, matrix.M12);
+        Assert.Equal(0, matrix.M21);
+        Assert.Equal(1, matrix.M22);
+        Assert.Equal(value, matrix.OffsetX);
+        Assert.Equal(0, matrix.OffsetY);
+        Assert.Equal(expectedIsIdentity, matrix.IsIdentity);
+
+        // Set again.
+        matrix.OffsetX = value;
+        Assert.Equal(1, matrix.M11);
+        Assert.Equal(0, matrix.M12);
+        Assert.Equal(0, matrix.M21);
+        Assert.Equal(1, matrix.M22);
+        Assert.Equal(value, matrix.OffsetX);
+        Assert.Equal(0, matrix.OffsetY);
+        Assert.Equal(expectedIsIdentity, matrix.IsIdentity);
+    }
+
+    [Theory]
+    [MemberData(nameof(MatrixElement_Set_TestData))]
+    public void OffsetX_Set_GetReturnsExpected(double value)
+    {
+        var matrix = new Matrix(2, 3, 4, 5, 6, 7);
+
+        // Set.
+        matrix.OffsetX = value;
+        Assert.Equal(2, matrix.M11);
+        Assert.Equal(3, matrix.M12);
+        Assert.Equal(4, matrix.M21);
+        Assert.Equal(5, matrix.M22);
+        Assert.Equal(value, matrix.OffsetX);
+        Assert.Equal(7, matrix.OffsetY);
+        Assert.False(matrix.IsIdentity);
+
+        // Set again.
+        matrix.OffsetX = value;
+        Assert.Equal(2, matrix.M11);
+        Assert.Equal(3, matrix.M12);
+        Assert.Equal(4, matrix.M21);
+        Assert.Equal(5, matrix.M22);
+        Assert.Equal(value, matrix.OffsetX);
+        Assert.Equal(7, matrix.OffsetY);
+        Assert.False(matrix.IsIdentity);
+    }
+
+    [Theory]
+    [MemberData(nameof(NonScale_SetIdentity_TestData))]
+    public void OffsetY_SetIdentity_GetReturnsExpected(Matrix matrix, double value, bool expectedIsIdentity)
+    {
+        // Set.
+        matrix.OffsetY = value;
+        Assert.Equal(1, matrix.M11);
+        Assert.Equal(0, matrix.M12);
+        Assert.Equal(0, matrix.M21);
+        Assert.Equal(1, matrix.M22);
+        Assert.Equal(0, matrix.OffsetX);
+        Assert.Equal(value, matrix.OffsetY);
+        Assert.Equal(expectedIsIdentity, matrix.IsIdentity);
+
+        // Set again.
+        matrix.OffsetY = value;
+        Assert.Equal(1, matrix.M11);
+        Assert.Equal(0, matrix.M12);
+        Assert.Equal(0, matrix.M21);
+        Assert.Equal(1, matrix.M22);
+        Assert.Equal(0, matrix.OffsetX);
+        Assert.Equal(value, matrix.OffsetY);
+        Assert.Equal(expectedIsIdentity, matrix.IsIdentity);
+    }
+
+    [Theory]
+    [MemberData(nameof(NonScale_SetToIdentity_TestData))]
+    public void OffsetY_SetScaleToIdentity_GetReturnsExpected(double value, bool expectedIsIdentity)
+    {
+        var matrix = new Matrix(1, 0, 0, 1, 0, 1);
+
+        // Set.
+        matrix.OffsetY = value;
+        Assert.Equal(1, matrix.M11);
+        Assert.Equal(0, matrix.M12);
+        Assert.Equal(0, matrix.M21);
+        Assert.Equal(1, matrix.M22);
+        Assert.Equal(0, matrix.OffsetX);
+        Assert.Equal(value, matrix.OffsetY);
+        Assert.Equal(expectedIsIdentity, matrix.IsIdentity);
+
+        // Set again.
+        matrix.OffsetY = value;
+        Assert.Equal(1, matrix.M11);
+        Assert.Equal(0, matrix.M12);
+        Assert.Equal(0, matrix.M21);
+        Assert.Equal(1, matrix.M22);
+        Assert.Equal(0, matrix.OffsetX);
+        Assert.Equal(value, matrix.OffsetY);
+        Assert.Equal(expectedIsIdentity, matrix.IsIdentity);
+    }
+
+    [Theory]
+    [MemberData(nameof(MatrixElement_Set_TestData))]
+    public void OffsetY_Set_GetReturnsExpected(double value)
+    {
+        var matrix = new Matrix(2, 3, 4, 5, 6, 7);
+
+        // Set.
+        matrix.OffsetY = value;
+        Assert.Equal(2, matrix.M11);
+        Assert.Equal(3, matrix.M12);
+        Assert.Equal(4, matrix.M21);
+        Assert.Equal(5, matrix.M22);
+        Assert.Equal(6, matrix.OffsetX);
+        Assert.Equal(value, matrix.OffsetY);
+        Assert.False(matrix.IsIdentity);
+
+        // Set again.
+        matrix.OffsetY = value;
+        Assert.Equal(2, matrix.M11);
+        Assert.Equal(3, matrix.M12);
+        Assert.Equal(4, matrix.M21);
+        Assert.Equal(5, matrix.M22);
+        Assert.Equal(6, matrix.OffsetX);
+        Assert.Equal(value, matrix.OffsetY);
+        Assert.False(matrix.IsIdentity);
+    }
+
+    [Fact]
+    public void TypeConverter_Get_ReturnsExpected()
+    {
+        Assert.IsType<MatrixConverter>(TypeDescriptor.GetConverter(typeof(Matrix)));
+    }
+
+    [Fact]
+    public void ValueSerializer_Get_ReturnsExpected()
+    {
+        Assert.IsType<MatrixValueSerializer>(ValueSerializer.GetSerializerFor(typeof(Matrix)));
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/NameScopeTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/NameScopeTests.cs
new file mode 100644
index 00000000000..c68af4339e2
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/NameScopeTests.cs
@@ -0,0 +1,1200 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections;
+using System.Linq;
+using System.Reflection;
+using System.Windows.Markup;
+
+namespace System.Windows.Tests;
+
+public class NameScopeTests
+{
+#pragma warning disable xUnit2013 // Do not use equality check to check for collection size.
+#pragma warning disable xUnit2017 // Do not use Contains() to check if a value exists in a collection
+
+    [Fact]
+    public void Ctor_Default()
+    {
+        var nameScope = new NameScope();
+        Assert.Equal(0, nameScope.Count);
+        Assert.False(nameScope.IsReadOnly);
+        Assert.Null(nameScope.Keys);
+        Assert.Null(nameScope.Values);
+    }
+
+    [Fact]
+    public void GetNameScope_InvokeDefault_ReturnsExpected()
+    {
+        var dependencyObject = new DependencyObject();
+        Assert.Null(NameScope.GetNameScope(dependencyObject));
+    }
+
+    [Fact]
+    public void GetNameScope_NullDependencyObject_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("dependencyObject", () => NameScope.GetNameScope(null));
+    }
+
+    [Fact]
+    public void SetNameScope_Invoke_GetNameScopeReturnsExpected()
+    {
+        var dependencyObject = new DependencyObject();
+        var nameScope1 = new CustomNameScope();
+        var nameScope2 = new CustomNameScope();
+
+        // Set.
+        NameScope.SetNameScope(dependencyObject, nameScope1);
+        Assert.Same(nameScope1, NameScope.GetNameScope(dependencyObject));
+        
+        // Set same.
+        NameScope.SetNameScope(dependencyObject, nameScope1);
+        Assert.Same(nameScope1, NameScope.GetNameScope(dependencyObject));
+        
+        // Set different.
+        NameScope.SetNameScope(dependencyObject, nameScope2);
+        Assert.Same(nameScope2, NameScope.GetNameScope(dependencyObject));
+    }
+
+    [Fact]
+    public void SetNameScope_NullDependencyObject_ThrowsArgumentNullException()
+    {
+        var nameScope = new CustomNameScope();
+        Assert.Throws<ArgumentNullException>("dependencyObject", () => NameScope.SetNameScope(null, nameScope));
+    }
+
+    [Fact]
+    public void Item_Get_ReturnsExpected()
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        nameScope.RegisterName("name", scopedElement);
+        Assert.Same(scopedElement, nameScope["name"]);
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData("0")]
+    [InlineData("0name")]
+    [InlineData("na\0me")]
+    [InlineData("name")]
+    [InlineData("NAME")]
+    [InlineData("_")]
+    [InlineData("na0me")]
+    [InlineData("_name")]
+    [InlineData("NaMe")]
+    public void Item_GetNoSuchNameEmpty_ReturnsNull(string name)
+    {
+        var nameScope = new NameScope();
+        Assert.Null(nameScope[name]);
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData("0")]
+    [InlineData("0name")]
+    [InlineData("na\0me")]
+    [InlineData("name")]
+    [InlineData("NAME")]
+    [InlineData("_")]
+    [InlineData("na0me")]
+    [InlineData("_name")]
+    [InlineData("NaMe")]
+    public void Item_GetNoSuchNameNotEmpty_ReturnsNull(string name)
+    {
+        var nameScope = new NameScope();
+        nameScope.RegisterName("name1", new object());
+
+        Assert.Null(nameScope[name]);
+    }
+
+    [Fact]
+    public void Item_GetNullKey_ThrowsArgumentNullException()
+    {
+        var nameScope = new NameScope();
+        Assert.Throws<ArgumentNullException>("key", () => nameScope[null]);
+    }
+
+    [Theory]
+    [InlineData("name")]
+    [InlineData("NAME")]
+    [InlineData("_")]
+    [InlineData("na0me")]
+    [InlineData("_name")]
+    [InlineData("NaMe")]
+    public void Item_SetInvoke_Success(string name)
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        nameScope[name] = scopedElement;
+        Assert.Equal(1, nameScope.Count);
+        Assert.Same(scopedElement, nameScope.FindName(name));
+        Assert.True(nameScope.ContainsKey(name));
+        Assert.True(nameScope.Contains(new KeyValuePair<string, object>(name, scopedElement)));
+        Assert.Equal(1, nameScope.Keys.Count);
+        Assert.NotSame(nameScope.Keys, nameScope.Keys);
+        Assert.Equal(name, nameScope.Keys.First());
+        Assert.Equal(1, nameScope.Values.Count);
+        Assert.NotSame(nameScope.Values, nameScope.Values);
+        Assert.Equal(scopedElement, nameScope.Values.First());
+
+        // Set same.
+        nameScope[name] = scopedElement;
+        Assert.Equal(1, nameScope.Count);
+        Assert.Same(scopedElement, nameScope.FindName(name));
+        Assert.True(nameScope.ContainsKey(name));
+        Assert.True(nameScope.Contains(new KeyValuePair<string, object>(name, scopedElement)));
+        Assert.Equal(1, nameScope.Keys.Count);
+        Assert.NotSame(nameScope.Keys, nameScope.Keys);
+        Assert.Equal(name, nameScope.Keys.First());
+        Assert.Equal(1, nameScope.Values.Count);
+        Assert.NotSame(nameScope.Values, nameScope.Values);
+        Assert.Equal(scopedElement, nameScope.Values.First());
+    }
+
+    [Fact]
+    public void Item_SetInvokeMultiple_Success()
+    {
+        var nameScope = new NameScope();
+        var scopedElement1 = new object();
+        var scopedElement2 = new object();
+
+        nameScope["name1"] = scopedElement1;
+        Assert.Same(scopedElement1, nameScope.FindName("name1"));
+        Assert.Equal(1, nameScope.Count);
+
+        nameScope["NAME1"] = scopedElement2;
+        Assert.Same(scopedElement1, nameScope.FindName("name1"));
+        Assert.Same(scopedElement2, nameScope.FindName("NAME1"));
+        Assert.Equal(2, nameScope.Count);
+
+        nameScope["name2"] = scopedElement2;
+        Assert.Same(scopedElement1, nameScope.FindName("name1"));
+        Assert.Same(scopedElement2, nameScope.FindName("NAME1"));
+        Assert.Same(scopedElement2, nameScope.FindName("name2"));
+        Assert.Equal(3, nameScope.Count);
+    }
+
+    [Fact]
+    public void Item_SetNullName_ThrowsArgumentNullException()
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        Assert.Throws<ArgumentNullException>("key", () => nameScope.Add(null, scopedElement));
+    }
+
+    [Fact]
+    public void Item_SetEmptyName_ThrowsArgumentException()
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        Assert.Throws<ArgumentException>(() => nameScope.Add(string.Empty, scopedElement));
+    }
+
+    [Theory]
+    [InlineData("0")]
+    [InlineData("0name")]
+    [InlineData("na\0me")]
+    public void Item_SetInvalidName_ThrowsArgumentException(string name)
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        Assert.Throws<ArgumentException>(() => nameScope[name] = scopedElement);
+    }
+
+    [Fact]
+    public void Item_SetNullValue_ThrowsArgumentNullException()
+    {
+        var nameScope = new NameScope();
+        Assert.Throws<ArgumentNullException>("value", () => nameScope["name"] = null);
+    }
+
+    [Fact]
+    public void Item_SetDuplicate_ThrowsArgumentException()
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        nameScope["name"] = scopedElement;
+        Assert.Throws<ArgumentException>(() => nameScope["name"] = new object());
+    }
+
+    [Fact]
+    public void NameScopeProperty_Get_ReturnsExpected()
+    {
+        DependencyProperty property = NameScope.NameScopeProperty;
+        Assert.NotNull(property.DefaultMetadata);
+        Assert.Same(property.DefaultMetadata, property.DefaultMetadata);
+        Assert.Null(property.DefaultMetadata.CoerceValueCallback);
+        Assert.Null(property.DefaultMetadata.DefaultValue);
+        Assert.Null(property.DefaultMetadata.PropertyChangedCallback);
+        Assert.True(property.GlobalIndex >= 0);
+        Assert.Equal("NameScope", property.Name);
+        Assert.Equal(typeof(NameScope), property.OwnerType);
+        Assert.Equal(typeof(INameScope), property.PropertyType);
+        Assert.False(property.ReadOnly);
+        Assert.Null(property.ValidateValueCallback);
+        Assert.Same(property, NameScope.NameScopeProperty);
+    }
+
+    [Theory]
+    [InlineData("name")]
+    [InlineData("NAME")]
+    [InlineData("_")]
+    [InlineData("na0me")]
+    [InlineData("_name")]
+    [InlineData("NaMe")]
+    public void Add_InvokeStringObject_Success(string name)
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        nameScope.Add(name, scopedElement);
+        Assert.Equal(1, nameScope.Count);
+        Assert.Same(scopedElement, nameScope.FindName(name));
+        Assert.True(nameScope.ContainsKey(name));
+        Assert.True(nameScope.Contains(new KeyValuePair<string, object>(name, scopedElement)));
+        Assert.Equal(1, nameScope.Keys.Count);
+        Assert.NotSame(nameScope.Keys, nameScope.Keys);
+        Assert.Equal(name, nameScope.Keys.First());
+        Assert.Equal(1, nameScope.Values.Count);
+        Assert.NotSame(nameScope.Values, nameScope.Values);
+        Assert.Equal(scopedElement, nameScope.Values.First());
+
+        // Set same.
+        nameScope.Add(name, scopedElement);
+        Assert.Equal(1, nameScope.Count);
+        Assert.Same(scopedElement, nameScope.FindName(name));
+        Assert.True(nameScope.ContainsKey(name));
+        Assert.True(nameScope.Contains(new KeyValuePair<string, object>(name, scopedElement)));
+        Assert.Equal(1, nameScope.Keys.Count);
+        Assert.NotSame(nameScope.Keys, nameScope.Keys);
+        Assert.Equal(name, nameScope.Keys.First());
+        Assert.Equal(1, nameScope.Values.Count);
+        Assert.NotSame(nameScope.Values, nameScope.Values);
+        Assert.Equal(scopedElement, nameScope.Values.First());
+    }
+
+    [Fact]
+    public void Add_InvokeStringObjectMultiple_Success()
+    {
+        var nameScope = new NameScope();
+        var scopedElement1 = new object();
+        var scopedElement2 = new object();
+
+        nameScope.Add("name1", scopedElement1);
+        Assert.Same(scopedElement1, nameScope.FindName("name1"));
+        Assert.Equal(1, nameScope.Count);
+
+        nameScope.Add("NAME1", scopedElement2);
+        Assert.Same(scopedElement1, nameScope.FindName("name1"));
+        Assert.Same(scopedElement2, nameScope.FindName("NAME1"));
+        Assert.Equal(2, nameScope.Count);
+
+        nameScope.Add("name2", scopedElement2);
+        Assert.Same(scopedElement1, nameScope.FindName("name1"));
+        Assert.Same(scopedElement2, nameScope.FindName("NAME1"));
+        Assert.Same(scopedElement2, nameScope.FindName("name2"));
+        Assert.Equal(3, nameScope.Count);
+    }
+
+    [Fact]
+    public void Add_NullKey_ThrowsArgumentNullException()
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        Assert.Throws<ArgumentNullException>(() => nameScope.Add(null, scopedElement));
+    }
+
+    [Fact]
+    public void Add_EmptyName_ThrowsArgumentException()
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        Assert.Throws<ArgumentException>(() => nameScope.Add(string.Empty, scopedElement));
+    }
+
+    [Theory]
+    [InlineData("0")]
+    [InlineData("0name")]
+    [InlineData("na\0me")]
+    public void Add_InvalidName_ThrowsArgumentException(string name)
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        Assert.Throws<ArgumentException>(() => nameScope.Add(name, scopedElement));
+    }
+
+    [Fact]
+    public void Add_NullScopedElement_ThrowsArgumentNullException()
+    {
+        var nameScope = new NameScope();
+        Assert.Throws<ArgumentNullException>("scopedElement", () => nameScope.Add("name", null!));
+    }
+
+    [Theory]
+    [InlineData("name")]
+    [InlineData("NAME")]
+    [InlineData("_")]
+    [InlineData("na0me")]
+    [InlineData("_name")]
+    [InlineData("NaMe")]
+    public void Add_InvokeKVPStringObject_Success(string name)
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        nameScope.Add(new KeyValuePair<string, object>(name, scopedElement));
+        Assert.Equal(1, nameScope.Count);
+        Assert.Same(scopedElement, nameScope.FindName(name));
+        Assert.True(nameScope.ContainsKey(name));
+        Assert.True(nameScope.Contains(new KeyValuePair<string, object>(name, scopedElement)));
+        Assert.Equal(1, nameScope.Keys.Count);
+        Assert.NotSame(nameScope.Keys, nameScope.Keys);
+        Assert.Equal(name, nameScope.Keys.First());
+        Assert.Equal(1, nameScope.Values.Count);
+        Assert.NotSame(nameScope.Values, nameScope.Values);
+        Assert.Equal(scopedElement, nameScope.Values.First());
+
+        // Set same.
+        nameScope.Add(new KeyValuePair<string, object>(name, scopedElement));
+        Assert.Equal(1, nameScope.Count);
+        Assert.Same(scopedElement, nameScope.FindName(name));
+        Assert.True(nameScope.ContainsKey(name));
+        Assert.True(nameScope.Contains(new KeyValuePair<string, object>(name, scopedElement)));
+        Assert.Equal(1, nameScope.Keys.Count);
+        Assert.NotSame(nameScope.Keys, nameScope.Keys);
+        Assert.Equal(name, nameScope.Keys.First());
+        Assert.Equal(1, nameScope.Values.Count);
+        Assert.NotSame(nameScope.Values, nameScope.Values);
+        Assert.Equal(scopedElement, nameScope.Values.First());
+    }
+
+    [Fact]
+    public void Add_InvokeKVPStringObjectMultiple_Success()
+    {
+        var nameScope = new NameScope();
+        var scopedElement1 = new object();
+        var scopedElement2 = new object();
+
+        nameScope.Add(new KeyValuePair<string, object>("name1", scopedElement1));
+        Assert.Same(scopedElement1, nameScope.FindName("name1"));
+        Assert.Equal(1, nameScope.Count);
+
+        nameScope.Add(new KeyValuePair<string, object>("NAME1", scopedElement2));
+        Assert.Same(scopedElement1, nameScope.FindName("name1"));
+        Assert.Same(scopedElement2, nameScope.FindName("NAME1"));
+        Assert.Equal(2, nameScope.Count);
+
+        nameScope.Add(new KeyValuePair<string, object>("name2", scopedElement2));
+        Assert.Same(scopedElement1, nameScope.FindName("name1"));
+        Assert.Same(scopedElement2, nameScope.FindName("NAME1"));
+        Assert.Same(scopedElement2, nameScope.FindName("name2"));
+        Assert.Equal(3, nameScope.Count);
+    }
+
+    [Fact]
+    public void Add_NullItemKey_ThrowsArgumentException()
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        Assert.Throws<ArgumentException>("item", () => nameScope.Add(new KeyValuePair<string, object>(null!, scopedElement)));
+    }
+
+    [Fact]
+    public void Add_EmptyItemKey_ThrowsArgumentException()
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        Assert.Throws<ArgumentException>(() => nameScope.Add(new KeyValuePair<string, object>(string.Empty, scopedElement)));
+    }
+
+    [Theory]
+    [InlineData("0")]
+    [InlineData("0name")]
+    [InlineData("na\0me")]
+    public void Add_InvalidItemKey_ThrowsArgumentException(string name)
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        Assert.Throws<ArgumentException>(() => nameScope.Add(new KeyValuePair<string, object>(name, scopedElement)));
+    }
+
+    [Fact]
+    public void Add_NullItemValue_ThrowsArgumentException()
+    {
+        var nameScope = new NameScope();
+        Assert.Throws<ArgumentException>("item", () => nameScope.Add(new KeyValuePair<string, object>("name", null!)));
+    }
+
+    [Fact]
+    public void Add_Duplicate_ThrowsArgumentException()
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        nameScope.Add("name", scopedElement);
+        Assert.Throws<ArgumentException>(() => nameScope.Add("name", new object()));
+        Assert.Throws<ArgumentException>(() => nameScope.Add(new KeyValuePair<string, object>("name", new object())));
+    }
+
+    [Fact]
+    public void Clear_Invoke_Success()
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        nameScope.Add("name", scopedElement);
+        Assert.Equal(1, nameScope.Count);
+
+        nameScope.Clear();
+        Assert.Equal(0, nameScope.Count);
+        Assert.Null(nameScope.FindName("name"));
+        Assert.False(nameScope.ContainsKey("name"));
+        Assert.False(nameScope.Contains(new KeyValuePair<string, object>("name", scopedElement)));
+        Assert.Null(nameScope.Keys);
+        Assert.Null(nameScope.Values);
+
+        // Clear again.
+        nameScope.Clear();
+        Assert.Equal(0, nameScope.Count);
+        Assert.Null(nameScope.FindName("name"));
+        Assert.False(nameScope.ContainsKey("name"));
+        Assert.False(nameScope.Contains(new KeyValuePair<string, object>("name", scopedElement)));
+        Assert.Null(nameScope.Keys);
+        Assert.Null(nameScope.Values);
+    }
+
+    [Fact]
+    public void Clear_InvokeEmpty_Success()
+    {
+        var nameScope = new NameScope();
+
+        // Clear.
+        nameScope.Clear();
+        Assert.Equal(0, nameScope.Count);
+        Assert.Null(nameScope.FindName("name"));
+        Assert.False(nameScope.ContainsKey("name"));
+        Assert.False(nameScope.Contains(new KeyValuePair<string, object>("name", new object())));
+        Assert.Null(nameScope.Keys);
+        Assert.Null(nameScope.Values);
+
+        // Clear again.
+        nameScope.Clear();
+        Assert.Equal(0, nameScope.Count);
+        Assert.Null(nameScope.FindName("name"));
+        Assert.False(nameScope.ContainsKey("name"));
+        Assert.False(nameScope.Contains(new KeyValuePair<string, object>("name", new object())));
+        Assert.Null(nameScope.Keys);
+        Assert.Null(nameScope.Values);
+    }
+
+    [Fact]
+    public void CopyTo_Invoke_Success()
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        nameScope.RegisterName("name", scopedElement);
+
+        var array = new KeyValuePair<string, object>[3];
+
+        // Copy to start.
+        nameScope.CopyTo(array, 0);
+        Assert.Equal(new KeyValuePair<string, object>("name", scopedElement), array[0]);
+
+        // Copy to middle.
+        nameScope.CopyTo(array, 1);
+        Assert.Equal(new KeyValuePair<string, object>("name", scopedElement), array[1]);
+
+        // Copy to end.
+        nameScope.CopyTo(array, 2);
+        Assert.Equal(new KeyValuePair<string, object>("name", scopedElement), array[1]);
+    }
+
+    [Theory]
+    [InlineData(-1)]
+    [InlineData(0)]
+    [InlineData(1)]
+    public void CopyTo_InvokeEmpty_Nop(int arrayIndex)
+    {
+        var nameScope = new NameScope();
+
+        // Not null.
+        var array = new KeyValuePair<string, object>[1];
+        nameScope.CopyTo(array, arrayIndex);
+        Assert.Equal(default, array[0]);
+
+        // Null.
+        nameScope.CopyTo(null, arrayIndex);
+    }
+
+    [Fact]
+    public void CopyTo_NullArray_ThrowsNullReferenceException()
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        nameScope.RegisterName("name", scopedElement);
+
+        Assert.Throws<NullReferenceException>(() => nameScope.CopyTo(null, 0));
+    }
+
+    [Fact]
+    public void CopyTo_ArrayTooShort_ThrowsIndexOutOfRangeException()
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        nameScope.RegisterName("name", scopedElement);
+
+        var array = new KeyValuePair<string, object>[0];
+        Assert.Throws<IndexOutOfRangeException>(() => nameScope.CopyTo(array, 0));
+    }
+
+    [Fact]
+    public void CopyTo_InvalidIndex_ThrowsIndexOutOfRangeException()
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        nameScope.RegisterName("name", scopedElement);
+
+        var array = new KeyValuePair<string, object>[1];
+        Assert.Throws<IndexOutOfRangeException>(() => nameScope.CopyTo(array, -1));
+        Assert.Throws<IndexOutOfRangeException>(() => nameScope.CopyTo(array, 1));
+    }
+
+    [Fact]
+    public void Contains_Invoke_ReturnsExpected()
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        nameScope.RegisterName("name", scopedElement);
+
+        Assert.True(nameScope.Contains(new KeyValuePair<string, object>("name", scopedElement)));
+        Assert.True(nameScope.Contains(new KeyValuePair<string, object>("name", 1)));
+        Assert.True(nameScope.Contains(new KeyValuePair<string, object>("name", new object())));
+        Assert.False(nameScope.Contains(new KeyValuePair<string, object>("NAME", scopedElement)));
+        Assert.False(nameScope.Contains(new KeyValuePair<string, object>("nAmE", scopedElement)));
+        Assert.False(nameScope.Contains(new KeyValuePair<string, object>("name2", scopedElement)));
+        Assert.False(nameScope.Contains(new KeyValuePair<string, object>("", scopedElement)));
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData("0")]
+    [InlineData("0name")]
+    [InlineData("na\0me")]
+    [InlineData("name")]
+    [InlineData("NAME")]
+    [InlineData("_")]
+    [InlineData("na0me")]
+    [InlineData("_name")]
+    [InlineData("NaMe")]
+    public void Contains_InvokeNoSuchNameEmpty_ReturnsFalse(string name)
+    {
+        var nameScope = new NameScope();
+        Assert.False(nameScope.Contains(new KeyValuePair<string, object>(name, new object())));
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData("0")]
+    [InlineData("0name")]
+    [InlineData("na\0me")]
+    [InlineData("name")]
+    [InlineData("NAME")]
+    [InlineData("_")]
+    [InlineData("na0me")]
+    [InlineData("_name")]
+    [InlineData("NaMe")]
+    public void Contains_InvokeNoSuchNameNotEmpty_ReturnsFalse(string name)
+    {
+        var nameScope = new NameScope();
+        nameScope.RegisterName("name1", new object());
+
+        Assert.False(nameScope.Contains(new KeyValuePair<string, object>(name, new object())));
+    }
+
+    [Fact]
+    public void Contains_NullKey_ThrowsArgumentException()
+    {
+        var nameScope = new NameScope();
+        Assert.Throws<ArgumentException>("item", () => nameScope.Contains(new KeyValuePair<string, object>(null!, new object())));
+        Assert.Throws<ArgumentException>("item", () => nameScope.Contains(default));
+    }
+
+    [Fact]
+    public void ContainsKey_Invoke_ReturnsExpected()
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        nameScope.RegisterName("name", scopedElement);
+
+        Assert.True(nameScope.ContainsKey("name"));
+        Assert.True(nameScope.ContainsKey("name"));
+        Assert.False(nameScope.ContainsKey("NAME"));
+        Assert.False(nameScope.ContainsKey("nAmE"));
+        Assert.False(nameScope.ContainsKey("name2"));
+        Assert.False(nameScope.ContainsKey(""));
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData("0")]
+    [InlineData("0name")]
+    [InlineData("na\0me")]
+    [InlineData("name")]
+    [InlineData("NAME")]
+    [InlineData("_")]
+    [InlineData("na0me")]
+    [InlineData("_name")]
+    [InlineData("NaMe")]
+    public void ContainsKey_InvokeNoSuchNameEmpty_ReturnsFalse(string name)
+    {
+        var nameScope = new NameScope();
+        Assert.False(nameScope.ContainsKey(name));
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData("0")]
+    [InlineData("0name")]
+    [InlineData("na\0me")]
+    [InlineData("name")]
+    [InlineData("NAME")]
+    [InlineData("_")]
+    [InlineData("na0me")]
+    [InlineData("_name")]
+    [InlineData("NaMe")]
+    public void ContainsKey_InvokeNoSuchNameNotEmpty_ReturnsFalse(string name)
+    {
+        var nameScope = new NameScope();
+        nameScope.RegisterName("name1", new object());
+
+        Assert.False(nameScope.ContainsKey(name));
+    }
+
+    [Fact]
+    public void ContainsKey_NullKey_ThrowsArgumentNullException()
+    {
+        var nameScope = new NameScope();
+        Assert.Throws<ArgumentNullException>("key", () => nameScope.ContainsKey(null!));
+    }
+
+    [Fact]
+    public void FindName_Invoke_ReturnsExpected()
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        nameScope.RegisterName("name", scopedElement);
+        Assert.Same(scopedElement, nameScope.FindName("name"));
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("")]
+    [InlineData("0")]
+    [InlineData("0name")]
+    [InlineData("na\0me")]
+    [InlineData("name")]
+    [InlineData("NAME")]
+    [InlineData("_")]
+    [InlineData("na0me")]
+    [InlineData("_name")]
+    [InlineData("NaMe")]
+    public void FindName_InvokeNoSuchNameEmpty_ReturnsNull(string? name)
+    {
+        var nameScope = new NameScope();
+        Assert.Null(nameScope.FindName(name));
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("")]
+    [InlineData("0")]
+    [InlineData("0name")]
+    [InlineData("na\0me")]
+    [InlineData("name")]
+    [InlineData("NAME")]
+    [InlineData("_")]
+    [InlineData("na0me")]
+    [InlineData("_name")]
+    [InlineData("NaMe")]
+    public void FindName_InvokeNoSuchNameNotEmpty_ReturnsNull(string? name)
+    {
+        var nameScope = new NameScope();
+        nameScope.RegisterName("name1", new object());
+
+        Assert.Null(nameScope.FindName(name));
+    }
+
+    [Fact]
+    public void GetEnumerator_InvokeIEnumerableKVPNotEmpty_ReturnsExpected()
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        nameScope.RegisterName("name", scopedElement);
+
+        IEnumerable<KeyValuePair<string, object>> collection = nameScope;
+
+        using IEnumerator<KeyValuePair<string, object>> enumerator = collection.GetEnumerator();
+        for (int i = 0; i < 2; i++)
+        {
+            Assert.Throws<InvalidOperationException>(() => enumerator.Current);
+
+            // Move.
+            Assert.True(enumerator.MoveNext());
+            Assert.Equal("name", enumerator.Current.Key);
+            Assert.Same(scopedElement, enumerator.Current.Value);
+
+            // Move end.
+            Assert.False(enumerator.MoveNext());
+            Assert.Throws<InvalidOperationException>(() => enumerator.Current);
+            
+            // Move again.
+            Assert.False(enumerator.MoveNext());
+            Assert.Throws<InvalidOperationException>(() => enumerator.Current);
+
+            // Reset.
+            enumerator.Reset();
+        }
+    }
+
+    [Fact]
+    public void GetEnumerator_InvokeIEnumerableKVPEmpty_ReturnsExpected()
+    {
+        var nameScope = new NameScope();
+        IEnumerable<KeyValuePair<string, object>> collection = nameScope;
+
+        using IEnumerator<KeyValuePair<string, object>> enumerator = collection.GetEnumerator();
+        for (int i = 0; i < 2; i++)
+        {
+            Assert.Equal(default, enumerator.Current);
+
+            // Move end.
+            Assert.False(enumerator.MoveNext());
+            Assert.Equal(default, enumerator.Current);
+            
+            // Move again.
+            Assert.False(enumerator.MoveNext());
+            Assert.Equal(default, enumerator.Current);
+
+            // Reset.
+            enumerator.Reset();
+        }
+    }
+
+    [Fact]
+    public void GetEnumerator_InvokeIEnumerableNotEmpty_ReturnsExpected()
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        nameScope.RegisterName("name", scopedElement);
+
+        IEnumerable collection = nameScope;
+
+        IEnumerator enumerator = collection.GetEnumerator();
+        for (int i = 0; i < 2; i++)
+        {
+            Assert.Throws<InvalidOperationException>(() => enumerator.Current);
+
+            // Move.
+            Assert.True(enumerator.MoveNext());
+            Assert.Equal("name", ((KeyValuePair<string, object>)enumerator.Current).Key);
+            Assert.Same(scopedElement, ((KeyValuePair<string, object>)enumerator.Current).Value);
+
+            // Move end.
+            Assert.False(enumerator.MoveNext());
+            Assert.Throws<InvalidOperationException>(() => enumerator.Current);
+            
+            // Move again.
+            Assert.False(enumerator.MoveNext());
+            Assert.Throws<InvalidOperationException>(() => enumerator.Current);
+
+            // Reset.
+            enumerator.Reset();
+        }
+    }
+
+    [Fact]
+    public void GetEnumerator_InvokeIEnumerableEmpty_ReturnsExpected()
+    {
+        var nameScope = new NameScope();
+        IEnumerable collection = nameScope;
+
+        IEnumerator enumerator = collection.GetEnumerator();
+        for (int i = 0; i < 2; i++)
+        {
+            Assert.Equal(default(KeyValuePair<string, object>), enumerator.Current);
+
+            // Move end.
+            Assert.False(enumerator.MoveNext());
+            Assert.Equal(default(KeyValuePair<string, object>), enumerator.Current);
+            
+            // Move again.
+            Assert.False(enumerator.MoveNext());
+            Assert.Equal(default(KeyValuePair<string, object>), enumerator.Current);
+
+            // Reset.
+            enumerator.Reset();
+        }
+    }
+
+    [Theory]
+    [InlineData("name")]
+    [InlineData("NAME")]
+    [InlineData("_")]
+    [InlineData("na0me")]
+    [InlineData("_name")]
+    [InlineData("NaMe")]
+    public void RegisterName_Invoke_Success(string name)
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        nameScope.RegisterName(name, scopedElement);
+        Assert.Equal(1, nameScope.Count);
+        Assert.Same(scopedElement, nameScope.FindName(name));
+        Assert.True(nameScope.ContainsKey(name));
+        Assert.True(nameScope.Contains(new KeyValuePair<string, object>(name, scopedElement)));
+        Assert.Equal(1, nameScope.Keys.Count);
+        Assert.NotSame(nameScope.Keys, nameScope.Keys);
+        Assert.Equal(name, nameScope.Keys.First());
+        Assert.Equal(1, nameScope.Values.Count);
+        Assert.NotSame(nameScope.Values, nameScope.Values);
+        Assert.Equal(scopedElement, nameScope.Values.First());
+
+        // Set same.
+        nameScope.RegisterName(name, scopedElement);
+        Assert.Equal(1, nameScope.Count);
+        Assert.Same(scopedElement, nameScope.FindName(name));
+        Assert.True(nameScope.ContainsKey(name));
+        Assert.True(nameScope.Contains(new KeyValuePair<string, object>(name, scopedElement)));
+        Assert.Equal(1, nameScope.Keys.Count);
+        Assert.NotSame(nameScope.Keys, nameScope.Keys);
+        Assert.Equal(name, nameScope.Keys.First());
+        Assert.Equal(1, nameScope.Values.Count);
+        Assert.NotSame(nameScope.Values, nameScope.Values);
+        Assert.Equal(scopedElement, nameScope.Values.First());
+    }
+
+    [Fact]
+    public void RegisterName_InvokeMultiple_Success()
+    {
+        var nameScope = new NameScope();
+        var scopedElement1 = new object();
+        var scopedElement2 = new object();
+
+        nameScope.RegisterName("name1", scopedElement1);
+        Assert.Same(scopedElement1, nameScope.FindName("name1"));
+        Assert.Equal(1, nameScope.Count);
+
+        nameScope.RegisterName("NAME1", scopedElement2);
+        Assert.Same(scopedElement1, nameScope.FindName("name1"));
+        Assert.Same(scopedElement2, nameScope.FindName("NAME1"));
+        Assert.Equal(2, nameScope.Count);
+
+        nameScope.RegisterName("name2", scopedElement2);
+        Assert.Same(scopedElement1, nameScope.FindName("name1"));
+        Assert.Same(scopedElement2, nameScope.FindName("NAME1"));
+        Assert.Same(scopedElement2, nameScope.FindName("name2"));
+        Assert.Equal(3, nameScope.Count);
+    }
+
+    [Fact]
+    public void RegisterName_NullName_ThrowsArgumentNullException()
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        Assert.Throws<ArgumentNullException>("name", () => nameScope.RegisterName(null, scopedElement));
+    }
+
+    [Fact]
+    public void RegisterName_EmptyName_ThrowsArgumentException()
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        Assert.Throws<ArgumentException>(() => nameScope.RegisterName(string.Empty, scopedElement));
+    }
+
+    [Theory]
+    [InlineData("0")]
+    [InlineData("0name")]
+    [InlineData("na\0me")]
+    public void RegisterName_InvalidName_ThrowsArgumentException(string name)
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        Assert.Throws<ArgumentException>(() => nameScope.RegisterName(name, scopedElement));
+    }
+
+    [Fact]
+    public void RegisterName_NullScopedElement_ThrowsArgumentNullException()
+    {
+        var nameScope = new NameScope();
+        Assert.Throws<ArgumentNullException>("scopedElement", () => nameScope.RegisterName("name", null!));
+    }
+
+    [Fact]
+    public void RegisterName_Duplicate_ThrowsArgumentException()
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        nameScope.RegisterName("name", scopedElement);
+        Assert.Throws<ArgumentException>(() => nameScope.RegisterName("name", new object()));
+    }
+
+    [Fact]
+    public void Remove_InvokeString_Success()
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        nameScope.RegisterName("name", scopedElement);
+        nameScope.Remove("name");
+        Assert.Null(nameScope.FindName("name"));
+        Assert.Equal(0, nameScope.Count);
+
+        // Remove again.
+        Assert.False(nameScope.Remove("name"));
+        Assert.Null(nameScope.FindName("name"));
+        Assert.Equal(0, nameScope.Count);
+    }
+
+    [Fact]
+    public void Remove_NullKey_ThrowsArgumentNullException()
+    {
+        var nameScope = new NameScope();
+        Assert.Throws<ArgumentNullException>("key", () => nameScope.Remove(null));
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData("0")]
+    [InlineData("0name")]
+    [InlineData("na\0me")]
+    [InlineData("name")]
+    [InlineData("NAME")]
+    [InlineData("_")]
+    [InlineData("na0me")]
+    [InlineData("_name")]
+    [InlineData("NaMe")]
+    public void Remove_NoSuchKeyEmpty_ReturnsFalse(string name)
+    {
+        var nameScope = new NameScope();
+        Assert.False(nameScope.Remove(name));
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData("0")]
+    [InlineData("0name")]
+    [InlineData("na\0me")]
+    [InlineData("name")]
+    [InlineData("NAME")]
+    [InlineData("_")]
+    [InlineData("na0me")]
+    [InlineData("_name")]
+    [InlineData("NaMe")]
+    public void Remove_NoSuchKeyNotEmpty_ReturnsFalse(string name)
+    {
+        var nameScope = new NameScope();
+        nameScope.RegisterName("name1", new object());
+
+        Assert.False(nameScope.Remove(name));
+        Assert.Equal(1, nameScope.Count);
+    }
+
+    [Fact]
+    public void Remove_InvokeKVPStringObject_Success()
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        nameScope.RegisterName("name", scopedElement);
+        nameScope.Remove(new KeyValuePair<string, object>("name", scopedElement));
+        Assert.Null(nameScope.FindName("name"));
+        Assert.Equal(0, nameScope.Count);
+
+        // Remove again.
+        Assert.False(nameScope.Remove(new KeyValuePair<string, object>("name", scopedElement)));
+        Assert.Null(nameScope.FindName("name"));
+        Assert.Equal(0, nameScope.Count);
+    }
+
+    [Fact]
+    public void Remove_NullItemKey_ThrowsArgumentException()
+    {
+        var nameScope = new NameScope();
+        Assert.Throws<ArgumentException>("item", () => nameScope.Remove(new KeyValuePair<string, object>(null!, new object())));
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData("0")]
+    [InlineData("0name")]
+    [InlineData("na\0me")]
+    [InlineData("name")]
+    [InlineData("NAME")]
+    [InlineData("_")]
+    [InlineData("na0me")]
+    [InlineData("_name")]
+    [InlineData("NaMe")]
+    public void Remove_NoSuchItemKeyEmpty_ReturnsFalse(string name)
+    {
+        var nameScope = new NameScope();
+        Assert.False(nameScope.Remove(new KeyValuePair<string, object>(name, new object())));
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData("0")]
+    [InlineData("0name")]
+    [InlineData("na\0me")]
+    [InlineData("name")]
+    [InlineData("NAME")]
+    [InlineData("_")]
+    [InlineData("na0me")]
+    [InlineData("_name")]
+    [InlineData("NaMe")]
+    public void Remove_NoSuchItemKeyNotEmpty_ReturnsFalse(string name)
+    {
+        var nameScope = new NameScope();
+        nameScope.RegisterName("name1", new object());
+
+        Assert.False(nameScope.Remove(new KeyValuePair<string, object>(name, new object())));
+        Assert.Equal(1, nameScope.Count);
+    }
+
+    [Fact]
+    public void Remove_NoSuchItemValue_ReturnsFalse()
+    {
+        var nameScope = new NameScope();
+        nameScope.RegisterName("name", new object());
+
+        Assert.False(nameScope.Remove(new KeyValuePair<string, object>("name", new object())));
+        Assert.False(nameScope.Remove(new KeyValuePair<string, object>("name", null!)));
+        Assert.Equal(1, nameScope.Count);
+    }
+
+    [Fact]
+    public void TryGetValue_Invoke_ReturnsExpected()
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        nameScope.RegisterName("name", scopedElement);
+        
+        Assert.True(nameScope.TryGetValue("name", out object value));
+        Assert.Same(scopedElement, value);
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData("0")]
+    [InlineData("0name")]
+    [InlineData("na\0me")]
+    [InlineData("name")]
+    [InlineData("NAME")]
+    [InlineData("_")]
+    [InlineData("na0me")]
+    [InlineData("_name")]
+    [InlineData("NaMe")]
+    public void TryGetValue_InvokeNoSuchNameEmpty_ReturnsNull(string key)
+    {
+        var nameScope = new NameScope();
+        Assert.False(nameScope.TryGetValue(key, out object value));
+        Assert.Null(value);
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData("0")]
+    [InlineData("0name")]
+    [InlineData("na\0me")]
+    [InlineData("name")]
+    [InlineData("NAME")]
+    [InlineData("_")]
+    [InlineData("na0me")]
+    [InlineData("_name")]
+    [InlineData("NaMe")]
+    public void TryGetValue_InvokeNoSuchNameNotEmpty_ReturnsNull(string key)
+    {
+        var nameScope = new NameScope();
+        nameScope.RegisterName("name1", new object());
+
+        Assert.False(nameScope.TryGetValue(key, out object value));
+        Assert.Null(value);
+    }
+
+    [Fact]
+    public void TryGetValue_NullKey_ThrowsArgumentNullException()
+    {
+        var nameScope = new NameScope();
+        Assert.Throws<ArgumentNullException>("key", () => nameScope.TryGetValue(null, out object value));
+    }
+
+    [Fact]
+    public void UnregisterName_Invoke_Success()
+    {
+        var nameScope = new NameScope();
+        var scopedElement = new object();
+        nameScope.RegisterName("name", scopedElement);
+        nameScope.UnregisterName("name");
+        Assert.Null(nameScope.FindName("name"));
+        Assert.Equal(0, nameScope.Count);
+
+        // Unregister again.
+        Assert.Throws<ArgumentException>(() => nameScope.UnregisterName("name"));
+        Assert.Null(nameScope.FindName("name"));
+        Assert.Equal(0, nameScope.Count);
+    }
+
+    [Fact]
+    public void UnregisterName_NullName_ThrowsArgumentNullException()
+    {
+        var nameScope = new NameScope();
+        Assert.Throws<ArgumentNullException>("name", () => nameScope.UnregisterName(null));
+    }
+
+    [Fact]
+    public void UnregisterName_EmptyName_ThrowsArgumentException()
+    {
+        var nameScope = new NameScope();
+        Assert.Throws<ArgumentException>(() => nameScope.UnregisterName(string.Empty));
+    }
+
+    [Theory]
+    [InlineData("0")]
+    [InlineData("0name")]
+    [InlineData("na\0me")]
+    [InlineData("name")]
+    [InlineData("NAME")]
+    [InlineData("_")]
+    [InlineData("na0me")]
+    [InlineData("_name")]
+    [InlineData("NaMe")]
+    public void UnregisterName_NoSuchNameEmpty_ThrowsArgumentException(string name)
+    {
+        var nameScope = new NameScope();
+        Assert.Throws<ArgumentException>(() => nameScope.UnregisterName(name));
+    }
+
+    [Theory]
+    [InlineData("0")]
+    [InlineData("0name")]
+    [InlineData("na\0me")]
+    [InlineData("name")]
+    [InlineData("NAME")]
+    [InlineData("_")]
+    [InlineData("na0me")]
+    [InlineData("_name")]
+    [InlineData("NaMe")]
+    public void UnregisterName_NoSuchNameNotEmpty_ThrowsArgumentException(string name)
+    {
+        var nameScope = new NameScope();
+        nameScope.RegisterName("name1", new object());
+
+        Assert.Throws<ArgumentException>(() => nameScope.UnregisterName(name));
+        Assert.Equal(1, nameScope.Count);
+    }
+
+    private class CustomNameScope : INameScope
+    {
+        public object FindName(string name) => throw new NotImplementedException();
+
+        public void RegisterName(string name, object scopedElement) => throw new NotImplementedException();
+
+        public void UnregisterName(string name) => throw new NotImplementedException();
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/PointConverterTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/PointConverterTests.cs
new file mode 100644
index 00000000000..19be3704221
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/PointConverterTests.cs
@@ -0,0 +1,188 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.ComponentModel.Design.Serialization;
+using System.Globalization;
+
+namespace System.Windows.Tests;
+
+public class PointConverterTests
+{
+    [Theory]
+    [InlineData(null, false)]
+    [InlineData(typeof(object), false)]
+    [InlineData(typeof(string), true)]
+    [InlineData(typeof(InstanceDescriptor), false)]
+    [InlineData(typeof(Point), false)]
+    public void CanConvertTo_Invoke_ReturnsExpected(Type? destinationType, bool expected)
+    {
+        var converter = new PointConverter();
+        Assert.Equal(expected, converter.CanConvertTo(null, destinationType));
+        Assert.Equal(expected, converter.CanConvertTo(new CustomTypeDescriptorContext(), destinationType));
+    }
+    
+    [Theory]
+    [MemberData(nameof(PointTests.ToString_TestData), MemberType = typeof(PointTests))]
+    public void ConvertTo_InvokePointToString_ReturnsExpected(Point matrix, string expected)
+    {
+        var converter = new PointConverter();
+        Assert.Equal(expected, converter.ConvertTo(matrix, typeof(string)));
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), null, matrix, typeof(string)));
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, matrix, typeof(string)));
+    }
+    
+    [Theory]
+    [MemberData(nameof(PointTests.ToString_IFormatProviderCustom_TestData), MemberType = typeof(PointTests))]
+    public void ConvertTo_InvokePointToStringCustomCulture_ReturnsExpected(Point matrix, string numberDecimalSeparator, string expected)
+    {
+        var culture = new CultureInfo("en-US");
+        NumberFormatInfo formatInfo = culture.NumberFormat;
+        formatInfo.NumberDecimalSeparator = numberDecimalSeparator;
+
+        var converter = new PointConverter();
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), culture, matrix, typeof(string)));
+    }
+
+    [Theory]
+    [InlineData(null, "")]
+    [InlineData("", "")]
+    [InlineData("value", "value")]
+    [InlineData(1, "1")]
+    public void ConvertTo_InvokeNotPointToString_ReturnsExpected(object? value, string expected)
+    {
+        var converter = new PointConverter();
+        Assert.Equal(expected, converter.ConvertTo(value, typeof(string)));
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), null, value, typeof(string)));
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value, typeof(string)));
+    }
+
+    public static IEnumerable<object?[]> ConvertTo_CantConvert_TestData()
+    {
+        yield return new object?[] { null, typeof(object) };
+        yield return new object?[] { string.Empty, typeof(object) };
+        yield return new object?[] { "value", typeof(object) };
+        yield return new object?[] { new object(), typeof(object) };
+        yield return new object?[] { new Point(), typeof(object) };
+        
+        yield return new object?[] { null, typeof(Point) };
+        yield return new object?[] { string.Empty, typeof(Point) };
+        yield return new object?[] { "value", typeof(Point) };
+        yield return new object?[] { new object(), typeof(Point) };
+        yield return new object?[] { new Point(), typeof(Point) };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertTo_CantConvert_TestData))]
+    public void ConvertTo_CantConvert_ThrowsNotSupportedException(object value, Type destinationType)
+    {
+        var converter = new PointConverter();
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(value, destinationType));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(null, null, value, destinationType));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value, destinationType));
+    }
+
+    public static IEnumerable<object?[]> ConvertTo_NullDestinationType_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { string.Empty };
+        yield return new object?[] { "value" };
+        yield return new object?[] { new object() };
+        yield return new object?[] { new Point() };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertTo_NullDestinationType_TestData))]
+    public void ConvertTo_NullDestinationType_ThrowsArgumentNullException(object value)
+    {
+        var converter = new PointConverter();
+        Assert.Throws<ArgumentNullException>("destinationType", () => converter.ConvertTo(value, null!));
+        Assert.Throws<ArgumentNullException>("destinationType", () => converter.ConvertTo(null, null, new Point(), null!));
+        Assert.Throws<ArgumentNullException>("destinationType", () => converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, new Point(), null!));
+    }
+
+    [Theory]
+    [InlineData(null, false)]
+    [InlineData(typeof(object), false)]
+    [InlineData(typeof(string), true)]
+    [InlineData(typeof(InstanceDescriptor), true)]
+    [InlineData(typeof(Point), false)]
+    public void CanConvertFrom_Invoke_ReturnsExpected(Type? sourceType, bool expected)
+    {
+        var converter = new PointConverter();
+        Assert.Equal(expected, converter.CanConvertFrom(sourceType!));
+        Assert.Equal(expected, converter.CanConvertFrom(null, sourceType));
+        Assert.Equal(expected, converter.CanConvertFrom(new CustomTypeDescriptorContext(), sourceType));
+    }
+
+    [Theory]
+    [MemberData(nameof(PointTests.Parse_TestData), MemberType = typeof(PointTests))]
+    public void ConvertFrom_InvokeStringValue_ReturnsExpected(object value, Point expected)
+    {
+        var converter = new PointConverter();
+        Assert.Equal(expected, converter.ConvertFrom(value));
+        Assert.Equal(expected, converter.ConvertFrom(null, null, value));
+        Assert.Equal(expected, converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    [Fact]
+    public void ConvertFrom_NullValue_ThrowsNotSupportedException()
+    {
+        var converter = new PointConverter();
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(null!));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(null, null, null));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, null));
+    }
+
+    [Theory]
+    [MemberData(nameof(PointTests.Parse_InvalidSource_TestData), MemberType = typeof(PointTests))]
+    public void ConvertFrom_InvalidValue_ThrowsInvalidOperationException(object value)
+    {
+        var converter = new PointConverter();
+        Assert.Throws<InvalidOperationException>(() => converter.ConvertFrom(value));
+        Assert.Throws<InvalidOperationException>(() => converter.ConvertFrom(null, null, value));
+        Assert.Throws<InvalidOperationException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    [Theory]
+    [MemberData(nameof(PointTests.Parse_NotDouble_TestData), MemberType = typeof(PointTests))]
+    public void ConvertFrom_NotDoubleStringValue_ThrowsFormatException(object value)
+    {
+        var converter = new PointConverter();
+        Assert.Throws<FormatException>(() => converter.ConvertFrom(value));
+        Assert.Throws<FormatException>(() => converter.ConvertFrom(null, null, value));
+        Assert.Throws<FormatException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    public static IEnumerable<object[]> ConvertFrom_CantConvert_TestData()
+    {
+        yield return new object[] { new object() };
+        yield return new object[] { new Point() };
+    }
+    
+    [Theory]
+    [MemberData(nameof(ConvertFrom_CantConvert_TestData))]
+    public void ConvertFrom_CantConvert_ThrowsNotSupportedException(object value)
+    {
+        var converter = new PointConverter();
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(value));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(null, null, value));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    private class CustomTypeDescriptorContext : ITypeDescriptorContext
+    {
+        public IContainer Container => throw new NotImplementedException();
+
+        public object Instance => throw new NotImplementedException();
+
+        public PropertyDescriptor PropertyDescriptor => throw new NotImplementedException();
+
+        public object? GetService(Type serviceType) => throw new NotImplementedException();
+
+        public void OnComponentChanged() => throw new NotImplementedException();
+
+        public bool OnComponentChanging() => throw new NotImplementedException();
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/PointTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/PointTests.cs
new file mode 100644
index 00000000000..d100d5b2846
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/PointTests.cs
@@ -0,0 +1,580 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.Globalization;
+using System.Windows.Converters;
+using System.Windows.Markup;
+using System.Windows.Media;
+using System.Windows.Media.Tests;
+
+namespace System.Windows.Tests;
+
+public class PointTests
+{
+    [Fact]
+    public void Ctor_Default()
+    {
+        var point = new Point();
+        Assert.Equal(0, point.X);
+        Assert.Equal(0, point.Y);
+    }
+
+    [Theory]
+    [InlineData(double.NegativeInfinity, double.NegativeInfinity)]
+    [InlineData(double.MinValue, double.MinValue)]
+    [InlineData(-1, -2)]
+    [InlineData(0, 0)]
+    [InlineData(1, 0)]
+    [InlineData(0, 2)]
+    [InlineData(0.1, 0.2)]
+    [InlineData(double.NegativeZero, double.NegativeZero)]
+    [InlineData(1, 2)]
+    [InlineData(double.MaxValue, double.MaxValue)]
+    [InlineData(double.PositiveInfinity, double.PositiveInfinity)]
+    [InlineData(double.NaN, double.NaN)]
+    [InlineData(double.NaN, 1)]
+    [InlineData(1, double.NaN)]
+    public void Ctor_Double_Double(double x, double y)
+    {
+        var point = new Point(x, y);
+        Assert.Equal(x, point.X);
+        Assert.Equal(y, point.Y);
+    }
+
+    [Theory]
+    [InlineData(double.NegativeInfinity)]
+    [InlineData(double.MinValue)]
+    [InlineData(-1)]
+    [InlineData(double.NegativeZero)]
+    [InlineData(0)]
+    [InlineData(0.2)]
+    [InlineData(1)]
+    [InlineData(double.MaxValue)]
+    [InlineData(double.PositiveInfinity)]
+    [InlineData(double.NaN)]
+    public void X_Set_GetReturnsExpected(double value)
+    {
+        var point = new Point();
+
+        // Set.
+        point.X = value;
+        Assert.Equal(value, point.X);
+
+        // Set same.
+        point.X = value;
+        Assert.Equal(value, point.X);
+    }
+
+    [Theory]
+    [InlineData(double.NegativeInfinity)]
+    [InlineData(double.MinValue)]
+    [InlineData(-1)]
+    [InlineData(double.NegativeZero)]
+    [InlineData(0)]
+    [InlineData(0.2)]
+    [InlineData(1)]
+    [InlineData(double.MaxValue)]
+    [InlineData(double.PositiveInfinity)]
+    [InlineData(double.NaN)]
+    public void Y_Set_GetReturnsExpected(double value)
+    {
+        var point = new Point();
+
+        // Set.
+        point.Y = value;
+        Assert.Equal(value, point.Y);
+
+        // Set same.
+        point.Y = value;
+        Assert.Equal(value, point.Y);
+    }
+
+    public static IEnumerable<object[]> Add_TestData()
+    {
+        yield return new object[] { new Point(1, 2), 1, 2, new Point(2, 4) };
+        yield return new object[] { new Point(1, 2), 0.1, 0.2, new Point(1.1, 2.2) };
+        yield return new object[] { new Point(1.2, 2.3), 0.1, 0.2, new Point(1.3, 2.5) };
+        yield return new object[] { new Point(1, 2), 0, 0, new Point(1, 2) };
+        yield return new object[] { new Point(1, 2), -1, -2, new Point(0, 0) };
+
+        yield return new object[] { new Point(1.2, 2.3), double.NegativeInfinity, double.NegativeInfinity, new Point(double.NegativeInfinity, double.NegativeInfinity) };
+        yield return new object[] { new Point(1.2, 2.3), double.NegativeInfinity, 0.2, new Point(double.NegativeInfinity, 2.5) };
+        yield return new object[] { new Point(1.2, 2.3), 0.1, double.NegativeInfinity, new Point(1.3, double.NegativeInfinity) };
+
+        yield return new object[] { new Point(-1.2, -2.3), double.MinValue, double.MinValue, new Point(double.MinValue, double.MinValue) };
+        yield return new object[] { new Point(-1.2, -2.3), double.MinValue, 0.2, new Point(double.MinValue, -2.1) };
+        yield return new object[] { new Point(-1.2, -2.3), 0.1, double.MinValue, new Point(-1.1, double.MinValue) };
+
+        yield return new object[] { new Point(1.2, 2.3), double.MaxValue, double.MaxValue, new Point(double.MaxValue, double.MaxValue) };
+        yield return new object[] { new Point(1.2, 2.3), double.MaxValue, 0.2, new Point(double.MaxValue, 2.5) };
+        yield return new object[] { new Point(1.2, 2.3), 0.1, double.MaxValue, new Point(1.3, double.MaxValue) };
+
+        yield return new object[] { new Point(1.2, 2.3), double.PositiveInfinity, double.PositiveInfinity, new Point(double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Point(1.2, 2.3), double.PositiveInfinity, 0.2, new Point(double.PositiveInfinity, 2.5) };
+        yield return new object[] { new Point(1.2, 2.3), 0.1, double.PositiveInfinity, new Point(1.3, double.PositiveInfinity) };
+
+        yield return new object[] { new Point(1.2, 2.3), double.NaN, double.NaN, new Point(double.NaN, double.NaN) };
+        yield return new object[] { new Point(1.2, 2.3), double.NaN, 0.2, new Point(double.NaN, 2.5) };
+        yield return new object[] { new Point(1.2, 2.3), 0.1, double.NaN, new Point(1.3, double.NaN) };
+
+        yield return new object[] { new Point(), 1, 2, new Point(1, 2) };
+        yield return new object[] { new Point(), 0, 0, new Point() };
+        yield return new object[] { new Point(), -1, -2, new Point(-1, -2) };
+    }
+
+    [Theory]
+    [MemberData(nameof(Add_TestData))]
+    public void Add_InvokeVector_ReturnsExpected(Point point, double x, double y, Point expected)
+    {
+        Vector vector = new Vector(x, y);
+        Point result = Point.Add(point, vector);
+        Assert.Equal(expected.X, result.X, precision: 5);
+        Assert.Equal(expected.Y, result.Y, precision: 5);
+    }
+
+    [Theory]
+    [MemberData(nameof(Add_TestData))]
+    public void OperatorAdd_InvokeVector_ReturnsExpected(Point point, double x, double y, Point expected)
+    {
+        Vector vector = new Vector(x, y);
+        Point result = point + vector;
+        Assert.Equal(expected.X, result.X, precision: 5);
+        Assert.Equal(expected.Y, result.Y, precision: 5);
+    }
+
+    public static IEnumerable<object?[]> Equals_TestData()
+    {
+        // Normal size.
+        yield return new object?[] { new Point(1, 2), new Point(1, 2), true };
+        yield return new object?[] { new Point(1, 2), new Point(2, 2), false };
+        yield return new object?[] { new Point(1, 2), new Point(1, 3), false };
+        yield return new object?[] { new Point(1, 2), new Point(double.NaN, 2), false };
+        yield return new object?[] { new Point(1, 2), new Point(1, double.NaN), false };
+        yield return new object?[] { new Point(1, 2), new Point(double.NaN, double.NaN), false };
+        yield return new object?[] { new Point(1, 2), new Point(0, 0), false };
+        yield return new object?[] { new Point(1, 2), new Point(), false };
+
+        // NaN x.
+        yield return new object[] { new Point(double.NaN, 2), new Point(double.NaN, 2), true };
+        yield return new object[] { new Point(double.NaN, 2), new Point(2, 2), false };
+        yield return new object[] { new Point(double.NaN, 2), new Point(double.NaN, double.NaN), false };
+
+        // NaN y.
+        yield return new object[] { new Point(1, double.NaN), new Point(1, double.NaN), true };
+        yield return new object[] { new Point(1, double.NaN), new Point(1, 2), false };
+        yield return new object[] { new Point(1, double.NaN), new Point(double.NaN, double.NaN), false };
+
+        // NaN x & y.
+        yield return new object[] { new Point(double.NaN, double.NaN), new Point(double.NaN, double.NaN), true };
+        yield return new object[] { new Point(double.NaN, double.NaN), new Point(1, 2), false };
+        yield return new object[] { new Point(double.NaN, double.NaN), new Point(double.NaN, 2), false };
+        yield return new object[] { new Point(double.NaN, double.NaN), new Point(1, double.NaN), false };
+
+        // Zero.
+        yield return new object?[] { new Point(0, 0), new Point(), true };
+        yield return new object?[] { new Point(0, 0), new Point(0, 0), true };
+        yield return new object?[] { new Point(0, 0), new Point(1, 0), false };
+        yield return new object?[] { new Point(0, 0), new Point(0, 1), false };
+
+        // Default.
+        yield return new object?[] { new Point(), new Point(), true };
+        yield return new object?[] { new Point(), new Point(0, 0), true };
+        yield return new object?[] { new Point(), new Point(1, 0), false };
+        yield return new object?[] { new Point(), new Point(0, 1), false };
+    }
+
+    [Theory]
+    [MemberData(nameof(Equals_TestData))]
+    public void Equals_Object_ReturnsExpected(Point point, object o, bool expected)
+    {
+        Assert.Equal(expected, point.Equals(o));
+        if (o is Point other)
+        {
+            Assert.Equal(expected, point.Equals(other));
+            Assert.Equal(expected, other.Equals(point));
+            Assert.Equal(expected, Point.Equals(point, other));
+            Assert.Equal(expected, Point.Equals(other, point));
+            Assert.Equal(expected, point.GetHashCode().Equals(other.GetHashCode()));
+        }
+    }
+
+    public static IEnumerable<object[]> EqualityOperator_TestData()
+    {
+        // Normal size.
+        yield return new object[] { new Point(1, 2), new Point(1, 2), true };
+        yield return new object[] { new Point(1, 2), new Point(2, 2), false };
+        yield return new object[] { new Point(1, 2), new Point(1, 3), false };
+        yield return new object[] { new Point(1, 2), new Point(double.NaN, 2), false };
+        yield return new object[] { new Point(1, 2), new Point(1, double.NaN), false };
+        yield return new object[] { new Point(1, 2), new Point(double.NaN, double.NaN), false };
+        yield return new object[] { new Point(1, 2), new Point(0, 0), false };
+        yield return new object[] { new Point(1, 2), new Point(), false };
+
+        // NaN x.
+        yield return new object[] { new Point(double.NaN, 2), new Point(double.NaN, 2), false };
+        yield return new object[] { new Point(double.NaN, 2), new Point(2, 2), false };
+        yield return new object[] { new Point(double.NaN, 2), new Point(double.NaN, double.NaN), false };
+
+        // NaN y.
+        yield return new object[] { new Point(1, double.NaN), new Point(1, double.NaN), false };
+        yield return new object[] { new Point(1, double.NaN), new Point(1, 2), false };
+        yield return new object[] { new Point(1, double.NaN), new Point(double.NaN, double.NaN), false };
+
+        // NaN x & y.
+        yield return new object[] { new Point(double.NaN, double.NaN), new Point(double.NaN, double.NaN), false };
+        yield return new object[] { new Point(double.NaN, double.NaN), new Point(1, 2), false };
+        yield return new object[] { new Point(double.NaN, double.NaN), new Point(double.NaN, 2), false };
+        yield return new object[] { new Point(double.NaN, double.NaN), new Point(1, double.NaN), false };
+
+        // Zero.
+        yield return new object[] { new Point(0, 0), new Point(), true };
+        yield return new object[] { new Point(0, 0), new Point(0, 0), true };
+        yield return new object[] { new Point(0, 0), new Point(1, 0), false };
+        yield return new object[] { new Point(0, 0), new Point(0, 1), false };
+
+        // Default.
+        yield return new object[] { new Point(), new Point(), true };
+        yield return new object[] { new Point(), new Point(0, 0), true };
+        yield return new object[] { new Point(), new Point(1, 0), false };
+        yield return new object[] { new Point(), new Point(0, 1), false };
+    }
+
+    [Theory]
+    [MemberData(nameof(EqualityOperator_TestData))]
+    public void EqualityOperator_Invoke_ReturnsExpected(Point point1, Point point2, bool expected)
+    {
+        Assert.Equal(expected, point1 == point2);
+        Assert.Equal(expected, point2 == point1);
+        Assert.Equal(!expected, point1 != point2);
+        Assert.Equal(!expected, point2 != point1);
+    }
+
+    [Fact]
+    public void GetHashCode_InvokeDefault_ReturnsEqual()
+    {
+        var point = new Point(0, 0);
+        Assert.Equal(0, point.GetHashCode());
+        Assert.Equal(point.GetHashCode(), point.GetHashCode());
+    }
+
+    [Fact]
+    public void GetHashCode_InvokeNormal_ReturnsEqual()
+    {
+        var point = new Point(1, 2);
+        Assert.NotEqual(0, point.GetHashCode());
+        Assert.Equal(point.GetHashCode(), point.GetHashCode());
+    }
+
+    [Theory]
+    [MemberData(nameof(MatrixTests.Transform_Point_TestData), MemberType = typeof(MatrixTests))]
+    public void Multiply_InvokeMatrix_ReturnsExpected(Matrix matrix, Point point, Point expected)
+    {
+        Point result = Point.Multiply(point, matrix);
+        Assert.Equal(expected.X, result.X, precision: 5);
+        Assert.Equal(expected.Y, result.Y, precision: 5);
+    }
+
+    [Theory]
+    [MemberData(nameof(MatrixTests.Transform_Point_TestData), MemberType = typeof(MatrixTests))]
+    public void OperatorMultiply_InvokeMatrix_ReturnsExpected(Matrix matrix, Point point, Point expected)
+    {
+        Point result = point * matrix;
+        Assert.Equal(expected.X, result.X, precision: 5);
+        Assert.Equal(expected.Y, result.Y, precision: 5);
+    }
+
+    [Theory]
+    [MemberData(nameof(Add_TestData))]
+    public void Offset_Invoke_Success(Point point, double x, double y, Point expected)
+    {
+        point.Offset(x, y);
+        Assert.Equal(expected.X, point.X, precision: 5);
+        Assert.Equal(expected.Y, point.Y, precision: 5);
+    }
+
+    public static IEnumerable<object[]> Subtract_TestData()
+    {
+        yield return new object[] { new Point(1, 2), 1, 2, new Point(0, 0) };
+        yield return new object[] { new Point(1, 2), 0.1, 0.2, new Point(0.9, 1.8) };
+        yield return new object[] { new Point(1, 2), 0, 0, new Point(1, 2) };
+        yield return new object[] { new Point(1, 2), -1, -2, new Point(2, 4) };
+
+        yield return new object[] { new Point(-1, -2), 1, 2, new Point(-2, -4) };
+        yield return new object[] { new Point(-1, -2), 0.1, 0.2, new Point(-1.1, -2.2) };
+        yield return new object[] { new Point(-1, -2), 0, 0, new Point(-1, -2) };
+        yield return new object[] { new Point(-1, -2), -1, -2, new Point(0, 0) };
+
+        yield return new object[] { new Point(), 1, 2, new Point(-1, -2) };
+        yield return new object[] { new Point(), 0, 0, new Point() };
+        yield return new object[] { new Point(), -1, -2, new Point(1, 2) };
+    }
+
+    [Theory]
+    [MemberData(nameof(Subtract_TestData))]
+    public void Subtract_InvokePoint_ReturnsExpected(Point point, double x, double y, Point expected)
+    {
+        var other = new Point(x, y);
+        Vector result = Point.Subtract(point, other);
+        Assert.Equal(expected.X, result.X, precision: 5);
+        Assert.Equal(expected.Y, result.Y, precision: 5);
+        Assert.Equal(new Vector(-result.X, -result.Y), Point.Subtract(other, point));
+    }
+
+    [Theory]
+    [MemberData(nameof(Subtract_TestData))]
+    public void OperatorSubtract_InvokePoint_ReturnsExpected(Point point, double x, double y, Point expected)
+    {
+        var other = new Point(x, y);
+        Vector result = point - other;
+        Assert.Equal(expected.X, result.X, precision: 5);
+        Assert.Equal(expected.Y, result.Y, precision: 5);
+        Assert.Equal(new Vector(-result.X, -result.Y), other - point);
+    }
+
+    [Theory]
+    [MemberData(nameof(Subtract_TestData))]
+    public void Subtract_InvokeVector_ReturnsExpected(Point point, double x, double y, Point expected)
+    {
+        Vector vector = new Vector(x, y);
+        Point result = Point.Subtract(point, vector);
+        Assert.Equal(expected.X, result.X, precision: 5);
+        Assert.Equal(expected.Y, result.Y, precision: 5);
+    }
+
+    [Theory]
+    [MemberData(nameof(Subtract_TestData))]
+    public void OperatorSubtract_InvokeVector_ReturnsExpected(Point point, double x, double y, Point expected)
+    {
+        Vector vector = new Vector(x, y);
+        Point result = point - vector;
+        Assert.Equal(expected.X, result.X, precision: 5);
+        Assert.Equal(expected.Y, result.Y, precision: 5);
+    }
+
+    public static IEnumerable<object[]> Parse_TestData()
+    {
+        yield return new object[] { "0,0", new Point(0, 0) };
+        yield return new object[] { "1,2", new Point(1, 2) };
+        yield return new object[] { "1.1,2.2", new Point(1.1, 2.2) };
+        yield return new object[] { "   1   ,   2  ", new Point(1, 2) };
+        yield return new object[] { "-1,-2", new Point(-1, -2) };
+    }
+
+    [Theory]
+    [MemberData(nameof(Parse_TestData))]
+    public void Parse_Invoke_Success(string source, Point expected)
+    {
+        Point result = Point.Parse(source);
+        Assert.Equal(expected.X, result.X, precision: 5);
+        Assert.Equal(expected.Y, result.Y, precision: 5);
+    }
+
+    [Fact]
+    public void Parse_NullSource_ThrowsInvalidOperationException()
+    {
+        Assert.Throws<InvalidOperationException>(() => Point.Parse(null));
+    }
+
+    public static IEnumerable<object[]> Parse_InvalidSource_TestData()
+    {
+        yield return new object[] { "" };
+        yield return new object[] { "  " };
+        yield return new object[] { "," };
+        yield return new object[] { "1" };
+        yield return new object[] { "1," };
+        yield return new object[] { "1,2," };
+        yield return new object[] { "1,2,3" };
+        yield return new object[] { "1,2,test" };
+        yield return new object[] { "Empty," };
+        yield return new object[] { "Identity," };
+    }
+
+    [Theory]
+    [MemberData(nameof(Parse_InvalidSource_TestData))]
+    public void Parse_InvalidSource_ThrowsInvalidOperationException(string source)
+    {
+        Assert.Throws<InvalidOperationException>(() => Point.Parse(source));
+    }
+
+    public static IEnumerable<object[]> Parse_NotDouble_TestData()
+    {
+        yield return new object[] { "Empty" };
+        yield return new object[] { " Empty " };
+        yield return new object[] { "Empty,2" };
+        yield return new object[] { "Identity" };
+        yield return new object[] { " Identity " };
+        yield return new object[] { "Identity,2" };
+        yield return new object[] { "test" };
+        yield return new object[] { "test,2" };
+        yield return new object[] { "1,test" };
+        yield return new object[] { "1,test,3" };
+        yield return new object[] { "1;2" };
+        yield return new object[] { "1.2.3" };
+        yield return new object[] { """1"",""2""" };
+    }
+
+    [Theory]
+    [MemberData(nameof(Parse_NotDouble_TestData))]
+    public void Parse_NotDouble_ThrowsFormatException(string source)
+    {
+        Assert.Throws<FormatException>(() => Point.Parse(source));
+    }
+
+    public static IEnumerable<object[]> ToString_TestData()
+    {
+        yield return new object[] { new Point(), "0,0" };
+        yield return new object[] { new Point(0, 0), "0,0" };
+        yield return new object[] { new Point(1, 2), "1,2" };
+        yield return new object[] { new Point(1.1, 2.2), "1.1,2.2" };
+        yield return new object[] { new Point(-1, -2), "-1,-2" };
+    }
+
+    [Theory]
+    [MemberData(nameof(ToString_TestData))]
+    public void ToString_Invoke_ReturnsExpected(Point point, string expected)
+    {
+        Assert.Equal(expected, point.ToString());
+    }
+
+    [Theory]
+    [MemberData(nameof(ToString_TestData))]
+    public void ToString_InvokeIFormatProviderInvariantCulture_ReturnsExpected(Point point, string expected)
+    {
+        Assert.Equal(expected, point.ToString(CultureInfo.InvariantCulture));
+    }
+
+    public static IEnumerable<object[]> ToString_IFormatProviderCustom_TestData()
+    {
+        yield return new object[] { new Point(), "|", "0,0" };
+        yield return new object[] { new Point(), "|_", "0,0" };
+        yield return new object[] { new Point(), ",_", "0;0" };
+        yield return new object[] { new Point(), ",", "0;0" };
+        yield return new object[] { new Point(), ";", "0,0" };
+        yield return new object[] { new Point(), " ", "0,0" };
+
+        yield return new object[] { new Point(0, 0), "|", "0,0" };
+        yield return new object[] { new Point(0, 0), "|_", "0,0" };
+        yield return new object[] { new Point(0, 0), ",_", "0;0" };
+        yield return new object[] { new Point(0, 0), ",", "0;0" };
+        yield return new object[] { new Point(0, 0), ";", "0,0" };
+        yield return new object[] { new Point(0, 0), " ", "0,0" };
+
+        yield return new object[] { new Point(1, 2), "|", "1,2" };
+        yield return new object[] { new Point(1, 2), "|_", "1,2" };
+        yield return new object[] { new Point(1, 2), ",_", "1;2" };
+        yield return new object[] { new Point(1, 2), ",", "1;2" };
+        yield return new object[] { new Point(1, 2), ";", "1,2" };
+        yield return new object[] { new Point(1, 2), " ", "1,2" };
+        
+        yield return new object[] { new Point(1.1, 2.2), "|", "1|1,2|2" };
+        yield return new object[] { new Point(1.1, 2.2), "|_", "1|_1,2|_2" };
+        yield return new object[] { new Point(1.1, 2.2), ",_", "1,_1;2,_2" };
+        yield return new object[] { new Point(1.1, 2.2), ",", "1,1;2,2" };
+        yield return new object[] { new Point(1.1, 2.2), ";", "1;1,2;2" };
+        yield return new object[] { new Point(1.1, 2.2), " ", "1 1,2 2" };
+
+        yield return new object[] { new Point(-1, -2), "|", "-1,-2" };
+        yield return new object[] { new Point(-1, -2), "|_", "-1,-2" };
+        yield return new object[] { new Point(-1, -2), ",_", "-1;-2" };
+        yield return new object[] { new Point(-1, -2), ",", "-1;-2" };
+        yield return new object[] { new Point(-1, -2), ";", "-1,-2" };
+        yield return new object[] { new Point(-1, -2), " ", "-1,-2" };
+    }
+
+    [Theory]
+    [MemberData(nameof(ToString_IFormatProviderCustom_TestData))]
+    public void ToString_InvokeIFormatProviderCustom_ReturnsExpected(Point point, string numberDecimalSeparator, string expected)
+    {
+        var culture = new CultureInfo("en-US");
+        NumberFormatInfo formatInfo = culture.NumberFormat;
+        formatInfo.NumberDecimalSeparator = numberDecimalSeparator;
+
+        Assert.Equal(expected, point.ToString(formatInfo));
+    }
+
+    [Theory]
+    [MemberData(nameof(ToString_TestData))]
+    public void ToString_InvokeIFormattableInvariantCulture_ReturnsExpected(Point point, string expected)
+    {
+        IFormattable formattable = point;
+
+        Assert.Equal(expected, formattable.ToString(null, null));
+        Assert.Equal(expected, formattable.ToString(null, CultureInfo.InvariantCulture));
+    }
+
+    public static IEnumerable<object[]> ToString_IFormattableCustomFormat_TestData()
+    {    
+        yield return new object[] { "|", "1|23,2|35" };
+        yield return new object[] { "|_", "1|_23,2|_35" };
+        yield return new object[] { ",_", "1,_23;2,_35" };
+        yield return new object[] { ",", "1,23;2,35" };
+        yield return new object[] { ";", "1;23,2;35" };
+        yield return new object[] { " ", "1 23,2 35" };
+    }
+
+    [Theory]
+    [MemberData(nameof(ToString_IFormattableCustomFormat_TestData))]
+    public void ToString_InvokeIFormattableCustomFormat_ReturnsExpected(string numberDecimalSeparator, string expected)
+    {
+        var point = new Point(1.23456, 2.34567);
+        IFormattable formattable = point;
+
+        var culture = new CultureInfo("en-US");
+        NumberFormatInfo formatInfo = culture.NumberFormat;
+        formatInfo.NumberDecimalSeparator = numberDecimalSeparator;
+
+        Assert.Equal(expected, formattable.ToString("F2", formatInfo));
+    }
+
+    [Fact]
+    public void OperatorConvertVector_InvokeEmpty_ReturnsExpected()
+    {
+        Vector result = (Vector)new Point();
+        Assert.Equal(0, result.X);
+        Assert.Equal(0, result.Y);
+    }
+
+    [Theory]
+    [InlineData(1, 2)]
+    [InlineData(1.1, 2.2)]
+    [InlineData(-1, -2)]
+    public void OperatorConvertVector_InvokeNormal_ReturnsExpected(double x, double y)
+    {
+        Vector result = (Vector)new Point(x, y);
+        Assert.Equal(x, result.X);
+        Assert.Equal(y, result.Y);
+    }
+
+    [Fact]
+    public void OperatorConvertSize_InvokeEmpty_ReturnsExpected()
+    {
+        Size result = (Size)new Point();
+        Assert.Equal(0, result.Width);
+        Assert.Equal(0, result.Height);
+    }
+
+    [Theory]
+    [InlineData(1, 2, 1, 2)]
+    [InlineData(1.1, 2.2, 1.1, 2.2)]
+    [InlineData(-1, -2, 1, 2)]
+    public void OperatorConvertSize_InvokeNormal_ReturnsExpected(double x, double y, double expectedWidth, double expectedHeight)
+    {
+        Size result = (Size)new Point(x, y);
+        Assert.Equal(expectedWidth, result.Width);
+        Assert.Equal(expectedHeight, result.Height);
+    }
+
+    [Fact]
+    public void TypeConverter_Get_ReturnsExpected()
+    {
+        Assert.IsType<PointConverter>(TypeDescriptor.GetConverter(typeof(Point)));
+    }
+    
+    [Fact]
+    public void ValueSerializer_Get_ReturnsExpected()
+    {
+        Assert.IsType<PointValueSerializer>(ValueSerializer.GetSerializerFor(typeof(Point)));
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/PropertyMetadataTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/PropertyMetadataTests.cs
new file mode 100644
index 00000000000..e6cc37f8b03
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/PropertyMetadataTests.cs
@@ -0,0 +1,558 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Reflection;
+
+namespace System.Windows.Tests;
+
+public class PropertyMetadataTests
+{
+    [Fact]
+    public void Ctor_Default()
+    {
+        var metadata = new SubPropertyMetadata();
+        Assert.Null(metadata.CoerceValueCallback);
+        Assert.Null(metadata.DefaultValue);
+        Assert.False(metadata.IsSealed);
+        Assert.Null(metadata.PropertyChangedCallback);
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("value")]
+    [InlineData(1)]
+    public void Ctor_Object(object? defaultValue)
+    {
+        var metadata = new SubPropertyMetadata(defaultValue!);
+        Assert.Null(metadata.CoerceValueCallback);
+        Assert.Equal(defaultValue, metadata.DefaultValue);
+        Assert.False(metadata.IsSealed);
+        Assert.Null(metadata.PropertyChangedCallback);
+    }
+
+    [Fact]
+    public void Ctor_PropertyChangedCallback()
+    {
+        int propertyChangedCallbackCallCount = 0;
+        PropertyChangedCallback propertyChangedCallback = (d, e) => propertyChangedCallbackCallCount++;
+        var metadata = new SubPropertyMetadata(propertyChangedCallback);
+        Assert.Null(metadata.CoerceValueCallback);
+        Assert.Null(metadata.DefaultValue);
+        Assert.False(metadata.IsSealed);
+        Assert.Equal(propertyChangedCallback, metadata.PropertyChangedCallback);
+        Assert.Equal(0, propertyChangedCallbackCallCount);
+    }
+
+    [Fact]
+    public void Ctor_NullPropertyChangedCallback()
+    {
+        var metadata = new SubPropertyMetadata((PropertyChangedCallback)null!);
+        Assert.Null(metadata.CoerceValueCallback);
+        Assert.Null(metadata.DefaultValue);
+        Assert.False(metadata.IsSealed);
+        Assert.Null(metadata.PropertyChangedCallback);
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("value")]
+    [InlineData(1)]
+    public void Ctor_Object_PropertyChangedCallback(object? defaultValue)
+    {
+        int propertyChangedCallbackCallCount = 0;
+        PropertyChangedCallback propertyChangedCallback = (d, e) => propertyChangedCallbackCallCount++;
+        var metadata = new SubPropertyMetadata(defaultValue!, propertyChangedCallback);
+        Assert.Null(metadata.CoerceValueCallback);
+        Assert.Equal(defaultValue, metadata.DefaultValue);
+        Assert.False(metadata.IsSealed);
+        Assert.Equal(propertyChangedCallback, metadata.PropertyChangedCallback);
+        Assert.Equal(0, propertyChangedCallbackCallCount);
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("value")]
+    [InlineData(1)]
+    public void Ctor_Object_NullPropertyChangedCallback(object? defaultValue)
+    {
+        var metadata = new SubPropertyMetadata(defaultValue!, (PropertyChangedCallback)null!);
+        Assert.Null(metadata.CoerceValueCallback);
+        Assert.False(metadata.IsSealed);
+        Assert.Equal(defaultValue, metadata.DefaultValue);
+        Assert.Null(metadata.PropertyChangedCallback);
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("value")]
+    [InlineData(1)]
+    public void Ctor_Object_PropertyChangedCallback_CoerceValueCallback(object? defaultValue)
+    {
+        int propertyChangedCallbackCallCount = 0;
+        int coerceValueCallbackCallCount = 0;
+        PropertyChangedCallback propertyChangedCallback = (d, e) => propertyChangedCallbackCallCount++;
+        CoerceValueCallback coerceValueCallback = (d, v) => coerceValueCallbackCallCount++;
+        var metadata = new SubPropertyMetadata(defaultValue!, propertyChangedCallback, coerceValueCallback);
+        Assert.Equal(coerceValueCallback, metadata.CoerceValueCallback);
+        Assert.Equal(defaultValue, metadata.DefaultValue);
+        Assert.False(metadata.IsSealed);
+        Assert.Equal(propertyChangedCallback, metadata.PropertyChangedCallback);
+        Assert.Equal(0, propertyChangedCallbackCallCount);
+        Assert.Equal(0, coerceValueCallbackCallCount);
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("value")]
+    [InlineData(1)]
+    public void Ctor_Object_NullPropertyChangedCallback_NullCoerceValueCallback(object? defaultValue)
+    {
+        var metadata = new SubPropertyMetadata(defaultValue!, (PropertyChangedCallback)null!, (CoerceValueCallback)null!);
+        Assert.Null(metadata.CoerceValueCallback);
+        Assert.Equal(defaultValue, metadata.DefaultValue);
+        Assert.False(metadata.IsSealed);
+        Assert.Null(metadata.PropertyChangedCallback);
+    }
+
+    [Fact]
+    public void Ctor_UnsetDefaultValue_ThrowsArgumentException()
+    {
+        // TODO: add paramName.
+        Assert.Throws<ArgumentException>(() => new PropertyMetadata(DependencyProperty.UnsetValue));
+        Assert.Throws<ArgumentException>(() => new PropertyMetadata(DependencyProperty.UnsetValue, null));
+        Assert.Throws<ArgumentException>(() => new PropertyMetadata(DependencyProperty.UnsetValue, null, null));
+    }
+
+    [Fact]
+    public void CoerceValueCallback_Set_GetReturnsExpected()
+    {
+        var metadata = new PropertyMetadata();
+        
+        // Set value.
+        int coerceValueCallbackCallCount = 0;
+        CoerceValueCallback coerceValueCallback = (d, e) => coerceValueCallbackCallCount++;
+        metadata.CoerceValueCallback = coerceValueCallback;
+        Assert.Equal(coerceValueCallback, metadata.CoerceValueCallback);
+        Assert.Equal(0, coerceValueCallbackCallCount);
+
+        // Set same.
+        metadata.CoerceValueCallback = coerceValueCallback;
+        Assert.Equal(coerceValueCallback, metadata.CoerceValueCallback);
+        Assert.Equal(0, coerceValueCallbackCallCount);
+
+        // Set null.
+        metadata.CoerceValueCallback = null;
+        Assert.Null(metadata.CoerceValueCallback);
+        Assert.Equal(0, coerceValueCallbackCallCount);
+    }
+
+    [Fact]
+    public void CoerceValueCallback_SetSealed_ThrowsInvalidOperationException()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(PropertyMetadataTests) + MethodBase.GetCurrentMethod()!.Name, typeof(int), typeof(DependencyObjectTests));
+        PropertyMetadata metadata = property.DefaultMetadata;
+        Assert.Throws<InvalidOperationException>(() => metadata.CoerceValueCallback = (d, v) => v);
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("value")]
+    [InlineData(1)]
+    public void DefaultValue_Set_GetReturnsExpected(object? value)
+    {
+        var metadata = new PropertyMetadata();
+        
+        // Set value.
+        metadata.DefaultValue = value;
+        Assert.Equal(value, metadata.DefaultValue);
+
+        // Set same.
+        metadata.DefaultValue = value;
+        Assert.Equal(value, metadata.DefaultValue);
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("value")]
+    [InlineData(1)]
+    public void DefaultValue_SetDifferent_GetReturnsExpected(object? value)
+    {
+        var metadata = new PropertyMetadata
+        {
+            DefaultValue = new object()
+        };
+        
+        // Set value.
+        metadata.DefaultValue = value;
+        Assert.Equal(value, metadata.DefaultValue);
+
+        // Set same.
+        metadata.DefaultValue = value;
+        Assert.Equal(value, metadata.DefaultValue);
+    }
+
+    [Fact]
+    public void DefaultValue_SetUnset_ThrowsArgumentException()
+    {
+        var metadata = new PropertyMetadata();
+        // TODO: add paramName.
+        Assert.Throws<ArgumentException>(() => metadata.DefaultValue = DependencyProperty.UnsetValue);
+    }
+
+    [Fact]
+    public void DefaultValue_SetSealed_ThrowsInvalidOperationException()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(PropertyMetadataTests) + MethodBase.GetCurrentMethod()!.Name, typeof(int), typeof(DependencyObjectTests));
+        PropertyMetadata metadata = property.DefaultMetadata;
+        Assert.Throws<InvalidOperationException>(() => metadata.DefaultValue = new object());
+    }
+
+    [Fact]
+    public void IsSealed_GetSealed_ReturnsTrue()
+    {
+        DependencyProperty property = DependencyProperty.RegisterAttached(nameof(PropertyMetadataTests) + MethodBase.GetCurrentMethod()!.Name, typeof(bool), typeof(DependencyObject), new SubPropertyMetadata());
+        SubPropertyMetadata metadata = Assert.IsType<SubPropertyMetadata>(property.DefaultMetadata);
+        Assert.True(metadata.IsSealed);
+    }
+
+    [Fact]
+    public void PropertyChangedCallback_Set_GetReturnsExpected()
+    {
+        var metadata = new PropertyMetadata();
+        
+        // Set value.
+        int propertyChangedCallbackCallCount = 0;
+        PropertyChangedCallback propertyChangedCallback = (d, e) => propertyChangedCallbackCallCount++;
+        metadata.PropertyChangedCallback = propertyChangedCallback;
+        Assert.Equal(propertyChangedCallback, metadata.PropertyChangedCallback);
+        Assert.Equal(0, propertyChangedCallbackCallCount);
+
+        // Set same.
+        metadata.PropertyChangedCallback = propertyChangedCallback;
+        Assert.Equal(propertyChangedCallback, metadata.PropertyChangedCallback);
+        Assert.Equal(0, propertyChangedCallbackCallCount);
+
+        // Set null.
+        metadata.PropertyChangedCallback = null;
+        Assert.Null(metadata.PropertyChangedCallback);
+        Assert.Equal(0, propertyChangedCallbackCallCount);
+    }
+
+    [Fact]
+    public void PropertyChangedCallback_SetSealed_ThrowsInvalidOperationException()
+    {
+        DependencyProperty property = DependencyProperty.Register(nameof(PropertyMetadataTests) + MethodBase.GetCurrentMethod()!.Name, typeof(int), typeof(DependencyObjectTests));
+        PropertyMetadata metadata = property.DefaultMetadata;
+        Assert.Throws<InvalidOperationException>(() => metadata.PropertyChangedCallback = (d, e) => { });
+    }
+
+    [Fact]
+    public void Merge_InvokeUnchangedOnUnchanged_Success()
+    {
+        var metadata = new SubPropertyMetadata();
+        var baseMetadata = new PropertyMetadata();
+        
+        metadata.Merge(baseMetadata, null!);
+        Assert.Null(metadata.CoerceValueCallback);
+        Assert.Null(metadata.DefaultValue);
+        Assert.False(metadata.IsSealed);
+        Assert.Null(metadata.PropertyChangedCallback);
+
+        // Make sure base metadata is unchanged.
+        Assert.Null(baseMetadata.CoerceValueCallback);
+        Assert.Null(baseMetadata.DefaultValue);
+        Assert.Null(baseMetadata.PropertyChangedCallback);
+    }
+
+    [Fact]
+    public void Merge_InvokeCustomOnUnchanged_Success()
+    {
+        var metadata = new SubPropertyMetadata();
+        var defaultValue = new object();
+        int propertyChangedCallbackCallCount = 0;
+        int coerceValueCallbackCallCount = 0;
+        PropertyChangedCallback propertyChangedCallback = (d, e) => propertyChangedCallbackCallCount++;
+        CoerceValueCallback coerceValueCallback = (d, v) => coerceValueCallbackCallCount++;
+        var baseMetadata = new PropertyMetadata(defaultValue, propertyChangedCallback, coerceValueCallback);
+        
+        metadata.Merge(baseMetadata, null!);
+        Assert.Equal(coerceValueCallback, metadata.CoerceValueCallback);
+        Assert.Equal(defaultValue, metadata.DefaultValue);
+        Assert.False(metadata.IsSealed);
+        Assert.Equal(propertyChangedCallback, metadata.PropertyChangedCallback);
+        Assert.Equal(0, propertyChangedCallbackCallCount);
+        Assert.Equal(0, coerceValueCallbackCallCount);
+
+        // Make sure base metadata is unchanged.
+        Assert.Equal(coerceValueCallback, baseMetadata.CoerceValueCallback);
+        Assert.Equal(defaultValue, baseMetadata.DefaultValue);
+        Assert.Equal(propertyChangedCallback, baseMetadata.PropertyChangedCallback);
+    }
+
+    [Fact]
+    public void Merge_InvokeUnchangedOnCustom_Success()
+    {
+        var defaultValue = new object();
+        int propertyChangedCallbackCallCount = 0;
+        int coerceValueCallbackCallCount = 0;
+        PropertyChangedCallback propertyChangedCallback = (d, e) => propertyChangedCallbackCallCount++;
+        CoerceValueCallback coerceValueCallback = (d, v) => coerceValueCallbackCallCount++;
+        var metadata = new SubPropertyMetadata(defaultValue, propertyChangedCallback, coerceValueCallback);
+        var baseMetadata = new PropertyMetadata();
+        
+        metadata.Merge(baseMetadata, null!);
+        Assert.Equal(coerceValueCallback, metadata.CoerceValueCallback);
+        Assert.Equal(defaultValue, metadata.DefaultValue);
+        Assert.False(metadata.IsSealed);
+        Assert.Equal(propertyChangedCallback, metadata.PropertyChangedCallback);
+        Assert.Equal(0, propertyChangedCallbackCallCount);
+        Assert.Equal(0, coerceValueCallbackCallCount);
+
+        // Make sure base metadata is unchanged.
+        Assert.Null(baseMetadata.CoerceValueCallback);
+        Assert.Null(baseMetadata.DefaultValue);
+        Assert.Null(baseMetadata.PropertyChangedCallback);
+    }
+
+    [Fact]
+    public void Merge_InvokeCustomOnCustom_Success()
+    {
+        var defaultValue1 = new object();
+        int propertyChangedCallbackCallCount1 = 0;
+        int coerceValueCallbackCallCount1 = 0;
+        PropertyChangedCallback propertyChangedCallback1 = (d, e) => propertyChangedCallbackCallCount1++;
+        CoerceValueCallback coerceValueCallback1 = (d, v) => coerceValueCallbackCallCount1++;
+        var metadata = new SubPropertyMetadata(defaultValue1, propertyChangedCallback1, coerceValueCallback1);
+        
+        var defaultValue2 = new object();
+        int propertyChangedCallbackCallCount2 = 0;
+        int coerceValueCallbackCallCount2 = 0;
+        PropertyChangedCallback propertyChangedCallback2 = (d, e) => propertyChangedCallbackCallCount2++;
+        CoerceValueCallback coerceValueCallback2 = (d, v) => coerceValueCallbackCallCount2++;
+        var baseMetadata = new SubPropertyMetadata(defaultValue2, propertyChangedCallback2, coerceValueCallback2);
+        
+        metadata.Merge(baseMetadata, null!);
+        Assert.Equal(coerceValueCallback1, metadata.CoerceValueCallback);
+        Assert.Equal(defaultValue1, metadata.DefaultValue);
+        Assert.False(metadata.IsSealed);
+        Assert.NotNull(metadata.PropertyChangedCallback);
+        Assert.Same(metadata.PropertyChangedCallback, metadata.PropertyChangedCallback);
+        Assert.NotEqual(propertyChangedCallback1, metadata.PropertyChangedCallback);
+        Assert.NotEqual(propertyChangedCallback2, metadata.PropertyChangedCallback);
+        Assert.Equal(0, propertyChangedCallbackCallCount1);
+        Assert.Equal(0, coerceValueCallbackCallCount1);
+        Assert.Equal(0, propertyChangedCallbackCallCount2);
+        Assert.Equal(0, coerceValueCallbackCallCount2);
+
+        // Make sure base metadata is unchanged.
+        Assert.Equal(coerceValueCallback2, baseMetadata.CoerceValueCallback);
+        Assert.Equal(defaultValue2, baseMetadata.DefaultValue);
+        Assert.Equal(propertyChangedCallback2, baseMetadata.PropertyChangedCallback);
+    }
+
+    [Fact]
+    public void Merge_InvokeSelfUnchanged_Success()
+    {
+        var metadata = new SubPropertyMetadata();
+        metadata.Merge(metadata, null!);
+        Assert.Null(metadata.CoerceValueCallback);
+        Assert.Null(metadata.DefaultValue);
+        Assert.False(metadata.IsSealed);
+        Assert.Null(metadata.PropertyChangedCallback);
+    }
+
+    [Fact]
+    public void Merge_InvokeSelfChanged_Success()
+    {
+        var defaultValue = new object();
+        int propertyChangedCallbackCallCount = 0;
+        PropertyChangedCallback propertyChangedCallback = (d, e) => propertyChangedCallbackCallCount++;
+        int coerceValueCallbackCallCount = 0;
+        CoerceValueCallback coerceValueCallback = (d, v) => coerceValueCallbackCallCount++;
+        var metadata = new SubPropertyMetadata(defaultValue, propertyChangedCallback, coerceValueCallback);
+
+        metadata.Merge(metadata, null!);
+        Assert.Same(coerceValueCallback, metadata.CoerceValueCallback);
+        Assert.Same(defaultValue, metadata.DefaultValue);
+        Assert.False(metadata.IsSealed);
+        Assert.NotNull(metadata.PropertyChangedCallback);
+        Assert.NotSame(propertyChangedCallback, metadata.PropertyChangedCallback);
+    }
+
+    [Fact]
+    public void Merge_InvokeBaseHasPropertyChangedCallback_AddsBaseHandlers()
+    {
+        var metadata = new SubPropertyMetadata();
+        var events = new List<string>();
+        var baseMetadata = new PropertyMetadata();
+        baseMetadata.PropertyChangedCallback += (d, e) => events.Add("Event3");
+        baseMetadata.PropertyChangedCallback += (d, e) => events.Add("Event4");
+
+        metadata.Merge(baseMetadata, null!);
+        Assert.Equal(baseMetadata.PropertyChangedCallback, metadata.PropertyChangedCallback);
+
+        var obj = new DependencyObject();
+        var e = new DependencyPropertyChangedEventArgs();
+        metadata.PropertyChangedCallback.Invoke(obj, e);
+        Assert.Equal(new[] { "Event3", "Event4" }, events);
+    }
+
+    [Fact]
+    public void Merge_InvokeCurrentHasPropertyChangedCallback_KeepsCurrentHandlers()
+    {
+        var events = new List<string>();
+        var metadata = new SubPropertyMetadata();
+        metadata.PropertyChangedCallback += (d, e) => events.Add("Event1");
+        metadata.PropertyChangedCallback += (d, e) => events.Add("Event2");
+        var baseMetadata = new PropertyMetadata();
+
+        metadata.Merge(baseMetadata, null!);
+        Assert.NotEqual(baseMetadata.PropertyChangedCallback, metadata.PropertyChangedCallback);
+
+        var obj = new DependencyObject();
+        var e = new DependencyPropertyChangedEventArgs();
+        metadata.PropertyChangedCallback.Invoke(obj, e);
+        Assert.Equal(new[] { "Event1", "Event2" }, events);
+    }
+
+    [Fact]
+    public void Merge_InvokeCurrentAndBaseHavePropertyChangedCallback_AddsBaseHandlersAtStart()
+    {
+        var events = new List<string>();
+        var metadata = new SubPropertyMetadata();
+        metadata.PropertyChangedCallback += (d, e) => events.Add("Event1");
+        metadata.PropertyChangedCallback += (d, e) => events.Add("Event2");
+        var baseMetadata = new PropertyMetadata();
+        baseMetadata.PropertyChangedCallback += (d, e) => events.Add("Event3");
+        baseMetadata.PropertyChangedCallback += (d, e) => events.Add("Event4");
+
+        metadata.Merge(baseMetadata, null!);
+        Assert.NotEqual(baseMetadata.PropertyChangedCallback, metadata.PropertyChangedCallback);
+
+        var obj = new DependencyObject();
+        var e = new DependencyPropertyChangedEventArgs();
+        metadata.PropertyChangedCallback.Invoke(obj, e);
+        Assert.Equal(new[] { "Event3", "Event4", "Event1", "Event2" }, events);
+    }
+    
+    [Fact]
+    public void Merge_InvokeBaseHasCoerceValueCallback_AddsBaseHandlers()
+    {
+        var events = new List<string>();
+        var metadata = new SubPropertyMetadata();
+        var baseMetadata = new PropertyMetadata();
+        baseMetadata.CoerceValueCallback += (d, e) => { events.Add("Event3"); return 1; };
+        baseMetadata.CoerceValueCallback += (d, e) => { events.Add("Event4"); return 1; };
+
+        metadata.Merge(baseMetadata, null!);
+        Assert.Equal(baseMetadata.CoerceValueCallback, metadata.CoerceValueCallback);
+
+        var obj = new DependencyObject();
+        var e = new DependencyPropertyChangedEventArgs();
+        metadata.CoerceValueCallback.Invoke(obj, e);
+        Assert.Equal(new[] { "Event3", "Event4" }, events);
+    }
+    
+    [Fact]
+    public void Merge_InvokeCurrentHasCoerceValueCallback_KeepsCurrentHandlers()
+    {
+        var events = new List<string>();
+        var metadata = new SubPropertyMetadata();
+        metadata.CoerceValueCallback += (d, e) => { events.Add("Event1"); return 1; };
+        metadata.CoerceValueCallback += (d, e) => { events.Add("Event2"); return 1; };
+        var baseMetadata = new PropertyMetadata();
+
+        metadata.Merge(baseMetadata, null!);
+        Assert.NotEqual(baseMetadata.CoerceValueCallback, metadata.CoerceValueCallback);
+
+        var obj = new DependencyObject();
+        var e = new DependencyPropertyChangedEventArgs();
+        metadata.CoerceValueCallback.Invoke(obj, e);
+        Assert.Equal(new[] { "Event1", "Event2" }, events);
+    }
+    
+    [Fact]
+    public void Merge_InvokeCurrentAndBaseHaveCoerceValueCallback_DoesNotAddBaseHandlers()
+    {
+        var events = new List<string>();
+        var metadata = new SubPropertyMetadata();
+        metadata.CoerceValueCallback += (d, e) => { events.Add("Event1"); return 1; };
+        metadata.CoerceValueCallback += (d, e) => { events.Add("Event2"); return 1; };
+        var baseMetadata = new PropertyMetadata();
+        baseMetadata.CoerceValueCallback += (d, e) => { events.Add("Event3"); return 1; };
+        baseMetadata.CoerceValueCallback += (d, e) => { events.Add("Event4"); return 1; };
+
+        metadata.Merge(baseMetadata, null!);
+        Assert.NotEqual(baseMetadata.CoerceValueCallback, metadata.CoerceValueCallback);
+
+        var obj = new DependencyObject();
+        var e = new DependencyPropertyChangedEventArgs();
+        metadata.CoerceValueCallback.Invoke(obj, e);
+        Assert.Equal(new[] { "Event1", "Event2" }, events);
+    }
+
+    [Fact]
+    public void Merge_NullBaseMetadata_ThrowsArgumentNullException()
+    {
+        var metadata = new SubPropertyMetadata();
+        Assert.Throws<ArgumentNullException>("baseMetadata", () => metadata.Merge(null!, null!));
+    }
+
+    [Fact]
+    public void Merge_InvokeSealed_ThrowsInvalidOperationException()
+    {
+        DependencyProperty property = DependencyProperty.RegisterAttached(nameof(PropertyMetadataTests) + MethodBase.GetCurrentMethod()!.Name, typeof(int), typeof(DependencyObject), new SubPropertyMetadata());
+        SubPropertyMetadata metadata = Assert.IsType<SubPropertyMetadata>(property.DefaultMetadata);
+        Assert.Throws<InvalidOperationException>(() => metadata.Merge(new PropertyMetadata(), null!));
+    }
+
+    private static DependencyProperty s_property = DependencyProperty.Register(nameof(PropertyMetadataTests), typeof(string), typeof(DependencyObject));
+
+    public static IEnumerable<object?[]> OnApply_TestData()
+    {
+        yield return new object?[] { s_property, typeof(bool) };
+        yield return new object?[] { s_property, null };
+        yield return new object?[] { null, typeof(bool) };
+        yield return new object?[] { null, null };
+    }
+
+    [Theory]
+    [MemberData(nameof(OnApply_TestData))]
+    public void OnApply_Invoke_Nop(DependencyProperty dp, Type targetType)
+    {
+        var metadata = new SubPropertyMetadata();
+        metadata.OnApply(dp, targetType);
+    }
+
+    private class SubPropertyMetadata : PropertyMetadata
+    {
+        public SubPropertyMetadata() : base()
+        {
+        }
+
+        public SubPropertyMetadata(object defaultValue) : base(defaultValue)
+        {
+        }
+
+        public SubPropertyMetadata(PropertyChangedCallback propertyChangedCallback) : base(propertyChangedCallback)
+        {
+        }
+
+        public SubPropertyMetadata(object defaultValue, PropertyChangedCallback propertyChangedCallback) : base(defaultValue, propertyChangedCallback)
+        {
+        }
+
+        public SubPropertyMetadata(object defaultValue, PropertyChangedCallback propertyChangedCallback, CoerceValueCallback coerceValueCallback) : base(defaultValue, propertyChangedCallback, coerceValueCallback)
+        {
+        }
+
+        public new bool IsSealed => base.IsSealed;
+
+        public new void Merge(PropertyMetadata baseMetadata, DependencyProperty dp)
+            => base.Merge(baseMetadata, dp);
+
+        public new void OnApply(DependencyProperty dp, Type targetType)
+            => base.OnApply(dp, targetType);
+    }
+}
\ No newline at end of file
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/RectConverterTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/RectConverterTests.cs
new file mode 100644
index 00000000000..835dd4d5089
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/RectConverterTests.cs
@@ -0,0 +1,198 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.ComponentModel.Design.Serialization;
+using System.Globalization;
+
+namespace System.Windows.Tests;
+
+public class RectConverterTests
+{
+    [Theory]
+    [InlineData(null, false)]
+    [InlineData(typeof(object), false)]
+    [InlineData(typeof(string), true)]
+    [InlineData(typeof(InstanceDescriptor), false)]
+    [InlineData(typeof(Rect), false)]
+    public void CanConvertTo_Invoke_ReturnsExpected(Type? destinationType, bool expected)
+    {
+        var converter = new RectConverter();
+        Assert.Equal(expected, converter.CanConvertTo(null, destinationType));
+        Assert.Equal(expected, converter.CanConvertTo(new CustomTypeDescriptorContext(), destinationType));
+    }
+    
+    [Theory]
+    [MemberData(nameof(RectTests.ToString_TestData), MemberType = typeof(RectTests))]
+    public void ConvertTo_InvokeRectToString_ReturnsExpected(Rect matrix, string expected)
+    {
+        var converter = new RectConverter();
+        Assert.Equal(expected, converter.ConvertTo(matrix, typeof(string)));
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), null, matrix, typeof(string)));
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, matrix, typeof(string)));
+    }
+    
+    [Theory]
+    [MemberData(nameof(RectTests.ToString_IFormatProviderCustom_TestData), MemberType = typeof(RectTests))]
+    public void ConvertTo_InvokeRectToStringCustomCulture_ReturnsExpected(Rect matrix, string numberDecimalSeparator, string expected)
+    {
+        var culture = new CultureInfo("en-US");
+        NumberFormatInfo formatInfo = culture.NumberFormat;
+        formatInfo.NumberDecimalSeparator = numberDecimalSeparator;
+
+        var converter = new RectConverter();
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), culture, matrix, typeof(string)));
+    }
+
+    [Theory]
+    [InlineData(null, "")]
+    [InlineData("", "")]
+    [InlineData("value", "value")]
+    [InlineData(1, "1")]
+    public void ConvertTo_InvokeNotRectToString_ReturnsExpected(object? value, string expected)
+    {
+        var converter = new RectConverter();
+        Assert.Equal(expected, converter.ConvertTo(value, typeof(string)));
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), null, value, typeof(string)));
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value, typeof(string)));
+    }
+
+    public static IEnumerable<object?[]> ConvertTo_CantConvert_TestData()
+    {
+        yield return new object?[] { null, typeof(object) };
+        yield return new object?[] { string.Empty, typeof(object) };
+        yield return new object?[] { "value", typeof(object) };
+        yield return new object?[] { new object(), typeof(object) };
+        yield return new object?[] { new Rect(), typeof(object) };
+        
+        yield return new object?[] { null, typeof(Rect) };
+        yield return new object?[] { string.Empty, typeof(Rect) };
+        yield return new object?[] { "value", typeof(Rect) };
+        yield return new object?[] { new object(), typeof(Rect) };
+        yield return new object?[] { new Rect(), typeof(Rect) };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertTo_CantConvert_TestData))]
+    public void ConvertTo_CantConvert_ThrowsNotSupportedException(object value, Type destinationType)
+    {
+        var converter = new RectConverter();
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(value, destinationType));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(null, null, value, destinationType));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value, destinationType));
+    }
+
+    public static IEnumerable<object?[]> ConvertTo_NullDestinationType_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { string.Empty };
+        yield return new object?[] { "value" };
+        yield return new object?[] { new object() };
+        yield return new object?[] { new Rect() };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertTo_NullDestinationType_TestData))]
+    public void ConvertTo_NullDestinationType_ThrowsArgumentNullException(object value)
+    {
+        var converter = new RectConverter();
+        Assert.Throws<ArgumentNullException>("destinationType", () => converter.ConvertTo(value, null!));
+        Assert.Throws<ArgumentNullException>("destinationType", () => converter.ConvertTo(null, null, new Rect(), null!));
+        Assert.Throws<ArgumentNullException>("destinationType", () => converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, new Rect(), null!));
+    }
+
+    [Theory]
+    [InlineData(null, false)]
+    [InlineData(typeof(object), false)]
+    [InlineData(typeof(string), true)]
+    [InlineData(typeof(InstanceDescriptor), true)]
+    [InlineData(typeof(Rect), false)]
+    public void CanConvertFrom_Invoke_ReturnsExpected(Type? sourceType, bool expected)
+    {
+        var converter = new RectConverter();
+        Assert.Equal(expected, converter.CanConvertFrom(sourceType!));
+        Assert.Equal(expected, converter.CanConvertFrom(null, sourceType));
+        Assert.Equal(expected, converter.CanConvertFrom(new CustomTypeDescriptorContext(), sourceType));
+    }
+
+    [Theory]
+    [MemberData(nameof(RectTests.Parse_TestData), MemberType = typeof(RectTests))]
+    public void ConvertFrom_InvokeStringValue_ReturnsExpected(object value, Rect expected)
+    {
+        var converter = new RectConverter();
+        Assert.Equal(expected, converter.ConvertFrom(value));
+        Assert.Equal(expected, converter.ConvertFrom(null, null, value));
+        Assert.Equal(expected, converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    [Fact]
+    public void ConvertFrom_NullValue_ThrowsNotSupportedException()
+    {
+        var converter = new RectConverter();
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(null!));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(null, null, null));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, null));
+    }
+
+    [Theory]
+    [MemberData(nameof(RectTests.Parse_InvalidSource_TestData), MemberType = typeof(RectTests))]
+    public void ConvertFrom_InvalidStringValue_ThrowsInvalidOperationException(object value)
+    {
+        var converter = new RectConverter();
+        Assert.Throws<InvalidOperationException>(() => converter.ConvertFrom(value));
+        Assert.Throws<InvalidOperationException>(() => converter.ConvertFrom(null, null, value));
+        Assert.Throws<InvalidOperationException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    [Theory]
+    [MemberData(nameof(RectTests.Parse_NotDouble_TestData), MemberType = typeof(RectTests))]
+    public void ConvertFrom_NotDoubleStringValue_ThrowsFormatException(object value)
+    {
+        var converter = new RectConverter();
+        Assert.Throws<FormatException>(() => converter.ConvertFrom(value));
+        Assert.Throws<FormatException>(() => converter.ConvertFrom(null, null, value));
+        Assert.Throws<FormatException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    [Theory]
+    [MemberData(nameof(RectTests.Parse_Negative_TestData), MemberType = typeof(RectTests))]
+    public void ConvertFrom_Negative_ThrowsArgumentException(object value)
+    {
+        var converter = new RectConverter();
+        Assert.Throws<ArgumentException>(() => converter.ConvertFrom(value));
+        Assert.Throws<ArgumentException>(() => converter.ConvertFrom(null, null, value));
+        Assert.Throws<ArgumentException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    public static IEnumerable<object[]> ConvertFrom_CantConvert_TestData()
+    {
+        yield return new object[] { new object() };
+        yield return new object[] { new Rect() };
+    }
+    
+    [Theory]
+    [MemberData(nameof(ConvertFrom_CantConvert_TestData))]
+    public void ConvertFrom_CantConvert_ThrowsNotSupportedException(object value)
+    {
+        var converter = new RectConverter();
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(value));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(null, null, value));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    private class CustomTypeDescriptorContext : ITypeDescriptorContext
+    {
+        public IContainer Container => throw new NotImplementedException();
+
+        public object Instance => throw new NotImplementedException();
+
+        public PropertyDescriptor PropertyDescriptor => throw new NotImplementedException();
+
+        public object? GetService(Type serviceType) => throw new NotImplementedException();
+
+        public void OnComponentChanged() => throw new NotImplementedException();
+
+        public bool OnComponentChanging() => throw new NotImplementedException();
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/RectTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/RectTests.cs
new file mode 100644
index 00000000000..6d071b6defe
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/RectTests.cs
@@ -0,0 +1,3327 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.Globalization;
+using System.Windows.Converters;
+using System.Windows.Markup;
+using System.Windows.Media;
+using System.Windows.Media.Tests;
+
+namespace System.Windows.Tests;
+
+public class RectTests
+{
+    [Fact]
+    public void Ctor_Default()
+    {
+        var rect = new Rect();
+        Assert.Equal(0, rect.X);
+        Assert.Equal(0, rect.Y);
+        Assert.Equal(0, rect.Width);
+        Assert.Equal(0, rect.Height);
+        Assert.False(rect.IsEmpty);
+    }
+
+    public static IEnumerable<object[]> Ctor_Size_TestData()
+    {
+        yield return new object[] { new Size(1, 2) };
+        yield return new object[] { new Size(1, 0) };
+        yield return new object[] { new Size(0, 2) };
+        yield return new object[] { new Size(0, 0) };
+        yield return new object[] { new Size(double.NaN, double.NaN) };
+        yield return new object[] { new Size(double.NaN, 2) };
+        yield return new object[] { new Size(1, double.NaN) };
+        yield return new object[] { new Size() };
+    }
+
+    [Theory]
+    [MemberData(nameof(Ctor_Size_TestData))]
+    public void Ctor_Size(Size size)
+    {
+        var rect = new Rect(size);
+        Assert.Equal(0, rect.X);
+        Assert.Equal(0, rect.Y);
+        Assert.Equal(size.Width, rect.Width);
+        Assert.Equal(size.Height, rect.Height);
+        Assert.Equal(0, rect.Location.X);
+        Assert.Equal(0, rect.Location.Y);
+        Assert.Equal(size.Width, rect.Size.Width);
+        Assert.Equal(size.Height, rect.Size.Height);
+        Assert.Equal(0, rect.Top);
+        Assert.Equal(0, rect.TopLeft.X);
+        Assert.Equal(0, rect.TopLeft.Y);
+        Assert.Equal(size.Width, rect.TopRight.X);
+        Assert.Equal(0, rect.TopRight.Y);
+        Assert.Equal(size.Height, rect.Bottom);
+        Assert.Equal(0, rect.BottomLeft.X);
+        Assert.Equal(size.Height, rect.BottomLeft.Y);
+        Assert.Equal(size.Width, rect.BottomRight.X);
+        Assert.Equal(size.Height, rect.BottomRight.Y);
+        Assert.False(rect.IsEmpty);
+    }
+
+    [Fact]
+    public void Ctor_SizeEmpty()
+    {
+        var rect = new Rect(Size.Empty);
+        Assert.Equal(double.PositiveInfinity, rect.X);
+        Assert.Equal(double.PositiveInfinity, rect.Y);
+        Assert.Equal(double.NegativeInfinity, rect.Width);
+        Assert.Equal(double.NegativeInfinity, rect.Height);
+        Assert.Equal(double.PositiveInfinity, rect.Location.X);
+        Assert.Equal(double.PositiveInfinity, rect.Location.Y);
+        Assert.Equal(double.NegativeInfinity, rect.Size.Width);
+        Assert.Equal(double.NegativeInfinity, rect.Size.Height);
+        Assert.Equal(double.PositiveInfinity, rect.Top);
+        Assert.Equal(double.PositiveInfinity, rect.TopLeft.X);
+        Assert.Equal(double.PositiveInfinity, rect.TopLeft.Y);
+        Assert.Equal(double.NegativeInfinity, rect.TopRight.X);
+        Assert.Equal(double.PositiveInfinity, rect.TopRight.Y);
+        Assert.Equal(double.NegativeInfinity, rect.Bottom);
+        Assert.Equal(double.PositiveInfinity, rect.BottomLeft.X);
+        Assert.Equal(double.NegativeInfinity, rect.BottomLeft.Y);
+        Assert.Equal(double.NegativeInfinity, rect.BottomRight.X);
+        Assert.Equal(double.NegativeInfinity, rect.BottomRight.Y);
+        Assert.True(rect.IsEmpty);
+    }
+
+    [Theory]
+    [InlineData(double.NegativeZero, double.NegativeZero, double.NegativeZero, double.NegativeZero)]
+    [InlineData(double.NegativeInfinity, double.NegativeInfinity, 3, 4)]
+    [InlineData(double.MinValue, double.MinValue, 3, 4)]
+    [InlineData(0, 0, 0, 0)]
+    [InlineData(0.1, 0.2, 0.3, 0.4)]
+    [InlineData(-1, -2, 3, 4)]
+    [InlineData(1, 2, 3, 4)]
+    [InlineData(double.MaxValue, double.MaxValue, double.MaxValue, double.MaxValue)]
+    [InlineData(double.PositiveInfinity, double.PositiveInfinity, double.PositiveInfinity, double.PositiveInfinity)]
+    [InlineData(double.NaN, double.NaN, double.NaN, double.NaN)]
+    public void Ctor_Double_Double_Double_Double(double x, double y, double width, double height)
+    {
+        var rect = new Rect(x, y, width, height);
+        Assert.Equal(x, rect.X);
+        Assert.Equal(y, rect.Y);
+        Assert.Equal(width, rect.Width);
+        Assert.Equal(height, rect.Height);
+        Assert.Equal(x, rect.Location.X);
+        Assert.Equal(y, rect.Location.Y);
+        Assert.Equal(width, rect.Size.Width);
+        Assert.Equal(height, rect.Size.Height);
+        Assert.Equal(y, rect.Top);
+        Assert.Equal(x, rect.TopLeft.X);
+        Assert.Equal(y, rect.TopLeft.Y);
+        Assert.Equal(x + width, rect.TopRight.X);
+        Assert.Equal(y, rect.TopRight.Y);
+        Assert.Equal(y + height, rect.Bottom);
+        Assert.Equal(x, rect.BottomLeft.X);
+        Assert.Equal(y + height, rect.BottomLeft.Y);
+        Assert.Equal(x + width, rect.BottomRight.X);
+        Assert.Equal(y + height, rect.BottomRight.Y);
+        Assert.False(rect.IsEmpty);
+    }
+
+    [Theory]
+    [InlineData(double.NegativeInfinity)]
+    [InlineData(double.MinValue)]
+    [InlineData(-1)]
+    public void Ctor_NegativeWidth_ThrowsArgumentException(double width)
+    {
+        // TODO: should have paramName
+        Assert.Throws<ArgumentException>(() => new Rect(0, 0, width, 0));
+    }
+
+    [Theory]
+    [InlineData(double.NegativeInfinity)]
+    [InlineData(double.MinValue)]
+    [InlineData(-1)]
+    public void Ctor_NegativeHeight_ThrowsArgumentException(double height)
+    {
+        // TODO: should have paramName
+        Assert.Throws<ArgumentException>(() => new Rect(0, 0, 0, height));
+    }
+
+    public static IEnumerable<object[]> Ctor_Point_Point_TestData()
+    {
+        // Normal.
+        yield return new object[] { new Point(1, 2), new Point(1, 2), 1, 2, 0, 0 };
+        yield return new object[] { new Point(1, 2), new Point(3, 4), 1, 2, 2, 2 };
+        yield return new object[] { new Point(1.5, 2.5), new Point(3.5, 4.5), 1.5, 2.5, 2, 2 };
+        yield return new object[] { new Point(-1, -2), new Point(3, 4), -1, -2, 4, 6 };
+        yield return new object[] { new Point(1, 2), new Point(-3, -4), -3, -4, 4, 6 };
+        yield return new object[] { new Point(1, 2), new Point(0, 0), 0, 0, 1, 2 };
+        yield return new object[] { new Point(1, 2), new Point(), 0, 0, 1, 2 };
+
+        // Infinity.
+        yield return new object[] { new Point(double.PositiveInfinity, double.PositiveInfinity), new Point(1, 2), 1, 2, double.PositiveInfinity, double.PositiveInfinity };
+        yield return new object[] { new Point(1, 2), new Point(double.PositiveInfinity, double.PositiveInfinity), 1, 2, double.PositiveInfinity, double.PositiveInfinity };
+        yield return new object[] { new Point(double.NegativeInfinity, double.NegativeInfinity), new Point(1, 2), double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity };
+        yield return new object[] { new Point(1, 2), new Point(double.NegativeInfinity, double.NegativeInfinity), double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity };
+        yield return new object[] { new Point(double.NegativeInfinity, double.NegativeInfinity), new Point(double.NegativeInfinity, double.NegativeInfinity), double.NegativeInfinity, double.NegativeInfinity, double.NaN, double.NaN };        
+
+        // NaN.
+        yield return new object[] { new Point(double.NaN, double.NaN), new Point(1, 2), double.NaN, double.NaN, double.NaN, double.NaN };
+        yield return new object[] { new Point(1, 2), new Point(double.NaN, double.NaN), double.NaN, double.NaN, double.NaN, double.NaN };
+        yield return new object[] { new Point(double.NaN, double.NaN), new Point(double.NaN, double.NaN), double.NaN, double.NaN, double.NaN, double.NaN };
+
+        // Zero.
+        yield return new object[] { new Point(0, 0), new Point(0, 0), 0, 0, 0, 0 };
+        yield return new object[] { new Point(0, 0), new Point(), 0, 0, 0, 0 };
+        yield return new object[] { new Point(0, 0), new Point(1, 2), 0, 0, 1, 2 };
+        yield return new object[] { new Point(0, 0), new Point(-1, -2), -1, -2, 1, 2 };
+        
+        // Default.
+        yield return new object[] { new Point(), new Point(0, 0), 0, 0, 0, 0 };
+        yield return new object[] { new Point(), new Point(), 0, 0, 0, 0 };
+        yield return new object[] { new Point(), new Point(1, 2), 0, 0, 1, 2 };
+        yield return new object[] { new Point(), new Point(-1, -2), -1, -2, 1, 2 };
+    }
+
+    [Theory]
+    [MemberData(nameof(Ctor_Point_Point_TestData))]
+    public void Ctor_Point_Point(Point point1, Point point2, double expectedX, double expectedY, double expectedWidth, double expectedHeight)
+    {
+        var rect = new Rect(point1, point2);
+        Assert.Equal(new Rect(expectedX, expectedY, expectedWidth, expectedHeight), rect);
+        Assert.Equal(expectedX, rect.X);
+        Assert.Equal(expectedY, rect.Y);
+        Assert.Equal(expectedWidth, rect.Width);
+        Assert.Equal(expectedHeight, rect.Height);
+        Assert.Equal(expectedX, rect.Location.X);
+        Assert.Equal(expectedY, rect.Location.Y);
+        Assert.Equal(expectedWidth, rect.Size.Width);
+        Assert.Equal(expectedHeight, rect.Size.Height);
+        Assert.Equal(expectedY, rect.Top);
+        Assert.Equal(expectedX, rect.TopLeft.X);
+        Assert.Equal(expectedY, rect.TopLeft.Y);
+        Assert.Equal(expectedX + expectedWidth, rect.TopRight.X);
+        Assert.Equal(expectedY, rect.TopRight.Y);
+        Assert.Equal(expectedY + expectedHeight, rect.Bottom);
+        Assert.Equal(expectedX, rect.BottomLeft.X);
+        Assert.Equal(expectedY + expectedHeight, rect.BottomLeft.Y);
+        Assert.Equal(expectedX + expectedWidth, rect.BottomRight.X);
+        Assert.Equal(expectedY + expectedHeight, rect.BottomRight.Y);
+        Assert.False(rect.IsEmpty);
+    }
+
+    public static IEnumerable<object[]> Ctor_Point_Size_TestData()
+    {
+        // Normal.
+        yield return new object[] { new Point(1, 2), new Size(1, 2), 1, 2, 1, 2 };
+        yield return new object[] { new Point(1.25, 2.25), new Size(1.5, 2.5), 1.25, 2.25, 1.5, 2.5 };
+        yield return new object[] { new Point(-1, -2), new Size(1, 2), -1, -2, 1, 2 };
+
+        // Infinite.
+        yield return new object[] { new Point(double.PositiveInfinity, double.PositiveInfinity), new Size(double.PositiveInfinity, double.PositiveInfinity), double.PositiveInfinity, double.PositiveInfinity, double.PositiveInfinity, double.PositiveInfinity };
+        yield return new object[] { new Point(double.PositiveInfinity, double.PositiveInfinity), new Size(1, 2), double.PositiveInfinity, double.PositiveInfinity, 1, 2 };
+        yield return new object[] { new Point(1, 2), new Size(double.PositiveInfinity, double.PositiveInfinity), 1, 2, double.PositiveInfinity, double.PositiveInfinity };
+        yield return new object[] { new Point(double.NegativeInfinity, double.NegativeInfinity), new Size(double.PositiveInfinity, double.PositiveInfinity), double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity };
+        yield return new object[] { new Point(double.NegativeInfinity, double.NegativeInfinity), new Size(1, 2), double.NegativeInfinity, double.NegativeInfinity, 1, 2 };
+
+        // NaN.
+        yield return new object[] { new Point(double.NaN, double.NaN), new Size(double.NaN, double.NaN), double.NaN, double.NaN, double.NaN, double.NaN };
+        yield return new object[] { new Point(double.NaN, double.NaN), new Size(1, 2), double.NaN, double.NaN, 1, 2 };
+        yield return new object[] { new Point(1, 2), new Size(double.NaN, double.NaN), 1, 2, double.NaN, double.NaN };
+
+        // Zero.
+        yield return new object[] { new Point(0, 0), new Size(1, 2), 0, 0, 1, 2 };
+        yield return new object[] { new Point(0, 0), new Size(0, 0), 0, 0, 0, 0 };
+        yield return new object[] { new Point(0, 0), new Size(), 0, 0, 0, 0 };
+        
+        // Default.
+        yield return new object[] { new Point(), new Size(1, 2), 0, 0, 1, 2 };
+        yield return new object[] { new Point(), new Size(0, 0), 0, 0, 0, 0 };
+        yield return new object[] { new Point(), new Size(), 0, 0, 0, 0 };
+    }
+
+    [Theory]
+    [MemberData(nameof(Ctor_Point_Size_TestData))]
+    public void Ctor_Point_Size(Point point, Size size, double expectedX, double expectedY, double expectedWidth, double expectedHeight)
+    {
+        var rect = new Rect(point, size);
+        Assert.Equal(new Rect(expectedX, expectedY, expectedWidth, expectedHeight), rect);
+        Assert.Equal(expectedX, rect.X);
+        Assert.Equal(expectedY, rect.Y);
+        Assert.Equal(expectedWidth, rect.Width);
+        Assert.Equal(expectedHeight, rect.Height);
+        Assert.Equal(expectedX, rect.Location.X);
+        Assert.Equal(expectedY, rect.Location.Y);
+        Assert.Equal(expectedWidth, rect.Size.Width);
+        Assert.Equal(expectedHeight, rect.Size.Height);
+        Assert.Equal(expectedY, rect.Top);
+        Assert.Equal(expectedX, rect.TopLeft.X);
+        Assert.Equal(expectedY, rect.TopLeft.Y);
+        Assert.Equal(expectedX + expectedWidth, rect.TopRight.X);
+        Assert.Equal(expectedY, rect.TopRight.Y);
+        Assert.Equal(expectedY + expectedHeight, rect.Bottom);
+        Assert.Equal(expectedX, rect.BottomLeft.X);
+        Assert.Equal(expectedY + expectedHeight, rect.BottomLeft.Y);
+        Assert.Equal(expectedX + expectedWidth, rect.BottomRight.X);
+        Assert.Equal(expectedY + expectedHeight, rect.BottomRight.Y);
+        Assert.False(rect.IsEmpty);
+    }
+
+    public static IEnumerable<object[]> Ctor_Point_Size_Empty_TestData()
+    {
+        yield return new object[] { new Point(1, 2) };
+        yield return new object[] { new Point(0, 0) };
+        yield return new object[] { new Point() };
+    }
+
+    [Theory]
+    [MemberData(nameof(Ctor_Point_Size_Empty_TestData))]
+    public void Ctor_Point_Size_Empty(Point point)
+    {
+        var rect = new Rect(point, Size.Empty);
+        Assert.Equal(Rect.Empty, rect);
+        Assert.Equal(double.PositiveInfinity, rect.X);
+        Assert.Equal(double.PositiveInfinity, rect.Y);
+        Assert.Equal(double.NegativeInfinity, rect.Width);
+        Assert.Equal(double.NegativeInfinity, rect.Height);
+        Assert.Equal(double.PositiveInfinity, rect.Location.X);
+        Assert.Equal(double.PositiveInfinity, rect.Location.Y);
+        Assert.Equal(double.NegativeInfinity, rect.Size.Width);
+        Assert.Equal(double.NegativeInfinity, rect.Size.Height);
+        Assert.Equal(double.PositiveInfinity, rect.Top);
+        Assert.Equal(double.PositiveInfinity, rect.TopLeft.X);
+        Assert.Equal(double.PositiveInfinity, rect.TopLeft.Y);
+        Assert.Equal(double.NegativeInfinity, rect.TopRight.X);
+        Assert.Equal(double.PositiveInfinity, rect.TopRight.Y);
+        Assert.Equal(double.NegativeInfinity, rect.Bottom);
+        Assert.Equal(double.PositiveInfinity, rect.BottomLeft.X);
+        Assert.Equal(double.NegativeInfinity, rect.BottomLeft.Y);
+        Assert.Equal(double.NegativeInfinity, rect.BottomRight.X);
+        Assert.Equal(double.NegativeInfinity, rect.BottomRight.Y);
+        Assert.True(rect.IsEmpty);
+    }
+
+    public static IEnumerable<object[]> Ctor_Point_Vector_TestData()
+    {
+        // Normal.
+        yield return new object[] { new Point(1, 2), new Vector(3, 4), 1, 2, 3, 4 };
+        yield return new object[] { new Point(1.25, 2.25), new Vector(1.5, 2.5), 1.25, 2.25, 1.5, 2.5 };
+        yield return new object[] { new Point(1.25, 2.25), new Vector(-1.5, -2.5), -0.25, -0.25, 1.5, 2.5 };
+        yield return new object[] { new Point(1, 2), new Vector(0, 0), 1, 2, 0, 0 };
+        yield return new object[] { new Point(1, 2), new Vector(), 1, 2, 0, 0 };
+
+        // Infinite.
+        yield return new object[] { new Point(double.PositiveInfinity, double.PositiveInfinity), new Vector(double.PositiveInfinity, double.PositiveInfinity), double.PositiveInfinity, double.PositiveInfinity, double.NaN, double.NaN };
+        yield return new object[] { new Point(double.PositiveInfinity, double.PositiveInfinity), new Vector(1, 2), double.PositiveInfinity, double.PositiveInfinity, double.NaN, double.NaN };
+        yield return new object[] { new Point(1, 2), new Vector(double.PositiveInfinity, double.PositiveInfinity), 1, 2, double.PositiveInfinity, double.PositiveInfinity };
+        yield return new object[] { new Point(double.NegativeInfinity, double.NegativeInfinity), new Vector(1, 2), double.NegativeInfinity, double.NegativeInfinity, double.NaN, double.NaN };
+        yield return new object[] { new Point(1, 2), new Vector(double.NegativeInfinity, double.NegativeInfinity), double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity };
+        yield return new object[] { new Point(double.NegativeInfinity, double.NegativeInfinity), new Vector(double.NegativeInfinity, double.NegativeInfinity), double.NegativeInfinity, double.NegativeInfinity, double.NaN, double.NaN };
+
+        // NaN.
+        yield return new object[] { new Point(double.NaN, double.NaN), new Vector(double.NaN, double.NaN), double.NaN, double.NaN, double.NaN, double.NaN };
+        yield return new object[] { new Point(double.NaN, double.NaN), new Vector(1, 2), double.NaN, double.NaN, double.NaN, double.NaN };
+        yield return new object[] { new Point(1, 2), new Vector(double.NaN, double.NaN), double.NaN, double.NaN, double.NaN, double.NaN };
+
+        // Zero.
+        yield return new object[] { new Point(0, 0), new Vector(1, 2), 0, 0, 1, 2 };
+        yield return new object[] { new Point(0, 0), new Vector(0, 0), 0, 0, 0, 0 };
+        yield return new object[] { new Point(0, 0), new Vector(), 0, 0, 0, 0 };
+
+        // Default.
+        yield return new object[] { new Point(), new Vector(1, 2), 0, 0, 1, 2 };
+        yield return new object[] { new Point(), new Vector(0, 0), 0, 0, 0, 0 };
+        yield return new object[] { new Point(), new Vector(), 0, 0, 0, 0 };
+    }
+
+    [Theory]
+    [MemberData(nameof(Ctor_Point_Vector_TestData))]
+    public void Ctor_Point_Vector(Point point, Vector vector, double expectedX, double expectedY, double expectedWidth, double expectedHeight)
+    {
+        var rect = new Rect(point, vector);
+        Assert.Equal(new Rect(expectedX, expectedY, expectedWidth, expectedHeight), rect);
+        Assert.Equal(expectedX, rect.X);
+        Assert.Equal(expectedY, rect.Y);
+        Assert.Equal(expectedWidth, rect.Width);
+        Assert.Equal(expectedHeight, rect.Height);
+        Assert.Equal(expectedX, rect.Location.X);
+        Assert.Equal(expectedY, rect.Location.Y);
+        Assert.Equal(expectedWidth, rect.Size.Width);
+        Assert.Equal(expectedHeight, rect.Size.Height);
+        Assert.Equal(expectedY, rect.Top);
+        Assert.Equal(expectedX, rect.TopLeft.X);
+        Assert.Equal(expectedY, rect.TopLeft.Y);
+        Assert.Equal(expectedX + expectedWidth, rect.TopRight.X);
+        Assert.Equal(expectedY, rect.TopRight.Y);
+        Assert.Equal(expectedY + expectedHeight, rect.Bottom);
+        Assert.Equal(expectedX, rect.BottomLeft.X);
+        Assert.Equal(expectedY + expectedHeight, rect.BottomLeft.Y);
+        Assert.Equal(expectedX + expectedWidth, rect.BottomRight.X);
+        Assert.Equal(expectedY + expectedHeight, rect.BottomRight.Y);
+        Assert.False(rect.IsEmpty);
+    }
+
+    [Fact]
+    public void Empty_Get_ReturnsExpected()
+    {
+        Rect rect = Rect.Empty;
+        Assert.Equal(double.PositiveInfinity, rect.X);
+        Assert.Equal(double.PositiveInfinity, rect.Y);
+        Assert.Equal(double.NegativeInfinity, rect.Width);
+        Assert.Equal(double.NegativeInfinity, rect.Height);
+        Assert.Equal(double.PositiveInfinity, rect.Location.X);
+        Assert.Equal(double.PositiveInfinity, rect.Location.Y);
+        Assert.Equal(double.NegativeInfinity, rect.Size.Width);
+        Assert.Equal(double.NegativeInfinity, rect.Size.Height);
+        Assert.Equal(double.PositiveInfinity, rect.Top);
+        Assert.Equal(double.PositiveInfinity, rect.TopLeft.X);
+        Assert.Equal(double.PositiveInfinity, rect.TopLeft.Y);
+        Assert.Equal(double.NegativeInfinity, rect.TopRight.X);
+        Assert.Equal(double.PositiveInfinity, rect.TopRight.Y);
+        Assert.Equal(double.NegativeInfinity, rect.Bottom);
+        Assert.Equal(double.PositiveInfinity, rect.BottomLeft.X);
+        Assert.Equal(double.NegativeInfinity, rect.BottomLeft.Y);
+        Assert.Equal(double.NegativeInfinity, rect.BottomRight.X);
+        Assert.Equal(double.NegativeInfinity, rect.BottomRight.Y);
+        Assert.True(rect.IsEmpty);
+    }
+
+    public static IEnumerable<object[]> Location_Set_TestData()
+    {
+        yield return new object[] { new Point(1, 2) };
+        yield return new object[] { new Point(1, 0) };
+        yield return new object[] { new Point(0, 2) };
+        yield return new object[] { new Point(0, 0) };
+        yield return new object[] { new Point(double.NaN, double.NaN) };
+        yield return new object[] { new Point(0, double.NaN) };
+        yield return new object[] { new Point(double.NaN, 0) };
+    }
+
+    [Theory]
+    [MemberData(nameof(Location_Set_TestData))]
+    public void Location_Set_GetReturnsExpected(Point value)
+    {
+        var rect = new Rect(1, 2, 3, 4);
+
+        // Set.
+        rect.Location = value;
+        Assert.Equal(value.X, rect.X);
+        Assert.Equal(value.Y, rect.Y);
+        Assert.Equal(3, rect.Width);
+        Assert.Equal(4, rect.Height);
+        Assert.Equal(value.X, rect.Location.X);
+        Assert.Equal(value.Y, rect.Location.Y);
+        Assert.Equal(3, rect.Size.Width);
+        Assert.Equal(4, rect.Size.Height);
+        Assert.Equal(value.Y, rect.Top);
+        Assert.Equal(value.X, rect.TopLeft.X);
+        Assert.Equal(value.Y, rect.TopLeft.Y);
+        Assert.Equal(value.X + 3, rect.TopRight.X);
+        Assert.Equal(value.Y, rect.TopRight.Y);
+        Assert.Equal(value.Y + 4, rect.Bottom);
+        Assert.Equal(value.X, rect.BottomLeft.X);
+        Assert.Equal(value.Y + 4, rect.BottomLeft.Y);
+        Assert.Equal(value.X + 3, rect.BottomRight.X);
+        Assert.Equal(value.Y + 4, rect.BottomRight.Y);
+        Assert.False(rect.IsEmpty);
+        
+        // Set same.
+        rect.Location = value;
+        Assert.Equal(value.X, rect.X);
+        Assert.Equal(value.Y, rect.Y);
+        Assert.Equal(3, rect.Width);
+        Assert.Equal(4, rect.Height);
+        Assert.Equal(value.X, rect.Location.X);
+        Assert.Equal(value.Y, rect.Location.Y);
+        Assert.Equal(3, rect.Size.Width);
+        Assert.Equal(4, rect.Size.Height);
+        Assert.Equal(value.Y, rect.Top);
+        Assert.Equal(value.X, rect.TopLeft.X);
+        Assert.Equal(value.Y, rect.TopLeft.Y);
+        Assert.Equal(value.X + 3, rect.TopRight.X);
+        Assert.Equal(value.Y, rect.TopRight.Y);
+        Assert.Equal(value.Y + 4, rect.Bottom);
+        Assert.Equal(value.X, rect.BottomLeft.X);
+        Assert.Equal(value.Y + 4, rect.BottomLeft.Y);
+        Assert.Equal(value.X + 3, rect.BottomRight.X);
+        Assert.Equal(value.Y + 4, rect.BottomRight.Y);
+        Assert.False(rect.IsEmpty);
+    }
+
+    [Fact]
+    public void Location_SetIsEmpty_ThrowsInvalidOperationException()
+    {
+        Rect rect = Rect.Empty;
+        Assert.Throws<InvalidOperationException>(() => rect.Location = rect.Location);
+        Assert.Throws<InvalidOperationException>(() => rect.Location = new Point(1, 2));
+    }
+    
+    public static IEnumerable<object[]> Size_Set_TestData()
+    {
+        yield return new object[] { new Size(1, 2) };
+        yield return new object[] { new Size(1, 0) };
+        yield return new object[] { new Size(0, 2) };
+        yield return new object[] { new Size(0, 0) };
+        yield return new object[] { new Size(double.NaN, double.NaN) };
+        yield return new object[] { new Size(double.NaN, 2) };
+        yield return new object[] { new Size(1, double.NaN) };
+        yield return new object[] { new Size() };
+    }
+
+    [Theory]
+    [MemberData(nameof(Size_Set_TestData))]
+    public void Size_Set_GetReturnsExpected(Size value)
+    {
+        var rect = new Rect(1, 2, 3, 4);
+
+        // Set.
+        rect.Size = value;
+        Assert.Equal(1, rect.X);
+        Assert.Equal(2, rect.Y);
+        Assert.Equal(value.Width, rect.Width);
+        Assert.Equal(value.Height, rect.Height);
+        Assert.Equal(1, rect.Location.X);
+        Assert.Equal(2, rect.Location.Y);
+        Assert.Equal(value.Width, rect.Size.Width);
+        Assert.Equal(value.Height, rect.Size.Height);
+        Assert.Equal(2, rect.Top);
+        Assert.Equal(1, rect.TopLeft.X);
+        Assert.Equal(2, rect.TopLeft.Y);
+        Assert.Equal(1 + value.Width, rect.TopRight.X);
+        Assert.Equal(2, rect.TopRight.Y);
+        Assert.Equal(2 + value.Height, rect.Bottom);
+        Assert.Equal(1, rect.BottomLeft.X);
+        Assert.Equal(2 + value.Height, rect.BottomLeft.Y);
+        Assert.Equal(1 + value.Width, rect.BottomRight.X);
+        Assert.Equal(2 + value.Height, rect.BottomRight.Y);
+        Assert.False(rect.IsEmpty);
+        
+        // Set same.
+        rect.Size = value;
+        Assert.Equal(1, rect.X);
+        Assert.Equal(2, rect.Y);
+        Assert.Equal(value.Width, rect.Width);
+        Assert.Equal(value.Height, rect.Height);
+        Assert.Equal(1, rect.Location.X);
+        Assert.Equal(2, rect.Location.Y);
+        Assert.Equal(value.Width, rect.Size.Width);
+        Assert.Equal(value.Height, rect.Size.Height);
+        Assert.Equal(2, rect.Top);
+        Assert.Equal(1, rect.TopLeft.X);
+        Assert.Equal(2, rect.TopLeft.Y);
+        Assert.Equal(1 + value.Width, rect.TopRight.X);
+        Assert.Equal(2, rect.TopRight.Y);
+        Assert.Equal(2 + value.Height, rect.Bottom);
+        Assert.Equal(1, rect.BottomLeft.X);
+        Assert.Equal(2 + value.Height, rect.BottomLeft.Y);
+        Assert.Equal(1 + value.Width, rect.BottomRight.X);
+        Assert.Equal(2 + value.Height, rect.BottomRight.Y);
+        Assert.False(rect.IsEmpty);
+    }
+
+    [Fact]
+    public void Size_SetEmpty_Success()
+    {
+        var rect = new Rect(1, 2, 3, 4);
+
+        // Set.
+        rect.Size = Size.Empty;
+        Assert.Equal(double.PositiveInfinity, rect.X);
+        Assert.Equal(double.PositiveInfinity, rect.Y);
+        Assert.Equal(double.NegativeInfinity, rect.Width);
+        Assert.Equal(double.NegativeInfinity, rect.Height);
+        Assert.Equal(double.PositiveInfinity, rect.Location.X);
+        Assert.Equal(double.PositiveInfinity, rect.Location.Y);
+        Assert.Equal(double.NegativeInfinity, rect.Size.Width);
+        Assert.Equal(double.NegativeInfinity, rect.Size.Height);
+        Assert.Equal(double.PositiveInfinity, rect.Top);
+        Assert.Equal(double.PositiveInfinity, rect.TopLeft.X);
+        Assert.Equal(double.PositiveInfinity, rect.TopLeft.Y);
+        Assert.Equal(double.NegativeInfinity, rect.TopRight.X);
+        Assert.Equal(double.PositiveInfinity, rect.TopRight.Y);
+        Assert.Equal(double.NegativeInfinity, rect.Bottom);
+        Assert.Equal(double.PositiveInfinity, rect.BottomLeft.X);
+        Assert.Equal(double.NegativeInfinity, rect.BottomLeft.Y);
+        Assert.Equal(double.NegativeInfinity, rect.BottomRight.X);
+        Assert.Equal(double.NegativeInfinity, rect.BottomRight.Y);
+        Assert.True(rect.IsEmpty);
+    }
+    
+    [Fact]
+    public void Size_SetIsEmpty_ThrowsInvalidOperationException()
+    {
+        Rect rect = Rect.Empty;
+        Assert.Throws<InvalidOperationException>(() => rect.Size = new Size(1, 2));
+        
+        // Setting to Size.Empty should work.
+        rect.Size = rect.Size;
+        Assert.Equal(double.PositiveInfinity, rect.X);
+        Assert.Equal(double.PositiveInfinity, rect.Y);
+        Assert.Equal(double.NegativeInfinity, rect.Width);
+        Assert.Equal(double.NegativeInfinity, rect.Height);
+        Assert.Equal(double.PositiveInfinity, rect.Location.X);
+        Assert.Equal(double.PositiveInfinity, rect.Location.Y);
+        Assert.Equal(double.NegativeInfinity, rect.Size.Width);
+        Assert.Equal(double.NegativeInfinity, rect.Size.Height);
+        Assert.Equal(double.PositiveInfinity, rect.Top);
+        Assert.Equal(double.PositiveInfinity, rect.TopLeft.X);
+        Assert.Equal(double.PositiveInfinity, rect.TopLeft.Y);
+        Assert.Equal(double.NegativeInfinity, rect.TopRight.X);
+        Assert.Equal(double.PositiveInfinity, rect.TopRight.Y);
+        Assert.Equal(double.NegativeInfinity, rect.Bottom);
+        Assert.Equal(double.PositiveInfinity, rect.BottomLeft.X);
+        Assert.Equal(double.NegativeInfinity, rect.BottomLeft.Y);
+        Assert.Equal(double.NegativeInfinity, rect.BottomRight.X);
+        Assert.Equal(double.NegativeInfinity, rect.BottomRight.Y);
+        Assert.True(rect.IsEmpty);
+    }
+
+    public static IEnumerable<object[]> X_Set_TestData()
+    {
+        yield return new object[] { double.NegativeInfinity };
+        yield return new object[] { double.MinValue };
+        yield return new object[] { -1 };
+        yield return new object[] { double.NegativeZero };
+        yield return new object[] { 0 };
+        yield return new object[] { 0.1 };
+        yield return new object[] { 1 };
+        yield return new object[] { double.MaxValue };
+        yield return new object[] { double.PositiveInfinity };
+    }
+
+    [Theory]
+    [MemberData(nameof(X_Set_TestData))]
+    public void X_Set_GetReturnsExpected(double value)
+    {
+        var rect = new Rect(1, 2, 3, 4);
+
+        // Set.
+        rect.X = value;
+        Assert.Equal(value, rect.X);
+        Assert.Equal(2, rect.Y);
+        Assert.Equal(3, rect.Width);
+        Assert.Equal(4, rect.Height);
+        Assert.Equal(value, rect.Location.X);
+        Assert.Equal(2, rect.Location.Y);
+        Assert.Equal(3, rect.Size.Width);
+        Assert.Equal(4, rect.Size.Height);
+        Assert.Equal(2, rect.Top);
+        Assert.Equal(value, rect.TopLeft.X);
+        Assert.Equal(2, rect.TopLeft.Y);
+        Assert.Equal(value + 3, rect.TopRight.X);
+        Assert.Equal(2, rect.TopRight.Y);
+        Assert.Equal(6, rect.Bottom);
+        Assert.Equal(value, rect.BottomLeft.X);
+        Assert.Equal(6, rect.BottomLeft.Y);
+        Assert.Equal(value + 3, rect.BottomRight.X);
+        Assert.Equal(6, rect.BottomRight.Y);
+        Assert.False(rect.IsEmpty);
+        
+        // Set same.
+        rect.X = value;
+        Assert.Equal(value, rect.X);
+        Assert.Equal(2, rect.Y);
+        Assert.Equal(3, rect.Width);
+        Assert.Equal(4, rect.Height);
+        Assert.Equal(value, rect.Location.X);
+        Assert.Equal(2, rect.Location.Y);
+        Assert.Equal(3, rect.Size.Width);
+        Assert.Equal(4, rect.Size.Height);
+        Assert.Equal(2, rect.Top);
+        Assert.Equal(value, rect.TopLeft.X);
+        Assert.Equal(2, rect.TopLeft.Y);
+        Assert.Equal(value + 3, rect.TopRight.X);
+        Assert.Equal(2, rect.TopRight.Y);
+        Assert.Equal(6, rect.Bottom);
+        Assert.Equal(value, rect.BottomLeft.X);
+        Assert.Equal(6, rect.BottomLeft.Y);
+        Assert.Equal(value + 3, rect.BottomRight.X);
+        Assert.Equal(6, rect.BottomRight.Y);
+        Assert.False(rect.IsEmpty);
+    }
+
+    [Fact]
+    public void X_SetIsEmpty_ThrowsInvalidOperationException()
+    {
+        Rect rect = Rect.Empty;
+        Assert.Throws<InvalidOperationException>(() => rect.X = rect.X);
+        Assert.Throws<InvalidOperationException>(() => rect.X = 1);
+    }
+
+    public static IEnumerable<object[]> Y_Set_TestData()
+    {
+        yield return new object[] { double.NegativeInfinity };
+        yield return new object[] { double.MinValue };
+        yield return new object[] { -1 };
+        yield return new object[] { double.NegativeZero };
+        yield return new object[] { 0 };
+        yield return new object[] { 0.1 };
+        yield return new object[] { 1 };
+        yield return new object[] { double.MaxValue };
+        yield return new object[] { double.PositiveInfinity };
+    }
+
+    [Theory]
+    [MemberData(nameof(Y_Set_TestData))]
+    public void Y_Set_GetReturnsExpected(double value)
+    {
+        var rect = new Rect(1, 2, 3, 4);
+
+        // Set.
+        rect.Y = value;
+        Assert.Equal(1, rect.X);
+        Assert.Equal(value, rect.Y);
+        Assert.Equal(3, rect.Width);
+        Assert.Equal(4, rect.Height);
+        Assert.Equal(1, rect.Location.X);
+        Assert.Equal(value, rect.Location.Y);
+        Assert.Equal(3, rect.Size.Width);
+        Assert.Equal(4, rect.Size.Height);
+        Assert.Equal(value, rect.Top);
+        Assert.Equal(1, rect.TopLeft.X);
+        Assert.Equal(value, rect.TopLeft.Y);
+        Assert.Equal(4, rect.TopRight.X);
+        Assert.Equal(value, rect.TopRight.Y);
+        Assert.Equal(value + 4, rect.Bottom);
+        Assert.Equal(1, rect.BottomLeft.X);
+        Assert.Equal(value + 4, rect.BottomLeft.Y);
+        Assert.Equal(4, rect.BottomRight.X);
+        Assert.Equal(value + 4, rect.BottomRight.Y);
+        Assert.False(rect.IsEmpty);
+
+        // Set same.
+        rect.Y = value;
+        Assert.Equal(1, rect.X);
+        Assert.Equal(value, rect.Y);
+        Assert.Equal(3, rect.Width);
+        Assert.Equal(4, rect.Height);
+        Assert.Equal(1, rect.Location.X);
+        Assert.Equal(value, rect.Location.Y);
+        Assert.Equal(3, rect.Size.Width);
+        Assert.Equal(4, rect.Size.Height);
+        Assert.Equal(value, rect.Top);
+        Assert.Equal(1, rect.TopLeft.X);
+        Assert.Equal(value, rect.TopLeft.Y);
+        Assert.Equal(4, rect.TopRight.X);
+        Assert.Equal(value, rect.TopRight.Y);
+        Assert.Equal(value + 4, rect.Bottom);
+        Assert.Equal(1, rect.BottomLeft.X);
+        Assert.Equal(value + 4, rect.BottomLeft.Y);
+        Assert.Equal(4, rect.BottomRight.X);
+        Assert.Equal(value + 4, rect.BottomRight.Y);
+        Assert.False(rect.IsEmpty);
+    }
+
+    [Fact]
+    public void Y_SetIsEmpty_ThrowsInvalidOperationException()
+    {
+        Rect rect = Rect.Empty;
+        Assert.Throws<InvalidOperationException>(() => rect.Y = rect.Y);
+        Assert.Throws<InvalidOperationException>(() => rect.Y = 1);
+    }
+
+    public static IEnumerable<object[]> Width_Set_TestData()
+    {
+        yield return new object[] { double.NegativeZero };
+        yield return new object[] { 0 };
+        yield return new object[] { 0.2 };
+        yield return new object[] { 1 };
+        yield return new object[] { double.MaxValue };
+        yield return new object[] { double.PositiveInfinity };
+    }
+
+    [Theory]
+    [MemberData(nameof(Width_Set_TestData))]
+    public void Width_Set_GetReturnsExpected(double value)
+    {
+        var rect = new Rect(1, 2, 3, 4);
+
+        // Set.
+        rect.Width = value;
+        Assert.Equal(1, rect.X);
+        Assert.Equal(2, rect.Y);
+        Assert.Equal(value, rect.Width);
+        Assert.Equal(4, rect.Height);
+        Assert.Equal(1, rect.Location.X);
+        Assert.Equal(2, rect.Location.Y);
+        Assert.Equal(value, rect.Size.Width);
+        Assert.Equal(4, rect.Size.Height);
+        Assert.Equal(2, rect.Top);
+        Assert.Equal(1, rect.TopLeft.X);
+        Assert.Equal(2, rect.TopLeft.Y);
+        Assert.Equal(value + 1, rect.TopRight.X);
+        Assert.Equal(2, rect.TopRight.Y);
+        Assert.Equal(6, rect.Bottom);
+        Assert.Equal(1, rect.BottomLeft.X);
+        Assert.Equal(6, rect.BottomLeft.Y);
+        Assert.Equal(value + 1, rect.BottomRight.X);
+        Assert.Equal(6, rect.BottomRight.Y);
+        Assert.False(rect.IsEmpty);
+
+        // Set same.
+        rect.Width = value;
+        Assert.Equal(1, rect.X);
+        Assert.Equal(2, rect.Y);
+        Assert.Equal(value, rect.Width);
+        Assert.Equal(4, rect.Height);
+        Assert.Equal(1, rect.Location.X);
+        Assert.Equal(2, rect.Location.Y);
+        Assert.Equal(value, rect.Size.Width);
+        Assert.Equal(4, rect.Size.Height);
+        Assert.Equal(2, rect.Top);
+        Assert.Equal(1, rect.TopLeft.X);
+        Assert.Equal(2, rect.TopLeft.Y);
+        Assert.Equal(value + 1, rect.TopRight.X);
+        Assert.Equal(2, rect.TopRight.Y);
+        Assert.Equal(6, rect.Bottom);
+        Assert.Equal(1, rect.BottomLeft.X);
+        Assert.Equal(6, rect.BottomLeft.Y);
+        Assert.Equal(value + 1, rect.BottomRight.X);
+        Assert.Equal(6, rect.BottomRight.Y);
+        Assert.False(rect.IsEmpty);
+    }
+
+    [Fact]
+    public void Width_SetIsEmpty_ThrowsInvalidOperationException()
+    {
+        Rect rect = Rect.Empty;
+        Assert.Throws<InvalidOperationException>(() => rect.Width = rect.Width);
+        Assert.Throws<InvalidOperationException>(() => rect.Width = 1);
+        Assert.Throws<InvalidOperationException>(() => rect.Width = -1);
+    }
+
+    [Theory]
+    [InlineData(double.NegativeInfinity)]
+    [InlineData(double.MinValue)]
+    [InlineData(-1)]
+    public void Width_SetNegative_ThrowsArgumentException(double width)
+    {
+        var rect = new Rect(1, 2, 3, 4);
+        // TODO: should have paramName
+        Assert.Throws<ArgumentException>(() => rect.Width = width);
+    }
+
+    public static IEnumerable<object[]> Height_Set_TestData()
+    {
+        yield return new object[] { double.NegativeZero };
+        yield return new object[] { 0 };
+        yield return new object[] { 0.2 };
+        yield return new object[] { 1 };
+        yield return new object[] { double.MaxValue };
+        yield return new object[] { double.PositiveInfinity };
+    }
+
+    [Theory]
+    [MemberData(nameof(Height_Set_TestData))]
+    public void Height_Set_GetReturnsExpected(double value)
+    {
+        var rect = new Rect(1, 2, 3, 4);
+
+        // Set.
+        rect.Height = value;
+        Assert.Equal(1, rect.X);
+        Assert.Equal(2, rect.Y);
+        Assert.Equal(3, rect.Width);
+        Assert.Equal(value, rect.Height);
+        Assert.Equal(1, rect.Location.X);
+        Assert.Equal(2, rect.Location.Y);
+        Assert.Equal(3, rect.Size.Width);
+        Assert.Equal(value, rect.Size.Height);
+        Assert.Equal(2, rect.Top);
+        Assert.Equal(1, rect.TopLeft.X);
+        Assert.Equal(2, rect.TopLeft.Y);
+        Assert.Equal(4, rect.TopRight.X);
+        Assert.Equal(2, rect.TopRight.Y);
+        Assert.Equal(value + 2, rect.Bottom);
+        Assert.Equal(1, rect.BottomLeft.X);
+        Assert.Equal(value + 2, rect.BottomLeft.Y);
+        Assert.Equal(4, rect.BottomRight.X);
+        Assert.Equal(value + 2, rect.BottomRight.Y);
+        Assert.False(rect.IsEmpty);
+
+        // Set same.
+        rect.Height = value;
+        Assert.Equal(1, rect.X);
+        Assert.Equal(2, rect.Y);
+        Assert.Equal(3, rect.Width);
+        Assert.Equal(value, rect.Height);
+        Assert.Equal(1, rect.Location.X);
+        Assert.Equal(2, rect.Location.Y);
+        Assert.Equal(3, rect.Size.Width);
+        Assert.Equal(value, rect.Size.Height);
+        Assert.Equal(2, rect.Top);
+        Assert.Equal(1, rect.TopLeft.X);
+        Assert.Equal(2, rect.TopLeft.Y);
+        Assert.Equal(4, rect.TopRight.X);
+        Assert.Equal(2, rect.TopRight.Y);
+        Assert.Equal(value + 2, rect.Bottom);
+        Assert.Equal(1, rect.BottomLeft.X);
+        Assert.Equal(value + 2, rect.BottomLeft.Y);
+        Assert.Equal(4, rect.BottomRight.X);
+        Assert.Equal(value + 2, rect.BottomRight.Y);
+        Assert.False(rect.IsEmpty);
+    }
+
+    [Fact]
+    public void Height_SetIsEmpty_ThrowsInvalidOperationException()
+    {
+        Rect rect = Rect.Empty;
+        Assert.Throws<InvalidOperationException>(() => rect.Height = rect.Height);
+        Assert.Throws<InvalidOperationException>(() => rect.Height = 1);
+        Assert.Throws<InvalidOperationException>(() => rect.Height = -1);
+    }
+
+    [Theory]
+    [InlineData(double.NegativeInfinity)]
+    [InlineData(double.MinValue)]
+    [InlineData(-1)]
+    public void Height_SetNegative_ThrowsArgumentException(double height)
+    {
+        var rect = new Rect(1, 2, 3, 4);
+        // TODO: should have paramName
+        Assert.Throws<ArgumentException>(() => rect.Height = height);
+    }
+
+    public static IEnumerable<object[]> Contains_Point_TestData()
+    {
+        // Normal.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(0, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(1, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(1, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(1, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(1, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(1, 6), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(1, 7), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(2, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(2, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(2, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(2, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(2, 6), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(2, 7), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(3, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(3, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(3, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(3, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(3, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(3, 6), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(3, 7), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(4, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(4, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(4, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(4, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(4, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(4, 6), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(4, 7), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(5, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(5, 2), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(5, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(5, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(5, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(5, 6), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(5, 7), false };
+
+        // Empty width.
+        yield return new object[] { new Rect(1, 2, 0, 4), new Point(), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Point(0, 0), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Point(0, 1), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Point(0, 2), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Point(0, 3), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Point(0, 4), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Point(0, 5), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Point(0, 6), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Point(0, 7), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Point(1, 1), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Point(1, 2), true };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Point(1, 3), true };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Point(1, 4), true };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Point(1, 5), true };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Point(1, 6), true };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Point(1, 6), true };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Point(1, 7), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Point(2, 1), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Point(2, 2), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Point(2, 3), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Point(2, 4), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Point(2, 5), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Point(2, 6), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Point(2, 6), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Point(2, 7), false };
+
+        // Empty height.
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(0, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(0, 2), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(0, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(0, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(0, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(0, 6), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(0, 7), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(1, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(1, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(1, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(1, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(1, 6), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(1, 7), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(2, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(2, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(2, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(2, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(2, 6), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(2, 7), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(3, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(3, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(3, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(3, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(3, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(3, 6), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(3, 7), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(4, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(4, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(4, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(4, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(4, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(4, 6), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(4, 7), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(5, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(5, 2), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(5, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(5, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(5, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(5, 6), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Point(5, 7), false };
+
+        // Empty width & height.
+        yield return new object[] { new Rect(1, 2, 0, 0), new Point(), false };
+        yield return new object[] { new Rect(1, 2, 0, 0), new Point(0, 0), false };
+        yield return new object[] { new Rect(1, 2, 0, 0), new Point(0, 1), false };
+        yield return new object[] { new Rect(1, 2, 0, 0), new Point(0, 2), false };
+        yield return new object[] { new Rect(1, 2, 0, 0), new Point(1, 1), false };
+        yield return new object[] { new Rect(1, 2, 0, 0), new Point(1, 2), true };
+        yield return new object[] { new Rect(1, 2, 0, 0), new Point(1, 3), false };
+        yield return new object[] { new Rect(1, 2, 0, 0), new Point(2, 1), false };
+        yield return new object[] { new Rect(1, 2, 0, 0), new Point(2, 2), false };
+        yield return new object[] { new Rect(1, 2, 0, 0), new Point(2, 3), false };
+
+        // Zero.
+        yield return new object[] { new Rect(0, 0, 0, 0), new Point(), true };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Point(0, 0), true };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Point(1, 0), false };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Point(0, 1), false };
+
+        // Default.
+        yield return new object[] { new Rect(), new Point(), true };
+        yield return new object[] { new Rect(), new Point(0, 0), true };
+        yield return new object[] { new Rect(), new Point(1, 0), false };
+        yield return new object[] { new Rect(), new Point(0, 1), false };
+
+        // Infinite bounds.
+        yield return new object[] { new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity), new Point(0, 0), true };
+        yield return new object[] { new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity), new Point(1, 2), true };
+        yield return new object[] { new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity), new Point(double.NegativeInfinity, double.NegativeInfinity), true };
+        yield return new object[] { new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity), new Point(double.MinValue, double.MinValue), true };
+        yield return new object[] { new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity), new Point(double.MaxValue, double.MaxValue), true };
+        yield return new object[] { new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity), new Point(double.PositiveInfinity, double.PositiveInfinity), false };
+
+        yield return new object[] { new Rect(double.PositiveInfinity, double.PositiveInfinity, double.PositiveInfinity, double.PositiveInfinity), new Point(double.PositiveInfinity, double.PositiveInfinity), false };
+        yield return new object[] { new Rect(double.PositiveInfinity, double.PositiveInfinity, double.PositiveInfinity, double.PositiveInfinity), new Point(double.MaxValue, double.MaxValue), false };
+
+        // Infinite width/height.
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), new Point(0, 0), false };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), new Point(1, 2), true };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), new Point(2, 3), true };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), new Point(double.PositiveInfinity, double.PositiveInfinity), false };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), new Point(double.NegativeInfinity, double.NegativeInfinity), false };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), new Point(double.NaN, double.NaN), false };
+
+        // NaN
+        yield return new object[] { new Rect(double.NaN, 2, 3, 4), new Point(1, 2), false };
+        yield return new object[] { new Rect(double.NaN, 2, 3, 4), new Point(double.NaN, 2), false };
+        yield return new object[] { new Rect(1, double.NaN, 3, 4), new Point(1, 2), false };
+        yield return new object[] { new Rect(1, double.NaN, 3, 4), new Point(1, double.NaN), false };
+        yield return new object[] { new Rect(1, 2, double.NaN, 4), new Point(1, 2), false };
+        yield return new object[] { new Rect(1, 2, double.NaN, 4), new Point(1, double.NaN), false };
+        yield return new object[] { new Rect(1, 2, 3, double.NaN), new Point(1, 2), false };
+        yield return new object[] { new Rect(1, 2, 3, double.NaN), new Point(1, double.NaN), false };
+
+        // Empty.
+        yield return new object[] { Rect.Empty, new Point(), false };
+        yield return new object[] { Rect.Empty, new Point(0, 0), false };
+        yield return new object[] { Rect.Empty, new Point(1, 2), false };
+        yield return new object[] { Rect.Empty, new Point(double.PositiveInfinity, double.PositiveInfinity), false };
+        yield return new object[] { Rect.Empty, new Point(double.NaN, double.NaN), false };
+    }
+
+    [Theory]
+    [MemberData(nameof(Contains_Point_TestData))]
+    public void Contains_InvokePoint_ReturnsExpected(Rect rect, Point point, bool expected)
+    {
+        Assert.Equal(expected, rect.Contains(point));
+    }
+
+    [Theory]
+    [MemberData(nameof(Contains_Point_TestData))]
+    public void Contains_InvokeDoubleDouble_ReturnsExpected(Rect rect, Point point, bool expected)
+    {
+        Assert.Equal(expected, rect.Contains(point.X, point.Y));
+    }
+
+    public static IEnumerable<object[]> Contains_Rect_TestData()
+    {
+        // Normal - from top left.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 2, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 2, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 2, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 2, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 2, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 2, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 1, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 1, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 1, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 1, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 1, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 1, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 0, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 0, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 0, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 0, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 0, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 0, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 4, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 4, 5), false };
+
+        // Normal - from middle left.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 3, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 3, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 3, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 3, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 3, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 3, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 2, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 2, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 2, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 2, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 2, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 2, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 1, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 1, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 1, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 1, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 1, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 1, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 0, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 0, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 0, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 0, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 0, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 0, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 4, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 3, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 4, 5), false };
+
+        // Normal - from bottom left.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 3, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 3, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 3, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 3, 2), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 3, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 3, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 2, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 2, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 2, 2), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 2, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 2, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 1, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 1, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 1, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 1, 2), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 1, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 1, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 0, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 0, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 0, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 0, 2), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 0, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 0, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 4, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 3, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 4, 5), false };
+        
+        // Normal - from bottom middle.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 3, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 3, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 3, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 3, 2), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 3, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 3, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 2, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 2, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 2, 2), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 2, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 2, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 1, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 1, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 1, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 1, 2), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 1, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 0, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 0, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 0, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 0, 2), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 0, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 4, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 3, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 4, 5), false };
+        
+        // Normal - from bottom right.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 3, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 3, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 3, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 3, 2), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 3, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 3, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 2, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 2, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 2, 2), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 2, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 2, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 1, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 1, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 1, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 1, 2), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 1, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 0, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 0, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 0, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 0, 2), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 0, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 4, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 3, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 4, 5), false };
+        
+        // Normal - from middle right.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 3, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 3, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 3, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 3, 2), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 3, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 3, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 2, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 2, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 2, 2), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 2, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 2, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 1, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 1, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 1, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 1, 2), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 1, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 0, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 0, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 0, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 0, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 0, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 0, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 4, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 3, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 4, 5), false };
+        
+        // Normal - from top right.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 3, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 3, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 3, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 3, 2), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 3, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 3, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 2, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 2, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 2, 2), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 2, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 2, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 1, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 1, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 1, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 1, 2), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 1, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 0, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 0, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 0, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 0, 2), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 0, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 4, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 3, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 4, 5), false };
+
+        // Normal - from middle.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 3, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 3, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 3, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 3, 2), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 3, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 3, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 2, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 2, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 2, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 2, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 2, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 1, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 1, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 1, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 1, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 1, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 1, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 0, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 0, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 0, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 0, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 0, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 0, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 4, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 3, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 4, 5), false };
+
+        // Normal - from outside top left.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 0, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 0, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 0, 0.5, 0.5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 0, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 0, 1, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 0, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 1, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 1, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 1, 0, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 1, 2, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 1, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 0, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 0, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 0, 1, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 0, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 0, 0, 0), false };
+
+        // Normal - from outside middle left.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 4, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 4, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 4, 0.5, 0.5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 4, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 4, 1, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 4, 0, 0), false };
+
+        // Normal - from outside bottom left.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 6, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 6, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 6, 0.5, 0.5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 6, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 6, 1, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 6, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 7, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 7, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 7, 0.5, 0.5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 7, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 7, 1, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 7, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 7, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 7, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 7, 0.5, 0.5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 7, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 7, 1, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 7, 0, 0), false };
+
+        // Normal - from outside bottom middle.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 7, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 7, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 7, 0.5, 0.5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 7, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 7, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 7, 0, 0), false };
+
+        // Normal - from outside bottom right.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 7, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 7, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 7, 0.5, 0.5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 7, 1, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 7, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 7, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 7, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 7, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 7, 0.5, 0.5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 7, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 7, 1, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 7, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 5, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 5, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 5, 0.5, 0.5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 5, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 5, 1, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 5, 0, 0), false };
+
+        // From outside middle right.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 3, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 3, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 3, 0.5, 0.5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 3, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 3, 1, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 3, 0, 0), false };
+
+        // From outside top right.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 1, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 1, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 1, 0.5, 0.5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 1, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 1, 1, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 1, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 0, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 0, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 0, 0.5, 0.5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 0, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 0, 1, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 0, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 0, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 0, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 0, 0.5, 0.5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 0, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 0, 1, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 0, 0, 0), false };
+
+        // Normal - empty.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 0, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), Rect.Empty, false };
+
+        // Empty width.
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 1, 5), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 1, 4), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 1, 3), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 1, 2), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 1, 0), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 0, 5), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 0, 4), true };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 0, 3), true };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 0, 2), true };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 0, 1), true };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 0, 0), true };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 1, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(0, 1, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(0, 0, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(0, 0, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), Rect.Empty, false };
+
+        // Empty height.
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 2, 4, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 2, 4, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 2, 3, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 2, 3, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 2, 2, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 2, 2, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 2, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 2, 1, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 2, 0, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 0, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(0, 1, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(0, 0, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), Rect.Empty, false };
+        
+        // Zero.
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(), true };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(0, 0, 0, 0), true };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(1, 0, 0, 0), false };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(0, 1, 0, 0), false };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(0, 0, 1, 0), false };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(0, 0, 0, 1), false };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(0, 0, 1, 1), false };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(1, 2, 3, 4), false };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(1, 2, 3, 0), false };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(1, 2, 0, 4), false };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(1, 2, 0, 0), false };
+        yield return new object[] { new Rect(0, 0, 0, 0), Rect.Empty, false };
+        
+        // Default.
+        yield return new object[] { new Rect(), new Rect(), true };
+        yield return new object[] { new Rect(), new Rect(0, 0, 0, 0), true };
+        yield return new object[] { new Rect(), new Rect(1, 0, 0, 0), false };
+        yield return new object[] { new Rect(), new Rect(0, 1, 0, 0), false };
+        yield return new object[] { new Rect(), new Rect(0, 0, 1, 0), false };
+        yield return new object[] { new Rect(), new Rect(0, 0, 0, 1), false };
+        yield return new object[] { new Rect(), new Rect(0, 0, 1, 1), false };
+        yield return new object[] { new Rect(), new Rect(1, 2, 3, 4), false };
+        yield return new object[] { new Rect(), new Rect(1, 2, 3, 0), false };
+        yield return new object[] { new Rect(), new Rect(1, 2, 0, 4), false };
+        yield return new object[] { new Rect(), new Rect(1, 2, 0, 0), false };
+        yield return new object[] { new Rect(), Rect.Empty, false };
+
+        // Empty.
+        yield return new object[] { Rect.Empty, Rect.Empty, false };
+        yield return new object[] { Rect.Empty, new Rect(), false };
+        yield return new object[] { Rect.Empty, new Rect(0, 0, 0, 0), false };
+        yield return new object[] { Rect.Empty, new Rect(1, 0, 0, 0), false };
+        yield return new object[] { Rect.Empty, new Rect(0, 1, 0, 0), false };
+        yield return new object[] { Rect.Empty, new Rect(0, 0, 1, 0), false };
+        yield return new object[] { Rect.Empty, new Rect(0, 0, 0, 1), false };
+        yield return new object[] { Rect.Empty, new Rect(1, 2, 3, 4), false };
+        yield return new object[] { Rect.Empty, new Rect(1, 2, 3, 0), false };
+        yield return new object[] { Rect.Empty, new Rect(1, 2, 0, 4), false };
+        yield return new object[] { Rect.Empty, new Rect(1, 2, 0, 0), false };
+    }
+
+    [Theory]
+    [MemberData(nameof(Contains_Rect_TestData))]
+    public void Contains_InvokeRect_ReturnsExpected(Rect rect, Rect other, bool expected)
+    {
+        Assert.Equal(expected, rect.Contains(other));
+    }
+
+    public static IEnumerable<object?[]> Equals_TestData()
+    {
+        // Normal.
+        yield return new object?[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 4), true, true };
+        yield return new object?[] { new Rect(1, 2, 3, 4), new Rect(2, 2, 3, 4), false, false };
+        yield return new object?[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 3, 4), false, false };
+        yield return new object?[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 4, 4), false, false };
+        yield return new object?[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 5), false, false };
+        yield return new object?[] { new Rect(1, 2, 3, 4), new Rect(double.NaN, 2, 3, 4), false, false };
+        yield return new object?[] { new Rect(1, 2, 3, 4), new Rect(1, double.NaN, 3, 4), false, false };
+        yield return new object?[] { new Rect(1, 2, 3, 4), new Rect(1, 2, double.NaN, 4), false, false };
+        yield return new object?[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, double.NaN), false, false };
+        yield return new object?[] { new Rect(1, 2, 3, 4), new Rect(0, 0, 0, 0), false, false };
+        yield return new object?[] { new Rect(1, 2, 3, 4), new Rect(), false, false };
+        yield return new object?[] { new Rect(1, 2, 3, 4), Rect.Empty, false, false };
+
+        // NaN x.
+        yield return new object?[] { new Rect(double.NaN, 2, 3, 4), new Rect(double.NaN, 2, 3, 4), true, true };
+        yield return new object?[] { new Rect(double.NaN, 2, 3, 4), new Rect(2, 2, 3, 4), false, false };
+        yield return new object?[] { new Rect(double.NaN, 2, 3, 4), new Rect(double.NaN, double.NaN, 3, 4), false, false };
+        yield return new object?[] { new Rect(double.NaN, 2, 3, 4), new Rect(double.NaN, 2, double.NaN, 4), false, false };
+        yield return new object?[] { new Rect(double.NaN, 2, 3, 4), new Rect(double.NaN, 2, 3, double.NaN), false, false };
+        
+        // NaN y.
+        yield return new object?[] { new Rect(1, double.NaN, 3, 4), new Rect(1, double.NaN, 3, 4), true, true };
+        yield return new object?[] { new Rect(1, double.NaN, 3, 4), new Rect(1, 3, 3, 4), false, false };
+        yield return new object?[] { new Rect(1, double.NaN, 3, 4), new Rect(double.NaN, double.NaN, 3, 4), false, false };
+        yield return new object?[] { new Rect(1, double.NaN, 3, 4), new Rect(1, double.NaN, double.NaN, 4), false, false };
+        yield return new object?[] { new Rect(1, double.NaN, 3, 4), new Rect(1, double.NaN, 3, double.NaN), false, false };
+
+        // NaN width.
+        yield return new object?[] { new Rect(1, 2, double.NaN, 4), new Rect(1, 2, double.NaN, 4), true, true };
+        yield return new object?[] { new Rect(1, 2, double.NaN, 4), new Rect(1, 2, 4, 4), false, false };
+        yield return new object?[] { new Rect(1, 2, double.NaN, 4), new Rect(double.NaN, 2, double.NaN, 4), false, false };
+        yield return new object?[] { new Rect(1, 2, double.NaN, 4), new Rect(1, double.NaN, double.NaN, 4), false, false };
+        yield return new object?[] { new Rect(1, 2, double.NaN, 4), new Rect(1, 2, double.NaN, double.NaN), false, false };
+
+        // NaN height.
+        yield return new object?[] { new Rect(1, 2, 3, double.NaN), new Rect(1, 2, 3, double.NaN), true, true };
+        yield return new object?[] { new Rect(1, 2, 3, double.NaN), new Rect(1, 2, 3, 4), false, false };
+        yield return new object?[] { new Rect(1, 2, 3, double.NaN), new Rect(double.NaN, 2, 3, double.NaN), false, false };
+        yield return new object?[] { new Rect(1, 2, 3, double.NaN), new Rect(1, double.NaN, 3, double.NaN), false, false };
+        yield return new object?[] { new Rect(1, 2, 3, double.NaN), new Rect(1, 2, double.NaN, double.NaN), false, false };
+
+        // NaN x, y, width, height.
+        yield return new object?[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), new Rect(double.NaN, double.NaN, double.NaN, double.NaN), true, true };
+        yield return new object?[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), new Rect(1, 2, 3, 4), false, false };
+        yield return new object?[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), new Rect(1, double.NaN, double.NaN, double.NaN), false, false };
+        yield return new object?[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), new Rect(double.NaN, 2, double.NaN, double.NaN), false, false };
+        yield return new object?[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), new Rect(double.NaN, double.NaN, 3, double.NaN), false, false };
+        yield return new object?[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), new Rect(double.NaN, double.NaN, double.NaN, 4), false, false };
+
+        // Zero.
+        yield return new object?[] { new Rect(0, 0, 0, 0), new Rect(), true, true };
+        yield return new object?[] { new Rect(0, 0, 0, 0), new Rect(0, 0, 0, 0), true, true };
+        yield return new object?[] { new Rect(0, 0, 0, 0), new Rect(1, 0, 0, 0), false, false };
+        yield return new object?[] { new Rect(0, 0, 0, 0), new Rect(0, 1, 0, 0), false, false };
+        yield return new object?[] { new Rect(0, 0, 0, 0), new Rect(0, 0, 1, 0), false, false };
+        yield return new object?[] { new Rect(0, 0, 0, 0), new Rect(0, 0, 0, 1), false, false };
+        yield return new object?[] { new Rect(0, 0, 0, 0), Rect.Empty, false, true };
+        
+        // Default.
+        yield return new object?[] { new Rect(), new Rect(), true, true };
+        yield return new object?[] { new Rect(), new Rect(0, 0, 0, 0), true, true };
+        yield return new object?[] { new Rect(), new Rect(1, 0, 0, 0), false, false };
+        yield return new object?[] { new Rect(), new Rect(0, 1, 0, 0), false, false };
+        yield return new object?[] { new Rect(), new Rect(0, 0, 1, 0), false, false };
+        yield return new object?[] { new Rect(), new Rect(0, 0, 0, 1), false, false };
+        yield return new object?[] { new Rect(), Rect.Empty, false, true };
+
+        // Empty.
+        yield return new object?[] { Rect.Empty, Rect.Empty, true, true };
+        yield return new object?[] { Rect.Empty, new Rect(1, 2, 3, 4), false, false };
+        yield return new object?[] { Rect.Empty, new Rect(0, 0, 0, 0), false, true };
+        yield return new object?[] { Rect.Empty, new Rect(), false, true };
+
+        // Other.
+        yield return new object?[] { Rect.Empty, new object(), false, false };
+        yield return new object?[] { Rect.Empty, null, false, false };
+        yield return new object?[] { new Rect(), new object(), false, false };
+        yield return new object?[] { new Rect(), null, false, false };
+        yield return new object?[] { new Rect(0, 0, 0, 0), new object(), false, false };
+        yield return new object?[] { new Rect(0, 0, 0, 0), null, false, false };
+        yield return new object?[] { new Rect(1, 2, 3, 4), new object(), false, false };
+        yield return new object?[] { new Rect(1, 2, 3, 4), null, false, false };
+    }
+
+    [Theory]
+    [MemberData(nameof(Equals_TestData))]
+    public void Equals_Object_ReturnsExpected(Rect rect, object o, bool expected, bool expectedHashCode)
+    {
+        Assert.Equal(expected, rect.Equals(o));
+        if (o is Rect value)
+        {
+            Assert.Equal(expected, rect.Equals(value));
+            Assert.Equal(expected, value.Equals(rect));
+            Assert.Equal(expected, Rect.Equals(rect, value));
+            Assert.Equal(expected, Rect.Equals(value, rect));
+            Assert.Equal(expectedHashCode, rect.GetHashCode().Equals(value.GetHashCode()));
+        }
+    }
+
+    public static IEnumerable<object?[]> EqualityOperator_TestData()
+    {
+        // Normal.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 2, 3, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 3, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 4, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(double.NaN, 2, 3, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, double.NaN, 3, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, double.NaN, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, double.NaN), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 0, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), Rect.Empty, false };
+
+        // NaN x.
+        yield return new object[] { new Rect(double.NaN, 2, 3, 4), new Rect(double.NaN, 2, 3, 4), false };
+        yield return new object[] { new Rect(double.NaN, 2, 3, 4), new Rect(2, 2, 3, 4), false };
+        yield return new object[] { new Rect(double.NaN, 2, 3, 4), new Rect(double.NaN, double.NaN, 3, 4), false };
+        yield return new object[] { new Rect(double.NaN, 2, 3, 4), new Rect(double.NaN, 2, double.NaN, 4), false };
+        yield return new object[] { new Rect(double.NaN, 2, 3, 4), new Rect(double.NaN, 2, 3, double.NaN), false };
+        
+        // NaN y.
+        yield return new object[] { new Rect(1, double.NaN, 3, 4), new Rect(1, double.NaN, 3, 4), false };
+        yield return new object[] { new Rect(1, double.NaN, 3, 4), new Rect(1, 3, 3, 4), false };
+        yield return new object[] { new Rect(1, double.NaN, 3, 4), new Rect(double.NaN, double.NaN, 3, 4), false };
+        yield return new object[] { new Rect(1, double.NaN, 3, 4), new Rect(1, double.NaN, double.NaN, 4), false };
+        yield return new object[] { new Rect(1, double.NaN, 3, 4), new Rect(1, double.NaN, 3, double.NaN), false };
+
+        // NaN width.
+        yield return new object[] { new Rect(1, 2, double.NaN, 4), new Rect(1, 2, double.NaN, 4), false };
+        yield return new object[] { new Rect(1, 2, double.NaN, 4), new Rect(1, 2, 4, 4), false };
+        yield return new object[] { new Rect(1, 2, double.NaN, 4), new Rect(double.NaN, 2, double.NaN, 4), false };
+        yield return new object[] { new Rect(1, 2, double.NaN, 4), new Rect(1, double.NaN, double.NaN, 4), false };
+        yield return new object[] { new Rect(1, 2, double.NaN, 4), new Rect(1, 2, double.NaN, double.NaN), false };
+
+        // NaN height.
+        yield return new object[] { new Rect(1, 2, 3, double.NaN), new Rect(1, 2, 3, double.NaN), false };
+        yield return new object[] { new Rect(1, 2, 3, double.NaN), new Rect(1, 2, 3, 4), false };
+        yield return new object[] { new Rect(1, 2, 3, double.NaN), new Rect(double.NaN, 2, 3, double.NaN), false };
+        yield return new object[] { new Rect(1, 2, 3, double.NaN), new Rect(1, double.NaN, 3, double.NaN), false };
+        yield return new object[] { new Rect(1, 2, 3, double.NaN), new Rect(1, 2, double.NaN, double.NaN), false };
+
+        // NaN x, y, width, height.
+        yield return new object[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), new Rect(double.NaN, double.NaN, double.NaN, double.NaN), false };
+        yield return new object[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), new Rect(1, 2, 3, 4), false };
+        yield return new object[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), new Rect(1, double.NaN, double.NaN, double.NaN), false };
+        yield return new object[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), new Rect(double.NaN, 2, double.NaN, double.NaN), false };
+        yield return new object[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), new Rect(double.NaN, double.NaN, 3, double.NaN), false };
+        yield return new object[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), new Rect(double.NaN, double.NaN, double.NaN, 4), false };
+
+        // Zero.
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(), true };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(0, 0, 0, 0), true };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(1, 0, 0, 0), false };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(0, 1, 0, 0), false };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(0, 0, 1, 0), false };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(0, 0, 0, 1), false };
+        yield return new object[] { new Rect(0, 0, 0, 0), Rect.Empty, false };
+        
+        // Default.
+        yield return new object[] { new Rect(), new Rect(), true };
+        yield return new object[] { new Rect(), new Rect(0, 0, 0, 0), true };
+        yield return new object[] { new Rect(), new Rect(1, 0, 0, 0), false };
+        yield return new object[] { new Rect(), new Rect(0, 1, 0, 0), false };
+        yield return new object[] { new Rect(), new Rect(0, 0, 1, 0), false };
+        yield return new object[] { new Rect(), new Rect(0, 0, 0, 1), false };
+        yield return new object[] { new Rect(), Rect.Empty, false };
+
+        // Empty.
+        yield return new object[] { Rect.Empty, Rect.Empty, true };
+        yield return new object[] { Rect.Empty, new Rect(1, 2, 3, 4), false };
+        yield return new object[] { Rect.Empty, new Rect(0, 0, 0, 0), false };
+        yield return new object[] { Rect.Empty, new Rect(), false };
+    }
+
+    [Theory]
+    [MemberData(nameof(EqualityOperator_TestData))]
+    public void EqualityOperator_Invoke_ReturnsExpected(Rect rect1, Rect rect2, bool expected)
+    {
+        Assert.Equal(expected, rect1 == rect2);
+        Assert.Equal(expected, rect2 == rect1);
+        Assert.Equal(!expected, rect1 != rect2);
+        Assert.Equal(!expected, rect2 != rect1);
+    }
+
+    [Fact]
+    public void GetHashCode_InvokeDefault_ReturnsEqual()
+    {
+        var rect = new Rect();
+        Assert.Equal(0, rect.GetHashCode());
+        Assert.Equal(rect.GetHashCode(), rect.GetHashCode());
+    }
+
+    [Fact]
+    public void GetHashCode_InvokeEmpty_ReturnsEqual()
+    {
+        Rect rect = Rect.Empty;
+        Assert.Equal(0, rect.GetHashCode());
+        Assert.Equal(rect.GetHashCode(), rect.GetHashCode());
+    }
+
+    [Fact]
+    public void GetHashCode_InvokeNormal_ReturnsEqual()
+    {
+        var rect = new Rect(1, 2, 3, 4);
+        Assert.NotEqual(0, rect.GetHashCode());
+        Assert.Equal(rect.GetHashCode(), rect.GetHashCode());
+    }
+
+    public static IEnumerable<object[]> Inflate_TestData()
+    {
+        // Normal.
+        yield return new object[] { new Rect(1, 2, 3, 4), 1, 2, new Rect(0, 0, 5, 8) };
+        yield return new object[] { new Rect(1, 2, 3, 4), 1.5, 2.5, new Rect(-0.5, -0.5, 6, 9) };
+        yield return new object[] { new Rect(1, 2, 3, 4), 0.5, 0.25, new Rect(0.5,1.75,4,4.5) };
+        yield return new object[] { new Rect(1, 2, 3, 4), 0, 0, new Rect(1, 2, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), -1, 0, new Rect(2, 2, 1, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), -1, 2, new Rect(2, 0, 1, 8) };
+        yield return new object[] { new Rect(1, 2, 3, 4), 0, -2, new Rect(1, 4, 3, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), 2, -2, new Rect(-1, 4, 7, 0) };
+
+        // Large.
+        yield return new object[] { new Rect(double.MaxValue, double.MaxValue, 3, 4), 1, 2, new Rect(double.MaxValue, double.MaxValue, 5, 8) };
+        yield return new object[] { new Rect(double.MaxValue, double.MaxValue, 3, 4), 0, 0, new Rect(double.MaxValue, double.MaxValue, 3, 4) };
+        yield return new object[] { new Rect(double.MaxValue, double.MaxValue, 3, 4), double.MaxValue, double.MaxValue, new Rect(0, 0, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(double.MinValue, double.MinValue, 3, 4), -1, -2, new Rect(double.MinValue, double.MinValue, 1, 0) };
+        yield return new object[] { new Rect(double.MinValue, double.MinValue, 3, 4), 0, 0, new Rect(double.MinValue, double.MinValue, 3, 4) };
+        yield return new object[] { new Rect(double.MinValue, double.MinValue, 3, 4), double.MinValue, double.MinValue, Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), double.MaxValue, double.MaxValue, new Rect(double.MinValue, double.MinValue, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(0, 0, 3, 4), double.MaxValue, double.MaxValue, new Rect(double.MinValue, double.MinValue, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(-1, -2, 3, 4), double.MinValue, double.MinValue, Rect.Empty };
+        yield return new object[] { new Rect(0, 0, 3, 4), double.MinValue, double.MinValue, Rect.Empty };
+
+        // Infinite.
+        yield return new object[] { new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity), 0, 0, new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity), 5, 6, new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity), -5, -6, new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity), double.PositiveInfinity, double.PositiveInfinity, new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity), double.NegativeInfinity, double.NegativeInfinity, Rect.Empty };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), 0, 0, new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), 5, 6, new Rect(-4, -4, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), -5, -6, new Rect(6 ,8, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), double.PositiveInfinity, double.PositiveInfinity, new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), double.NegativeInfinity, double.NegativeInfinity, Rect.Empty };
+
+        // NaN.
+        yield return new object[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), 0, 0, Rect.Empty };
+        yield return new object[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), 5, 6, Rect.Empty };
+        yield return new object[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), -5, -6, Rect.Empty };
+        yield return new object[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), double.PositiveInfinity, double.PositiveInfinity, Rect.Empty };
+        yield return new object[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), double.NegativeInfinity, double.NegativeInfinity, Rect.Empty };
+        yield return new object[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), double.NaN, double.NaN, Rect.Empty };
+        yield return new object[] { new Rect(1, 2, double.NaN, double.NaN), 0, 0, Rect.Empty };
+        yield return new object[] { new Rect(1, 2, double.NaN, double.NaN), 5, 6, Rect.Empty };
+        yield return new object[] { new Rect(1, 2, double.NaN, double.NaN), -5, -6, Rect.Empty };
+        yield return new object[] { new Rect(1, 2, double.NaN, double.NaN), double.PositiveInfinity, double.PositiveInfinity, Rect.Empty };
+        yield return new object[] { new Rect(1, 2, double.NaN, double.NaN), double.NegativeInfinity, double.NegativeInfinity, Rect.Empty };
+        yield return new object[] { new Rect(1, 2, double.NaN, double.NaN), double.NaN, double.NaN, Rect.Empty };
+
+        // Zero.
+        yield return new object[] { new Rect(0, 0, 0, 0), 1, 2, new Rect(-1, -2, 2, 4) };
+        yield return new object[] { new Rect(0, 0, 0, 0), -1, 0, Rect.Empty };
+        yield return new object[] { new Rect(0, 0, 0, 0), 0, -2, Rect.Empty };
+        yield return new object[] { new Rect(0, 0, 0, 0), -1, -2, Rect.Empty };
+        yield return new object[] { new Rect(0, 0, 0, 0), 0, 0, new Rect() };
+
+        // Default.
+        yield return new object[] { new Rect(), 1, 2, new Rect(-1, -2, 2, 4) };
+        yield return new object[] { new Rect(), -1, 0, Rect.Empty };
+        yield return new object[] { new Rect(), 0, -2, Rect.Empty };
+        yield return new object[] { new Rect(), -1, -2, Rect.Empty };
+        yield return new object[] { new Rect(), 0, 0, new Rect() };
+    }
+
+    [Theory]
+    [MemberData(nameof(Inflate_TestData))]
+    public void Inflate_Invoke_ReturnsExpected(Rect rect, double width, double height, Rect expected)
+    {
+        Rect copy = rect;
+
+        Assert.Equal(expected, Rect.Inflate(rect, width, height));
+        Assert.Equal(copy, rect);
+
+        if (width >= 0 && height >= 0)
+        {
+            Assert.Equal(expected, Rect.Inflate(rect, new Size(width, height)));
+            Assert.Equal(copy, rect);
+        }
+
+        rect.Inflate(width, height);
+        Assert.Equal(expected, rect);
+
+        if (width >= 0 && height >= 0)
+        {
+            rect = copy;
+            rect.Inflate(new Size(width, height));
+            Assert.Equal(expected, rect);
+        }
+    }
+    
+    [Fact]
+    public void Inflate_Empty_ThrowsInvalidOperationException()
+    {
+        Assert.Throws<InvalidOperationException>(() => Rect.Empty.Inflate(0, 0));
+        Assert.Throws<InvalidOperationException>(() => Rect.Empty.Inflate(new Size(0, 0)));
+        Assert.Throws<InvalidOperationException>(() => Rect.Inflate(Rect.Empty, 0, 0));
+        Assert.Throws<InvalidOperationException>(() => Rect.Inflate(Rect.Empty, new Size(0, 0)));
+    }
+
+    public static IEnumerable<object[]> Intersect_Rect_TestData()
+    {
+        // Normal - from top left.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 5), new Rect(1, 2, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 3), new Rect(1, 2, 3, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 2), new Rect(1, 2, 3, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 1), new Rect(1, 2, 3, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 0), new Rect(1, 2, 3, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 2, 5), new Rect(1, 2, 2, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 2, 4), new Rect(1, 2, 2, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 2, 3), new Rect(1, 2, 2, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 2, 2), new Rect(1, 2, 2, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 2, 1), new Rect(1, 2, 2, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 2, 0), new Rect(1, 2, 2, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 1, 5), new Rect(1, 2, 1, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 1, 4), new Rect(1, 2, 1, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 1, 3), new Rect(1, 2, 1, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 1, 2), new Rect(1, 2, 1, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 1, 1), new Rect(1, 2, 1, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 1, 0), new Rect(1, 2, 1, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 0, 5), new Rect(1, 2, 0, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 0, 4), new Rect(1, 2, 0, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 0, 3), new Rect(1, 2, 0, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 0, 2), new Rect(1, 2, 0, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 0, 1), new Rect(1, 2, 0, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 0, 0), new Rect(1, 2, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 4, 4), new Rect(1, 2, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 5), new Rect(1, 2, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 4, 5), new Rect(1, 2, 3, 4) };
+
+        // Normal - from middle left.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 3, 5), new Rect(1, 3, 3, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 3, 4), new Rect(1, 3, 3, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 3, 3), new Rect(1, 3, 3, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 3, 2), new Rect(1, 3, 3, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 3, 1), new Rect(1, 3, 3, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 3, 0), new Rect(1, 3, 3, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 2, 5), new Rect(1, 3, 2, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 2, 4), new Rect(1, 3, 2, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 2, 3), new Rect(1, 3, 2, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 2, 2), new Rect(1, 3, 2, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 2, 1), new Rect(1, 3, 2, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 2, 0), new Rect(1, 3, 2, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 1, 5), new Rect(1, 3, 1, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 1, 4), new Rect(1, 3, 1, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 1, 3), new Rect(1, 3, 1, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 1, 2), new Rect(1, 3, 1, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 1, 1), new Rect(1, 3, 1, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 1, 0), new Rect(1, 3, 1, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 0, 5), new Rect(1, 3, 0, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 0, 4), new Rect(1, 3, 0, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 0, 3), new Rect(1, 3, 0, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 0, 2), new Rect(1, 3, 0, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 0, 1), new Rect(1, 3, 0, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 0, 0), new Rect(1, 3, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 4, 4), new Rect(1, 3, 3, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 3, 5), new Rect(1, 3, 3, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 4, 5), new Rect(1, 3, 3, 3) };
+
+        // Normal - from bottom left.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 3, 5), new Rect(1, 5, 3, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 3, 4), new Rect(1, 5, 3, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 3, 3), new Rect(1, 5, 3, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 3, 2), new Rect(1, 5, 3, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 3, 1), new Rect(1, 5, 3, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 3, 0), new Rect(1, 5, 3, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 2, 5), new Rect(1, 5, 2, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 2, 4), new Rect(1, 5, 2, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 2, 3), new Rect(1, 5, 2, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 2, 2), new Rect(1, 5, 2, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 2, 1), new Rect(1, 5, 2, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 2, 0), new Rect(1, 5, 2, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 1, 5), new Rect(1, 5, 1, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 1, 4), new Rect(1, 5, 1, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 1, 3), new Rect(1, 5, 1, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 1, 2), new Rect(1, 5, 1, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 1, 1), new Rect(1, 5, 1, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 1, 0), new Rect(1, 5, 1, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 0, 5), new Rect(1, 5, 0, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 0, 4), new Rect(1, 5, 0, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 0, 3), new Rect(1, 5, 0, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 0, 2), new Rect(1, 5, 0, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 0, 1), new Rect(1, 5, 0, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 0, 0), new Rect(1, 5, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 4, 4), new Rect(1, 5, 3, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 3, 5), new Rect(1, 5, 3, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 4, 5), new Rect(1, 5, 3, 1) };
+
+        // Normal - from bottom middle.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 3, 5), new Rect(2, 6, 2, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 3, 4), new Rect(2, 6, 2, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 3, 3), new Rect(2, 6, 2, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 3, 2), new Rect(2, 6, 2, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 3, 1), new Rect(2, 6, 2, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 3, 0), new Rect(2, 6, 2, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 2, 5), new Rect(2, 6, 2, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 2, 4), new Rect(2, 6, 2, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 2, 3), new Rect(2, 6, 2, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 2, 2), new Rect(2, 6, 2, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 2, 1), new Rect(2, 6, 2, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 2, 0), new Rect(2, 6, 2, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 1, 5), new Rect(2, 6, 1, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 1, 4), new Rect(2, 6, 1, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 1, 3), new Rect(2, 6, 1, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 1, 2), new Rect(2, 6, 1, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 1, 1), new Rect(2, 6, 1, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 1, 0), new Rect(2, 6, 1, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 0, 5), new Rect(2, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 0, 4), new Rect(2, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 0, 3), new Rect(2, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 0, 2), new Rect(2, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 0, 1), new Rect(2, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 0, 0), new Rect(2, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 4, 4), new Rect(2, 6, 2, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 3, 5), new Rect(2, 6, 2, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 4, 5), new Rect(2, 6, 2, 0) };
+  
+        // Normal - from bottom right.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 3, 5), new Rect(4, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 3, 4), new Rect(4, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 3, 3), new Rect(4, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 3, 2), new Rect(4, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 3, 1), new Rect(4, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 3, 0), new Rect(4, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 2, 5), new Rect(4, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 2, 4), new Rect(4, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 2, 3), new Rect(4, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 2, 2), new Rect(4, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 2, 1), new Rect(4, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 2, 0), new Rect(4, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 1, 5), new Rect(4, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 1, 4), new Rect(4, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 1, 3), new Rect(4, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 1, 2), new Rect(4, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 1, 1), new Rect(4, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 1, 0), new Rect(4, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 0, 5), new Rect(4, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 0, 4), new Rect(4, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 0, 3), new Rect(4, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 0, 2), new Rect(4, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 0, 1), new Rect(4, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 0, 0), new Rect(4, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 4, 4), new Rect(4, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 3, 5), new Rect(4, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 4, 5), new Rect(4, 6, 0, 0) };
+        
+        // Normal - from middle right.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 3, 5), new Rect(4, 3, 0, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 3, 4), new Rect(4, 3, 0, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 3, 3), new Rect(4, 3, 0, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 3, 2), new Rect(4, 3, 0, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 3, 1), new Rect(4, 3, 0, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 3, 0), new Rect(4, 3, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 2, 5), new Rect(4, 3, 0, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 2, 4), new Rect(4, 3, 0, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 2, 3), new Rect(4, 3, 0, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 2, 2), new Rect(4, 3, 0, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 2, 1), new Rect(4, 3, 0, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 2, 0), new Rect(4, 3, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 1, 5), new Rect(4, 3, 0, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 1, 4), new Rect(4, 3, 0, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 1, 3), new Rect(4, 3, 0, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 1, 2), new Rect(4, 3, 0, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 1, 1), new Rect(4, 3, 0, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 1, 0), new Rect(4, 3, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 0, 5), new Rect(4, 3, 0, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 0, 4), new Rect(4, 3, 0, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 0, 3), new Rect(4, 3, 0, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 0, 2), new Rect(4, 3, 0, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 0, 1), new Rect(4, 3, 0, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 0, 0), new Rect(4, 3, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 4, 4), new Rect(4, 3, 0, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 3, 5), new Rect(4, 3, 0, 3) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 4, 5), new Rect(4, 3, 0, 3) };
+        
+        // Normal - from top right.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 3, 5), new Rect(1, 6, 3, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 3, 4), new Rect(1, 6, 3, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 3, 3), new Rect(1, 6, 3, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 3, 2), new Rect(1, 6, 3, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 3, 1), new Rect(1, 6, 3, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 3, 0), new Rect(1, 6, 3, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 2, 5), new Rect(1, 6, 2, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 2, 4), new Rect(1, 6, 2, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 2, 3), new Rect(1, 6, 2, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 2, 2), new Rect(1, 6, 2, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 2, 1), new Rect(1, 6, 2, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 2, 0), new Rect(1, 6, 2, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 1, 5), new Rect(1, 6, 1, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 1, 4), new Rect(1, 6, 1, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 1, 3), new Rect(1, 6, 1, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 1, 2), new Rect(1, 6, 1, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 1, 1), new Rect(1, 6, 1, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 1, 0), new Rect(1, 6, 1, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 0, 5), new Rect(1, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 0, 4), new Rect(1, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 0, 3), new Rect(1, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 0, 2), new Rect(1, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 0, 1), new Rect(1, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 0, 0), new Rect(1, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 4, 4), new Rect(1, 6, 3, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 3, 5), new Rect(1, 6, 3, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 4, 5), new Rect(1, 6, 3, 0) };
+
+        // Normal - from middle.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 3, 5), new Rect(2, 4, 2, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 3, 4), new Rect(2, 4, 2, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 3, 3), new Rect(2, 4, 2, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 3, 2), new Rect(2, 4, 2, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 3, 1), new Rect(2, 4, 2, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 3, 0), new Rect(2, 4, 2, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 2, 5), new Rect(2, 4, 2, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 2, 4), new Rect(2, 4, 2, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 2, 3), new Rect(2, 4, 2, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 2, 2), new Rect(2, 4, 2, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 2, 1), new Rect(2, 4, 2, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 2, 0), new Rect(2, 4, 2, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 1, 5), new Rect(2, 4, 1, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 1, 4), new Rect(2, 4, 1, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 1, 3), new Rect(2, 4, 1, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 1, 2), new Rect(2, 4, 1, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 1, 1), new Rect(2, 4, 1, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 1, 0), new Rect(2, 4, 1, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 0, 5), new Rect(2, 4, 0, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 0, 4), new Rect(2, 4, 0, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 0, 3), new Rect(2, 4, 0, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 0, 2), new Rect(2, 4, 0, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 0, 1), new Rect(2, 4, 0, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 0, 0), new Rect(2, 4, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 4, 4), new Rect(2, 4, 2, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 3, 5), new Rect(2, 4, 2, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 4, 5), new Rect(2, 4, 2, 2) };
+
+        // Normal - from outside top left.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 0, 2, 3), new Rect(1, 2, 1, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 0, 1, 1), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 0, 0.5, 0.5), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 0, 0, 1), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 0, 1, 0), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 0, 0, 0), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 1, 2, 3), new Rect(1, 2, 1, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 1, 1, 1), new Rect(1, 2, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 1, 0, 3), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 1, 2, 1), new Rect(1, 2, 1, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 1, 0, 0), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 0, 2, 3), new Rect(1, 2, 2, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 0, 1, 1), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 0, 1, 0), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 0, 0, 1), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 0, 0, 0), Rect.Empty };
+
+        // Normal - from outside middle left.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 4, 2, 3), new Rect(1, 4, 1, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 4, 1, 1), new Rect(1, 4, 0, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 4, 0.5, 0.5), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 4, 0, 1), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 4, 1, 0), new Rect(1, 4, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 4, 0, 0), Rect.Empty };
+
+        // Normal - from outside bottom left.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 6, 2, 3), new Rect(1, 6, 1, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 6, 1, 1), new Rect(1, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 6, 0.5, 0.5), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 6, 0, 1), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 6, 1, 0), new Rect(1, 6, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 6, 0, 0), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 7, 2, 3), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 7, 1, 1), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 7, 0.5, 0.5), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 7, 0, 1), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 7, 1, 0), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 7, 0, 0), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 7, 2, 3), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 7, 1, 1), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 7, 0.5, 0.5), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 7, 0, 1), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 7, 1, 0), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 7, 0, 0), Rect.Empty };
+
+        // Normal - from outside bottom middle.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 7, 2, 3), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 7, 1, 1), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 7, 0.5, 0.5), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 7, 0, 1), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 7, 0, 1), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 7, 0, 0), Rect.Empty };
+
+        // Normal - from outside bottom right.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 7, 2, 3), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 7, 1, 1), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 7, 0.5, 0.5), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 7, 1, 0), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 7, 0, 1), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 7, 0, 0), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 7, 2, 3), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 7, 1, 1), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 7, 0.5, 0.5), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 7, 0, 1), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 7, 1, 0), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 7, 0, 0), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 5, 2, 3), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 5, 1, 1), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 5, 0.5, 0.5), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 5, 0, 1), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 5, 1, 0), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 5, 0, 0), Rect.Empty };
+
+        // From outside middle right.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 3, 2, 3), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 3, 1, 1), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 3, 0.5, 0.5), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 3, 0, 1), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 3, 1, 0), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 3, 0, 0), Rect.Empty };
+
+        // From outside top right.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 1, 2, 3), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 1, 1, 1), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 1, 0.5, 0.5), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 1, 0, 1), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 1, 1, 0), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 1, 0, 0), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 0, 2, 3), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 0, 1, 1), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 0, 0.5, 0.5), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 0, 0, 1), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 0, 1, 0), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 0, 0, 0), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 0, 2, 3), new Rect(4, 2, 0, 1) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 0, 1, 1), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 0, 0.5, 0.5), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 0, 0, 0), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 0, 1, 0), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 0, 0, 0), Rect.Empty };
+
+        // Normal - empty.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 0, 0, 0), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 4), Rect.Empty, Rect.Empty };
+
+        // Empty width.
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 1, 5), new Rect(1, 2, 0, 4) };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 1, 4), new Rect(1, 2, 0, 4) };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 1, 3), new Rect(1, 2, 0, 3) };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 1, 2), new Rect(1, 2, 0, 2) };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 1, 1), new Rect(1, 2, 0, 1) };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 1, 0), new Rect(1, 2, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 0, 5), new Rect(1, 2, 0, 4) };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 0, 4), new Rect(1, 2, 0, 4) };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 0, 3), new Rect(1, 2, 0, 3) };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 0, 2), new Rect(1, 2, 0, 2) };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 0, 1), new Rect(1, 2, 0, 1) };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 0, 0), new Rect(1, 2, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 1, 0, 0), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(0, 1, 0, 0), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(0, 0, 0, 1), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(0, 0, 0, 0), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 0, 4), Rect.Empty, Rect.Empty };
+
+        // Empty height.
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 2, 4, 1), new Rect(1, 2, 3, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 2, 4, 0), new Rect(1, 2, 3, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 2, 3, 1), new Rect(1, 2, 3, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 2, 3, 0), new Rect(1, 2, 3, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 2, 2, 1), new Rect(1, 2, 2, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 2, 2, 0), new Rect(1, 2, 2, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 2, 1, 1), new Rect(1, 2, 1, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 2, 1, 0), new Rect(1, 2, 1, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 2, 0, 0), new Rect(1, 2, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 0, 0, 0), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(0, 1, 0, 0), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(0, 0, 0, 0), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(), Rect.Empty };
+        yield return new object[] { new Rect(1, 2, 3, 0), Rect.Empty, Rect.Empty };
+        
+        // Zero.
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(), new Rect(0, 0, 0, 0) };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(0, 0, 0, 0), new Rect(0, 0, 0, 0) };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(1, 0, 0, 0), Rect.Empty };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(0, 1, 0, 0), Rect.Empty };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(0, 0, 1, 0), new Rect(0, 0, 0, 0) };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(0, 0, 0, 1), new Rect(0, 0, 0, 0) };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(0, 0, 1, 1), new Rect(0, 0, 0, 0) };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(1, 2, 3, 4), Rect.Empty };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(1, 2, 3, 0), Rect.Empty };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(1, 2, 0, 4), Rect.Empty };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(1, 2, 0, 0), Rect.Empty };
+        yield return new object[] { new Rect(0, 0, 0, 0), Rect.Empty, Rect.Empty };
+        
+        // Default.
+        yield return new object[] { new Rect(), new Rect(), new Rect(0, 0, 0, 0) };
+        yield return new object[] { new Rect(), new Rect(0, 0, 0, 0), new Rect(0, 0, 0, 0) };
+        yield return new object[] { new Rect(), new Rect(1, 0, 0, 0), Rect.Empty };
+        yield return new object[] { new Rect(), new Rect(0, 1, 0, 0), Rect.Empty };
+        yield return new object[] { new Rect(), new Rect(0, 0, 1, 0), new Rect(0, 0, 0, 0) };
+        yield return new object[] { new Rect(), new Rect(0, 0, 0, 1), new Rect(0, 0, 0, 0) };
+        yield return new object[] { new Rect(), new Rect(0, 0, 1, 1), new Rect(0, 0, 0, 0) };
+        yield return new object[] { new Rect(), new Rect(1, 2, 3, 4), Rect.Empty };
+        yield return new object[] { new Rect(), new Rect(1, 2, 3, 0), Rect.Empty };
+        yield return new object[] { new Rect(), new Rect(1, 2, 0, 4), Rect.Empty };
+        yield return new object[] { new Rect(), new Rect(1, 2, 0, 0), Rect.Empty };
+        yield return new object[] { new Rect(), Rect.Empty, Rect.Empty };
+
+        // Empty.
+        yield return new object[] { Rect.Empty, Rect.Empty, Rect.Empty };
+        yield return new object[] { Rect.Empty, new Rect(), Rect.Empty };
+        yield return new object[] { Rect.Empty, new Rect(0, 0, 0, 0), Rect.Empty };
+        yield return new object[] { Rect.Empty, new Rect(1, 0, 0, 0), Rect.Empty };
+        yield return new object[] { Rect.Empty, new Rect(0, 1, 0, 0), Rect.Empty };
+        yield return new object[] { Rect.Empty, new Rect(0, 0, 1, 0), Rect.Empty };
+        yield return new object[] { Rect.Empty, new Rect(0, 0, 0, 1), Rect.Empty };
+        yield return new object[] { Rect.Empty, new Rect(1, 2, 3, 4), Rect.Empty };
+        yield return new object[] { Rect.Empty, new Rect(1, 2, 3, 0), Rect.Empty };
+        yield return new object[] { Rect.Empty, new Rect(1, 2, 0, 4), Rect.Empty };
+        yield return new object[] { Rect.Empty, new Rect(1, 2, 0, 0), Rect.Empty };
+    }
+
+    [Theory]
+    [MemberData(nameof(Intersect_Rect_TestData))]
+    public void Intersect_InvokeRect_ReturnsExpected(Rect rect1, Rect rect2, Rect expected)
+    {
+        Rect copy1 = rect1;
+        Rect copy2 = rect2;
+
+        Assert.Equal(expected, Rect.Intersect(rect1, rect2));
+        Assert.Equal(copy1, rect1);
+        Assert.Equal(copy2, rect2);
+        
+        rect1.Intersect(rect2);
+        Assert.Equal(expected, rect1);
+        Assert.Equal(copy2, rect2);
+    }
+
+    public static IEnumerable<object[]> IntersectsWith_Rect_TestData()
+    {
+        // Normal - from top left.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 2, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 2, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 2, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 2, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 2, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 2, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 1, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 1, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 1, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 1, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 1, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 1, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 0, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 0, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 0, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 0, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 0, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 0, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 4, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 4, 5), true };
+
+        // Normal - from middle left.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 3, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 3, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 3, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 3, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 3, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 3, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 2, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 2, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 2, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 2, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 2, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 2, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 1, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 1, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 1, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 1, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 1, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 1, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 0, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 0, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 0, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 0, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 0, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 0, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 4, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 3, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 3, 4, 5), true };
+
+        // Normal - from bottom left.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 3, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 3, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 3, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 3, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 3, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 3, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 2, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 2, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 2, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 2, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 2, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 2, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 1, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 1, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 1, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 1, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 1, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 1, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 0, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 0, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 0, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 0, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 0, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 0, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 4, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 3, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 5, 4, 5), true };
+        
+        // Normal - from bottom middle.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 3, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 3, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 3, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 3, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 3, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 3, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 2, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 2, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 2, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 2, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 2, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 2, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 1, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 1, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 1, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 1, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 1, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 1, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 0, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 0, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 0, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 0, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 0, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 0, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 4, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 3, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 6, 4, 5), true };
+        
+        // Normal - from bottom right.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 3, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 3, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 3, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 3, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 3, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 3, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 2, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 2, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 2, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 2, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 2, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 2, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 1, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 1, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 1, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 1, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 1, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 1, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 0, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 0, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 0, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 0, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 0, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 0, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 4, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 3, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 6, 4, 5), true };
+        
+        // Normal - from middle right.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 3, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 3, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 3, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 3, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 3, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 3, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 2, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 2, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 2, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 2, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 2, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 2, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 1, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 1, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 1, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 1, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 1, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 1, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 0, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 0, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 0, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 0, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 0, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 0, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 4, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 3, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 3, 4, 5), true };
+        
+        // Normal - from top right.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 3, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 3, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 3, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 3, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 3, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 3, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 2, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 2, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 2, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 2, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 2, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 2, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 1, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 1, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 1, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 1, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 1, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 1, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 0, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 0, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 0, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 0, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 0, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 0, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 4, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 3, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 6, 4, 5), true };
+
+        // Normal - from middle.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 3, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 3, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 3, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 3, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 3, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 3, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 2, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 2, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 2, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 2, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 2, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 2, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 1, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 1, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 1, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 1, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 1, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 1, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 0, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 0, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 0, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 0, 2), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 0, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 0, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 4, 4), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 3, 5), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 4, 4, 5), true };
+
+        // Normal - from outside top left.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 0, 2, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 0, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 0, 0.5, 0.5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 0, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 0, 1, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 0, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 1, 2, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 1, 1, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 1, 0, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 1, 2, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 1, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 0, 2, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 0, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 0, 1, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 0, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 0, 0, 0), false };
+
+        // Normal - from outside middle left.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 4, 2, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 4, 1, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 4, 0.5, 0.5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 4, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 4, 1, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 4, 0, 0), false };
+
+        // Normal - from outside bottom left.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 6, 2, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 6, 1, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 6, 0.5, 0.5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 6, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 6, 1, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 6, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 7, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 7, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 7, 0.5, 0.5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 7, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 7, 1, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 7, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 7, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 7, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 7, 0.5, 0.5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 7, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 7, 1, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 7, 0, 0), false };
+
+        // Normal - from outside bottom middle.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 7, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 7, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 7, 0.5, 0.5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 7, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 7, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 7, 0, 0), false };
+
+        // Normal - from outside bottom right.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 7, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 7, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 7, 0.5, 0.5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 7, 1, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 7, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 7, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 7, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 7, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 7, 0.5, 0.5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 7, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 7, 1, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 7, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 5, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 5, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 5, 0.5, 0.5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 5, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 5, 1, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 5, 0, 0), false };
+
+        // From outside middle right.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 3, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 3, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 3, 0.5, 0.5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 3, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 3, 1, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 3, 0, 0), false };
+
+        // From outside top right.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 1, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 1, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 1, 0.5, 0.5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 1, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 1, 1, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 1, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 0, 2, 3), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 0, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 0, 0.5, 0.5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 0, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 0, 1, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(5, 0, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 0, 2, 3), true };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 0, 1, 1), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 0, 0.5, 0.5), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 0, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 0, 1, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(4, 0, 0, 0), false };
+
+        // Normal - empty.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 0, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(), false };
+        yield return new object[] { new Rect(1, 2, 3, 4), Rect.Empty, false };
+
+        // Empty width.
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 1, 5), true };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 1, 4), true };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 1, 3), true };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 1, 2), true };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 1, 1), true };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 1, 0), true };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 0, 5), true };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 0, 4), true };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 0, 3), true };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 0, 2), true };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 0, 1), true };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 2, 0, 0), true };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(1, 1, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(0, 1, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(0, 0, 0, 1), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(0, 0, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), new Rect(), false };
+        yield return new object[] { new Rect(1, 2, 0, 4), Rect.Empty, false };
+
+        // Empty height.
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 2, 4, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 2, 4, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 2, 3, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 2, 3, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 2, 2, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 2, 2, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 2, 1, 1), true };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 2, 1, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 2, 0, 0), true };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(1, 0, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(0, 1, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(0, 0, 0, 0), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), new Rect(), false };
+        yield return new object[] { new Rect(1, 2, 3, 0), Rect.Empty, false };
+        
+        // Zero.
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(), true };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(0, 0, 0, 0), true };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(1, 0, 0, 0), false };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(0, 1, 0, 0), false };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(0, 0, 1, 0), true };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(0, 0, 0, 1), true };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(0, 0, 1, 1), true };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(1, 2, 3, 4), false };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(1, 2, 3, 0), false };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(1, 2, 0, 4), false };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(1, 2, 0, 0), false };
+        yield return new object[] { new Rect(0, 0, 0, 0), Rect.Empty, false };
+        
+        // Default.
+        yield return new object[] { new Rect(), new Rect(), true };
+        yield return new object[] { new Rect(), new Rect(0, 0, 0, 0), true };
+        yield return new object[] { new Rect(), new Rect(1, 0, 0, 0), false };
+        yield return new object[] { new Rect(), new Rect(0, 1, 0, 0), false };
+        yield return new object[] { new Rect(), new Rect(0, 0, 1, 0), true };
+        yield return new object[] { new Rect(), new Rect(0, 0, 0, 1), true };
+        yield return new object[] { new Rect(), new Rect(0, 0, 1, 1), true };
+        yield return new object[] { new Rect(), new Rect(1, 2, 3, 4), false };
+        yield return new object[] { new Rect(), new Rect(1, 2, 3, 0), false };
+        yield return new object[] { new Rect(), new Rect(1, 2, 0, 4), false };
+        yield return new object[] { new Rect(), new Rect(1, 2, 0, 0), false };
+        yield return new object[] { new Rect(), Rect.Empty, false };
+
+        // Empty.
+        yield return new object[] { Rect.Empty, Rect.Empty, false };
+        yield return new object[] { Rect.Empty, new Rect(), false };
+        yield return new object[] { Rect.Empty, new Rect(0, 0, 0, 0), false };
+        yield return new object[] { Rect.Empty, new Rect(1, 0, 0, 0), false };
+        yield return new object[] { Rect.Empty, new Rect(0, 1, 0, 0), false };
+        yield return new object[] { Rect.Empty, new Rect(0, 0, 1, 0), false };
+        yield return new object[] { Rect.Empty, new Rect(0, 0, 0, 1), false };
+        yield return new object[] { Rect.Empty, new Rect(1, 2, 3, 4), false };
+        yield return new object[] { Rect.Empty, new Rect(1, 2, 3, 0), false };
+        yield return new object[] { Rect.Empty, new Rect(1, 2, 0, 4), false };
+        yield return new object[] { Rect.Empty, new Rect(1, 2, 0, 0), false };
+    }
+
+    [Theory]
+    [MemberData(nameof(IntersectsWith_Rect_TestData))]
+    public void IntersectsWith_InvokeRect_ReturnsExpected(Rect rect, Rect other, bool expected)
+    {
+        Assert.Equal(expected, rect.IntersectsWith(other));
+        Assert.Equal(expected, other.IntersectsWith(rect));
+    }
+
+    public static IEnumerable<object[]> Offset_TestData()
+    {
+        // Normal.
+        yield return new object[] { new Rect(1, 2, 3, 4), 0, 0, new Rect(1, 2, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), 5, 6, new Rect(6, 8, 3, 4) };
+        yield return new object[] { new Rect(1.25, 2.25, 3, 4), 5.5, 6.5, new Rect(6.75, 8.75, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), 5, 0, new Rect(6, 2, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), 0, 6, new Rect(1, 8, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), -5, -6, new Rect(-4, -4, 3, 4) };
+
+        // Large.
+        yield return new object[] { new Rect(double.MaxValue, double.MaxValue, 3, 4), 1, 2, new Rect(double.MaxValue, double.MaxValue, 3, 4) };
+        yield return new object[] { new Rect(double.MaxValue, double.MaxValue, 3, 4), 0, 0, new Rect(double.MaxValue, double.MaxValue, 3, 4) };
+        yield return new object[] { new Rect(double.MaxValue, double.MaxValue, 3, 4), double.MaxValue, double.MaxValue, new Rect(double.PositiveInfinity, double.PositiveInfinity, 3, 4) };
+        yield return new object[] { new Rect(double.MinValue, double.MinValue, 3, 4), -1, -2, new Rect(double.MinValue, double.MinValue, 3, 4) };
+        yield return new object[] { new Rect(double.MinValue, double.MinValue, 3, 4), 0, 0, new Rect(double.MinValue, double.MinValue, 3, 4) };
+        yield return new object[] { new Rect(double.MinValue, double.MinValue, 3, 4), double.MinValue, double.MinValue, new Rect(double.NegativeInfinity, double.NegativeInfinity, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), double.MaxValue, double.MaxValue, new Rect(double.MaxValue, double.MaxValue, 3, 4) };
+        yield return new object[] { new Rect(0, 0, 3, 4), double.MaxValue, double.MaxValue, new Rect(double.MaxValue, double.MaxValue, 3, 4) };
+        yield return new object[] { new Rect(-1, -2, 3, 4), double.MinValue, double.MinValue, new Rect(double.MinValue, double.MinValue, 3, 4) };
+        yield return new object[] { new Rect(0, 0, 3, 4), double.MinValue, double.MinValue, new Rect(double.MinValue, double.MinValue, 3, 4) };
+
+        // Infinite.
+        yield return new object[] { new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity), 0, 0, new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity), 5, 6, new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity), -5, -6, new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity), double.PositiveInfinity, double.PositiveInfinity, new Rect(double.NaN, double.NaN, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity), double.NegativeInfinity, double.NegativeInfinity, new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), 0, 0, new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), 5, 6, new Rect(6, 8, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), -5, -6, new Rect(-4, -4, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), double.PositiveInfinity, double.PositiveInfinity, new Rect(double.PositiveInfinity, double.PositiveInfinity, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), double.NegativeInfinity, double.NegativeInfinity, new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity) };
+
+        // NaN.
+        yield return new object[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), 0, 0, new Rect(double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), 5, 6, new Rect(double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), -5, -6, new Rect(double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), double.PositiveInfinity, double.PositiveInfinity, new Rect(double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), double.NegativeInfinity, double.NegativeInfinity, new Rect(double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), double.NaN, double.NaN, new Rect(double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(1, 2, double.NaN, double.NaN), 0, 0, new Rect(1, 2, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(1, 2, double.NaN, double.NaN), 5, 6, new Rect(6, 8, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(1, 2, double.NaN, double.NaN), -5, -6, new Rect(-4, -4, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(1, 2, double.NaN, double.NaN), double.PositiveInfinity, double.PositiveInfinity, new Rect(double.PositiveInfinity, double.PositiveInfinity, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(1, 2, double.NaN, double.NaN), double.NegativeInfinity, double.NegativeInfinity, new Rect(double.NegativeInfinity, double.NegativeInfinity, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(1, 2, double.NaN, double.NaN), double.NaN, double.NaN, new Rect(double.NaN, double.NaN, double.NaN, double.NaN) };
+
+        // Zero.
+        yield return new object[] { new Rect(0, 0, 0, 0), 0, 0, new Rect(0, 0, 0, 0) };
+        yield return new object[] { new Rect(0, 0, 0, 0), 1, 2, new Rect(1, 2, 0, 0) };
+        yield return new object[] { new Rect(0, 0, 0, 0), -1, -2, new Rect(-1, -2, 0, 0) };
+    }
+
+    [Theory]
+    [MemberData(nameof(Offset_TestData))]
+    public void Offset_Invoke_ReturnsExpected(Rect rect, double offsetX, double offsetY, Rect expected)
+    {
+        Rect copy = rect;
+
+        Assert.Equal(expected, Rect.Offset(rect, offsetX, offsetY));
+        Assert.Equal(copy, rect);
+
+        Assert.Equal(expected, Rect.Offset(rect, new Vector(offsetX, offsetY)));
+        Assert.Equal(copy, rect);
+
+        rect.Offset(offsetX, offsetY);
+        Assert.Equal(expected, rect);
+
+        rect = copy;
+        rect.Offset(new Vector(offsetX, offsetY));
+        Assert.Equal(expected, rect);
+    }
+
+    [Fact]
+    public void Offset_Empty_ThrowsInvalidOperationException()
+    {
+        Assert.Throws<InvalidOperationException>(() => Rect.Empty.Offset(0, 0));
+        Assert.Throws<InvalidOperationException>(() => Rect.Empty.Offset(new Vector(0, 0)));
+        Assert.Throws<InvalidOperationException>(() => Rect.Offset(Rect.Empty, 0, 0));
+        Assert.Throws<InvalidOperationException>(() => Rect.Offset(Rect.Empty, new Vector(0, 0)));
+    }
+
+    public static IEnumerable<object[]> Parse_TestData()
+    {
+        yield return new object[] { "Empty", Rect.Empty };
+        yield return new object[] { "  Empty  ", Rect.Empty };
+        yield return new object[] { "0,0,0,0", new Rect() };
+        yield return new object[] { "1,2,3,4", new Rect(1, 2, 3, 4) };
+        yield return new object[] { "1.1,2.2,3.3,4.4", new Rect(1.1, 2.2, 3.3, 4.4) };
+        yield return new object[] { "   1   ,   2  ,  3,  4", new Rect(1, 2, 3, 4) };
+        yield return new object[] { "-1,-2,3,4", new Rect(-1, -2, 3, 4) };
+    }
+
+    [Theory]
+    [MemberData(nameof(Parse_TestData))]
+    public void Parse_Invoke_Success(string source, Rect expected)
+    {
+        Rect result = Rect.Parse(source);
+        Assert.Equal(expected.X, result.X, precision: 5);
+        Assert.Equal(expected.Y, result.Y, precision: 5);
+        Assert.Equal(expected.Width, result.Width, precision: 5);
+        Assert.Equal(expected.Height, result.Height, precision: 5);
+    }
+
+    [Fact]
+    public void Parse_NullSource_ThrowsInvalidOperationException()
+    {
+        Assert.Throws<InvalidOperationException>(() => Rect.Parse(null));
+    }
+
+    public static IEnumerable<object[]> Parse_InvalidSource_TestData()
+    {
+        yield return new object[] { "" };
+        yield return new object[] { "  " };
+        yield return new object[] { "," };
+        yield return new object[] { "1" };
+        yield return new object[] { "1," };
+        yield return new object[] { "1,2" };
+        yield return new object[] { "1,2," };
+        yield return new object[] { "1,2,3" };
+        yield return new object[] { "1,2,3," };
+        yield return new object[] { "1,2,3,4," };
+        yield return new object[] { "1,2,3,4,5" };
+        yield return new object[] { "1,2,4,5,test" };
+        yield return new object[] { "Empty," };
+        yield return new object[] { "Empty,2,3,4" };
+        yield return new object[] { "Identity," };
+    }
+
+    [Theory]
+    [MemberData(nameof(Parse_InvalidSource_TestData))]
+    public void Parse_InvalidSource_ThrowsInvalidOperationException(string source)
+    {
+        Assert.Throws<InvalidOperationException>(() => Rect.Parse(source));
+    }
+
+    public static IEnumerable<object[]> Parse_NotDouble_TestData()
+    {
+        yield return new object[] { "Identity" };
+        yield return new object[] { " Identity " };
+        yield return new object[] { "Identity,2,3,4" };
+        yield return new object[] { "test" };
+        yield return new object[] { "test,2,3,4" };
+        yield return new object[] { "1,test,3,4" };
+        yield return new object[] { "1,2,test,4" };
+        yield return new object[] { "1,2,3,test" };
+        yield return new object[] { "1;2;3;4" };
+        yield return new object[] { """1"",""2"",""3"",""4""" };
+    }
+
+    [Theory]
+    [MemberData(nameof(Parse_NotDouble_TestData))]
+    public void Parse_NotDouble_ThrowsFormatException(string source)
+    {
+        Assert.Throws<FormatException>(() => Rect.Parse(source));
+    }
+
+    public static IEnumerable<object[]> Parse_Negative_TestData()
+    {
+        yield return new object[] { "1,2,-3,4" };
+        yield return new object[] { "1,2,3,-4" };
+    }
+
+    [Theory]
+    [MemberData(nameof(Parse_Negative_TestData))]
+    public void Parse_Negative_ThrowsArgumentException(string source)
+    {
+        Assert.Throws<ArgumentException>(() => Rect.Parse(source));
+    }
+
+    public static IEnumerable<object[]> Scale_TestData()
+    {
+        // Normal.
+        yield return new object[] { new Rect(1, 2, 3, 4), 2, 3, new Rect(2, 6, 6, 12) };
+        yield return new object[] { new Rect(1, 2, 3, 4), 2, 1, new Rect(2, 2, 6, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), 1, 3, new Rect(1, 6, 3, 12) };
+        yield return new object[] { new Rect(1, 2, 3, 4), 1, 1, new Rect(1, 2, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), 0.5, 0.5, new Rect(0.5, 1, 1.5, 2) };
+        yield return new object[] { new Rect(1, 2, 3, 4), 1, 0, new Rect(1, 0, 3, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), 0, 1, new Rect(0, 2, 0, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), 0, 0, new Rect(0, 0, 0, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), -1, 1, new Rect(-4, 2, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), 1, -1, new Rect(1, -6, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), -1, -2, new Rect(-4, -12, 3, 8) };
+        yield return new object[] { new Rect(1, 2, 3, 4), -2, -3, new Rect(-8, -18, 6, 12) };
+
+        // Large.
+        yield return new object[] { new Rect(double.MaxValue, double.MaxValue, 3, 4), 1, 2, new Rect(double.MaxValue, double.PositiveInfinity, 3, 8) };
+        yield return new object[] { new Rect(double.MaxValue, double.MaxValue, 3, 4), 0, 0, new Rect(0, 0, 0, 0) };
+        yield return new object[] { new Rect(double.MaxValue, double.MaxValue, 3, 4), double.MaxValue, double.MaxValue, new Rect(double.PositiveInfinity, double.PositiveInfinity, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(double.MinValue, double.MinValue, 3, 4), -1, -2, new Rect(double.MaxValue, double.PositiveInfinity, 3, 8) };
+        yield return new object[] { new Rect(double.MinValue, double.MinValue, 3, 4), 0, 0, new Rect(0, 0, 0, 0) };
+        yield return new object[] { new Rect(double.MinValue, double.MinValue, 3, 4), double.MinValue, double.MinValue, new Rect(double.NaN, double.NaN, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, 3, 4), double.MaxValue, double.MaxValue, new Rect(double.MaxValue, double.PositiveInfinity, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(0, 0, 3, 4), double.MaxValue, double.MaxValue, new Rect(0, 0, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(-1, -2, 3, 4), double.MinValue, double.MinValue, new Rect(double.NegativeInfinity, double.NaN, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(0, 0, 3, 4), double.MinValue, double.MinValue, new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity) };
+
+        // Infinite.
+        yield return new object[] { new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity), 0, 0, new Rect(double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity), 5, 6, new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity), -5, -6, new Rect(double.NaN, double.NaN, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity), double.PositiveInfinity, double.PositiveInfinity, new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity), double.NegativeInfinity, double.NegativeInfinity, new Rect(double.NaN, double.NaN, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), 0, 0, new Rect(0, 0, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), 5, 6, new Rect(5, 12, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), -5, -6, new Rect(double.NegativeInfinity ,double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), double.PositiveInfinity, double.PositiveInfinity, new Rect(double.PositiveInfinity, double.PositiveInfinity, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), double.NegativeInfinity, double.NegativeInfinity, new Rect(double.NegativeInfinity,double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity) };
+
+        // NaN.
+        yield return new object[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), 0, 0, new Rect(double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), 5, 6, new Rect(double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), -5, -6, new Rect(double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), double.PositiveInfinity, double.PositiveInfinity, new Rect(double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), double.NegativeInfinity, double.NegativeInfinity, new Rect(double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(double.NaN, double.NaN, double.NaN, double.NaN), double.NaN, double.NaN, new Rect(double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(1, 2, double.NaN, double.NaN), 0, 0, new Rect(0, 0, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(1, 2, double.NaN, double.NaN), 5, 6, new Rect(5, 12, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(1, 2, double.NaN, double.NaN), -5, -6, new Rect(double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(1, 2, double.NaN, double.NaN), double.PositiveInfinity, double.PositiveInfinity, new Rect(double.PositiveInfinity, double.PositiveInfinity, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(1, 2, double.NaN, double.NaN), double.NegativeInfinity, double.NegativeInfinity, new Rect(double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(1, 2, double.NaN, double.NaN), double.NaN, double.NaN, new Rect(double.NaN, double.NaN, double.NaN, double.NaN) };
+
+        // Zero.
+        yield return new object[] { new Rect(0, 0, 0, 0), 2, 3, new Rect(0, 0, 0, 0) };
+        yield return new object[] { new Rect(0, 0, 0, 0), 1, 1, new Rect(0, 0, 0, 0) };
+        yield return new object[] { new Rect(0, 0, 0, 0), 0.5, 0.5, new Rect(0, 0, 0, 0) };
+        yield return new object[] { new Rect(0, 0, 0, 0), 0, 0, new Rect(0, 0, 0, 0) };
+        yield return new object[] { new Rect(0, 0, 0, 0), -1, -2, new Rect(0, 0, 0, 0) };
+
+        // Default.
+        yield return new object[] { new Rect(), 2, 3, new Rect(0, 0, 0, 0) };
+        yield return new object[] { new Rect(), 1, 1, new Rect(0, 0, 0, 0) };
+        yield return new object[] { new Rect(), 0.5, 0.5, new Rect(0, 0, 0, 0) };
+        yield return new object[] { new Rect(), 0, 0, new Rect(0, 0, 0, 0) };
+        yield return new object[] { new Rect(), -1, -2, new Rect(0, 0, 0, 0) };
+
+        // Empty.
+        yield return new object[] { Rect.Empty, 2, 3, Rect.Empty };
+        yield return new object[] { Rect.Empty, 1, 1, Rect.Empty };
+        yield return new object[] { Rect.Empty, 0.5, 0.5, Rect.Empty };
+        yield return new object[] { Rect.Empty, 0, 0, Rect.Empty };
+        yield return new object[] { Rect.Empty, -1, -2, Rect.Empty };
+    }
+
+    [Theory]
+    [MemberData(nameof(Scale_TestData))]
+    public void Scale_Invoke_ReturnsExpected(Rect rect, double scaleX, double scaleY, Rect expected)
+    {
+        rect.Scale(scaleX, scaleY);
+        Assert.Equal(expected, rect);
+    }
+
+    public static IEnumerable<object[]> ToString_TestData()
+    {
+        yield return new object[] { Rect.Empty, "Empty" };
+        yield return new object[] { new Rect(), "0,0,0,0" };
+        yield return new object[] { new Rect(0, 0, 0, 0), "0,0,0,0" };
+        yield return new object[] { new Rect(1, 2, 3, 4), "1,2,3,4" };
+        yield return new object[] { new Rect(1.1, 2.2, 3.3, 4.4), "1.1,2.2,3.3,4.4" };
+        yield return new object[] { new Rect(-1, -2, 3, 4), "-1,-2,3,4" };
+    }
+
+    [Theory]
+    [MemberData(nameof(ToString_TestData))]
+    public void ToString_Invoke_ReturnsExpected(Rect rect, string expected)
+    {
+        Assert.Equal(expected, rect.ToString());
+    }
+
+    [Theory]
+    [MemberData(nameof(ToString_TestData))]
+    public void ToString_InvokeIFormatProviderInvariantCulture_ReturnsExpected(Rect rect, string expected)
+    {
+        Assert.Equal(expected, rect.ToString(CultureInfo.InvariantCulture));
+    }
+
+    public static IEnumerable<object[]> ToString_IFormatProviderCustom_TestData()
+    {
+        yield return new object[] { Rect.Empty, "|", "Empty" };
+        yield return new object[] { Rect.Empty, "|_", "Empty" };
+        yield return new object[] { Rect.Empty, ",_", "Empty" };
+        yield return new object[] { Rect.Empty, ",", "Empty" };
+        yield return new object[] { Rect.Empty, ";", "Empty" };
+        yield return new object[] { Rect.Empty, " ", "Empty" };
+
+        yield return new object[] { new Rect(), "|", "0,0,0,0" };
+        yield return new object[] { new Rect(), "|_", "0,0,0,0" };
+        yield return new object[] { new Rect(), ",_", "0;0;0;0" };
+        yield return new object[] { new Rect(), ",", "0;0;0;0" };
+        yield return new object[] { new Rect(), ";", "0,0,0,0" };
+        yield return new object[] { new Rect(), " ", "0,0,0,0" };
+
+        yield return new object[] { new Rect(0, 0, 0, 0), "|", "0,0,0,0" };
+        yield return new object[] { new Rect(0, 0, 0, 0), "|_", "0,0,0,0" };
+        yield return new object[] { new Rect(0, 0, 0, 0), ",_", "0;0;0;0" };
+        yield return new object[] { new Rect(0, 0, 0, 0), ",", "0;0;0;0" };
+        yield return new object[] { new Rect(0, 0, 0, 0), ";", "0,0,0,0" };
+        yield return new object[] { new Rect(0, 0, 0, 0), " ", "0,0,0,0" };
+
+        yield return new object[] { new Rect(1, 2, 3, 4), "|", "1,2,3,4" };
+        yield return new object[] { new Rect(1, 2, 3, 4), "|_", "1,2,3,4" };
+        yield return new object[] { new Rect(1, 2, 3, 4), ",_", "1;2;3;4" };
+        yield return new object[] { new Rect(1, 2, 3, 4), ",", "1;2;3;4" };
+        yield return new object[] { new Rect(1, 2, 3, 4), ";", "1,2,3,4" };
+        yield return new object[] { new Rect(1, 2, 3, 4), " ", "1,2,3,4" };
+
+        yield return new object[] { new Rect(1.1, 2.2, 3.3, 4.4), "|", "1|1,2|2,3|3,4|4" };
+        yield return new object[] { new Rect(1.1, 2.2, 3.3, 4.4), "|_", "1|_1,2|_2,3|_3,4|_4" };
+        yield return new object[] { new Rect(1.1, 2.2, 3.3, 4.4), ",_", "1,_1;2,_2;3,_3;4,_4" };
+        yield return new object[] { new Rect(1.1, 2.2, 3.3, 4.4), ",", "1,1;2,2;3,3;4,4" };
+        yield return new object[] { new Rect(1.1, 2.2, 3.3, 4.4), ";", "1;1,2;2,3;3,4;4" };
+        yield return new object[] { new Rect(1.1, 2.2, 3.3, 4.4), " ", "1 1,2 2,3 3,4 4" };
+
+        yield return new object[] { new Rect(-1, -2, 3, 4), "|", "-1,-2,3,4" };
+        yield return new object[] { new Rect(-1, -2, 3, 4), "|_", "-1,-2,3,4" };
+        yield return new object[] { new Rect(-1, -2, 3, 4), ",_", "-1;-2;3;4" };
+        yield return new object[] { new Rect(-1, -2, 3, 4), ",", "-1;-2;3;4" };
+        yield return new object[] { new Rect(-1, -2, 3, 4), ";", "-1,-2,3,4" };
+        yield return new object[] { new Rect(-1, -2, 3, 4), " ", "-1,-2,3,4" };
+    }
+
+    [Theory]
+    [MemberData(nameof(ToString_IFormatProviderCustom_TestData))]
+    public void ToString_InvokeIFormatProviderCustom_ReturnsExpected(Rect rect, string numberDecimalSeparator, string expected)
+    {
+        var culture = new CultureInfo("en-US");
+        NumberFormatInfo formatInfo = culture.NumberFormat;
+        formatInfo.NumberDecimalSeparator = numberDecimalSeparator;
+
+        Assert.Equal(expected, rect.ToString(formatInfo));
+    }
+
+    [Theory]
+    [MemberData(nameof(ToString_TestData))]
+    public void ToString_InvokeIFormattableInvariantCulture_ReturnsExpected(Rect rect, string expected)
+    {
+        IFormattable formattable = rect;
+        Assert.Equal(expected, formattable.ToString(null, null));
+        Assert.Equal(expected, formattable.ToString(null, CultureInfo.InvariantCulture));
+    }
+
+    [Theory]
+    [InlineData("|", "1|23,2|35,3|46,4|57")]
+    [InlineData("|_", "1|_23,2|_35,3|_46,4|_57")]
+    [InlineData(",_", "1,_23;2,_35;3,_46;4,_57")]
+    [InlineData(",", "1,23;2,35;3,46;4,57")]
+    [InlineData(";", "1;23,2;35,3;46,4;57")]
+    [InlineData(" ", "1 23,2 35,3 46,4 57")]
+    public void ToString_InvokeIFormattableCustomFormat_ReturnsExpected(string numberDecimalSeparator, string expected)
+    {
+        var rect = new Rect(1.23456, 2.34567, 3.45678, 4.56789);
+        IFormattable formattable = rect;
+
+        var culture = new CultureInfo("en-US");
+        NumberFormatInfo formatInfo = culture.NumberFormat;
+        formatInfo.NumberDecimalSeparator = numberDecimalSeparator;
+        Assert.Equal(expected, formattable.ToString("F2", formatInfo));
+    }
+
+    public static IEnumerable<object[]> Transform_TestData()
+    {
+        // Identity.
+        foreach (Matrix matrix in MatrixTests.IdentityMatrices())
+        {
+            yield return new object[] { new Rect(1, 2, 3, 4), matrix, new Rect(1, 2, 3, 4) };
+        }
+
+        // Scale.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Matrix(2, 0, 0, 1, 0, 0), new Rect(2, 2, 6, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Matrix(1, 0, 0, 2, 0, 0), new Rect(1, 4, 3, 8) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Matrix(0, 0, 0, 3, 0, 0), new Rect(0, 6, 0, 12) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Matrix(2, 0, 0, 0, 0, 0), new Rect(2, 0, 6, 0) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Matrix(2, 0, 0, 3, 0, 0), new Rect(2, 6, 6, 12) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Matrix(-2, 0, 0, -3, 0, 0), new Rect(-8, -18, 6, 12) };
+
+        // Skew.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Matrix(1, 2, 0, 1, 0, 0), new Rect(1, 4, 3, 10) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Matrix(1, 0, 3, 1, 0, 0), new Rect(7, 2, 15, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Matrix(1, 2, 3, 1, 0, 0), new Rect(7, 4, 15, 10) };
+
+        // Translate.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Matrix(1, 0, 0, 1, 2, 0), new Rect(3, 2, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Matrix(1, 0, 0, 1, 0, 3), new Rect(1, 5, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Matrix(1, 0, 0, 1, 2, 3), new Rect(3, 5, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Matrix(1, 0, 0, 1, -2, 0), new Rect(-1, 2, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Matrix(1, 0, 0, 1, 0, -3), new Rect(1, -1, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Matrix(1, 0, 0, 1, -2, -3), new Rect(-1, -1, 3, 4) };
+
+        // Translate + Scale.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Matrix(2, 0, 0, 3, 4, 5), new Rect(6, 11, 6, 12) };
+
+        // Translate + Skew.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Matrix(1, 2, 3, 1, 4, 5), new Rect(11, 9, 15, 10) };
+
+        // Skew + Scale.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Matrix(2, 3, 4, 5, 0, 0), new Rect(10, 13, 22, 29) };
+
+        // Complex.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Matrix(2, 3, 4, 5, 6, 7), new Rect(16, 20, 22, 29) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Matrix(0, 0, 0, 0, 0, 0), new Rect(0, 0, 0, 0) };
+        yield return new object[] { new Rect(1.1, 2.2, 2.3, 3.3), new Matrix(2, 3, 4, 5, 6, 7), new Rect(17, 21.3, 17.8, 23.4) };
+
+        // Other cases.
+        yield return new object[] { new Rect(-1, -2, 1, 2), Matrix.Identity, new Rect(-1, -2, 1, 2) };
+        yield return new object[] { new Rect(-1, -2, 1, 2), new Matrix(), new Rect(-1, -2, 1, 2) };
+        yield return new object[] { new Rect(-1, -2, 1, 2), new Matrix(1, 0, 0, 1, 0, 0), new Rect(-1, -2, 1, 2) };
+        yield return new object[] { new Rect(-1, -2, 1, 2), new Matrix(2, 3, 4, 5, 6, 7), new Rect(-4, -6, 10, 13) };
+
+        // Zero.
+        yield return new object[] { new Rect(0, 0, 0, 0), Matrix.Identity, new Rect() };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Matrix(), new Rect() };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Matrix(1, 0, 0, 1, 0, 0), new Rect() };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Matrix(2, 3, 4, 5, 6, 7), new Rect(6, 7, 0, 0) };
+        
+        // Default.
+        yield return new object[] { new Rect(), Matrix.Identity, new Rect() };
+        yield return new object[] { new Rect(), new Matrix(), new Rect() };
+        yield return new object[] { new Rect(), new Matrix(1, 0, 0, 1, 0, 0), new Rect() };
+        yield return new object[] { new Rect(), new Matrix(2, 3, 4, 5, 6, 7), new Rect(6, 7, 0, 0) };
+        
+        // Empty.
+        yield return new object[] { Rect.Empty, Matrix.Identity, Rect.Empty };
+        yield return new object[] { Rect.Empty, new Matrix(), Rect.Empty };
+        yield return new object[] { Rect.Empty, new Matrix(1, 0, 0, 1, 0, 0), Rect.Empty };
+        yield return new object[] { Rect.Empty, new Matrix(2, 3, 4, 5, 6, 7), Rect.Empty };
+    }
+
+    [Theory]
+    [MemberData(nameof(Transform_TestData))]
+    public void Transform_Invoke_ReturnsExpected(Rect rect, Matrix matrix, Rect expected)
+    {
+        Rect copy = rect;
+
+        Helpers.AssertEqualRounded(expected, Rect.Transform(rect, matrix), precision: 5);
+        Assert.Equal(copy, rect);
+
+        rect.Transform(matrix);
+        Helpers.AssertEqualRounded(expected, rect, precision: 5);
+    }
+
+    public static IEnumerable<object[]> Union_Point_TestData()
+    {
+        // Normal.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(1, 2), new Rect(1, 2, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(1, 6), new Rect(1, 2, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(4, 2), new Rect(1, 2, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(4, 6), new Rect(1, 2, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(2, 3), new Rect(1, 2, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(2, 3), new Rect(1, 2, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(-1, -2), new Rect(-1, -2, 5, 8) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(0, 0), new Rect(0, 0, 4, 6) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(5, 7), new Rect(1, 2, 4, 5) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(), new Rect(0, 0, 4, 6) };
+
+        // Infinite width.
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, 4), new Point(1, 2), new Rect(1, 2, double.PositiveInfinity, 4) };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, 4), new Point(double.MaxValue, 2), new Rect(1, 2, double.PositiveInfinity, 4) };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, 4), new Point(double.PositiveInfinity, 2), new Rect(1, 2, double.PositiveInfinity, 4) };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, 4), new Point(double.NaN, 2), new Rect(double.NaN, 2, double.PositiveInfinity, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(double.PositiveInfinity, 2), new Rect(1, 2, double.NaN, 4) };
+
+        // Infinite height.
+        yield return new object[] { new Rect(1, 2, 3, double.PositiveInfinity), new Point(1, 2), new Rect(1, 2, 3, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, 3, double.PositiveInfinity), new Point(1, double.MaxValue), new Rect(1, 2, 3, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, 3, double.PositiveInfinity), new Point(1, double.PositiveInfinity), new Rect(1, 2, 3, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, 3, double.PositiveInfinity), new Point(1, double.NaN), new Rect(1, double.NaN, 3, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(1, double.PositiveInfinity), new Rect(1, 2, 3, double.NaN) };
+
+        // Infinite width & height.
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), new Point(1, 2), new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), new Point(double.MaxValue, double.MaxValue), new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), new Point(double.PositiveInfinity, double.PositiveInfinity), new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), new Point(double.NaN, double.NaN), new Rect(double.NaN, double.NaN, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(double.PositiveInfinity, double.PositiveInfinity), new Rect(1, 2, double.NaN, double.NaN) };
+
+        // NaN width.
+        yield return new object[] { new Rect(1, 2, double.NaN, 4), new Point(1, 2), new Rect(1, 2, double.NaN, 4) };
+        yield return new object[] { new Rect(1, 2, double.NaN, 4), new Point(double.MaxValue, 2), new Rect(1, 2, double.NaN, 4) };
+        yield return new object[] { new Rect(1, 2, double.NaN, 4), new Point(double.PositiveInfinity, 2), new Rect(1, 2, double.NaN, 4) };
+        yield return new object[] { new Rect(1, 2, double.NaN, 4), new Point(double.NaN, 2), new Rect(double.NaN, 2, double.NaN, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(double.NaN, 2), new Rect(double.NaN, 2, double.NaN, 4) };
+
+        // NaN height.
+        yield return new object[] { new Rect(1, 2, 3, double.NaN), new Point(1, 2), new Rect(1, 2, 3, double.NaN) };
+        yield return new object[] { new Rect(1, 2, 3, double.NaN), new Point(1, double.MaxValue), new Rect(1, 2, 3, double.NaN) };
+        yield return new object[] { new Rect(1, 2, 3, double.NaN), new Point(1, double.PositiveInfinity), new Rect(1, 2, 3, double.NaN) };
+        yield return new object[] { new Rect(1, 2, 3, double.NaN), new Point(1, double.NaN), new Rect(1, double.NaN, 3, double.NaN) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(1, double.NaN), new Rect(1, double.NaN, 3, double.NaN) };
+
+        // NaN width & height.
+        yield return new object[] { new Rect(1, 2, double.NaN, double.NaN), new Point(1, 2), new Rect(1, 2, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(1, 2, double.NaN, double.NaN), new Point(double.MaxValue, double.MaxValue), new Rect(1, 2, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(1, 2, double.NaN, double.NaN), new Point(double.PositiveInfinity, double.PositiveInfinity), new Rect(1, 2, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(1, 2, double.NaN, double.NaN), new Point(double.NaN, double.NaN), new Rect(double.NaN, double.NaN, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Point(double.NaN, double.NaN), new Rect(double.NaN, double.NaN, double.NaN, double.NaN) };
+
+        // Zero.
+        yield return new object[] { new Rect(0, 0, 0, 0), new Point(1, 2), new Rect(0, 0, 1, 2) };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Point(-1, -2), new Rect(-1, -2, 1, 2) };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Point(0, 0), new Rect(0, 0, 0, 0) };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Point(), new Rect(0, 0, 0, 0) };
+
+        // Default.
+        yield return new object[] { new Rect(), new Point(1, 2), new Rect(0, 0, 1, 2) };
+        yield return new object[] { new Rect(), new Point(-1, -2), new Rect(-1, -2, 1, 2) };
+        yield return new object[] { new Rect(), new Point(0, 0), new Rect(0, 0, 0, 0) };
+        yield return new object[] { new Rect(), new Point(), new Rect(0, 0, 0, 0) };
+
+        // Empty.
+        yield return new object[] {Rect.Empty, new Point(1, 2), new Rect(1, 2, 0, 0) };
+        yield return new object[] {Rect.Empty, new Point(-1, -2), new Rect(-1, -2, 0, 0) };
+        yield return new object[] {Rect.Empty, new Point(0, 0), new Rect(0, 0, 0, 0) };
+        yield return new object[] {Rect.Empty, new Point(), new Rect(0, 0, 0, 0) };
+    }
+
+    [Theory]
+    [MemberData(nameof(Union_Point_TestData))]
+    public void Union_InvokePoint_ReturnsExpected(Rect rect, Point point, Rect expected)
+    {
+        Rect copy = rect;
+
+        Assert.Equal(expected, Rect.Union(rect, point));
+        Assert.Equal(copy, rect);
+
+        rect.Union(point);
+        Assert.Equal(expected, rect);
+    }
+
+    public static IEnumerable<object[]> Union_Rect_TestData()
+    {
+        // Normal.
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 0, 4), new Rect(1, 2, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 0), new Rect(1, 2, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 0, 0), new Rect(1, 2, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 3, 1, 2), new Rect(1, 2, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 3, 2, 3), new Rect(1, 2, 3, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(2, 3, 3, 4), new Rect(1, 2, 4, 5) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(-1, -2, 1, 2), new Rect(-1, -2, 5, 8) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(-1, -2, 2, 4), new Rect(-1, -2, 5, 8) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(-1, -2, 7, 9), new Rect(-1, -2, 7, 9) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(0, 0, 0, 0), new Rect(0, 0, 4, 6) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(), new Rect(0, 0, 4, 6) };
+        yield return new object[] { new Rect(1, 2, 3, 4), Rect.Empty, new Rect(1, 2, 3, 4) };
+
+        // Infinite width.
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, 4), new Rect(1, 2, 3, 4), new Rect(1, 2, double.PositiveInfinity, 4) };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, 4), new Rect(1, 2, double.MaxValue, 4), new Rect(1, 2, double.PositiveInfinity, 4) };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, 4), new Rect(1, 2, double.PositiveInfinity, 4), new Rect(1, 2, double.PositiveInfinity, 4) };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, 4), new Rect(1, 2, double.NaN, 4), new Rect(1, 2, double.PositiveInfinity, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, double.PositiveInfinity, 4), new Rect(1, 2, double.PositiveInfinity, 4) };
+
+        // Infinite height.
+        yield return new object[] { new Rect(1, 2, 3, double.PositiveInfinity), new Rect(1, 2, 3, 4), new Rect(1, 2, 3, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, 3, double.PositiveInfinity), new Rect(1, 2, 3, double.MaxValue), new Rect(1, 2, 3, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, 3, double.PositiveInfinity), new Rect(1, 2, 3, double.PositiveInfinity), new Rect(1, 2, 3, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, 3, double.PositiveInfinity), new Rect(1, 2, 3, double.NaN), new Rect(1, 2, 3, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, double.PositiveInfinity), new Rect(1, 2, 3, double.PositiveInfinity) };
+
+        // Infinite width & height.
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), new Rect(1, 2, 3, 4), new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), new Rect(1, 2, double.MaxValue, double.MaxValue), new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), new Rect(1, 2, double.NaN, double.NaN), new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity) };
+
+        // NaN width.
+        yield return new object[] { new Rect(1, 2, double.NaN, 4), new Rect(1, 2, 3, 4), new Rect(1, 2, double.NaN, 4) };
+        yield return new object[] { new Rect(1, 2, double.NaN, 4), new Rect(1, 2, double.MaxValue, 4), new Rect(1, 2, double.NaN, 4) };
+        yield return new object[] { new Rect(1, 2, double.NaN, 4), new Rect(1, 2, double.PositiveInfinity, 4), new Rect(1, 2, double.PositiveInfinity, 4) };
+        yield return new object[] { new Rect(1, 2, double.NaN, 4), new Rect(1, 2, double.NaN, 4), new Rect(1, 2, double.NaN, 4) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, double.NaN, 4), new Rect(1, 2, double.NaN, 4) };
+
+        // NaN height.
+        yield return new object[] { new Rect(1, 2, 3, double.NaN), new Rect(1, 2, 3, 4), new Rect(1, 2, 3, double.NaN) };
+        yield return new object[] { new Rect(1, 2, 3, double.NaN), new Rect(1, 2, 3, double.MaxValue), new Rect(1, 2, 3, double.NaN) };
+        yield return new object[] { new Rect(1, 2, 3, double.NaN), new Rect(1, 2, 3, double.PositiveInfinity), new Rect(1, 2, 3, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, 3, double.NaN), new Rect(1, 2, 3, double.NaN), new Rect(1, 2, 3, double.NaN) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, 3, double.NaN), new Rect(1, 2, 3, double.NaN) };
+
+        // NaN width & height.
+        yield return new object[] { new Rect(1, 2, double.NaN, double.NaN), new Rect(1, 2, 3, 4), new Rect(1, 2, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(1, 2, double.NaN, double.NaN), new Rect(1, 2, double.MaxValue, double.MaxValue), new Rect(1, 2, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(1, 2, double.NaN, double.NaN), new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity), new Rect(1, 2, double.PositiveInfinity, double.PositiveInfinity) };
+        yield return new object[] { new Rect(1, 2, double.NaN, double.NaN), new Rect(1, 2, double.NaN, double.NaN), new Rect(1, 2, double.NaN, double.NaN) };
+        yield return new object[] { new Rect(1, 2, 3, 4), new Rect(1, 2, double.NaN, double.NaN), new Rect(1, 2, double.NaN, double.NaN) };
+
+        // Zero.
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(1, 2, 3, 4), new Rect(0, 0, 4, 6) };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(1, 2, 0, 4), new Rect(0, 0, 1, 6) };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(1, 2, 3, 0), new Rect(0, 0, 4, 2) };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(1, 0, 0, 0), new Rect(0, 0, 1, 0) };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(0, 1, 0, 0), new Rect(0, 0, 0, 1) };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(0, 0, 1, 0), new Rect(0, 0, 1, 0) };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(0, 0, 0, 1), new Rect(0, 0, 0, 1) };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(0, 0, 0, 0), new Rect(0, 0, 0, 0) };
+        yield return new object[] { new Rect(0, 0, 0, 0), new Rect(), new Rect(0, 0, 0, 0) };
+        yield return new object[] { new Rect(0, 0, 0, 0), Rect.Empty, new Rect(0, 0, 0, 0) };
+
+        // Default.
+        yield return new object[] { new Rect(), new Rect(1, 2, 3, 4), new Rect(0, 0, 4, 6) };
+        yield return new object[] { new Rect(), new Rect(1, 2, 0, 4), new Rect(0, 0, 1, 6) };
+        yield return new object[] { new Rect(), new Rect(1, 2, 3, 0), new Rect(0, 0, 4, 2) };
+        yield return new object[] { new Rect(), new Rect(1, 0, 0, 0), new Rect(0, 0, 1, 0) };
+        yield return new object[] { new Rect(), new Rect(0, 1, 0, 0), new Rect(0, 0, 0, 1) };
+        yield return new object[] { new Rect(), new Rect(0, 0, 1, 0), new Rect(0, 0, 1, 0) };
+        yield return new object[] { new Rect(), new Rect(0, 0, 0, 1), new Rect(0, 0, 0, 1) };
+        yield return new object[] { new Rect(), new Rect(0, 0, 0, 0), new Rect(0, 0, 0, 0) };
+        yield return new object[] { new Rect(), new Rect(), new Rect(0, 0, 0, 0) };
+        yield return new object[] { new Rect(), Rect.Empty, new Rect(0, 0, 0, 0) };
+
+        // Empty.
+        yield return new object[] { Rect.Empty, new Rect(1, 2, 3, 4), new Rect(1, 2, 3, 4) };
+        yield return new object[] { Rect.Empty, new Rect(1, 2, 0, 4), new Rect(1, 2, 0, 4) };
+        yield return new object[] { Rect.Empty, new Rect(1, 2, 3, 0), new Rect(1, 2, 3, 0) };
+        yield return new object[] { Rect.Empty, new Rect(1, 0, 0, 0), new Rect(1, 0, 0, 0) };
+        yield return new object[] { Rect.Empty, new Rect(0, 1, 0, 0), new Rect(0, 1, 0, 0) };
+        yield return new object[] { Rect.Empty, new Rect(0, 0, 1, 0), new Rect(0, 0, 1, 0) };
+        yield return new object[] { Rect.Empty, new Rect(0, 0, 0, 1), new Rect(0, 0, 0, 1) };
+        yield return new object[] { Rect.Empty, new Rect(0, 0, 0, 0), new Rect(0, 0, 0, 0) };
+        yield return new object[] { Rect.Empty, new Rect(), new Rect(0, 0, 0, 0) };
+        yield return new object[] { Rect.Empty, Rect.Empty, Rect.Empty };
+    }
+
+    [Theory]
+    [MemberData(nameof(Union_Rect_TestData))]
+    public void Union_InvokeRect_ReturnsExpected(Rect rect1, Rect rect2, Rect expected)
+    {
+        Rect copy1 = rect1;
+        Rect copy2 = rect2;
+
+        Assert.Equal(expected, Rect.Union(rect1, rect2));
+        Assert.Equal(copy1, rect1);
+        Assert.Equal(copy2, rect2);
+
+        Assert.Equal(expected, Rect.Union(rect2, rect1));
+        Assert.Equal(copy1, rect1);
+        Assert.Equal(copy2, rect2);
+        
+        rect1.Union(rect2);
+        Assert.Equal(expected, rect1);
+        Assert.Equal(copy2, rect2);
+    }
+
+    [Fact]
+    public void TypeConverter_Get_ReturnsExpected()
+    {
+        Assert.IsType<RectConverter>(TypeDescriptor.GetConverter(typeof(Rect)));
+    }
+
+    [Fact]
+    public void ValueSerializer_Get_ReturnsExpected()
+    {
+        Assert.IsType<RectValueSerializer>(ValueSerializer.GetSerializerFor(typeof(Rect)));
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/SizeConverterTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/SizeConverterTests.cs
new file mode 100644
index 00000000000..0afbb79c95e
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/SizeConverterTests.cs
@@ -0,0 +1,198 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.ComponentModel.Design.Serialization;
+using System.Globalization;
+
+namespace System.Windows.Tests;
+
+public class SizeConverterTests
+{
+    [Theory]
+    [InlineData(null, false)]
+    [InlineData(typeof(object), false)]
+    [InlineData(typeof(string), true)]
+    [InlineData(typeof(InstanceDescriptor), false)]
+    [InlineData(typeof(Size), false)]
+    public void CanConvertTo_Invoke_ReturnsExpected(Type? destinationType, bool expected)
+    {
+        var converter = new SizeConverter();
+        Assert.Equal(expected, converter.CanConvertTo(null, destinationType));
+        Assert.Equal(expected, converter.CanConvertTo(new CustomTypeDescriptorContext(), destinationType));
+    }
+    
+    [Theory]
+    [MemberData(nameof(SizeTests.ToString_TestData), MemberType = typeof(SizeTests))]
+    public void ConvertTo_InvokeSizeToString_ReturnsExpected(Size matrix, string expected)
+    {
+        var converter = new SizeConverter();
+        Assert.Equal(expected, converter.ConvertTo(matrix, typeof(string)));
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), null, matrix, typeof(string)));
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, matrix, typeof(string)));
+    }
+    
+    [Theory]
+    [MemberData(nameof(SizeTests.ToString_IFormatProviderCustom_TestData), MemberType = typeof(SizeTests))]
+    public void ConvertTo_InvokeSizeToStringCustomCulture_ReturnsExpected(Size matrix, string numberDecimalSeparator, string expected)
+    {
+        var culture = new CultureInfo("en-US");
+        NumberFormatInfo formatInfo = culture.NumberFormat;
+        formatInfo.NumberDecimalSeparator = numberDecimalSeparator;
+
+        var converter = new SizeConverter();
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), culture, matrix, typeof(string)));
+    }
+
+    [Theory]
+    [InlineData(null, "")]
+    [InlineData("", "")]
+    [InlineData("value", "value")]
+    [InlineData(1, "1")]
+    public void ConvertTo_InvokeNotSizeToString_ReturnsExpected(object? value, string expected)
+    {
+        var converter = new SizeConverter();
+        Assert.Equal(expected, converter.ConvertTo(value, typeof(string)));
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), null, value, typeof(string)));
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value, typeof(string)));
+    }
+
+    public static IEnumerable<object?[]> ConvertTo_CantConvert_TestData()
+    {
+        yield return new object?[] { null, typeof(object) };
+        yield return new object?[] { string.Empty, typeof(object) };
+        yield return new object?[] { "value", typeof(object) };
+        yield return new object?[] { new object(), typeof(object) };
+        yield return new object?[] { new Size(), typeof(object) };
+        
+        yield return new object?[] { null, typeof(Size) };
+        yield return new object?[] { string.Empty, typeof(Size) };
+        yield return new object?[] { "value", typeof(Size) };
+        yield return new object?[] { new object(), typeof(Size) };
+        yield return new object?[] { new Size(), typeof(Size) };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertTo_CantConvert_TestData))]
+    public void ConvertTo_CantConvert_ThrowsNotSupportedException(object value, Type destinationType)
+    {
+        var converter = new SizeConverter();
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(value, destinationType));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(null, null, value, destinationType));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value, destinationType));
+    }
+
+    public static IEnumerable<object?[]> ConvertTo_NullDestinationType_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { string.Empty };
+        yield return new object?[] { "value" };
+        yield return new object?[] { new object() };
+        yield return new object?[] { new Size() };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertTo_NullDestinationType_TestData))]
+    public void ConvertTo_NullDestinationType_ThrowsArgumentNullException(object value)
+    {
+        var converter = new SizeConverter();
+        Assert.Throws<ArgumentNullException>("destinationType", () => converter.ConvertTo(value, null!));
+        Assert.Throws<ArgumentNullException>("destinationType", () => converter.ConvertTo(null, null, new Size(), null!));
+        Assert.Throws<ArgumentNullException>("destinationType", () => converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, new Size(), null!));
+    }
+
+    [Theory]
+    [InlineData(null, false)]
+    [InlineData(typeof(object), false)]
+    [InlineData(typeof(string), true)]
+    [InlineData(typeof(InstanceDescriptor), true)]
+    [InlineData(typeof(Size), false)]
+    public void CanConvertFrom_Invoke_ReturnsExpected(Type? sourceType, bool expected)
+    {
+        var converter = new SizeConverter();
+        Assert.Equal(expected, converter.CanConvertFrom(sourceType!));
+        Assert.Equal(expected, converter.CanConvertFrom(null, sourceType));
+        Assert.Equal(expected, converter.CanConvertFrom(new CustomTypeDescriptorContext(), sourceType));
+    }
+
+    [Theory]
+    [MemberData(nameof(SizeTests.Parse_TestData), MemberType = typeof(SizeTests))]
+    public void ConvertFrom_InvokeStringValue_ReturnsExpected(object value, Size expected)
+    {
+        var converter = new SizeConverter();
+        Assert.Equal(expected, converter.ConvertFrom(value));
+        Assert.Equal(expected, converter.ConvertFrom(null, null, value));
+        Assert.Equal(expected, converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    [Fact]
+    public void ConvertFrom_NullValue_ThrowsNotSupportedException()
+    {
+        var converter = new SizeConverter();
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(null!));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(null, null, null));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, null));
+    }
+
+    [Theory]
+    [MemberData(nameof(SizeTests.Parse_InvalidSource_TestData), MemberType = typeof(SizeTests))]
+    public void ConvertFrom_InvalidStringValue_ThrowsInvalidOperationException(object value)
+    {
+        var converter = new SizeConverter();
+        Assert.Throws<InvalidOperationException>(() => converter.ConvertFrom(value));
+        Assert.Throws<InvalidOperationException>(() => converter.ConvertFrom(null, null, value));
+        Assert.Throws<InvalidOperationException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    [Theory]
+    [MemberData(nameof(SizeTests.Parse_NotDouble_TestData), MemberType = typeof(SizeTests))]
+    public void ConvertFrom_NotDoubleStringValue_ThrowsFormatException(object value)
+    {
+        var converter = new SizeConverter();
+        Assert.Throws<FormatException>(() => converter.ConvertFrom(value));
+        Assert.Throws<FormatException>(() => converter.ConvertFrom(null, null, value));
+        Assert.Throws<FormatException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    [Theory]
+    [MemberData(nameof(SizeTests.Parse_Negative_TestData), MemberType = typeof(SizeTests))]
+    public void ConvertFrom_Negative_ThrowsArgumentException(object value)
+    {
+        var converter = new SizeConverter();
+        Assert.Throws<ArgumentException>(() => converter.ConvertFrom(value));
+        Assert.Throws<ArgumentException>(() => converter.ConvertFrom(null, null, value));
+        Assert.Throws<ArgumentException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    public static IEnumerable<object[]> ConvertFrom_CantConvert_TestData()
+    {
+        yield return new object[] { new object() };
+        yield return new object[] { new Size() };
+    }
+    
+    [Theory]
+    [MemberData(nameof(ConvertFrom_CantConvert_TestData))]
+    public void ConvertFrom_CantConvert_ThrowsNotSupportedException(object value)
+    {
+        var converter = new SizeConverter();
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(value));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(null, null, value));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    private class CustomTypeDescriptorContext : ITypeDescriptorContext
+    {
+        public IContainer Container => throw new NotImplementedException();
+
+        public object Instance => throw new NotImplementedException();
+
+        public PropertyDescriptor PropertyDescriptor => throw new NotImplementedException();
+
+        public object? GetService(Type serviceType) => throw new NotImplementedException();
+
+        public void OnComponentChanged() => throw new NotImplementedException();
+
+        public bool OnComponentChanging() => throw new NotImplementedException();
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/SizeTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/SizeTests.cs
new file mode 100644
index 00000000000..5ae7ca1cf1a
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/SizeTests.cs
@@ -0,0 +1,576 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.Globalization;
+using System.Windows.Converters;
+using System.Windows.Markup;
+
+namespace System.Windows.Tests;
+
+public class SizeTests
+{
+    [Fact]
+    public void Ctor_Default()
+    {
+        var size = new Size();
+        Assert.Equal(0, size.Width);
+        Assert.Equal(0, size.Height);
+        Assert.False(size.IsEmpty);
+    }
+
+    [Theory]
+    [InlineData(double.NegativeZero, double.NegativeZero)]
+    [InlineData(0, 0)]
+    [InlineData(1, 0)]
+    [InlineData(0, 2)]
+    [InlineData(0.1, 0.2)]
+    [InlineData(1, 2)]
+    [InlineData(double.MaxValue, double.MaxValue)]
+    [InlineData(double.PositiveInfinity, double.PositiveInfinity)]
+    [InlineData(double.NaN, double.NaN)]
+    [InlineData(double.NaN, 1)]
+    [InlineData(1, double.NaN)]
+    public void Ctor_Double_Double(double width, double height)
+    {
+        var size = new Size(width, height);
+        Assert.Equal(width, size.Width);
+        Assert.Equal(height, size.Height);
+        Assert.False(size.IsEmpty);
+    }
+
+    [Theory]
+    [InlineData(double.NegativeInfinity)]
+    [InlineData(double.MinValue)]
+    [InlineData(-1)]
+    public void Ctor_NegativeWidth_ThrowsArgumentException(double width)
+    {
+        // TODO: should have paramName
+        Assert.Throws<ArgumentException>(() => new Size(width, 0));
+    }
+
+    [Theory]
+    [InlineData(double.NegativeInfinity)]
+    [InlineData(double.MinValue)]
+    [InlineData(-1)]
+    public void Ctor_NegativeHeight_ThrowsArgumentException(double height)
+    {
+        // TODO: should have paramName
+        Assert.Throws<ArgumentException>(() => new Size(0, height));
+    }
+
+    [Fact]
+    public void Empty_Get_ReturnsExpected()
+    {
+        Size size = Size.Empty;
+        Assert.Equal(double.NegativeInfinity, size.Width);
+        Assert.Equal(double.NegativeInfinity, size.Height);
+        Assert.True(size.IsEmpty);
+    }
+
+    [Theory]
+    [InlineData(double.NegativeZero)]
+    [InlineData(0)]
+    [InlineData(0.2)]
+    [InlineData(1)]
+    [InlineData(double.MaxValue)]
+    [InlineData(double.PositiveInfinity)]
+    [InlineData(double.NaN)]
+    public void Width_Set_GetReturnsExpected(double value)
+    {
+        var size = new Size();
+
+        // Set.
+        size.Width = value;
+        Assert.Equal(value, size.Width);
+
+        // Set same.
+        size.Width = value;
+        Assert.Equal(value, size.Width);
+    }
+
+    [Theory]
+    [InlineData(double.NegativeInfinity)]
+    [InlineData(double.MinValue)]
+    [InlineData(-1)]
+    public void Width_SetNegative_ThrowsArgumentException(double value)
+    {
+        var size = new Size();
+        // TODO: should have paramName
+        Assert.Throws<ArgumentException>(() => size.Width = value);
+    }
+
+    [Theory]
+    [InlineData(-1)]
+    [InlineData(1)]
+    public void Width_SetEmpty_ThrowsInvalidOperationException(double value)
+    {
+        var size = Size.Empty;
+        Assert.Throws<InvalidOperationException>(() => size.Width = value);
+    }
+
+    [Theory]
+    [InlineData(double.NegativeZero)]
+    [InlineData(0)]
+    [InlineData(0.2)]
+    [InlineData(1)]
+    [InlineData(double.MaxValue)]
+    [InlineData(double.PositiveInfinity)]
+    [InlineData(double.NaN)]
+    public void Height_Set_GetReturnsExpected(double value)
+    {
+        var size = new Size();
+
+        // Set.
+        size.Height = value;
+        Assert.Equal(value, size.Height);
+
+        // Set same.
+        size.Height = value;
+        Assert.Equal(value, size.Height);
+    }
+
+    [Theory]
+    [InlineData(double.NegativeInfinity)]
+    [InlineData(double.MinValue)]
+    [InlineData(-1)]
+    public void Height_SetNegative_ThrowsArgumentException(double value)
+    {
+        var size = new Size();
+        // TODO: should have paramName
+        Assert.Throws<ArgumentException>(() => size.Height = value);
+    }
+
+    [Theory]
+    [InlineData(-1)]
+    [InlineData(1)]
+    public void Height_SetEmpty_ThrowsInvalidOperationException(double value)
+    {
+        var size = Size.Empty;
+        Assert.Throws<InvalidOperationException>(() => size.Height = value);
+    }
+
+    public static IEnumerable<object?[]> Equals_TestData()
+    {
+        // Normal size.
+        yield return new object?[] { new Size(1, 2), new Size(1, 2), true, true };
+        yield return new object?[] { new Size(1, 2), new Size(2, 2), false, false };
+        yield return new object?[] { new Size(1, 2), new Size(1, 3), false, false };
+        yield return new object?[] { new Size(1, 2), new Size(double.NaN, 2), false, false };
+        yield return new object?[] { new Size(1, 2), new Size(1, double.NaN), false, false };
+        yield return new object?[] { new Size(1, 2), new Size(double.NaN, double.NaN), false, false };
+        yield return new object?[] { new Size(1, 2), new Size(0, 0), false, false };
+        yield return new object?[] { new Size(1, 2), new Size(), false, false };
+        yield return new object?[] { new Size(1, 2), Size.Empty, false, false };
+
+        // NaN width.
+        yield return new object[] { new Size(double.NaN, 2), new Size(double.NaN, 2), true, true };
+        yield return new object[] { new Size(double.NaN, 2), new Size(2, 2), false, false };
+        yield return new object[] { new Size(double.NaN, 2), new Size(double.NaN, double.NaN), false, false };
+
+        // NaN height.
+        yield return new object[] { new Size(1, double.NaN), new Size(1, double.NaN), true, true };
+        yield return new object[] { new Size(1, double.NaN), new Size(1, 2), false, false };
+        yield return new object[] { new Size(1, double.NaN), new Size(double.NaN, double.NaN), false, false };
+
+        // NaN width & height.
+        yield return new object[] { new Size(double.NaN, double.NaN), new Size(double.NaN, double.NaN), true, true };
+        yield return new object[] { new Size(double.NaN, double.NaN), new Size(1, 2), false, false };
+        yield return new object[] { new Size(double.NaN, double.NaN), new Size(double.NaN, 2), false, false };
+        yield return new object[] { new Size(double.NaN, double.NaN), new Size(1, double.NaN), false, false };
+
+        // Zero.
+        yield return new object?[] { new Size(0, 0), new Size(), true, true };
+        yield return new object?[] { new Size(0, 0), new Size(0, 0), true, true };
+        yield return new object?[] { new Size(0, 0), new Size(1, 0), false, false };
+        yield return new object?[] { new Size(0, 0), new Size(0, 1), false, false };
+        yield return new object?[] { new Size(0, 0), Size.Empty, false, true };
+
+        // Default.
+        yield return new object?[] { new Size(), new Size(), true, true };
+        yield return new object?[] { new Size(), new Size(0, 0), true, true };
+        yield return new object?[] { new Size(), new Size(1, 0), false, false };
+        yield return new object?[] { new Size(), new Size(0, 1), false, false };
+        yield return new object?[] { new Size(), Size.Empty, false, true };
+
+        // Empty.
+        yield return new object?[] { Size.Empty, Size.Empty, true, true };
+        yield return new object?[] { Size.Empty, new Size(1, 2), false, false };
+        yield return new object?[] { Size.Empty, new Size(), false, true };
+        yield return new object?[] { Size.Empty, new Size(0, 0), false, true };
+
+        // Other.
+        yield return new object?[] { Size.Empty, new object(), false, false };
+        yield return new object?[] { Size.Empty, null, false, false };
+        yield return new object?[] { new Size(), new object(), false, false };
+        yield return new object?[] { new Size(), null, false, false };
+        yield return new object?[] { new Size(0, 0), new object(), false, false };
+        yield return new object?[] { new Size(0, 0), null, false, false };
+        yield return new object?[] { new Size(1, 2), new object(), false, false };
+        yield return new object?[] { new Size(1, 2), null, false, false };
+    }
+
+    [Theory]
+    [MemberData(nameof(Equals_TestData))]
+    public void Equals_Object_ReturnsExpected(Size size, object o, bool expected, bool expectedHashCode)
+    {
+        Assert.Equal(expected, size.Equals(o));
+        if (o is Size value)
+        {
+            Assert.Equal(expected, size.Equals(value));
+            Assert.Equal(expected, value.Equals(size));
+            Assert.Equal(expected, Size.Equals(size, value));
+            Assert.Equal(expected, Size.Equals(value, size));
+            Assert.Equal(expectedHashCode, size.GetHashCode().Equals(value.GetHashCode()));
+        }
+    }
+
+    public static IEnumerable<object[]> EqualityOperator_TestData()
+    {
+        // Normal size.
+        yield return new object[] { new Size(1, 2), new Size(1, 2), true };
+        yield return new object[] { new Size(1, 2), new Size(2, 2), false };
+        yield return new object[] { new Size(1, 2), new Size(1, 3), false };
+        yield return new object[] { new Size(1, 2), new Size(double.NaN, 2), false };
+        yield return new object[] { new Size(1, 2), new Size(1, double.NaN), false };
+        yield return new object[] { new Size(1, 2), new Size(double.NaN, double.NaN), false };
+        yield return new object[] { new Size(1, 2), new Size(0, 0), false };
+        yield return new object[] { new Size(1, 2), new Size(), false };
+        yield return new object[] { new Size(1, 2), Size.Empty, false };
+
+        // NaN width.
+        yield return new object[] { new Size(double.NaN, 2), new Size(double.NaN, 2), false };
+        yield return new object[] { new Size(double.NaN, 2), new Size(2, 2), false };
+        yield return new object[] { new Size(double.NaN, 2), new Size(double.NaN, double.NaN), false };
+
+        // NaN height.
+        yield return new object[] { new Size(1, double.NaN), new Size(1, double.NaN), false };
+        yield return new object[] { new Size(1, double.NaN), new Size(1, 2), false };
+        yield return new object[] { new Size(1, double.NaN), new Size(double.NaN, double.NaN), false };
+
+        // NaN width & height.
+        yield return new object[] { new Size(double.NaN, double.NaN), new Size(double.NaN, double.NaN), false };
+        yield return new object[] { new Size(double.NaN, double.NaN), new Size(1, 2), false };
+        yield return new object[] { new Size(double.NaN, double.NaN), new Size(double.NaN, 2), false };
+        yield return new object[] { new Size(double.NaN, double.NaN), new Size(1, double.NaN), false };
+
+        // Zero.
+        yield return new object[] { new Size(0, 0), new Size(), true };
+        yield return new object[] { new Size(0, 0), new Size(0, 0), true };
+        yield return new object[] { new Size(0, 0), new Size(1, 0), false };
+        yield return new object[] { new Size(0, 0), new Size(0, 1), false };
+        yield return new object[] { new Size(0, 0), Size.Empty, false };
+
+        // Default.
+        yield return new object[] { new Size(), new Size(), true };
+        yield return new object[] { new Size(), new Size(0, 0), true };
+        yield return new object[] { new Size(), new Size(1, 0), false };
+        yield return new object[] { new Size(), new Size(0, 1), false };
+        yield return new object[] { new Size(), Size.Empty, false };
+
+        // Empty.
+        yield return new object[] { Size.Empty, Size.Empty, true };
+        yield return new object[] { Size.Empty, new Size(1, 2), false };
+        yield return new object[] { Size.Empty, new Size(), false };
+        yield return new object[] { Size.Empty, new Size(0, 0), false };
+    }
+
+    [Theory]
+    [MemberData(nameof(EqualityOperator_TestData))]
+    public void EqualityOperator_Invoke_ReturnsExpected(Size size, Size value, bool expected)
+    {
+        Assert.Equal(expected, size == value);
+        Assert.Equal(expected, value == size);
+        Assert.Equal(!expected, size != value);
+        Assert.Equal(!expected, value != size);
+    }
+
+    [Fact]
+    public void GetHashCode_InvokeDefault_ReturnsEqual()
+    {
+        var size = new Size();
+        Assert.Equal(0, size.GetHashCode());
+        Assert.Equal(size.GetHashCode(), size.GetHashCode());
+    }
+
+    [Fact]
+    public void GetHashCode_InvokeEmpty_ReturnsEqual()
+    {
+        Size size = Size.Empty;
+        Assert.Equal(0, size.GetHashCode());
+        Assert.Equal(size.GetHashCode(), size.GetHashCode());
+    }
+
+    [Fact]
+    public void GetHashCode_InvokeNormal_ReturnsEqual()
+    {
+        var size = new Size(1, 2);
+        Assert.NotEqual(0, size.GetHashCode());
+        Assert.Equal(size.GetHashCode(), size.GetHashCode());
+    }
+
+    public static IEnumerable<object[]> Parse_TestData()
+    {
+        yield return new object[] { "Empty", Size.Empty };
+        yield return new object[] { "  Empty  ", Size.Empty };
+        yield return new object[] { "0,0", new Size(0, 0) };
+        yield return new object[] { "1,2", new Size(1, 2) };
+        yield return new object[] { "1.1,2.2", new Size(1.1, 2.2) };
+        yield return new object[] { "   1   ,   2  ", new Size(1, 2) };
+    }
+
+    [Theory]
+    [MemberData(nameof(Parse_TestData))]
+    public void Parse_Invoke_Success(string source, Size expected)
+    {
+        Size result = Size.Parse(source);
+        Assert.Equal(expected.Width, result.Width, precision: 5);
+        Assert.Equal(expected.Height, result.Height, precision: 5);
+    }
+
+    [Fact]
+    public void Parse_NullSource_ThrowsInvalidOperationException()
+    {
+        Assert.Throws<InvalidOperationException>(() => Size.Parse(null));
+    }
+
+    public static IEnumerable<object[]> Parse_InvalidSource_TestData()
+    {
+        yield return new object[] { "" };
+        yield return new object[] { "  " };
+        yield return new object[] { "," };
+        yield return new object[] { "1" };
+        yield return new object[] { "1," };
+        yield return new object[] { "1,2," };
+        yield return new object[] { "1,2,3" };
+        yield return new object[] { "1,2,test" };
+        yield return new object[] { "Empty," };
+        yield return new object[] { "Identity," };
+    }
+
+    [Theory]
+    [MemberData(nameof(Parse_InvalidSource_TestData))]
+    public void Parse_InvalidSource_ThrowsInvalidOperationException(string source)
+    {
+        Assert.Throws<InvalidOperationException>(() => Size.Parse(source));
+    }
+
+    public static IEnumerable<object[]> Parse_NotDouble_TestData()
+    {
+        yield return new object[] { "Identity" };
+        yield return new object[] { " Identity " };
+        yield return new object[] { "Identity,2" };
+        yield return new object[] { "test" };
+        yield return new object[] { "test,2" };
+        yield return new object[] { "1,test" };
+        yield return new object[] { "1,test,3" };
+        yield return new object[] { "1;2" };
+        yield return new object[] { "1.2.3" };
+        yield return new object[] { """1"",""2""" };
+    }
+
+    [Theory]
+    [MemberData(nameof(Parse_NotDouble_TestData))]
+    public void Parse_NotDouble_ThrowsFormatException(string source)
+    {
+        Assert.Throws<FormatException>(() => Size.Parse(source));
+    }
+
+    public static IEnumerable<object[]> Parse_Negative_TestData()
+    {
+        yield return new object[] { "-1,2" };
+        yield return new object[] { "1,-2" };
+    }
+
+    [Theory]
+    [MemberData(nameof(Parse_Negative_TestData))]
+    public void Parse_Negative_ThrowsArgumentException(string source)
+    {
+        Assert.Throws<ArgumentException>(() => Size.Parse(source));
+    }
+
+    public static IEnumerable<object[]> ToString_TestData()
+    {
+        yield return new object[] { Size.Empty, "Empty" };
+        yield return new object[] { new Size(), "0,0" };
+        yield return new object[] { new Size(0, 0), "0,0" };
+        yield return new object[] { new Size(1.1, 2.2), "1.1,2.2" };
+        yield return new object[] { new Size(1, 2), "1,2" };
+    }
+
+    [Theory]
+    [MemberData(nameof(ToString_TestData))]
+    public void ToString_Invoke_ReturnsExpected(Size size, string expected)
+    {
+        Assert.Equal(expected, size.ToString());
+    }
+
+    [Theory]
+    [MemberData(nameof(ToString_TestData))]
+    public void ToString_InvokeIFormatProviderInvariantCulture_ReturnsExpected(Size size, string expected)
+    {
+        Assert.Equal(expected, size.ToString(CultureInfo.InvariantCulture));
+    }
+
+    public static IEnumerable<object[]> ToString_IFormatProviderCustom_TestData()
+    {
+        yield return new object[] { Size.Empty, "|", "Empty" };
+        yield return new object[] { Size.Empty, "|_", "Empty" };
+        yield return new object[] { Size.Empty, ",_", "Empty" };
+        yield return new object[] { Size.Empty, ",", "Empty" };
+        yield return new object[] { Size.Empty, ";", "Empty" };
+        yield return new object[] { Size.Empty, " ", "Empty" };
+
+        yield return new object[] { new Size(), "|", "0,0" };
+        yield return new object[] { new Size(), "|_", "0,0" };
+        yield return new object[] { new Size(), ",_", "0;0" };
+        yield return new object[] { new Size(), ",", "0;0" };
+        yield return new object[] { new Size(), ";", "0,0" };
+        yield return new object[] { new Size(), " ", "0,0" };
+
+        yield return new object[] { new Size(0, 0), "|", "0,0" };
+        yield return new object[] { new Size(0, 0), "|_", "0,0" };
+        yield return new object[] { new Size(0, 0), ",_", "0;0" };
+        yield return new object[] { new Size(0, 0), ",", "0;0" };
+        yield return new object[] { new Size(0, 0), ";", "0,0" };
+        yield return new object[] { new Size(0, 0), " ", "0,0" };
+
+        yield return new object[] { new Size(1, 2), "|", "1,2" };
+        yield return new object[] { new Size(1, 2), "|_", "1,2" };
+        yield return new object[] { new Size(1, 2), ",_", "1;2" };
+        yield return new object[] { new Size(1, 2), ",", "1;2" };
+        yield return new object[] { new Size(1, 2), ";", "1,2" };
+        yield return new object[] { new Size(1, 2), " ", "1,2" };
+        
+        yield return new object[] { new Size(1.1, 2.2), "|", "1|1,2|2" };
+        yield return new object[] { new Size(1.1, 2.2), "|_", "1|_1,2|_2" };
+        yield return new object[] { new Size(1.1, 2.2), ",_", "1,_1;2,_2" };
+        yield return new object[] { new Size(1.1, 2.2), ",", "1,1;2,2" };
+        yield return new object[] { new Size(1.1, 2.2), ";", "1;1,2;2" };
+        yield return new object[] { new Size(1.1, 2.2), " ", "1 1,2 2" };
+    }
+
+    [Theory]
+    [MemberData(nameof(ToString_IFormatProviderCustom_TestData))]
+    public void ToString_InvokeIFormatProviderCustom_ReturnsExpected(Size size, string numberDecimalSeparator, string expected)
+    {
+        var culture = new CultureInfo("en-US");
+        NumberFormatInfo formatInfo = culture.NumberFormat;
+        formatInfo.NumberDecimalSeparator = numberDecimalSeparator;
+
+        Assert.Equal(expected, size.ToString(formatInfo));
+    }
+
+    [Theory]
+    [MemberData(nameof(ToString_TestData))]
+    public void ToString_InvokeIFormattableInvariantCulture_ReturnsExpected(Size size, string expected)
+    {
+        IFormattable formattable = size;
+
+        Assert.Equal(expected, formattable.ToString(null, null));
+        Assert.Equal(expected, formattable.ToString(null, CultureInfo.InvariantCulture));
+    }
+
+    public static IEnumerable<object[]> ToString_IFormattableCustomFormat_TestData()
+    {
+        yield return new object[] { "|", "1|23,2|35" };
+        yield return new object[] { "|_", "1|_23,2|_35" };
+        yield return new object[] { ",_", "1,_23;2,_35" };
+        yield return new object[] { ",", "1,23;2,35" };
+        yield return new object[] { ";", "1;23,2;35" };
+        yield return new object[] { " ", "1 23,2 35" };
+    }
+
+    [Theory]
+    [MemberData(nameof(ToString_IFormattableCustomFormat_TestData))]
+    public void ToString_InvokeIFormattableCustomFormat_ReturnsExpected(string numberDecimalSeparator, string expected)
+    {
+        var size = new Size(1.23456, 2.34567);
+        IFormattable formattable = size;
+
+        var culture = new CultureInfo("en-US");
+        NumberFormatInfo formatInfo = culture.NumberFormat;
+        formatInfo.NumberDecimalSeparator = numberDecimalSeparator;
+
+        Assert.Equal(expected, formattable.ToString("F2", formatInfo));
+    }
+
+    [Fact]
+    public void OperatorConvertPoint_InvokeDefault_ReturnsExpected()
+    {
+        Point result = (Point)new Size();
+        Assert.Equal(0, result.X);
+        Assert.Equal(0, result.Y);
+    }
+
+    [Fact]
+    public void OperatorConvertPoint_InvokeEmpty_ReturnsExpected()
+    {
+        Point result = (Point)Size.Empty;
+        Assert.Equal(double.NegativeInfinity, result.X);
+        Assert.Equal(double.NegativeInfinity, result.Y);
+    }
+
+    [Theory]
+    [InlineData(0, 0)]
+    [InlineData(1, 0)]
+    [InlineData(0, 1)]
+    [InlineData(1, 1)]
+    [InlineData(1, 2)]
+    [InlineData(1.1, 2.2)]
+    [InlineData(double.NaN, double.NaN)]
+    [InlineData(double.NaN, 0)]
+    [InlineData(0, double.NaN)]
+    public void OperatorConvertPoint_InvokeNormal_ReturnsExpected(double x, double y)
+    {
+        Point result = (Point)new Size(x, y);
+        Assert.Equal(x, result.X);
+        Assert.Equal(y, result.Y);
+    }
+
+    [Fact]
+    public void OperatorConvertVector_InvokeDefault_ReturnsExpected()
+    {
+        Vector result = (Vector)new Size();
+        Assert.Equal(0, result.X);
+        Assert.Equal(0, result.Y);
+    }
+
+    [Fact]
+    public void OperatorConvertVector_InvokeEmpty_ReturnsExpected()
+    {
+        Vector result = (Vector)Size.Empty;
+        Assert.Equal(double.NegativeInfinity, result.X);
+        Assert.Equal(double.NegativeInfinity, result.Y);
+    }
+
+    [Theory]
+    [InlineData(0, 0)]
+    [InlineData(1, 0)]
+    [InlineData(0, 1)]
+    [InlineData(1, 1)]
+    [InlineData(1, 2)]
+    [InlineData(1.1, 2.2)]
+    [InlineData(double.NaN, double.NaN)]
+    [InlineData(double.NaN, 0)]
+    [InlineData(0, double.NaN)]
+    public void OperatorConvertVector_InvokeNormal_ReturnsExpected(double x, double y)
+    {
+        Vector result = (Vector)new Size(x, y);
+        Assert.Equal(x, result.X);
+        Assert.Equal(y, result.Y);
+    }
+
+    [Fact]
+    public void TypeConverter_Get_ReturnsExpected()
+    {
+        Assert.IsType<SizeConverter>(TypeDescriptor.GetConverter(typeof(Size)));
+    }
+
+    [Fact]
+    public void ValueSerializer_Get_ReturnsExpected()
+    {
+        Assert.IsType<SizeValueSerializer>(ValueSerializer.GetSerializerFor(typeof(Size)));
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/SplashScreenTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/SplashScreenTests.cs
new file mode 100644
index 00000000000..b5b16c6d116
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/SplashScreenTests.cs
@@ -0,0 +1,70 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Reflection;
+using System.Resources;
+
+namespace System.Windows.Tests;
+
+public class SplashScreenTests
+{
+    [Theory]
+    [InlineData(" ")]
+    [InlineData("resourceName")]
+    public void Ctor_String(string resourceName)
+    {
+        new SplashScreen(resourceName);
+    }
+
+    [Theory]
+    [InlineData(" ")]
+    [InlineData("resourceName")]
+    public void Ctor_Assembly_String(string resourceName)
+    {
+        new SplashScreen(Assembly.GetEntryAssembly(), resourceName);
+    }
+
+    [Fact]
+    public void Ctor_NullResourceName_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("resourceName", () => new SplashScreen(null));
+        Assert.Throws<ArgumentNullException>("resourceName", () => new SplashScreen(Assembly.GetEntryAssembly(), null));
+    }
+    
+    [Fact]
+    public void Ctor_EmptyResourceName_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("resourceName", () => new SplashScreen(string.Empty));
+        Assert.Throws<ArgumentNullException>("resourceName", () => new SplashScreen(Assembly.GetEntryAssembly(), string.Empty));
+    }
+
+    [Fact]
+    public void Ctor_NullResourceAssembly_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("resourceAssembly", () => new SplashScreen(null!, "resourceName"));
+    }
+    
+    [Theory]
+    [InlineData(" ")]
+    [InlineData("resourceName")]
+    public void Close_NotShown_Nop(string resourceName)
+    {
+        var splashScreen = new SplashScreen(resourceName);
+        splashScreen.Close(TimeSpan.Zero);
+    }
+    
+    [Theory]
+    [InlineData(" ")]
+    [InlineData("resourceName")]
+    public void Show_NoSuchResource_ThrowsMissingManifestResourceException(string resourceName)
+    {
+        var splashScreen = new SplashScreen(resourceName);
+        Assert.Throws<MissingManifestResourceException>(() => splashScreen.Show(false));
+        Assert.Throws<MissingManifestResourceException>(() => splashScreen.Show(true));
+        Assert.Throws<MissingManifestResourceException>(() => splashScreen.Show(false, false));
+        Assert.Throws<MissingManifestResourceException>(() => splashScreen.Show(false, true));
+        Assert.Throws<MissingManifestResourceException>(() => splashScreen.Show(true, false));
+        Assert.Throws<MissingManifestResourceException>(() => splashScreen.Show(true, true));
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherFrameTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherFrameTests.cs
new file mode 100644
index 00000000000..2345c87f14c
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherFrameTests.cs
@@ -0,0 +1,46 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Windows.Threading.Tests;
+
+public class DispatcherFrameTests
+{
+    [Fact]
+    public void Ctor_Default()
+    {
+        var frame = new DispatcherFrame();
+        Assert.True(frame.Continue);
+        Assert.NotNull(frame.Dispatcher);
+        Assert.Same(frame.Dispatcher, frame.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, frame.Dispatcher);
+    }
+
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void Ctor_Bool(bool exitWhenRequested)
+    {
+        var frame = new DispatcherFrame(exitWhenRequested);
+        Assert.True(frame.Continue);
+        Assert.NotNull(frame.Dispatcher);
+        Assert.Same(frame.Dispatcher, frame.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, frame.Dispatcher);
+    }
+
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void Continue_Set_GetReturnsExpected(bool value)
+    {
+        var frame = new DispatcherFrame();
+
+        // Set same.
+        frame.Continue = value;
+        Assert.Equal(value, frame.Continue);
+
+        // Set different.
+        frame.Continue = !value;
+        Assert.Equal(!value, frame.Continue);
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherHookEventArgsTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherHookEventArgsTests.cs
new file mode 100644
index 00000000000..c2dd90de9a8
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherHookEventArgsTests.cs
@@ -0,0 +1,27 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Windows.Threading.Tests;
+
+public class DispatcherHookEventArgsTests
+{
+    [Fact]
+    public void Ctor_DispatcherOperation()
+    {
+        Dispatcher dispatcher = Dispatcher.CurrentDispatcher;
+        DispatcherOperation operation = dispatcher.BeginInvoke(() => {});
+
+        var args = new DispatcherHookEventArgs(operation);
+        Assert.Same(dispatcher, args.Dispatcher);
+        Assert.Same(operation, args.Operation);
+    }
+
+    [Fact]
+    public void Ctor_NullOperation()
+    {
+        var args = new DispatcherHookEventArgs(null);
+        Assert.Null(args.Dispatcher);
+        Assert.Null(args.Operation);
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherHooksTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherHooksTests.cs
new file mode 100644
index 00000000000..74e1789aaca
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherHooksTests.cs
@@ -0,0 +1,167 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Windows.Threading.Tests;
+
+public class DispatcherHooksTests
+{
+    // TODO
+    // - actually raising events
+
+    [Fact]
+    public void DispatcherInactive_AddRemove_Success()
+    {
+        Dispatcher dispatcher = Dispatcher.CurrentDispatcher;
+        DispatcherHooks hooks = dispatcher.Hooks;
+        int callCount = 0;
+        EventHandler handler = (s, e) => callCount++;
+        hooks.DispatcherInactive += handler;
+        Assert.Equal(0, callCount);
+
+        hooks.DispatcherInactive -= handler;
+        Assert.Equal(0, callCount);
+
+        // Remove non existent.
+        hooks.DispatcherInactive -= handler;
+        Assert.Equal(0, callCount);
+
+        // Add null.
+        hooks.DispatcherInactive += null;
+        Assert.Equal(0, callCount);
+
+        // Remove null.
+        hooks.DispatcherInactive -= null;
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void OperationPosted_AddRemove_Success()
+    {
+        Dispatcher dispatcher = Dispatcher.CurrentDispatcher;
+        DispatcherHooks hooks = dispatcher.Hooks;
+        int callCount = 0;
+        DispatcherHookEventHandler handler = (s, e) => callCount++;
+        hooks.OperationPosted += handler;
+        Assert.Equal(0, callCount);
+
+        hooks.OperationPosted -= handler;
+        Assert.Equal(0, callCount);
+
+        // Remove non existent.
+        hooks.OperationPosted -= handler;
+        Assert.Equal(0, callCount);
+
+        // Add null.
+        hooks.OperationPosted += null;
+        Assert.Equal(0, callCount);
+
+        // Remove null.
+        hooks.OperationPosted -= null;
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void OperationAborted_AddRemove_Success()
+    {
+        Dispatcher dispatcher = Dispatcher.CurrentDispatcher;
+        DispatcherHooks hooks = dispatcher.Hooks;
+        int callCount = 0;
+        DispatcherHookEventHandler handler = (s, e) => callCount++;
+        hooks.OperationAborted += handler;
+        Assert.Equal(0, callCount);
+
+        hooks.OperationAborted -= handler;
+        Assert.Equal(0, callCount);
+
+        // Remove non existent.
+        hooks.OperationAborted -= handler;
+        Assert.Equal(0, callCount);
+
+        // Add null.
+        hooks.OperationAborted += null;
+        Assert.Equal(0, callCount);
+
+        // Remove null.
+        hooks.OperationAborted -= null;
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void OperationCompleted_AddRemove_Success()
+    {
+        Dispatcher dispatcher = Dispatcher.CurrentDispatcher;
+        DispatcherHooks hooks = dispatcher.Hooks;
+        int callCount = 0;
+        DispatcherHookEventHandler handler = (s, e) => callCount++;
+        hooks.OperationCompleted += handler;
+        Assert.Equal(0, callCount);
+
+        hooks.OperationCompleted -= handler;
+        Assert.Equal(0, callCount);
+
+        // Remove non existent.
+        hooks.OperationCompleted -= handler;
+        Assert.Equal(0, callCount);
+
+        // Add null.
+        hooks.OperationCompleted += null;
+        Assert.Equal(0, callCount);
+
+        // Remove null.
+        hooks.OperationCompleted -= null;
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void OperationPriorityChanged_AddRemove_Success()
+    {
+        Dispatcher dispatcher = Dispatcher.CurrentDispatcher;
+        DispatcherHooks hooks = dispatcher.Hooks;
+        int callCount = 0;
+        DispatcherHookEventHandler handler = (s, e) => callCount++;
+        hooks.OperationPriorityChanged += handler;
+        Assert.Equal(0, callCount);
+
+        hooks.OperationPriorityChanged -= handler;
+        Assert.Equal(0, callCount);
+
+        // Remove non existent.
+        hooks.OperationPriorityChanged -= handler;
+        Assert.Equal(0, callCount);
+
+        // Add null.
+        hooks.OperationPriorityChanged += null;
+        Assert.Equal(0, callCount);
+
+        // Remove null.
+        hooks.OperationPriorityChanged -= null;
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void OperationStarted_AddRemove_Success()
+    {
+        Dispatcher dispatcher = Dispatcher.CurrentDispatcher;
+        DispatcherHooks hooks = dispatcher.Hooks;
+        int callCount = 0;
+        DispatcherHookEventHandler handler = (s, e) => callCount++;
+        hooks.OperationStarted += handler;
+        Assert.Equal(0, callCount);
+
+        hooks.OperationStarted -= handler;
+        Assert.Equal(0, callCount);
+
+        // Remove non existent.
+        hooks.OperationStarted -= handler;
+        Assert.Equal(0, callCount);
+
+        // Add null.
+        hooks.OperationStarted += null;
+        Assert.Equal(0, callCount);
+
+        // Remove null.
+        hooks.OperationStarted -= null;
+        Assert.Equal(0, callCount);
+    }
+}
\ No newline at end of file
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherObjectTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherObjectTests.cs
new file mode 100644
index 00000000000..e34186e4d05
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherObjectTests.cs
@@ -0,0 +1,102 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Threading;
+
+namespace System.Windows.Threading.Tests;
+
+public class DispatcherObjectTests
+{
+    [Fact]
+    public void Ctor_Default()
+    {
+        var obj = new SubDispatcherObject();
+        Assert.NotNull(obj.Dispatcher);
+        Assert.Same(obj.Dispatcher, obj.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, obj.Dispatcher);
+    }
+
+    [Fact]
+    public void CheckAccess_InvokeOnCurrentThread_ReturnsTrue()
+    {
+        var obj = new SubDispatcherObject();
+        Assert.True(obj.CheckAccess());
+    }
+
+    [Fact]
+    public void CheckAccess_InvokeOnDifferentThread_ReturnsFalse()
+    {
+        var obj = new SubDispatcherObject();
+        bool? access = null;
+        var thread = new Thread(() =>
+        {
+            access = obj.CheckAccess();
+        });
+        thread.Start();
+        thread.Join();
+        Assert.False(access);
+    }
+
+    [Fact]
+    public void CheckAccess_InvokeDetachedDispatcher_ReturnsTrue()
+    {
+        var obj = new SubFreezable();
+        obj.Freeze();
+        Assert.Null(obj.Dispatcher);
+
+        Assert.True(obj.CheckAccess());
+    }
+
+    [Fact]
+    public void VerifyAccess_InvokeOnCurrentThread_Success()
+    {
+        var obj = new SubDispatcherObject();
+        obj.VerifyAccess();
+    }
+
+    [Fact]
+    public void VerifyAccess_InvokeDetachedDispatcher_Success()
+    {
+        var obj = new SubFreezable();
+        obj.Freeze();
+        Assert.Null(obj.Dispatcher);
+        
+        obj.VerifyAccess();
+    }
+
+    [Fact]
+    public void VerifyAccess_InvokeOnDifferentThread_ThrowsInvalidOperationException()
+    {
+        var obj = new SubDispatcherObject();
+        bool? threwInvalidOperationException = null;
+        var thread = new Thread(() =>
+        {
+            try
+            {
+                obj.VerifyAccess();
+                threwInvalidOperationException = false;
+            }
+            catch (InvalidOperationException)
+            {
+                threwInvalidOperationException = true;
+            }
+            catch
+            {
+                threwInvalidOperationException = false;
+            }
+        });
+        thread.Start();
+        thread.Join();
+        Assert.True(threwInvalidOperationException);
+    }
+
+    private class SubFreezable : Freezable
+    {
+        protected override Freezable CreateInstanceCore() => throw new NotImplementedException();
+    }
+
+    public class SubDispatcherObject : DispatcherObject
+    {
+    }
+}
\ No newline at end of file
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherOperationTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherOperationTests.cs
new file mode 100644
index 00000000000..0e291cebec9
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherOperationTests.cs
@@ -0,0 +1,346 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+
+namespace System.Windows.Threading.Tests;
+
+public class DispatcherOperationTests
+{
+    [Fact]
+    public void Aborted_AddRemove_Success()
+    {
+        Dispatcher dispatcher = Dispatcher.CurrentDispatcher;
+        DispatcherOperation operation = dispatcher.BeginInvoke(() => {});
+
+        int callCount = 0;
+        EventHandler handler = (s, e) => callCount++;
+        operation.Aborted += handler;
+        Assert.Equal(0, callCount);
+
+        operation.Aborted -= handler;
+        Assert.Equal(0, callCount);
+
+        // Remove non existent.
+        operation.Aborted -= handler;
+        Assert.Equal(0, callCount);
+
+        // Add null.
+        operation.Aborted += null;
+        Assert.Equal(0, callCount);
+
+        // Remove null.
+        operation.Aborted -= null;
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void Completed_AddRemove_Success()
+    {
+        Dispatcher dispatcher = Dispatcher.CurrentDispatcher;
+        DispatcherOperation operation = dispatcher.BeginInvoke(() => {});
+
+        int callCount = 0;
+        EventHandler handler = (s, e) => callCount++;
+        operation.Completed += handler;
+        Assert.Equal(0, callCount);
+
+        operation.Completed -= handler;
+        Assert.Equal(0, callCount);
+
+        // Remove non existent.
+        operation.Completed -= handler;
+        Assert.Equal(0, callCount);
+
+        // Add null.
+        operation.Completed += null;
+        Assert.Equal(0, callCount);
+
+        // Remove null.
+        operation.Completed -= null;
+        Assert.Equal(0, callCount);
+    }
+
+    [Theory]
+    [InlineData(DispatcherPriority.ApplicationIdle)]
+    [InlineData(DispatcherPriority.Background)]
+    [InlineData(DispatcherPriority.ContextIdle)]
+    [InlineData(DispatcherPriority.DataBind)]
+    [InlineData(DispatcherPriority.Inactive)]
+    [InlineData(DispatcherPriority.Input)]
+    [InlineData(DispatcherPriority.Loaded)]
+    [InlineData(DispatcherPriority.Normal)]
+    [InlineData(DispatcherPriority.Render)]
+    [InlineData(DispatcherPriority.Send)]
+    [InlineData(DispatcherPriority.SystemIdle)]
+    public void Priority_Set_GetReturnsExpected(DispatcherPriority value)
+    {
+        Dispatcher dispatcher = Dispatcher.CurrentDispatcher;
+        DispatcherOperation operation = dispatcher.BeginInvoke(() => { });
+        
+        // Set.
+        operation.Priority = value;
+        Assert.Equal(value, operation.Priority);
+
+        // Set same.
+        operation.Priority = value;
+        Assert.Equal(value, operation.Priority);
+    }
+
+    [Theory]
+    [InlineData(DispatcherPriority.Invalid)]
+    [InlineData(DispatcherPriority.Invalid - 1)]
+    [InlineData(DispatcherPriority.Send + 1)]
+    public void Priority_SetInvalid_ThrowsInvalidEnumArgumentException(DispatcherPriority value)
+    {
+        Dispatcher dispatcher = Dispatcher.CurrentDispatcher;
+        DispatcherOperation operation = dispatcher.BeginInvoke(() => { });
+
+        Assert.Throws<InvalidEnumArgumentException>("value", () => operation.Priority = value);
+    }
+
+    [Fact]
+    public void Abort_Invoke_Success()
+    {
+        Dispatcher dispatcher = Dispatcher.CurrentDispatcher;
+
+        int callCount = 0;
+        DispatcherOperation operation = null!;
+        Delegate method = new Action(() => callCount++);
+        operation = dispatcher.BeginInvoke(method);
+
+        // Abort.
+        Assert.True(operation.Abort());
+        Assert.Equal(0, callCount);
+        Assert.Equal(DispatcherOperationStatus.Aborted, operation.Status);
+        Assert.Null(operation.Result);
+
+        // Abort again.
+        Assert.False(operation.Abort());
+        Assert.Equal(0, callCount);
+        Assert.Equal(DispatcherOperationStatus.Aborted, operation.Status);
+        Assert.Null(operation.Result);
+    }
+
+    [Fact]
+    public void Abort_InvokeCompleted_Success()
+    {
+        Dispatcher dispatcher = Dispatcher.CurrentDispatcher;
+
+        int callCount = 0;
+        DispatcherOperation operation = null!;
+        Delegate method = new Action(() => callCount++);
+        operation = dispatcher.BeginInvoke(method);
+
+        // Wait.
+        Assert.Equal(DispatcherOperationStatus.Completed, operation.Wait());
+        Assert.Equal(1, callCount);
+        Assert.Equal(DispatcherOperationStatus.Completed, operation.Status);
+        Assert.Null(operation.Result);
+
+        // Abort.
+        Assert.False(operation.Abort());
+        Assert.Equal(1, callCount);
+        Assert.Equal(DispatcherOperationStatus.Completed, operation.Status);
+        Assert.Null(operation.Result);
+
+        // Abort again.
+        Assert.False(operation.Abort());
+        Assert.Equal(1, callCount);
+        Assert.Equal(DispatcherOperationStatus.Completed, operation.Status);
+        Assert.Null(operation.Result);
+    }
+
+    [Fact]
+    public void Abort_InvokeWithHandler_CallsAborted()
+    {
+        Dispatcher dispatcher = Dispatcher.CurrentDispatcher;
+
+        int callCount = 0;
+        DispatcherOperation operation = null!;
+        Delegate method = new Action(() => callCount++);
+        operation = dispatcher.BeginInvoke(method);
+
+        int abortedCallCount = 0;
+        EventHandler aborted = (sender, e) =>
+        {
+            Assert.Same(operation, sender);
+            Assert.Equal(EventArgs.Empty, e);
+            abortedCallCount++;
+        };
+        operation.Aborted += aborted;
+
+        // Abort.
+        Assert.True(operation.Abort());
+        Assert.Equal(0, callCount);
+        Assert.Equal(1, abortedCallCount);
+        Assert.Equal(DispatcherOperationStatus.Aborted, operation.Status);
+        Assert.Null(operation.Result);
+
+        // Abort again.
+        Assert.False(operation.Abort());
+        Assert.Equal(0, callCount);
+        Assert.Equal(1, abortedCallCount);
+        Assert.Equal(DispatcherOperationStatus.Aborted, operation.Status);
+        Assert.Null(operation.Result);
+    }
+
+    [Fact]
+    public void Abort_InvokeWithRemovedHandler_DoesNotCallAborted()
+    {
+        Dispatcher dispatcher = Dispatcher.CurrentDispatcher;
+
+        int callCount = 0;
+        DispatcherOperation operation = null!;
+        Delegate method = new Action(() => callCount++);
+        operation = dispatcher.BeginInvoke(method);
+
+        int abortedCallCount = 0;
+        EventHandler aborted = (sender, e) => abortedCallCount++;
+        operation.Aborted += aborted;
+        operation.Aborted -= aborted;
+
+        // Abort.
+        Assert.True(operation.Abort());
+        Assert.Equal(0, callCount);
+        Assert.Equal(0, abortedCallCount);
+        Assert.Equal(DispatcherOperationStatus.Aborted, operation.Status);
+        Assert.Null(operation.Result);
+
+        // Abort again.
+        Assert.False(operation.Abort());
+        Assert.Equal(0, callCount);
+        Assert.Equal(0, abortedCallCount);
+        Assert.Equal(DispatcherOperationStatus.Aborted, operation.Status);
+        Assert.Null(operation.Result);
+    }
+
+    [Fact]
+    public void Wait_InvokeNoResult_Success()
+    {
+        Dispatcher dispatcher = Dispatcher.CurrentDispatcher;
+
+        int callCount = 0;
+        DispatcherOperation operation = null!;
+        Delegate method = new Action(() =>
+        {
+            Assert.Equal(DispatcherOperationStatus.Executing, operation.Status);
+            callCount++;
+        }); 
+        operation = dispatcher.BeginInvoke(method);
+        
+        // Wait.
+        Assert.Equal(DispatcherOperationStatus.Completed, operation.Wait());
+        Assert.Equal(1, callCount);
+        Assert.Equal(DispatcherOperationStatus.Completed, operation.Status);
+        Assert.Null(operation.Result);
+
+        // Wait again.
+        Assert.Equal(DispatcherOperationStatus.Completed, operation.Wait());
+        Assert.Equal(1, callCount);
+        Assert.Equal(DispatcherOperationStatus.Completed, operation.Status);
+        Assert.Null(operation.Result);
+    }
+    
+    [Fact]
+    public void Wait_InvokeResult_Success()
+    {
+        Dispatcher dispatcher = Dispatcher.CurrentDispatcher;
+
+        int callCount = 0;
+        DispatcherOperation operation = null!;
+        var result = new object();
+        Delegate method = new Func<object>(() =>
+        {
+            Assert.Equal(DispatcherOperationStatus.Executing, operation.Status);
+            callCount++;
+            return result;
+        }); 
+        operation = dispatcher.BeginInvoke(method);
+
+        // Wait.
+        Assert.Equal(DispatcherOperationStatus.Completed, operation.Wait());
+        Assert.Equal(1, callCount);
+        Assert.Equal(DispatcherOperationStatus.Completed, operation.Status);
+        Assert.Same(result, operation.Result);
+        
+        // Wait again.
+        Assert.Equal(DispatcherOperationStatus.Completed, operation.Wait());
+        Assert.Equal(1, callCount);
+        Assert.Equal(DispatcherOperationStatus.Completed, operation.Status);
+        Assert.Same(result, operation.Result);
+    }
+
+    [Fact]
+    public void Wait_InvokeWithHandler_CallsCompleted()
+    {
+        Dispatcher dispatcher = Dispatcher.CurrentDispatcher;
+
+        int callCount = 0;
+        DispatcherOperation operation = null!;
+        Delegate method = new Action(() =>
+        {
+            Assert.Equal(DispatcherOperationStatus.Executing, operation.Status);
+            callCount++;
+        }); 
+        operation = dispatcher.BeginInvoke(method);
+
+        int completedCallCount = 0;
+        EventHandler handler = (sender, e) =>
+        {
+            Assert.Same(operation, sender);
+            Assert.Equal(EventArgs.Empty, e);
+            completedCallCount++;
+        };
+        operation.Completed += handler;
+        
+        // Wait.
+        Assert.Equal(DispatcherOperationStatus.Completed, operation.Wait());
+        Assert.Equal(1, callCount);
+        Assert.Equal(1, completedCallCount);
+        Assert.Equal(DispatcherOperationStatus.Completed, operation.Status);
+        Assert.Null(operation.Result);
+
+        // Wait again.
+        Assert.Equal(DispatcherOperationStatus.Completed, operation.Wait());
+        Assert.Equal(1, callCount);
+        Assert.Equal(1, completedCallCount);
+        Assert.Equal(DispatcherOperationStatus.Completed, operation.Status);
+        Assert.Null(operation.Result);
+    }
+
+    [Fact]
+    public void Wait_InvokeWithRemovedHandler_DoesNotCallCompleted()
+    {
+        Dispatcher dispatcher = Dispatcher.CurrentDispatcher;
+
+        int callCount = 0;
+        DispatcherOperation operation = null!;
+        Delegate method = new Action(() =>
+        {
+            Assert.Equal(DispatcherOperationStatus.Executing, operation.Status);
+            callCount++;
+        }); 
+        operation = dispatcher.BeginInvoke(method);
+
+        int completedCallCount = 0;
+        EventHandler handler = (sender, e) => completedCallCount++;
+        operation.Completed += handler;
+        operation.Completed -= handler;
+        
+        // Wait.
+        Assert.Equal(DispatcherOperationStatus.Completed, operation.Wait());
+        Assert.Equal(1, callCount);
+        Assert.Equal(0, completedCallCount);
+        Assert.Equal(DispatcherOperationStatus.Completed, operation.Status);
+        Assert.Null(operation.Result);
+
+        // Wait again.
+        Assert.Equal(DispatcherOperationStatus.Completed, operation.Wait());
+        Assert.Equal(1, callCount);
+        Assert.Equal(0, completedCallCount);
+        Assert.Equal(DispatcherOperationStatus.Completed, operation.Status);
+        Assert.Null(operation.Result);
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherPriorityAwaitableTests..cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherPriorityAwaitableTests..cs
new file mode 100644
index 00000000000..2adce5e9514
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherPriorityAwaitableTests..cs
@@ -0,0 +1,47 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Windows.Threading.Tests;
+
+public class DispatcherPriorityAwaitableTests
+{
+    [Theory]
+    [InlineData(DispatcherPriority.ApplicationIdle)]
+    [InlineData(DispatcherPriority.Background)]
+    [InlineData(DispatcherPriority.ContextIdle)]
+    [InlineData(DispatcherPriority.DataBind)]
+    [InlineData(DispatcherPriority.Inactive)]
+    [InlineData(DispatcherPriority.Input)]
+    [InlineData(DispatcherPriority.Loaded)]
+    [InlineData(DispatcherPriority.Normal)]
+    [InlineData(DispatcherPriority.Render)]
+    [InlineData(DispatcherPriority.Send)]
+    [InlineData(DispatcherPriority.SystemIdle)]
+    public void GetAwaiter_InvokeWithDispatcher_ReturnsExpected(DispatcherPriority priority)
+    {
+        DispatcherPriorityAwaitable awaitable;
+        try
+        {
+            awaitable = Dispatcher.Yield(priority);
+        }
+        catch (InvalidOperationException)
+        {
+            // Yield throws if there is no dispatcher.
+            return;
+        }
+
+        DispatcherPriorityAwaiter awaiter = awaitable.GetAwaiter();
+        Assert.False(awaiter.IsCompleted);
+        Assert.Equal(awaiter, awaitable.GetAwaiter());
+    }
+    
+    [Fact]
+    public void GetAwaiter_InvokeDefault_ReturnsExpected()
+    {
+        var awaitable = new DispatcherPriorityAwaitable();
+        DispatcherPriorityAwaiter awaiter = awaitable.GetAwaiter();
+        Assert.False(awaiter.IsCompleted);
+        Assert.Equal(awaiter, awaitable.GetAwaiter());
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherPriorityAwaiterTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherPriorityAwaiterTests.cs
new file mode 100644
index 00000000000..2f219f32fb0
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherPriorityAwaiterTests.cs
@@ -0,0 +1,151 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Windows.Threading.Tests;
+
+public class DispatcherPriorityAwaiterTests
+{
+    [Fact]
+    public void Ctor_Default()
+    {
+        var awaiter = new DispatcherPriorityAwaiter();
+        Assert.False(awaiter.IsCompleted);
+    }
+
+    [Theory]
+    [InlineData(DispatcherPriority.ApplicationIdle)]
+    [InlineData(DispatcherPriority.Background)]
+    [InlineData(DispatcherPriority.ContextIdle)]
+    [InlineData(DispatcherPriority.DataBind)]
+    [InlineData(DispatcherPriority.Inactive)]
+    [InlineData(DispatcherPriority.Input)]
+    [InlineData(DispatcherPriority.Loaded)]
+    [InlineData(DispatcherPriority.Normal)]
+    [InlineData(DispatcherPriority.Render)]
+    [InlineData(DispatcherPriority.Send)]
+    [InlineData(DispatcherPriority.SystemIdle)]
+    public void GetResult_InvokeWithDispatcher_Nop(DispatcherPriority priority)
+    {
+        DispatcherPriorityAwaitable awaitable;
+        try
+        {
+            awaitable = Dispatcher.Yield(priority);
+        }
+        catch (InvalidOperationException)
+        {
+            // Yield throws if there is no dispatcher.
+            return;
+        }
+
+        DispatcherPriorityAwaiter awaiter = awaitable.GetAwaiter();
+        
+        // Invoke.
+        awaiter.GetResult();
+
+        // Invoke again.
+        awaiter.GetResult();
+    }
+
+    [Fact]
+    public void GetResult_InvokeDefaultAwaitable_Nop()
+    {
+        var awaitable = new DispatcherPriorityAwaitable();
+        DispatcherPriorityAwaiter awaiter = awaitable.GetAwaiter();
+
+        // Invoke.
+        awaiter.GetResult();
+
+        // Invoke again.
+        awaiter.GetResult();
+    }
+
+    [Fact]
+    public void GetResult_InvokeDefault_Nop()
+    {
+        var awaiter = new DispatcherPriorityAwaiter();
+
+        // Invoke.
+        awaiter.GetResult();
+
+        // Invoke again.
+        awaiter.GetResult();
+    }
+
+    [Theory]
+    [InlineData(DispatcherPriority.ApplicationIdle)]
+    [InlineData(DispatcherPriority.Background)]
+    [InlineData(DispatcherPriority.ContextIdle)]
+    [InlineData(DispatcherPriority.DataBind)]
+    [InlineData(DispatcherPriority.Inactive)]
+    [InlineData(DispatcherPriority.Input)]
+    [InlineData(DispatcherPriority.Loaded)]
+    [InlineData(DispatcherPriority.Normal)]
+    [InlineData(DispatcherPriority.Render)]
+    [InlineData(DispatcherPriority.Send)]
+    [InlineData(DispatcherPriority.SystemIdle)]
+    public void OnCompleted_InvokeWithDispatcher_Success(DispatcherPriority priority)
+    {
+        DispatcherPriorityAwaitable awaitable;
+        try
+        {
+            awaitable = Dispatcher.Yield(priority);
+        }
+        catch (InvalidOperationException)
+        {
+            // Yield throws if there is no dispatcher.
+            return;
+        }
+
+        DispatcherPriorityAwaiter awaiter = awaitable.GetAwaiter();
+
+        int callCount = 0;
+        Action action = () =>
+        {
+            callCount++;
+        };
+        
+        // Invoke.
+        awaiter.OnCompleted(action);
+        Assert.Equal(0, callCount);
+
+        // Invoke again.
+        awaiter.OnCompleted(action);
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void OnCompleted_NullAction_ThrowsArgumentNullException()
+    {
+        DispatcherPriorityAwaitable awaitable;
+        try
+        {
+            awaitable = Dispatcher.Yield(DispatcherPriority.Normal);
+        }
+        catch (InvalidOperationException)
+        {
+            // Yield throws if there is no dispatcher.
+            return;
+        }
+
+        DispatcherPriorityAwaiter awaiter = awaitable.GetAwaiter();
+        Assert.Throws<ArgumentNullException>(() => awaiter.OnCompleted(null));
+    }
+
+    [Fact]
+    public void OnCompleted_InvokeDefaultAwaitable_ThrowsInvalidOperationException()
+    {
+        var awaitable = new DispatcherPriorityAwaitable();
+        DispatcherPriorityAwaiter awaiter = awaitable.GetAwaiter();
+        Assert.Throws<InvalidOperationException>(() => awaiter.OnCompleted(null));
+        Assert.Throws<InvalidOperationException>(() => awaiter.OnCompleted(() => { }));
+    }
+
+    [Fact]
+    public void OnCompleted_InvokeDefault_ThrowsInvalidOperationException()
+    {
+        var awaiter = new DispatcherPriorityAwaiter();
+        Assert.Throws<InvalidOperationException>(() => awaiter.OnCompleted(null));
+        Assert.Throws<InvalidOperationException>(() => awaiter.OnCompleted(() => { }));
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherProcessingDisabledTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherProcessingDisabledTests.cs
new file mode 100644
index 00000000000..146f2a3ff7c
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherProcessingDisabledTests.cs
@@ -0,0 +1,45 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Windows.Threading.Tests;
+
+public class DispatcherProcessingDisabledTests
+{
+    [Fact]
+    public void Dispose_Default_Nop()
+    {
+        var disabled = new DispatcherProcessingDisabled();
+        disabled.Dispose();
+
+        // Call again.
+        disabled.Dispose();
+    }
+    
+    public static IEnumerable<object?[]> Equals_TestData()
+    {
+        yield return new object?[] { new DispatcherProcessingDisabled(), new DispatcherProcessingDisabled(), true };
+        yield return new object?[] { new DispatcherProcessingDisabled(), new object(), false };
+        yield return new object?[] { new DispatcherProcessingDisabled(), null, false };
+    }
+
+    [Theory]
+    [MemberData(nameof(Equals_TestData))]
+    public void Equals_Invoke_Success(DispatcherProcessingDisabled disabled, object? obj, bool expected)
+    {
+        Assert.Equal(expected, disabled.Equals(obj));
+        if (obj is DispatcherProcessingDisabled other)
+        {
+            Assert.Equal(expected, disabled.GetHashCode().Equals(other.GetHashCode()));
+            Assert.Equal(expected, disabled == other);
+            Assert.Equal(!expected, disabled != other);
+        }
+    }
+    
+    [Fact]
+    public void GetHashCode_Invoke_ReturnsExpected()
+    {
+        var disabled = new DispatcherProcessingDisabled();
+        Assert.Equal(disabled.GetHashCode(), disabled.GetHashCode());
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherSynchronizationContextTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherSynchronizationContextTests.cs
new file mode 100644
index 00000000000..29f18e834d5
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherSynchronizationContextTests.cs
@@ -0,0 +1,74 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+
+namespace System.Windows.Threading.Tests;
+
+public class DispatcherSynchronizationContextTests
+{
+    [Fact]
+    public void Ctor_Default()
+    {
+        new DispatcherSynchronizationContext();
+    }
+
+    [Fact]
+    public void Ctor_Dispatcher()
+    {
+        new DispatcherSynchronizationContext(Dispatcher.CurrentDispatcher);
+    }
+
+    [Theory]
+    [InlineData(DispatcherPriority.ApplicationIdle)]
+    [InlineData(DispatcherPriority.Background)]
+    [InlineData(DispatcherPriority.ContextIdle)]
+    [InlineData(DispatcherPriority.DataBind)]
+    [InlineData(DispatcherPriority.Inactive)]
+    [InlineData(DispatcherPriority.Input)]
+    [InlineData(DispatcherPriority.Loaded)]
+    [InlineData(DispatcherPriority.Normal)]
+    [InlineData(DispatcherPriority.Render)]
+    [InlineData(DispatcherPriority.Send)]
+    [InlineData(DispatcherPriority.SystemIdle)]
+    public void Ctor_Dispatcher_DispatcherPriority(DispatcherPriority priority)
+    {
+        new DispatcherSynchronizationContext(Dispatcher.CurrentDispatcher, priority);
+    }
+
+    [Fact]
+    public void Ctor_NullDispatcher_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("dispatcher", () => new DispatcherSynchronizationContext(null));
+        Assert.Throws<ArgumentNullException>("dispatcher", () => new DispatcherSynchronizationContext(null, DispatcherPriority.Normal));
+    }
+
+    [Theory]
+    [InlineData(DispatcherPriority.Invalid)]
+    [InlineData(DispatcherPriority.Invalid - 1)]
+    [InlineData(DispatcherPriority.Send + 1)]
+    public void Ctor_InvalidPriority_ThrowsInvalidEnumArgumentException(DispatcherPriority priority)
+    {
+        Assert.Throws<InvalidEnumArgumentException>("priority", () => new DispatcherSynchronizationContext(Dispatcher.CurrentDispatcher, priority));
+    }
+
+    [Fact]
+    public void CreateCopy_Default_ReturnsSelf()
+    {
+        var context = new DispatcherSynchronizationContext();
+        DispatcherSynchronizationContext copy = Assert.IsType<DispatcherSynchronizationContext>(context.CreateCopy());
+        Assert.NotNull(copy);
+        Assert.NotSame(context, copy);
+    }
+
+    [Theory]
+    [InlineData(DispatcherPriority.ApplicationIdle)]
+    public void CreateCopy_Custom_ReturnsSelf(DispatcherPriority priority)
+    {
+        var context = new DispatcherSynchronizationContext(Dispatcher.CurrentDispatcher, priority);
+        DispatcherSynchronizationContext copy = Assert.IsType<DispatcherSynchronizationContext>(context.CreateCopy());
+        Assert.NotNull(copy);
+        Assert.NotSame(context, copy);
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherTests.cs
new file mode 100644
index 00000000000..b45867daffd
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherTests.cs
@@ -0,0 +1,204 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.Threading;
+
+namespace System.Windows.Threading.Tests;
+
+public class DispatcherTests
+{
+    [Fact]
+    public void CurrentDispatcher_Get_ReturnsExpected()
+    {
+        Dispatcher dispatcher = Dispatcher.CurrentDispatcher;
+        Assert.NotNull(dispatcher);
+        Assert.Same(dispatcher, Dispatcher.CurrentDispatcher);
+        Assert.False(dispatcher.HasShutdownFinished);
+        Assert.False(dispatcher.HasShutdownStarted);
+        Assert.NotNull(dispatcher.Hooks);
+        Assert.Same(dispatcher.Hooks, dispatcher.Hooks);
+        Assert.Same(Thread.CurrentThread, dispatcher.Thread);
+    }
+
+    [Fact]
+    public void PushFrame_NullFrame_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("frame", () => Dispatcher.PushFrame(null!));
+    }
+
+    [Fact]
+    public void FromThread_CurrentThread_ReturnsExpected()
+    {
+        Dispatcher dispatcher = Dispatcher.FromThread(Thread.CurrentThread);
+        Assert.NotNull(dispatcher);
+        Assert.Same(dispatcher, Dispatcher.CurrentDispatcher);
+        Assert.False(dispatcher.HasShutdownFinished);
+        Assert.False(dispatcher.HasShutdownStarted);
+        Assert.NotNull(dispatcher.Hooks);
+        Assert.Same(dispatcher.Hooks, dispatcher.Hooks);
+        Assert.Same(Thread.CurrentThread, dispatcher.Thread);
+    }
+
+    [Fact]
+    public void FromThread_NoSuchThread_ReturnsNull()
+    {
+        var thread = new Thread(() => { });
+        Assert.Null(Dispatcher.FromThread(thread));
+    }
+
+    [Fact]
+    public void FromThread_NullThread_ReturnsNull()
+    {
+        Assert.Null(Dispatcher.FromThread(null));
+    }
+
+    [Theory]
+    [InlineData(DispatcherPriority.ApplicationIdle)]
+    [InlineData(DispatcherPriority.Background)]
+    [InlineData(DispatcherPriority.ContextIdle)]
+    [InlineData(DispatcherPriority.DataBind)]
+    [InlineData(DispatcherPriority.Inactive)]
+    [InlineData(DispatcherPriority.Input)]
+    [InlineData(DispatcherPriority.Loaded)]
+    [InlineData(DispatcherPriority.Normal)]
+    [InlineData(DispatcherPriority.Render)]
+    [InlineData(DispatcherPriority.Send)]
+    [InlineData(DispatcherPriority.SystemIdle)]
+    public void ValidatePriority_InvokeValidPriority_Nop(DispatcherPriority priority)
+    {
+        Dispatcher.ValidatePriority(priority, "priority");
+        Dispatcher.ValidatePriority(priority, string.Empty);
+        Dispatcher.ValidatePriority(priority, null);
+    }
+
+    [Theory]
+    [InlineData(DispatcherPriority.Invalid)]
+    [InlineData(DispatcherPriority.Invalid - 1)]
+    [InlineData(DispatcherPriority.Send + 1)]
+    public void ValidatePriority_InvokeInvalidPriority_ThrowsInvalidEnumArgumentException(DispatcherPriority priority)
+    {
+        Assert.Throws<InvalidEnumArgumentException>("priority", () => Dispatcher.ValidatePriority(priority, "priority"));
+        Assert.Throws<InvalidEnumArgumentException>("", () => Dispatcher.ValidatePriority(priority, ""));
+        Assert.Throws<InvalidEnumArgumentException>(() => Dispatcher.ValidatePriority(priority, null));
+    }
+
+    [Theory]
+    [InlineData(DispatcherPriority.ApplicationIdle)]
+    [InlineData(DispatcherPriority.Background)]
+    [InlineData(DispatcherPriority.ContextIdle)]
+    [InlineData(DispatcherPriority.DataBind)]
+    [InlineData(DispatcherPriority.Inactive)]
+    [InlineData(DispatcherPriority.Input)]
+    [InlineData(DispatcherPriority.Loaded)]
+    [InlineData(DispatcherPriority.Normal)]
+    [InlineData(DispatcherPriority.Render)]
+    [InlineData(DispatcherPriority.Send)]
+    [InlineData(DispatcherPriority.SystemIdle)]
+    public void Yield_Invoke_ReturnsExpected(DispatcherPriority priority)
+    {
+        DispatcherPriorityAwaitable awaitable;
+        try
+        {
+            awaitable = Dispatcher.Yield(priority);
+        }
+        catch (InvalidOperationException)
+        {
+            // Yield throws if there is no dispatcher.
+            return;
+        }
+
+        Assert.Equal(awaitable, Dispatcher.Yield(priority));
+    }
+
+    [Theory]
+    [InlineData(DispatcherPriority.Invalid)]
+    [InlineData(DispatcherPriority.Invalid - 1)]
+    [InlineData(DispatcherPriority.Send + 1)]
+    public void Yield_InvokeInvalidPriority_ThrowsInvalidEnumArgumentException(DispatcherPriority priority)
+    {
+        Assert.Throws<InvalidEnumArgumentException>("priority", () => Dispatcher.Yield(priority));
+    }
+
+    [Fact]
+    public void BeginInvoke_InvokeDelegateObjectArray_Success()
+    {
+        Dispatcher dispatcher = Dispatcher.CurrentDispatcher;
+
+        Delegate action = new Action(() => { });
+        DispatcherOperation operation = dispatcher.BeginInvoke(action, Array.Empty<object>());
+        Assert.NotNull(operation);
+        Assert.Same(dispatcher, operation.Dispatcher);
+        Assert.Equal(DispatcherPriority.Normal, operation.Priority);
+        Assert.Equal(DispatcherOperationStatus.Pending, operation.Status);
+        Assert.NotNull(operation.Task);
+    }
+
+    [Theory]
+    [InlineData(DispatcherPriority.Invalid)]
+    [InlineData(DispatcherPriority.Invalid - 1)]
+    [InlineData(DispatcherPriority.Send + 1)]
+    public void BeginInvoke_InvokeInvalidPriority_ThrowsInvalidEnumArgumentException(DispatcherPriority priority)
+    {
+        Dispatcher dispatcher = Dispatcher.CurrentDispatcher;
+        Assert.Throws<InvalidEnumArgumentException>("priority", () => dispatcher.BeginInvoke(priority, (Action)(() => { })));
+        Assert.Throws<InvalidEnumArgumentException>("priority", () => dispatcher.BeginInvoke(priority, (Action<object>)((arg) => { }), new object()));
+        Assert.Throws<InvalidEnumArgumentException>("priority", () => dispatcher.BeginInvoke(priority, (Action<object, object>)((arg1, arg2) => { }), new object(), new object[] { new object() }));
+        Assert.Throws<InvalidEnumArgumentException>("priority", () => dispatcher.BeginInvoke(priority, (Action<object, object>)((arg1, arg2) => { }), new object[] { new object(), new object() }));
+    }
+
+    [Fact]
+    public void CheckAccess_InvokeOnCurrentThread_ReturnsTrue()
+    {
+        Dispatcher dispatcher = Dispatcher.CurrentDispatcher;
+        Assert.True(dispatcher.CheckAccess());
+    }
+
+    [Fact]
+    public void CheckAccess_InvokeOnDifferentThread_ReturnsFalse()
+    {
+        Dispatcher dispatcher = Dispatcher.CurrentDispatcher;
+        bool? access = null;
+        var thread = new Thread(() =>
+        {
+            access = dispatcher.CheckAccess();
+        });
+        thread.Start();
+        thread.Join();
+        Assert.False(access);
+    }
+
+    [Fact]
+    public void VerifyAccess_InvokeOnCurrentThread_Success()
+    {
+        Dispatcher dispatcher = Dispatcher.CurrentDispatcher;
+        dispatcher.VerifyAccess();
+    }
+
+    [Fact]
+    public void VerifyAccess_InvokeOnDifferentThread_ThrowsInvalidOperationException()
+    {
+        Dispatcher dispatcher = Dispatcher.CurrentDispatcher;
+        bool? threwInvalidOperationException = null;
+        var thread = new Thread(() =>
+        {
+            try
+            {
+                dispatcher.VerifyAccess();
+                threwInvalidOperationException = false;
+            }
+            catch (InvalidOperationException)
+            {
+                threwInvalidOperationException = true;
+            }
+            catch
+            {
+                threwInvalidOperationException = false;
+            }
+        });
+        thread.Start();
+        thread.Join();
+        Assert.True(threwInvalidOperationException);
+    }
+}
\ No newline at end of file
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherTimerTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherTimerTests.cs
new file mode 100644
index 00000000000..5701ea9ecd1
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/Threading/DispatcherTimerTests.cs
@@ -0,0 +1,305 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+
+namespace System.Windows.Threading.Tests;
+
+public class DispatcherTimerTests
+{
+    [Fact]
+    public void Ctor_Default()
+    {
+        var timer = new DispatcherTimer();
+        Assert.Same(Dispatcher.CurrentDispatcher, timer.Dispatcher);
+        Assert.Equal(TimeSpan.Zero, timer.Interval);
+        Assert.False(timer.IsEnabled);
+        Assert.Null(timer.Tag);
+    }
+
+    [Theory]
+    [InlineData(DispatcherPriority.ApplicationIdle)]
+    [InlineData(DispatcherPriority.Background)]
+    [InlineData(DispatcherPriority.ContextIdle)]
+    [InlineData(DispatcherPriority.DataBind)]
+    [InlineData(DispatcherPriority.Input)]
+    [InlineData(DispatcherPriority.Loaded)]
+    [InlineData(DispatcherPriority.Normal)]
+    [InlineData(DispatcherPriority.Render)]
+    [InlineData(DispatcherPriority.Send)]
+    [InlineData(DispatcherPriority.SystemIdle)]
+    public void Ctor_DispatcherPriority(DispatcherPriority priority)
+    {
+        var timer = new DispatcherTimer(priority);
+        Assert.Same(Dispatcher.CurrentDispatcher, timer.Dispatcher);
+        Assert.Equal(TimeSpan.Zero, timer.Interval);
+        Assert.False(timer.IsEnabled);
+        Assert.Null(timer.Tag);
+    }
+
+    [Theory]
+    [InlineData(DispatcherPriority.ApplicationIdle)]
+    [InlineData(DispatcherPriority.Background)]
+    [InlineData(DispatcherPriority.ContextIdle)]
+    [InlineData(DispatcherPriority.DataBind)]
+    [InlineData(DispatcherPriority.Input)]
+    [InlineData(DispatcherPriority.Loaded)]
+    [InlineData(DispatcherPriority.Normal)]
+    [InlineData(DispatcherPriority.Render)]
+    [InlineData(DispatcherPriority.Send)]
+    [InlineData(DispatcherPriority.SystemIdle)]
+    public void Ctor_DispatcherPriority_Dispatcher(DispatcherPriority priority)
+    {
+        var timer = new DispatcherTimer(priority, Dispatcher.CurrentDispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, timer.Dispatcher);
+        Assert.Equal(TimeSpan.Zero, timer.Interval);
+        Assert.False(timer.IsEnabled);
+        Assert.Null(timer.Tag);
+    }
+
+    public static IEnumerable<object?[]> Ctor_TimeSpan_DispatcherPriority_EventHandler_Dispatcher_TestData()
+    {
+        yield return new object?[] { TimeSpan.FromMilliseconds(0), DispatcherPriority.ApplicationIdle };
+        yield return new object?[] { TimeSpan.FromMilliseconds(0), DispatcherPriority.Background };
+        yield return new object?[] { TimeSpan.FromMilliseconds(int.MaxValue), DispatcherPriority.ContextIdle };
+        yield return new object?[] { TimeSpan.FromMilliseconds(0), DispatcherPriority.DataBind };
+        yield return new object?[] { TimeSpan.FromMilliseconds(1), DispatcherPriority.Input };
+        yield return new object?[] { TimeSpan.FromMilliseconds(2), DispatcherPriority.Loaded };
+        yield return new object?[] { TimeSpan.FromMilliseconds(3), DispatcherPriority.Normal };
+        yield return new object?[] { TimeSpan.FromMilliseconds(4), DispatcherPriority.Render };
+        yield return new object?[] { TimeSpan.FromMilliseconds(5), DispatcherPriority.Send };
+        yield return new object?[] { TimeSpan.FromMilliseconds(6), DispatcherPriority.SystemIdle };
+    }
+
+    [Theory]
+    [MemberData(nameof(Ctor_TimeSpan_DispatcherPriority_EventHandler_Dispatcher_TestData))]
+    public void Ctor_TimeSpan_DispatcherPriority_EventHandler_Dispatcher(TimeSpan interval, DispatcherPriority priority)
+    {
+        EventHandler callback = (s, e) => {};
+        var timer = new DispatcherTimer(interval, priority, callback, Dispatcher.CurrentDispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, timer.Dispatcher);
+        Assert.Equal(interval, timer.Interval);
+        Assert.True(timer.IsEnabled);
+        Assert.Null(timer.Tag);
+    }
+
+    [Theory]
+    [InlineData(DispatcherPriority.Invalid)]
+    [InlineData(DispatcherPriority.Invalid - 1)]
+    [InlineData(DispatcherPriority.Send + 1)]
+    public void Ctor_InvalidPriority_ThrowsInvalidEnumArgumentException(DispatcherPriority priority)
+    {
+        Assert.Throws<InvalidEnumArgumentException>("priority", () => new DispatcherTimer(priority));
+        Assert.Throws<InvalidEnumArgumentException>("priority", () => new DispatcherTimer(priority, Dispatcher.CurrentDispatcher));
+        Assert.Throws<InvalidEnumArgumentException>("priority", () => new DispatcherTimer(TimeSpan.Zero, priority, (s, e) => {}, Dispatcher.CurrentDispatcher));
+    }
+
+    [Fact]
+    public void Ctor_InactivePriority_ThrowsArgumentException()
+    {
+        Assert.Throws<ArgumentException>("priority", () => new DispatcherTimer(DispatcherPriority.Inactive));
+        Assert.Throws<ArgumentException>("priority", () => new DispatcherTimer(DispatcherPriority.Inactive, Dispatcher.CurrentDispatcher));
+        Assert.Throws<ArgumentException>("priority", () => new DispatcherTimer(TimeSpan.Zero, DispatcherPriority.Inactive, (s, e) => {}, Dispatcher.CurrentDispatcher));
+    }
+
+    [Fact]
+    public void Ctor_NullDispatcher_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("dispatcher", () => new DispatcherTimer(DispatcherPriority.Normal, null));
+        Assert.Throws<ArgumentNullException>("dispatcher", () => new DispatcherTimer(TimeSpan.Zero, DispatcherPriority.Normal, (s, e) => {}, null));
+    }
+
+    public static IEnumerable<object[]> InvalidInterval_TestData()
+    {
+        yield return new object[] { TimeSpan.FromTicks(-1) };
+        yield return new object[] { TimeSpan.FromMilliseconds((double)int.MaxValue + 1) };
+        yield return new object[] { TimeSpan.MinValue };
+        yield return new object[] { TimeSpan.MaxValue };
+    }
+
+    [Theory]
+    [MemberData(nameof(InvalidInterval_TestData))]
+    public void Ctor_InvalidInterval_ThrowsArgumentOutOfRangeException(TimeSpan interval)
+    {
+        Assert.Throws<ArgumentOutOfRangeException>("interval", () => new DispatcherTimer(interval, DispatcherPriority.Normal, (s, e) => {}, Dispatcher.CurrentDispatcher));
+    }
+
+    [Fact]
+    public void Ctor_NullCallback_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("callback", () => new DispatcherTimer(TimeSpan.Zero, DispatcherPriority.Normal, null, Dispatcher.CurrentDispatcher));
+    }
+
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void IsEnabled_Set_GetReturnsExpected(bool value)
+    {
+        var timer = new DispatcherTimer
+        {
+            IsEnabled = value
+        };
+        Assert.Equal(value, timer.IsEnabled);
+
+        // Set same.
+        timer.IsEnabled = value;
+        Assert.Equal(value, timer.IsEnabled);
+
+        // Set different.
+        timer.IsEnabled = !value;
+        Assert.Equal(!value, timer.IsEnabled);
+    }
+
+    public static IEnumerable<object[]> Interval_Set_TestData()
+    {
+        yield return new object[] { TimeSpan.Zero };
+        yield return new object[] { TimeSpan.FromMilliseconds(1) };
+        yield return new object[] { TimeSpan.FromMilliseconds(int.MaxValue) };
+    }
+
+    [Theory]
+    [MemberData(nameof(Interval_Set_TestData))]
+    public void Interval_Set_GetReturnsExpected(TimeSpan value)
+    {
+        var timer = new DispatcherTimer
+        {
+            Interval = value
+        };
+        Assert.Equal(value, timer.Interval);
+
+        // Set same.
+        timer.Interval = value;
+        Assert.Equal(value, timer.Interval);
+    }
+
+    [Theory]
+    [MemberData(nameof(Interval_Set_TestData))]
+    public void Interval_SetEnabled_GetReturnsExpected(TimeSpan value)
+    {
+        var timer = new DispatcherTimer();
+        timer.IsEnabled = true;
+        
+        // Set.
+        timer.Interval = value;
+        Assert.Equal(value, timer.Interval);
+
+        // Set same.
+        timer.Interval = value;
+        Assert.Equal(value, timer.Interval);
+    }
+
+    [Theory]
+    [MemberData(nameof(InvalidInterval_TestData))]
+    public void Interval_SetInvalid_ThrowsArgumentOutOfRangeException(TimeSpan value)
+    {
+        var timer = new DispatcherTimer();
+        Assert.Throws<ArgumentOutOfRangeException>("value", () => timer.Interval = value);
+    }
+
+    public static IEnumerable<object?[]> Tag_Set_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { new object() };
+    }
+
+    [Theory]
+    [MemberData(nameof(Tag_Set_TestData))]
+    public void Tag_Set_GetReturnsExpected(object? value)
+    {
+        var timer = new DispatcherTimer();
+
+        // Set.
+        timer.Tag = value;
+        Assert.Same(value, timer.Tag);
+
+        // Set same.
+        timer.Tag = value;
+        Assert.Same(value, timer.Tag);
+    }
+
+    [Fact]
+    public void Tick_AddRemove_Success()
+    {
+        var timer = new DispatcherTimer();
+
+        int callCount = 0;
+        EventHandler handler = (s, e) => callCount++;
+        timer.Tick += handler;
+        Assert.Equal(0, callCount);
+
+        timer.Tick -= handler;
+        Assert.Equal(0, callCount);
+
+        // Remove non existent.
+        timer.Tick -= handler;
+        Assert.Equal(0, callCount);
+
+        // Add null.
+        timer.Tick += null;
+        Assert.Equal(0, callCount);
+
+        // Remove null.
+        timer.Tick -= null;
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void Start_Invoke_Success()
+    {
+        var timer = new DispatcherTimer();
+        int callCount = 0;
+        timer.Tick += (s, e) => callCount++;
+
+        // Start.
+        timer.Start();
+        Assert.True(timer.IsEnabled);
+        Assert.Equal(0, callCount);
+
+        // Start again.
+        timer.Start();
+        Assert.True(timer.IsEnabled);
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void Stop_InvokeStarted_Success()
+    {
+        var timer = new DispatcherTimer();
+        int callCount = 0;
+        timer.Tick += (s, e) => callCount++;
+
+        // Start.
+        timer.Start();
+        Assert.True(timer.IsEnabled);
+        Assert.Equal(0, callCount);
+
+        // Stop.
+        timer.Stop();
+        Assert.False(timer.IsEnabled);
+        Assert.Equal(0, callCount);
+
+        // Stop again.
+        timer.Stop();
+        Assert.False(timer.IsEnabled);
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void Stop_InvokeNotStarted_Success()
+    {
+        var timer = new DispatcherTimer();
+        int callCount = 0;
+        timer.Tick += (s, e) => callCount++;
+
+        // Stop.
+        timer.Stop();
+        Assert.False(timer.IsEnabled);
+        Assert.Equal(0, callCount);
+
+        // Stop again.
+        timer.Stop();
+        Assert.False(timer.IsEnabled);
+        Assert.Equal(0, callCount);
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/VectorConverterTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/VectorConverterTests.cs
new file mode 100644
index 00000000000..0fc0307cec4
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/VectorConverterTests.cs
@@ -0,0 +1,188 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.ComponentModel.Design.Serialization;
+using System.Globalization;
+
+namespace System.Windows.Tests;
+
+public class VectorConverterTests
+{
+    [Theory]
+    [InlineData(null, false)]
+    [InlineData(typeof(object), false)]
+    [InlineData(typeof(string), true)]
+    [InlineData(typeof(InstanceDescriptor), false)]
+    [InlineData(typeof(Vector), false)]
+    public void CanConvertTo_Invoke_ReturnsExpected(Type? destinationType, bool expected)
+    {
+        var converter = new VectorConverter();
+        Assert.Equal(expected, converter.CanConvertTo(null, destinationType));
+        Assert.Equal(expected, converter.CanConvertTo(new CustomTypeDescriptorContext(), destinationType));
+    }
+    
+    [Theory]
+    [MemberData(nameof(VectorTests.ToString_TestData), MemberType = typeof(VectorTests))]
+    public void ConvertTo_InvokeVectorToString_ReturnsExpected(Vector matrix, string expected)
+    {
+        var converter = new VectorConverter();
+        Assert.Equal(expected, converter.ConvertTo(matrix, typeof(string)));
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), null, matrix, typeof(string)));
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, matrix, typeof(string)));
+    }
+    
+    [Theory]
+    [MemberData(nameof(VectorTests.ToString_IFormatProviderCustom_TestData), MemberType = typeof(VectorTests))]
+    public void ConvertTo_InvokeVectorToStringCustomCulture_ReturnsExpected(Vector matrix, string numberDecimalSeparator, string expected)
+    {
+        var culture = new CultureInfo("en-US");
+        NumberFormatInfo formatInfo = culture.NumberFormat;
+        formatInfo.NumberDecimalSeparator = numberDecimalSeparator;
+
+        var converter = new VectorConverter();
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), culture, matrix, typeof(string)));
+    }
+
+    [Theory]
+    [InlineData(null, "")]
+    [InlineData("", "")]
+    [InlineData("value", "value")]
+    [InlineData(1, "1")]
+    public void ConvertTo_InvokeNotVectorToString_ReturnsExpected(object? value, string expected)
+    {
+        var converter = new VectorConverter();
+        Assert.Equal(expected, converter.ConvertTo(value, typeof(string)));
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), null, value, typeof(string)));
+        Assert.Equal(expected, converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value, typeof(string)));
+    }
+
+    public static IEnumerable<object?[]> ConvertTo_CantConvert_TestData()
+    {
+        yield return new object?[] { null, typeof(object) };
+        yield return new object?[] { string.Empty, typeof(object) };
+        yield return new object?[] { "value", typeof(object) };
+        yield return new object?[] { new object(), typeof(object) };
+        yield return new object?[] { new Vector(), typeof(object) };
+        
+        yield return new object?[] { null, typeof(Vector) };
+        yield return new object?[] { string.Empty, typeof(Vector) };
+        yield return new object?[] { "value", typeof(Vector) };
+        yield return new object?[] { new object(), typeof(Vector) };
+        yield return new object?[] { new Vector(), typeof(Vector) };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertTo_CantConvert_TestData))]
+    public void ConvertTo_CantConvert_ThrowsNotSupportedException(object value, Type destinationType)
+    {
+        var converter = new VectorConverter();
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(value, destinationType));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(null, null, value, destinationType));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value, destinationType));
+    }
+
+    public static IEnumerable<object?[]> ConvertTo_NullDestinationType_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { string.Empty };
+        yield return new object?[] { "value" };
+        yield return new object?[] { new object() };
+        yield return new object?[] { new Vector() };
+    }
+
+    [Theory]
+    [MemberData(nameof(ConvertTo_NullDestinationType_TestData))]
+    public void ConvertTo_NullDestinationType_ThrowsArgumentNullException(object value)
+    {
+        var converter = new VectorConverter();
+        Assert.Throws<ArgumentNullException>("destinationType", () => converter.ConvertTo(value, null!));
+        Assert.Throws<ArgumentNullException>("destinationType", () => converter.ConvertTo(null, null, new Vector(), null!));
+        Assert.Throws<ArgumentNullException>("destinationType", () => converter.ConvertTo(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, new Vector(), null!));
+    }
+
+    [Theory]
+    [InlineData(null, false)]
+    [InlineData(typeof(object), false)]
+    [InlineData(typeof(string), true)]
+    [InlineData(typeof(InstanceDescriptor), true)]
+    [InlineData(typeof(Vector), false)]
+    public void CanConvertFrom_Invoke_ReturnsExpected(Type? sourceType, bool expected)
+    {
+        var converter = new VectorConverter();
+        Assert.Equal(expected, converter.CanConvertFrom(sourceType!));
+        Assert.Equal(expected, converter.CanConvertFrom(null, sourceType));
+        Assert.Equal(expected, converter.CanConvertFrom(new CustomTypeDescriptorContext(), sourceType));
+    }
+
+    [Theory]
+    [MemberData(nameof(VectorTests.Parse_TestData), MemberType = typeof(VectorTests))]
+    public void ConvertFrom_InvokeStringValue_ReturnsExpected(object value, Vector expected)
+    {
+        var converter = new VectorConverter();
+        Assert.Equal(expected, converter.ConvertFrom(value));
+        Assert.Equal(expected, converter.ConvertFrom(null, null, value));
+        Assert.Equal(expected, converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    [Fact]
+    public void ConvertFrom_NullValue_ThrowsNotSupportedException()
+    {
+        var converter = new VectorConverter();
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(null!));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(null, null, null));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, null));
+    }
+
+    [Theory]
+    [MemberData(nameof(VectorTests.Parse_InvalidSource_TestData), MemberType = typeof(VectorTests))]
+    public void ConvertFrom_InvalidStringValue_ThrowsInvalidOperationException(object value)
+    {
+        var converter = new VectorConverter();
+        Assert.Throws<InvalidOperationException>(() => converter.ConvertFrom(value));
+        Assert.Throws<InvalidOperationException>(() => converter.ConvertFrom(null, null, value));
+        Assert.Throws<InvalidOperationException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    [Theory]
+    [MemberData(nameof(VectorTests.Parse_NotDouble_TestData), MemberType = typeof(VectorTests))]
+    public void ConvertFrom_NotDoubleStringValue_ThrowsFormatException(object value)
+    {
+        var converter = new VectorConverter();
+        Assert.Throws<FormatException>(() => converter.ConvertFrom(value));
+        Assert.Throws<FormatException>(() => converter.ConvertFrom(null, null, value));
+        Assert.Throws<FormatException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    public static IEnumerable<object[]> ConvertFrom_CantConvert_TestData()
+    {
+        yield return new object[] { new object() };
+        yield return new object[] { new Vector() };
+    }
+    
+    [Theory]
+    [MemberData(nameof(ConvertFrom_CantConvert_TestData))]
+    public void ConvertFrom_CantConvert_ThrowsNotSupportedException(object value)
+    {
+        var converter = new VectorConverter();
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(value));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(null, null, value));
+        Assert.Throws<NotSupportedException>(() => converter.ConvertFrom(new CustomTypeDescriptorContext(), CultureInfo.InvariantCulture, value));
+    }
+
+    private class CustomTypeDescriptorContext : ITypeDescriptorContext
+    {
+        public IContainer Container => throw new NotImplementedException();
+
+        public object Instance => throw new NotImplementedException();
+
+        public PropertyDescriptor PropertyDescriptor => throw new NotImplementedException();
+
+        public object? GetService(Type serviceType) => throw new NotImplementedException();
+
+        public void OnComponentChanged() => throw new NotImplementedException();
+
+        public bool OnComponentChanging() => throw new NotImplementedException();
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/VectorTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/VectorTests.cs
new file mode 100644
index 00000000000..42f945d64fe
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/VectorTests.cs
@@ -0,0 +1,861 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.Globalization;
+using System.Windows.Converters;
+using System.Windows.Markup;
+using System.Windows.Media;
+using System.Windows.Media.Tests;
+
+namespace System.Windows.Tests;
+
+public class VectorTests
+{
+    [Fact]
+    public void Ctor_Default()
+    {
+        var vector = new Vector();
+        Assert.Equal(0, vector.X);
+        Assert.Equal(0, vector.Y);
+    }
+
+    [Theory]
+    [InlineData(double.NegativeInfinity, double.NegativeInfinity)]
+    [InlineData(double.MinValue, double.MinValue)]
+    [InlineData(-1, -2)]
+    [InlineData(-1, 2)]
+    [InlineData(1, -2)]
+    [InlineData(double.NegativeZero, double.NegativeZero)]
+    [InlineData(0, 0)]
+    [InlineData(1, 0)]
+    [InlineData(0, 2)]
+    [InlineData(0.1, 0.2)]
+    [InlineData(1, 2)]
+    [InlineData(double.MaxValue, double.MaxValue)]
+    [InlineData(double.PositiveInfinity, double.PositiveInfinity)]
+    [InlineData(double.NaN, double.NaN)]
+    [InlineData(1, double.NaN)]
+    [InlineData(double.NaN, 2)]
+    public void Ctor_Double_Double(double x, double y)
+    {
+        var vector = new Vector(x, y);
+        Assert.Equal(x, vector.X);
+        Assert.Equal(y, vector.Y);
+    }
+
+    public static IEnumerable<object[]> Length_TestData()
+    {
+        yield return new object[] { 0, 0, 0 };
+        yield return new object[] { 1, 2, Math.Sqrt(5) };
+        yield return new object[] { 1.1, 2.2, Math.Sqrt(6.05) };
+        yield return new object[] { -1.1, -2.2, Math.Sqrt(6.05) };
+        yield return new object[] { double.MaxValue, double.MaxValue, Math.Sqrt(double.PositiveInfinity) };
+    }
+
+    [Theory]
+    [MemberData(nameof(Length_TestData))]
+    public void Length_Get_ReturnsExpected(double x, double y, double expected)
+    {
+        var vector = new Vector(x, y);
+        Assert.Equal(expected, vector.Length, precision: 5);
+        Assert.Equal(Math.Sqrt(vector.LengthSquared), vector.Length, precision: 5);
+    }
+
+    [Theory]
+    [MemberData(nameof(Length_TestData))]
+    public void LengthSquared_Get_ReturnsExpected(double x, double y, double expected)
+    {
+        var vector = new Vector(x, y);
+        Assert.Equal(expected * expected, vector.LengthSquared, precision: 5);
+        Assert.Equal(vector.Length * vector.Length, vector.LengthSquared, precision: 5);
+    }
+
+    [Theory]
+    [InlineData(double.NegativeInfinity)]
+    [InlineData(double.MinValue)]
+    [InlineData(-1)]
+    [InlineData(double.NegativeZero)]
+    [InlineData(0)]
+    [InlineData(0.2)]
+    [InlineData(1)]
+    [InlineData(double.MaxValue)]
+    [InlineData(double.PositiveInfinity)]
+    [InlineData(double.NaN)]
+    public void X_Set_GetReturnsExpected(double value)
+    {
+        var vector = new Vector();
+
+        // Set.
+        vector.X = value;
+        Assert.Equal(value, vector.X);
+
+        // Set same.
+        vector.X = value;
+        Assert.Equal(value, vector.X);
+    }
+
+    [Theory]
+    [InlineData(double.NegativeInfinity)]
+    [InlineData(double.MinValue)]
+    [InlineData(-1)]
+    [InlineData(double.NegativeZero)]
+    [InlineData(0)]
+    [InlineData(0.2)]
+    [InlineData(1)]
+    [InlineData(double.MaxValue)]
+    [InlineData(double.PositiveInfinity)]
+    [InlineData(double.NaN)]
+    public void Y_Set_GetReturnsExpected(double value)
+    {
+        var vector = new Vector();
+
+        // Set.
+        vector.Y = value;
+        Assert.Equal(value, vector.Y);
+
+        // Set same.
+        vector.Y = value;
+        Assert.Equal(value, vector.Y);
+    }
+
+    public static IEnumerable<object[]> AngleBetween_TestData()
+    {
+        yield return new object[] { new Vector(1, 2), new Vector(1, 2), 0 };
+        yield return new object[] { new Vector(1, 2), new Vector(3, 4), -10.30485 };
+        yield return new object[] { new Vector(1, 2), new Vector(-3, -4), 169.69515 };
+        yield return new object[] { new Vector(1, 2), new Vector(1, 0), -63.43495 };
+        yield return new object[] { new Vector(1, 2), new Vector(0, 1), 26.56505 };
+        yield return new object[] { new Vector(1, 2), new Vector(0, -1), -153.43495 };
+        yield return new object[] { new Vector(1, 2), new Vector(-1, 0), 116.56505 };
+        yield return new object[] { new Vector(1, 2), new Vector(-1, -2), 180 };
+        yield return new object[] { new Vector(1, 2), new Vector(1, -2), -126.8699 };
+        yield return new object[] { new Vector(1, 2), new Vector(), 0 };
+        yield return new object[] { new Vector(-1, -2), new Vector(-3, -4), -10.30485 };
+
+        yield return new object[] { new Vector(), new Vector(), 0 };
+        yield return new object[] { new Vector(), new Vector(1, 2), 0 };
+    }
+
+    [Theory]
+    [MemberData(nameof(AngleBetween_TestData))]
+    public void AngleBetween_Invoke_ReturnsExpected(Vector vector1, Vector vector2, double expected)
+    {
+        Assert.Equal(expected, Vector.AngleBetween(vector1, vector2), precision: 5);
+    }
+
+    public static IEnumerable<object[]> CrossProduct_TestData()
+    {
+        yield return new object[] { new Vector(1, 2), new Vector(3, 4), -2 };
+        yield return new object[] { new Vector(1.1, 2.2), new Vector(3.3, 4.4), -2.42 };
+        yield return new object[] { new Vector(1, 2), new Vector(-3, -4), 2 };
+        yield return new object[] { new Vector(1, 2), new Vector(1, 2), 0 };
+        yield return new object[] { new Vector(1, 2), new Vector(0, 0), 0 };
+        yield return new object[] { new Vector(1, 2), new Vector(double.MaxValue, double.MaxValue), double.NegativeInfinity };
+        yield return new object[] { new Vector(1, 2), new Vector(double.PositiveInfinity, double.PositiveInfinity), double.NaN };
+        yield return new object[] { new Vector(1, 2), new Vector(double.NaN, double.NaN), double.NaN };
+        yield return new object[] { new Vector(-1, -2), new Vector(-3, -4), -2 };
+
+        yield return new object[] { new Vector(), new Vector(), 0 };
+        yield return new object[] { new Vector(), new Vector(1, 2), 0 };
+    }
+
+    [Theory]
+    [MemberData(nameof(CrossProduct_TestData))]
+    public void CrossProduct_Invoke_ReturnsExpected(Vector vector1, Vector vector2, double expected)
+    {
+        Assert.Equal(expected, Vector.CrossProduct(vector1, vector2), precision: 5);
+        Assert.Equal(-expected, Vector.CrossProduct(vector2, vector1), precision: 5);
+    }
+
+    public static IEnumerable<object?[]> Equals_TestData()
+    {
+        // Normal size.
+        yield return new object?[] { new Vector(1, 2), new Vector(1, 2), true };
+        yield return new object?[] { new Vector(1, 2), new Vector(2, 2), false };
+        yield return new object?[] { new Vector(1, 2), new Vector(1, 3), false };
+        yield return new object?[] { new Vector(1, 2), new Vector(double.NaN, 2), false };
+        yield return new object?[] { new Vector(1, 2), new Vector(1, double.NaN), false };
+        yield return new object?[] { new Vector(1, 2), new Vector(double.NaN, double.NaN), false };
+        yield return new object?[] { new Vector(1, 2), new Vector(0, 0), false };
+        yield return new object?[] { new Vector(1, 2), new Vector(), false };
+
+        // NaN x.
+        yield return new object[] { new Vector(double.NaN, 2), new Vector(double.NaN, 2), true };
+        yield return new object[] { new Vector(double.NaN, 2), new Vector(1, 2), false };
+        yield return new object[] { new Vector(double.NaN, 2), new Vector(double.NaN, double.NaN), false };
+
+        // NaN y.
+        yield return new object[] { new Vector(1, double.NaN), new Vector(1, double.NaN), true };
+        yield return new object[] { new Vector(1, double.NaN), new Vector(1, 2), false };
+        yield return new object[] { new Vector(1, double.NaN), new Vector(double.NaN, double.NaN), false };
+
+        // NaN x & y.
+        yield return new object[] { new Vector(double.NaN, double.NaN), new Vector(double.NaN, double.NaN), true };
+        yield return new object[] { new Vector(double.NaN, double.NaN), new Vector(1, 2), false };
+        yield return new object[] { new Vector(double.NaN, double.NaN), new Vector(double.NaN, 2), false };
+        yield return new object[] { new Vector(double.NaN, double.NaN), new Vector(1, double.NaN), false };
+
+        // Zero.
+        yield return new object?[] { new Vector(0, 0), new Vector(), true };
+        yield return new object?[] { new Vector(0, 0), new Vector(0, 0), true };
+        yield return new object?[] { new Vector(0, 0), new Vector(1, 0), false };
+        yield return new object?[] { new Vector(0, 0), new Vector(0, 1), false };
+
+        // Default.
+        yield return new object?[] { new Vector(), new Vector(), true };
+        yield return new object?[] { new Vector(), new Vector(0, 0), true };
+        yield return new object?[] { new Vector(), new Vector(1, 0), false };
+        yield return new object?[] { new Vector(), new Vector(0, 1), false };
+    }
+
+    [Theory]
+    [MemberData(nameof(Equals_TestData))]
+    public void Equals_Object_ReturnsExpected(Vector vector, object o, bool expected)
+    {
+        Assert.Equal(expected, vector.Equals(o));
+        if (o is Vector other)
+        {
+            Assert.Equal(expected, vector.Equals(other));
+            Assert.Equal(expected, other.Equals(vector));
+            Assert.Equal(expected, Vector.Equals(vector, other));
+            Assert.Equal(expected, Vector.Equals(other, vector));
+            Assert.Equal(expected, vector.GetHashCode().Equals(other.GetHashCode()));
+        }
+    }
+
+    public static IEnumerable<object[]> EqualityOperator_TestData()
+    {
+        // Normal size.
+        yield return new object[] { new Vector(1, 2), new Vector(1, 2), true };
+        yield return new object[] { new Vector(1, 2), new Vector(2, 2), false };
+        yield return new object[] { new Vector(1, 2), new Vector(1, 3), false };
+        yield return new object[] { new Vector(1, 2), new Vector(double.NaN, 2), false };
+        yield return new object[] { new Vector(1, 2), new Vector(1, double.NaN), false };
+        yield return new object[] { new Vector(1, 2), new Vector(double.NaN, double.NaN), false };
+        yield return new object[] { new Vector(1, 2), new Vector(0, 0), false };
+        yield return new object[] { new Vector(1, 2), new Vector(), false };
+
+        // NaN x.
+        yield return new object[] { new Vector(double.NaN, 2), new Vector(double.NaN, 2), false };
+        yield return new object[] { new Vector(double.NaN, 2), new Vector(1, 2), false };
+        yield return new object[] { new Vector(double.NaN, 2), new Vector(double.NaN, double.NaN), false };
+
+        // NaN y.
+        yield return new object[] { new Vector(1, double.NaN), new Vector(1, double.NaN), false };
+        yield return new object[] { new Vector(1, double.NaN), new Vector(1, 2), false };
+        yield return new object[] { new Vector(1, double.NaN), new Vector(double.NaN, double.NaN), false };
+
+        // NaN x & y.
+        yield return new object[] { new Vector(double.NaN, double.NaN), new Vector(double.NaN, double.NaN), false };
+        yield return new object[] { new Vector(double.NaN, double.NaN), new Vector(1, 2), false };
+        yield return new object[] { new Vector(double.NaN, double.NaN), new Vector(double.NaN, 2), false };
+        yield return new object[] { new Vector(double.NaN, double.NaN), new Vector(1, double.NaN), false };
+
+        // Zero.
+        yield return new object[] { new Vector(0, 0), new Vector(), true };
+        yield return new object[] { new Vector(0, 0), new Vector(0, 0), true };
+        yield return new object[] { new Vector(0, 0), new Vector(1, 0), false };
+        yield return new object[] { new Vector(0, 0), new Vector(0, 1), false };
+
+        // Default.
+        yield return new object[] { new Vector(), new Vector(), true };
+        yield return new object[] { new Vector(), new Vector(0, 0), true };
+        yield return new object[] { new Vector(), new Vector(1, 0), false };
+        yield return new object[] { new Vector(), new Vector(0, 1), false };
+    }
+
+    [Theory]
+    [MemberData(nameof(EqualityOperator_TestData))]
+    public void EqualityOperator_Invoke_ReturnsExpected(Vector vector1, Vector vector2, bool expected)
+    {
+        Assert.Equal(expected, vector1 == vector2);
+        Assert.Equal(expected, vector2 == vector1);
+        Assert.Equal(!expected, vector1 != vector2);
+        Assert.Equal(!expected, vector2 != vector1);
+    }
+
+    [Fact]
+    public void GetHashCode_InvokeDefault_ReturnsEqual()
+    {
+        var vector = new Vector();
+        Assert.Equal(0, vector.GetHashCode());
+        Assert.Equal(vector.GetHashCode(), vector.GetHashCode());
+    }
+
+    [Fact]
+    public void GetHashCode_InvokeNormal_ReturnsEqual()
+    {
+        var vector = new Vector(1, 2);
+        Assert.NotEqual(0, vector.GetHashCode());
+        Assert.Equal(vector.GetHashCode(), vector.GetHashCode());
+    }
+
+    [Fact]
+    public void Normalize_InvokeDefault_ReturnsExpected()
+    {
+        var vector = new Vector();
+        vector.Normalize();
+        Assert.Equal(double.NaN, vector.X);
+        Assert.Equal(double.NaN, vector.Y);
+        Assert.Equal(double.NaN, vector.Length);
+        Assert.Equal(double.NaN, vector.LengthSquared);
+    }
+
+    [Fact]
+    public void Normalize_InvokeZero_ReturnsExpected()
+    {
+        var vector = new Vector(0, 0);
+        vector.Normalize();
+        Assert.Equal(double.NaN, vector.X);
+        Assert.Equal(double.NaN, vector.Y);
+        Assert.Equal(double.NaN, vector.Length);
+        Assert.Equal(double.NaN, vector.LengthSquared);
+    }
+
+    [Fact]
+    public void Normalize_InvokeNormal_ReturnsExpected()
+    {
+        var vector = new Vector(1, 2);
+        vector.Normalize();
+        Assert.Equal(1 / Math.Sqrt(5), vector.X, precision: 5);
+        Assert.Equal(2 / Math.Sqrt(5), vector.Y, precision: 5);
+        Assert.Equal(1, vector.Length, precision: 5);
+        Assert.Equal(1, vector.LengthSquared, precision: 5);
+    }
+
+    [Fact]
+    public void Normalize_InvokeNegative_ReturnsExpected()
+    {
+        var vector = new Vector(-1, -2);
+        vector.Normalize();
+        Assert.Equal(-1 / Math.Sqrt(5), vector.X, precision: 5);
+        Assert.Equal(-2 / Math.Sqrt(5), vector.Y, precision: 5);
+        Assert.Equal(1, vector.Length, precision: 5);
+        Assert.Equal(1, vector.LengthSquared, precision: 5);
+    }
+
+    [Fact]
+    public void Normalize_InvokeLarge_ReturnsExpected()
+    {
+        var vector = new Vector(double.MaxValue, double.MaxValue);
+        vector.Normalize();
+        Assert.Equal(0.70711, vector.X, precision: 5);
+        Assert.Equal(0.70711, vector.Y, precision: 5);
+        Assert.Equal(1, vector.Length, precision: 5);
+        Assert.Equal(1, vector.LengthSquared, precision: 5);
+    }
+
+    public static IEnumerable<object[]> Add_Vector_TestData()
+    {
+        yield return new object[] { new Vector(1, 2), new Vector(3, 4), new Vector(4, 6) };
+        yield return new object[] { new Vector(1, 2), new Vector(-3, -4), new Vector(-2, -2) };
+        yield return new object[] { new Vector(1.1, 2.2), new Vector(3.3, 4.4), new Vector(4.4, 6.6) };
+        yield return new object[] { new Vector(1, 2), new Vector(), new Vector(1, 2) };
+
+        yield return new object[] { new Vector(), new Vector(), new Vector() };
+        yield return new object[] { new Vector(), new Vector(1, 2), new Vector(1, 2) };
+    }
+
+    [Theory]
+    [MemberData(nameof(Add_Vector_TestData))]
+    public void Add_InvokeVector_ReturnsExpected(Vector vector1, Vector vector2, Vector expected)
+    {
+        Vector result = Vector.Add(vector1, vector2);
+        Assert.Equal(expected.X, result.X, precision: 5);
+        Assert.Equal(expected.Y, result.Y, precision: 5);
+        Assert.Equal(result, Vector.Add(vector2, vector1));
+    }
+
+    [Theory]
+    [MemberData(nameof(Add_Vector_TestData))]
+    public void OperatorAdd_InvokeVector_ReturnsExpected(Vector vector1, Vector vector2, Vector expected)
+    {
+        Vector result = vector1 + vector2;
+        Assert.Equal(expected.X, result.X, precision: 5);
+        Assert.Equal(expected.Y, result.Y, precision: 5);
+        Assert.Equal(result, vector2 + vector1);
+    }
+
+    public static IEnumerable<object[]> Add_Point_TestData()
+    {
+        yield return new object[] { new Vector(1, 2), new Point(3, 4), new Point(4, 6) };
+        yield return new object[] { new Vector(1, 2), new Point(-3, -4), new Point(-2, -2) };
+        yield return new object[] { new Vector(1.1, 2.2), new Point(3.3, 4.4), new Point(4.4, 6.6) };
+        yield return new object[] { new Vector(1, 2), new Point(), new Point(1, 2) };
+
+        yield return new object[] { new Vector(), new Point(), new Point() };
+        yield return new object[] { new Vector(), new Point(1, 2), new Point(1, 2) };
+    }
+
+    [Theory]
+    [MemberData(nameof(Add_Point_TestData))]
+    public void Add_InvokePoint_ReturnsExpected(Vector vector, Point point, Point expected)
+    {
+        Point result = Vector.Add(vector, point);
+        Assert.Equal(expected.X, result.X, precision: 5);
+        Assert.Equal(expected.Y, result.Y, precision: 5);
+    }
+
+    [Theory]
+    [MemberData(nameof(Add_Point_TestData))]
+    public void OperatorAdd_InvokePoint_ReturnsExpected(Vector vector, Point point, Point expected)
+    {
+        Point result = vector + point;
+        Assert.Equal(expected.X, result.X, precision: 5);
+        Assert.Equal(expected.Y, result.Y, precision: 5);
+    }
+
+    public static IEnumerable<object[]> Determinant_TestData()
+    {
+        yield return new object[] { new Vector(1, 2), new Vector(3, 4), -2 };
+        yield return new object[] { new Vector(1, 2), new Vector(-3, -4), 2 };
+        yield return new object[] { new Vector(1.1, 2.2), new Vector(3.3, 4.4), -2.42 };
+        yield return new object[] { new Vector(1, 2), new Vector(), 0 };
+
+        yield return new object[] { new Vector(-1, -2), new Vector(3, 4), 2 };
+        yield return new object[] { new Vector(-1, -2), new Vector(-3, -4), -2 };
+        yield return new object[] { new Vector(-1, -2), new Vector(), 0 };
+
+        yield return new object[] { new Vector(), new Vector(), 0 };
+        yield return new object[] { new Vector(), new Vector(1, 2), 0 };
+        yield return new object[] { new Vector(), new Vector(-1, -2), 0 };
+    }
+
+    [Theory]
+    [MemberData(nameof(Determinant_TestData))]
+    public void Determinant_Invoke_ReturnsExpected(Vector vector1, Vector vector2, double expected)
+    {
+        Assert.Equal(expected, Vector.Determinant(vector1, vector2), precision: 5);
+    }
+
+    public static IEnumerable<object[]> Divide_TestData()
+    {
+        yield return new object[] { new Vector(1, 2), 2, new Vector(0.5, 1) };
+        yield return new object[] { new Vector(1, 2), 1, new Vector(1, 2) };
+        yield return new object[] { new Vector(1, 2), -2, new Vector(-0.5, -1) };
+        yield return new object[] { new Vector(1.1, 2.2), 2, new Vector(0.55, 1.1) };
+        yield return new object[] { new Vector(1, 2), 0, new Vector(double.PositiveInfinity, double.PositiveInfinity) };
+
+        yield return new object[] { new Vector(-1, -2), 2, new Vector(-0.5, -1) };
+        yield return new object[] { new Vector(-1, -2), 1, new Vector(-1, -2) };
+        yield return new object[] { new Vector(-1, -2), -2, new Vector(0.5, 1) };
+
+        yield return new object[] { new Vector(), 2, new Vector() };
+        yield return new object[] { new Vector(), 1, new Vector() };
+        yield return new object[] { new Vector(), -2, new Vector() };
+        yield return new object[] { new Vector(), 0, new Vector(double.NaN, double.NaN) };
+    }
+
+    [Theory]
+    [MemberData(nameof(Divide_TestData))]
+    public void Divide_Invoke_ReturnsExpected(Vector vector, double scalar, Vector expected)
+    {
+        Vector result = Vector.Divide(vector, scalar);
+        Assert.Equal(expected.X, result.X, precision: 5);
+        Assert.Equal(expected.Y, result.Y, precision: 5);
+    }
+
+    [Theory]
+    [MemberData(nameof(Divide_TestData))]
+    public void OperatorDivide_Invoke_ReturnsExpected(Vector vector, double scalar, Vector expected)
+    {
+        Vector result = vector / scalar;
+        Assert.Equal(expected.X, result.X, precision: 5);
+        Assert.Equal(expected.Y, result.Y, precision: 5);
+    }
+
+    public static IEnumerable<object[]> Subtract_Vector_TestData()
+    {
+        yield return new object[] { new Vector(1, 2), new Vector(3, 4), new Vector(-2, -2) };
+        yield return new object[] { new Vector(1, 2), new Vector(-3, -4), new Vector(4, 6) };
+        yield return new object[] { new Vector(1.1, 2.2), new Vector(3.3, 4.4), new Vector(-2.2, -2.2) };
+        yield return new object[] { new Vector(1, 2), new Vector(), new Vector(1, 2) };
+
+        yield return new object[] { new Vector(), new Vector(1, 2), new Vector(-1, -2) };
+        yield return new object[] { new Vector(), new Vector(), new Vector() };
+    }
+
+    [Theory]
+    [MemberData(nameof(Subtract_Vector_TestData))]
+    public void Subtract_InvokeVector_ReturnsExpected(Vector vector1, Vector vector2, Vector expected)
+    {
+        Vector result = Vector.Subtract(vector1, vector2);
+        Assert.Equal(expected.X, result.X, precision: 5);
+        Assert.Equal(expected.Y, result.Y, precision: 5);
+        Assert.Equal(new Vector(-result.X, -result.Y), Vector.Subtract(vector2, vector1));
+    }
+
+    [Theory]
+    [MemberData(nameof(Subtract_Vector_TestData))]
+    public void OperatorSubtract_InvokeVector_ReturnsExpected(Vector vector1, Vector vector2, Vector expected)
+    {
+        Vector result = vector1 - vector2;
+        Assert.Equal(expected.X, result.X, precision: 5);
+        Assert.Equal(expected.Y, result.Y, precision: 5);
+        Assert.Equal(new Vector(-result.X, -result.Y), vector2 - vector1);
+    }
+
+    public static IEnumerable<object[]> Multiply_Double_TestData()
+    {
+        yield return new object[] { new Vector(1, 2), 2, new Vector(2, 4) };
+        yield return new object[] { new Vector(1, 2), -2, new Vector(-2, -4) };
+        yield return new object[] { new Vector(1.1, 2.2), 2, new Vector(2.2, 4.4) };
+        yield return new object[] { new Vector(1, 2), 0, new Vector(0, 0) };
+        yield return new object[] { new Vector(1, 2), 1, new Vector(1, 2) };
+        yield return new object[] { new Vector(1, 2), double.PositiveInfinity, new Vector(double.PositiveInfinity, double.PositiveInfinity) };
+
+        yield return new object[] { new Vector(-1, -2), 2, new Vector(-2, -4) };
+        yield return new object[] { new Vector(-1, -2), -2, new Vector(2, 4) };
+        yield return new object[] { new Vector(-1, -2), 0, new Vector(0, 0) };
+        yield return new object[] { new Vector(-1, -2), 1, new Vector(-1, -2) };
+
+        yield return new object[] { new Vector(), 2, new Vector() };
+        yield return new object[] { new Vector(), -2, new Vector() };
+        yield return new object[] { new Vector(), 0, new Vector() };
+        yield return new object[] { new Vector(), 1, new Vector() };
+    }
+
+    [Theory]
+    [MemberData(nameof(Multiply_Double_TestData))]
+    public void Multiply_InvokeDouble_ReturnsExpected(Vector vector, double scalar, Vector expected)
+    {
+        Vector result = Vector.Multiply(vector, scalar);
+        Assert.Equal(expected.X, result.X, precision: 5);
+        Assert.Equal(expected.Y, result.Y, precision: 5);
+        Assert.Equal(result, Vector.Multiply(scalar, vector));
+    }
+
+    [Theory]
+    [MemberData(nameof(Multiply_Double_TestData))]
+    public void OperatorMultiply_InvokeDouble_ReturnsExpected(Vector vector, double scalar, Vector expected)
+    {
+        Vector result = vector * scalar;
+        Assert.Equal(expected.X, result.X, precision: 5);
+        Assert.Equal(expected.Y, result.Y, precision: 5);
+        Assert.Equal(result, scalar * vector);
+    }
+
+    [Theory]
+    [MemberData(nameof(MatrixTests.Transform_Vector_TestData), MemberType = typeof(MatrixTests))]
+    public void Multiply_InvokeMatrix_ReturnsExpected(Matrix matrix, Vector vector, Vector expected)
+    {
+        Vector result = Vector.Multiply(vector, matrix);
+        Assert.Equal(expected.X, result.X, precision: 5);
+        Assert.Equal(expected.Y, result.Y, precision: 5);
+    }
+
+    [Theory]
+    [MemberData(nameof(MatrixTests.Transform_Vector_TestData), MemberType = typeof(MatrixTests))]
+    public void OperatorMultiply_InvokeMatrix_ReturnsExpected(Matrix matrix, Vector vector, Vector expected)
+    {
+        Vector result = vector * matrix;
+        Assert.Equal(expected.X, result.X, precision: 5);
+        Assert.Equal(expected.Y, result.Y, precision: 5);
+    }
+
+    public static IEnumerable<object[]> Multiply_Vector_TestData()
+    {
+        yield return new object[] { new Vector(1, 2), new Vector(3, 4), 11 };
+        yield return new object[] { new Vector(1, 2), new Vector(1, 2), 5 };
+        yield return new object[] { new Vector(1, 2), new Vector(0, 0), 0 };
+        yield return new object[] { new Vector(1, 2), new Vector(-1, -2), -5 };
+
+        yield return new object[] { new Vector(-1, -2), new Vector(3, 4), -11 };
+        yield return new object[] { new Vector(-1, -2), new Vector(-1, -2), 5 };
+        yield return new object[] { new Vector(-1, -2), new Vector(0, 0), 0 };
+
+        yield return new object[] { new Vector(), new Vector(3, 4), 0 };
+        yield return new object[] { new Vector(), new Vector(), 0 };
+        yield return new object[] { new Vector(), new Vector(-1, -2), 0 };
+    }
+
+    [Theory]
+    [MemberData(nameof(Multiply_Vector_TestData))]
+    public void Multiply_InvokeVector_ReturnsExpected(Vector vector1, Vector vector2, double expected)
+    {
+        double result = Vector.Multiply(vector1, vector2);
+        Assert.Equal(expected, result, precision: 5);
+        Assert.Equal(result, Vector.Multiply(vector1, vector2));
+    }
+
+    [Theory]
+    [MemberData(nameof(Multiply_Vector_TestData))]
+    public void OperatorMultiply_InvokeVector_ReturnsExpected(Vector vector1, Vector vector2, double expected)
+    {
+        double result = vector1 * vector2;
+        Assert.Equal(expected, result, precision: 5);
+        Assert.Equal(result, vector2 * vector1);
+    }
+
+    [Fact]
+    public void Negate_InvokeEmpty_Success()
+    {
+        var vector = new Vector();
+        vector.Negate();
+        Assert.Equal(0, vector.X);
+        Assert.Equal(0, vector.Y);
+    }
+
+    [Fact]
+    public void Negate_InvokeNormal_Success()
+    {
+        var vector = new Vector(1, 2);
+        vector.Negate();
+        Assert.Equal(-1, vector.X);
+        Assert.Equal(-2, vector.Y);
+    }
+
+    [Fact]
+    public void OperatorNegate_InvokeEmpty_Success()
+    {
+        var vector = new Vector();
+        Vector result = -vector;
+        Assert.Equal(0, result.X);
+        Assert.Equal(0, result.Y);
+    }
+
+    [Fact]
+    public void OperatorNegate_InvokeNormal_Success()
+    {
+        var vector = new Vector(1, 2);
+        Vector result = -vector;
+        Assert.Equal(-1, result.X);
+        Assert.Equal(-2, result.Y);
+    }
+
+    public static IEnumerable<object[]> Parse_TestData()
+    {
+        yield return new object[] { "0,0", new Vector(0, 0) };
+        yield return new object[] { "1,2", new Vector(1, 2) };
+        yield return new object[] { "1.1,2.2", new Vector(1.1, 2.2) };
+        yield return new object[] { "   1   ,   2  ", new Vector(1, 2) };
+        yield return new object[] { "-1,-2", new Vector(-1, -2) };
+    }
+
+    [Theory]
+    [MemberData(nameof(Parse_TestData))]
+    public void Parse_Invoke_Success(string source, Vector expected)
+    {
+        Vector result = Vector.Parse(source);
+        Assert.Equal(expected.X, result.X, precision: 5);
+        Assert.Equal(expected.Y, result.Y, precision: 5);
+    }
+
+    [Fact]
+    public void Parse_NullSource_ThrowsInvalidOperationException()
+    {
+        Assert.Throws<InvalidOperationException>(() => Vector.Parse(null));
+    }
+
+    public static IEnumerable<object[]> Parse_InvalidSource_TestData()
+    {
+        yield return new object[] { "" };
+        yield return new object[] { "  " };
+        yield return new object[] { "," };
+        yield return new object[] { "1" };
+        yield return new object[] { "1," };
+        yield return new object[] { "1,2," };
+        yield return new object[] { "1,2,3" };
+        yield return new object[] { "1,2,test" };
+        yield return new object[] { "Empty," };
+        yield return new object[] { "Identity," };
+    }
+
+    [Theory]
+    [MemberData(nameof(Parse_InvalidSource_TestData))]
+    public void Parse_InvalidSource_ThrowsInvalidOperationException(string source)
+    {
+        Assert.Throws<InvalidOperationException>(() => Vector.Parse(source));
+    }
+
+    public static IEnumerable<object[]> Parse_NotDouble_TestData()
+    {
+        yield return new object[] { "Empty" };
+        yield return new object[] { " Empty " };
+        yield return new object[] { "Empty,2" };
+        yield return new object[] { "Identity" };
+        yield return new object[] { " Identity " };
+        yield return new object[] { "Identity,2" };
+        yield return new object[] { "test" };
+        yield return new object[] { "test,2" };
+        yield return new object[] { "1,test" };
+        yield return new object[] { "1,test,3" };
+        yield return new object[] { "1;2" };
+        yield return new object[] { "1.2.3" };
+        yield return new object[] { """1"",""2""" };
+    }
+
+    [Theory]
+    [MemberData(nameof(Parse_NotDouble_TestData))]
+    public void Parse_NotDouble_ThrowsFormatException(string source)
+    {
+        Assert.Throws<FormatException>(() => Vector.Parse(source));
+    }
+
+    public static IEnumerable<object[]> ToString_TestData()
+    {
+        yield return new object[] { new Vector(), "0,0" };
+        yield return new object[] { new Vector(0, 0), "0,0" };
+        yield return new object[] { new Vector(1, 2), "1,2" };
+        yield return new object[] { new Vector(1.1, 2.2), "1.1,2.2" };
+        yield return new object[] { new Vector(-1, -2), "-1,-2" };
+    }
+
+    [Theory]
+    [MemberData(nameof(ToString_TestData))]
+    public void ToString_Invoke_ReturnsExpected(Vector vector, string expected)
+    {
+        Assert.Equal(expected, vector.ToString());
+    }
+
+    [Theory]
+    [MemberData(nameof(ToString_TestData))]
+    public void ToString_InvokeInvariantCulture_ReturnsExpected(Vector vector, string expected)
+    {
+        Assert.Equal(expected, vector.ToString(CultureInfo.InvariantCulture));
+    }
+
+    public static IEnumerable<object[]> ToString_IFormatProviderCustom_TestData()
+    {
+        yield return new object[] { new Vector(), "|", "0,0" };
+        yield return new object[] { new Vector(), "|_", "0,0" };
+        yield return new object[] { new Vector(), ",_", "0;0" };
+        yield return new object[] { new Vector(), ",", "0;0" };
+        yield return new object[] { new Vector(), ";", "0,0" };
+        yield return new object[] { new Vector(), " ", "0,0" };
+
+        yield return new object[] { new Vector(0, 0), "|", "0,0" };
+        yield return new object[] { new Vector(0, 0), "|_", "0,0" };
+        yield return new object[] { new Vector(0, 0), ",_", "0;0" };
+        yield return new object[] { new Vector(0, 0), ",", "0;0" };
+        yield return new object[] { new Vector(0, 0), ";", "0,0" };
+        yield return new object[] { new Vector(0, 0), " ", "0,0" };
+
+        yield return new object[] { new Vector(1, 2), "|", "1,2" };
+        yield return new object[] { new Vector(1, 2), "|_", "1,2" };
+        yield return new object[] { new Vector(1, 2), ",_", "1;2" };
+        yield return new object[] { new Vector(1, 2), ",", "1;2" };
+        yield return new object[] { new Vector(1, 2), ";", "1,2" };
+        yield return new object[] { new Vector(1, 2), " ", "1,2" };
+        
+        yield return new object[] { new Vector(1.1, 2.2), "|", "1|1,2|2" };
+        yield return new object[] { new Vector(1.1, 2.2), "|_", "1|_1,2|_2" };
+        yield return new object[] { new Vector(1.1, 2.2), ",_", "1,_1;2,_2" };
+        yield return new object[] { new Vector(1.1, 2.2), ",", "1,1;2,2" };
+        yield return new object[] { new Vector(1.1, 2.2), ";", "1;1,2;2" };
+        yield return new object[] { new Vector(1.1, 2.2), " ", "1 1,2 2" };
+
+        yield return new object[] { new Vector(-1, -2), "|", "-1,-2" };
+        yield return new object[] { new Vector(-1, -2), "|_", "-1,-2" };
+        yield return new object[] { new Vector(-1, -2), ",_", "-1;-2" };
+        yield return new object[] { new Vector(-1, -2), ",", "-1;-2" };
+        yield return new object[] { new Vector(-1, -2), ";", "-1,-2" };
+        yield return new object[] { new Vector(-1, -2), " ", "-1,-2" };
+    }
+
+    [Theory]
+    [MemberData(nameof(ToString_IFormatProviderCustom_TestData))]
+    public void ToString_InvokeIFormatProviderCustom_ReturnsExpected(Vector vector, string numberDecimalSeparator, string expected)
+    {
+        var culture = new CultureInfo("en-US");
+        NumberFormatInfo formatInfo = culture.NumberFormat;
+        formatInfo.NumberDecimalSeparator = numberDecimalSeparator;
+
+        Assert.Equal(expected, vector.ToString(formatInfo));
+    }
+
+    [Theory]
+    [MemberData(nameof(ToString_TestData))]
+    public void ToString_InvokeIFormattableInvariantCulture_ReturnsExpected(Vector vector, string expected)
+    {
+        IFormattable formattable = vector;
+
+        Assert.Equal(expected, formattable.ToString(null, null));
+        Assert.Equal(expected, formattable.ToString(null, CultureInfo.InvariantCulture));
+    }
+
+    [Theory]
+    [InlineData("|", "1|23,2|35")]
+    [InlineData("|_", "1|_23,2|_35")]
+    [InlineData(",_", "1,_23;2,_35")]
+    [InlineData(",", "1,23;2,35")]
+    [InlineData(";", "1;23,2;35")]
+    [InlineData(" ", "1 23,2 35")]
+    public void ToString_InvokeIFormattableCustomFormat_ReturnsExpected(string numberDecimalSeparator, string expected)
+    {
+        var vector = new Vector(1.23456, 2.34567);
+        IFormattable formattable = vector;
+
+        var culture = new CultureInfo("en-US");
+        NumberFormatInfo formatInfo = culture.NumberFormat;
+        formatInfo.NumberDecimalSeparator = numberDecimalSeparator;
+
+        Assert.Equal(expected, formattable.ToString("F2", formatInfo));
+    }
+
+    [Fact]
+    public void OperatorConvertPoint_InvokeEmpty_ReturnsExpected()
+    {
+        Point result = (Point)new Vector();
+        Assert.Equal(0, result.X);
+        Assert.Equal(0, result.Y);
+    }
+
+    [Theory]
+    [InlineData(0, 0)]
+    [InlineData(1, 0)]
+    [InlineData(0, 1)]
+    [InlineData(1, 1)]
+    [InlineData(1, 2)]
+    [InlineData(1.1, 2.2)]
+    [InlineData(double.NaN, double.NaN)]
+    [InlineData(double.NaN, 0)]
+    [InlineData(0, double.NaN)]
+    [InlineData(-1, -2)]
+    public void OperatorConvertPoint_InvokeNormal_ReturnsExpected(double x, double y)
+    {
+        Point result = (Point)new Vector(x, y);
+        Assert.Equal(x, result.X);
+        Assert.Equal(y, result.Y);
+    }
+
+    [Fact]
+    public void OperatorConvertSize_InvokeEmpty_ReturnsExpected()
+    {
+        Size result = (Size)new Vector();
+        Assert.Equal(0, result.Width);
+        Assert.Equal(0, result.Height);
+    }
+
+    [Theory]
+    [InlineData(0, 0, 0, 0)]
+    [InlineData(1, 0, 1, 0)]
+    [InlineData(0, 1, 0, 1)]
+    [InlineData(1, 1, 1, 1)]
+    [InlineData(1, 2, 1, 2)]
+    [InlineData(1.1, 2.2, 1.1, 2.2)]
+    [InlineData(double.NaN, double.NaN, double.NaN, double.NaN)]
+    [InlineData(double.NaN, 0, double.NaN, 0)]
+    [InlineData(0, double.NaN, 0, double.NaN)]
+    [InlineData(-1, -2, 1, 2)]
+    public void OperatorConvertSize_InvokeNormal_ReturnsExpected(double x, double y, double expectedWidth, double expectedHeight)
+    {
+        Size result = (Size)new Vector(x, y);
+        Assert.Equal(expectedWidth, result.Width);
+        Assert.Equal(expectedHeight, result.Height);
+    }
+
+    [Fact]
+    public void TypeConverter_Get_ReturnsExpected()
+    {
+        Assert.IsType<VectorConverter>(TypeDescriptor.GetConverter(typeof(Vector)));
+    }
+    
+    [Fact]
+    public void ValueSerializer_Get_ReturnsExpected()
+    {
+        Assert.IsType<VectorValueSerializer>(ValueSerializer.GetSerializerFor(typeof(Vector)));
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/WeakEventManagerTTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/WeakEventManagerTTests.cs
new file mode 100644
index 00000000000..f25b355fcf3
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/WeakEventManagerTTests.cs
@@ -0,0 +1,412 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Reflection;
+
+namespace System.Windows.Tests;
+
+public class WeakEventManagerTTests
+{
+    public static IEnumerable<object?[]> AddHandler_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { new EventArgs() };
+        yield return new object?[] { EventArgs.Empty };
+    }
+
+    [Theory]
+    [MemberData(nameof(AddHandler_TestData))]
+    public void AddHandler_Invoke_Success(EventArgs e)
+    {
+        var source1 = new ClassWithEvents();
+        var source2 = new ClassWithEvents();
+        int callCount1 = 0;
+        int callCount2 = 0;
+        EventHandler<EventArgs> handler1 = (sender, actualE) =>
+        {
+            Assert.Same(source1, sender);
+            Assert.Same(e, actualE);
+            callCount1++;
+        };
+        EventHandler<EventArgs> handler2 = (sender, actualE) =>
+        {
+            Assert.Same(source1, sender);
+            Assert.Same(e, actualE);
+            callCount2++;
+        };
+
+        // Add.
+        WeakEventManager<ClassWithEvents, EventArgs>.AddHandler(source1, nameof(ClassWithEvents.CustomEvent), handler1);
+
+        // Call.
+        source1.OnCustomEvent(source1, e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Call invalid source1.
+        source1.OnCustomEvent(source2, e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        
+        source1.OnCustomEvent(new object(), e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        
+        source1.OnCustomEvent(null!, e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Add again.
+        WeakEventManager<ClassWithEvents, EventArgs>.AddHandler(source1, nameof(ClassWithEvents.CustomEvent), handler1);
+        source1.OnCustomEvent(source1, e);
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Add another.
+        WeakEventManager<ClassWithEvents, EventArgs>.AddHandler(source1, nameof(ClassWithEvents.CustomEvent), handler2);
+        source1.OnCustomEvent(source1, e);
+        Assert.Equal(5, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove second.
+        WeakEventManager<ClassWithEvents, EventArgs>.RemoveHandler(source1, nameof(ClassWithEvents.CustomEvent), handler2);
+        source1.OnCustomEvent(source1, e);
+        Assert.Equal(7, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove first.
+        WeakEventManager<ClassWithEvents, EventArgs>.RemoveHandler(source1, nameof(ClassWithEvents.CustomEvent), handler1);
+        source1.OnCustomEvent(source1, e);
+        Assert.Equal(8, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove again.
+        WeakEventManager<ClassWithEvents, EventArgs>.RemoveHandler(source1, nameof(ClassWithEvents.CustomEvent), handler1);
+        source1.OnCustomEvent(source1, e);
+        Assert.Equal(8, callCount1);
+        Assert.Equal(1, callCount2);
+    }
+
+    [Theory]
+    [MemberData(nameof(AddHandler_TestData))]
+    public void AddHandler_InvokeNoSource_Success(EventArgs e)
+    {
+        var source = new ClassWithEvents();
+        int callCount1 = 0;
+        int callCount2 = 0;
+        EventHandler<EventArgs> handler1 = (sender, actualE) =>
+        {
+            Assert.Null(sender);
+            //Assert.Same(e, actualE);
+            callCount1++;
+        };
+        EventHandler<EventArgs> handler2 = (sender, actualE) =>
+        {
+            Assert.Null(sender);
+            //Assert.Same(e, actualE);
+            callCount2++;
+        };
+
+        // Add.
+        WeakEventManager<ClassWithEvents, EventArgs>.AddHandler(null!, nameof(ClassWithEvents.StaticEvent1), handler1);
+
+        // Call.
+        ClassWithEvents.OnStaticEvent1(null, e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Call invalid source.
+        ClassWithEvents.OnStaticEvent1(source, e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+        
+        ClassWithEvents.OnStaticEvent1(new object(), e);
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Add again.
+        WeakEventManager<ClassWithEvents, EventArgs>.AddHandler(null!, nameof(ClassWithEvents.StaticEvent1), handler1);
+        ClassWithEvents.OnStaticEvent1(null, e);
+        Assert.Equal(3, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Add another.
+        WeakEventManager<ClassWithEvents, EventArgs>.AddHandler(null!, nameof(ClassWithEvents.StaticEvent1), handler2);
+        ClassWithEvents.OnStaticEvent1(null, e);
+        Assert.Equal(5, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove second.
+        WeakEventManager<ClassWithEvents, EventArgs>.RemoveHandler(null!, nameof(ClassWithEvents.StaticEvent1), handler2);
+        ClassWithEvents.OnStaticEvent1(null, e);
+        Assert.Equal(7, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove first.
+        WeakEventManager<ClassWithEvents, EventArgs>.RemoveHandler(null!, nameof(ClassWithEvents.StaticEvent1), handler1);
+        ClassWithEvents.OnStaticEvent1(null, e);
+        Assert.Equal(8, callCount1);
+        Assert.Equal(1, callCount2);
+
+        // Remove again.
+        WeakEventManager<ClassWithEvents, EventArgs>.RemoveHandler(null!, nameof(ClassWithEvents.StaticEvent1), handler1);
+        ClassWithEvents.OnStaticEvent1(null, e);
+        Assert.Equal(8, callCount1);
+        Assert.Equal(1, callCount2);
+    }
+
+    [Fact]
+    public void AddHandler_InvokeMultipleTimes_Success()
+    {
+        var source = new ClassWithEvents();
+        EventHandler<EventArgs> handler1 = (sender, e) => { };
+        EventHandler<EventArgs> handler2 = (sender, actualE) => { };
+
+        // Add.
+        WeakEventManager<ClassWithEvents, EventArgs>.AddHandler(source, nameof(ClassWithEvents.CustomEvent), handler1);
+
+        // Add again.
+        WeakEventManager<ClassWithEvents, EventArgs>.AddHandler(source, nameof(ClassWithEvents.CustomEvent), handler1);
+
+        // Add another.
+        WeakEventManager<ClassWithEvents, EventArgs>.AddHandler(source, nameof(ClassWithEvents.CustomEvent), handler2);
+    }
+
+    [Fact]
+    public void AddHandler_NullSourceNonStaticEvent_ThrowsTargetException()
+    {
+        // Add.
+        Assert.Throws<TargetException>(() => WeakEventManager<ClassWithEvents, EventArgs>.AddHandler(null!, nameof(ClassWithEvents.CustomEvent), (sender, e) => { }));
+
+        // Add again.
+        WeakEventManager<ClassWithEvents, EventArgs>.AddHandler(null!, nameof(ClassWithEvents.CustomEvent), (sender, e) => { });
+    }
+
+    [Fact]
+    public void AddHandler_NullEventName_ThrowsArgumentNullException()
+    {
+        // TODO: should throw ArgumentNullException
+        //Assert.Throws<ArgumentNullException>("eventName", () => WeakEventManager<object, EventArgs>.AddHandler(new object(), null, (sender, e) => { }));
+        Assert.Throws<NullReferenceException>(() => WeakEventManager<object, EventArgs>.AddHandler(new object(), null, (sender, e) => { }));
+
+        // Call again to test caching.
+        Assert.Throws<NullReferenceException>(() => WeakEventManager<object, EventArgs>.AddHandler(new object(), null, (sender, e) => { }));
+    }
+
+    public static IEnumerable<object?[]> AddHandler_NoSuchEvent_TestData()
+    {
+        yield return new object?[] { null, "" };
+        yield return new object?[] { null, " " };
+        yield return new object?[] { null, "eventName" };
+        yield return new object?[] { new object(), "" };
+        yield return new object?[] { new object(), " " };
+        yield return new object?[] { new object(), "eventName" };
+        yield return new object?[] { new ClassWithEvents(), nameof(ClassWithEvents.CustomEvent) };
+        yield return new object?[] { new ClassWithEvents(), nameof(ClassWithEvents.StaticEvent1) };
+    }
+    
+    [Theory]
+    [MemberData(nameof(AddHandler_NoSuchEvent_TestData))]
+    public void AddHandler_NoSuchEvent_ThrowsArgumentException(object source, string eventName)
+    {
+        var handler = new EventHandler<EventArgs>((sender, e) => { });
+        // TODO: this should have a paramName.
+        Assert.Throws<ArgumentException>(() => WeakEventManager<object, EventArgs>.AddHandler(source, eventName, handler));
+
+        // Call again to test caching.
+        Assert.Throws<ArgumentException>(() => WeakEventManager<object, EventArgs>.AddHandler(source, eventName, handler));
+    }
+
+    [Fact]
+    public void AddHandler_NullHandler_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("handler", () => WeakEventManager<object, EventArgs>.AddHandler(new object(), "EventName", null));
+    }
+
+    [Fact]
+    public void RemoveHandler_Invoke_Success()
+    {
+        var source = new ClassWithEvents();
+        int callCount = 0;
+        EventHandler<EventArgs> handler = (sender, e) => callCount++;
+
+        WeakEventManager<ClassWithEvents, EventArgs>.AddHandler(source, nameof(ClassWithEvents.CustomEvent), handler);
+
+        // Remove.
+        WeakEventManager<ClassWithEvents, EventArgs>.RemoveHandler(source, nameof(ClassWithEvents.CustomEvent), handler);
+        Assert.Equal(0, callCount);
+
+        // Call event.
+        source.OnCustomEvent(source, EventArgs.Empty);
+        Assert.Equal(0, callCount);
+
+        // Remove again.
+        WeakEventManager<ClassWithEvents, EventArgs>.RemoveHandler(source, nameof(ClassWithEvents.CustomEvent), handler);
+        Assert.Equal(0, callCount);
+
+        // Call event.
+        source.OnCustomEvent(source, EventArgs.Empty);
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void RemoveHandler_InvokeNoSource_Success()
+    {
+        int callCount = 0;
+        EventHandler<EventArgs> handler = (sender, e) => callCount++;
+
+        WeakEventManager<ClassWithEvents, EventArgs>.AddHandler(null!, nameof(ClassWithEvents.StaticEvent2), handler);
+
+        // Remove.
+        WeakEventManager<ClassWithEvents, EventArgs>.RemoveHandler(null!, nameof(ClassWithEvents.StaticEvent2), handler);
+        Assert.Equal(0, callCount);
+
+        // Call event.
+        ClassWithEvents.OnStaticEvent2(null!, EventArgs.Empty);
+        Assert.Equal(0, callCount);
+
+        // Remove again.
+        WeakEventManager<ClassWithEvents, EventArgs>.RemoveHandler(null!, nameof(ClassWithEvents.StaticEvent2), handler);
+        Assert.Equal(0, callCount);
+
+        // Call event.
+        ClassWithEvents.OnStaticEvent2(null!, EventArgs.Empty);
+        Assert.Equal(0, callCount);
+    }
+
+    [Fact]
+    public void RemoveHandler_NoSuchSource_Success()
+    {
+        var source1 = new ClassWithEvents();
+        var source2 = new ClassWithEvents();
+        int callCount = 0;
+        EventHandler<EventArgs> handler = (sender, e) => callCount++;
+
+        WeakEventManager<ClassWithEvents, EventArgs>.AddHandler(source1, nameof(ClassWithEvents.CustomEvent), handler);
+
+        // Remove.
+        WeakEventManager<ClassWithEvents, EventArgs>.RemoveHandler(source2, nameof(ClassWithEvents.CustomEvent), handler);
+        Assert.Equal(0, callCount);
+
+        // Call event.
+        source1.OnCustomEvent(source1, EventArgs.Empty);
+        Assert.Equal(1, callCount);
+
+        // Remove again.
+        WeakEventManager<ClassWithEvents, EventArgs>.RemoveHandler(source2, nameof(ClassWithEvents.CustomEvent), handler);
+        Assert.Equal(1, callCount);
+
+        // Call event.
+        source1.OnCustomEvent(source1, EventArgs.Empty);
+        Assert.Equal(2, callCount);
+    }
+
+    [Fact]
+    public void RemoveHandler_NoSuchHandler_Success()
+    {
+        var source = new ClassWithEvents();
+        int callCount1 = 0;
+        EventHandler<EventArgs> handler1 = (sender, e) => callCount1++;
+        int callCount2 = 0;
+        EventHandler<EventArgs> handler2 = (sender, e) => callCount2++;
+
+        WeakEventManager<ClassWithEvents, EventArgs>.AddHandler(source, nameof(ClassWithEvents.CustomEvent), handler1);
+
+        // Remove.
+        WeakEventManager<ClassWithEvents, EventArgs>.RemoveHandler(source, nameof(ClassWithEvents.CustomEvent), handler2);
+        Assert.Equal(0, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Call event.
+        source.OnCustomEvent(source, EventArgs.Empty);        
+        Assert.Equal(1, callCount1);
+        Assert.Equal(0, callCount2);
+
+        // Remove again.
+        WeakEventManager<ClassWithEvents, EventArgs>.RemoveHandler(source, nameof(ClassWithEvents.CustomEvent), handler2);
+
+        // Call event.
+        source.OnCustomEvent(source, EventArgs.Empty);        
+        Assert.Equal(2, callCount1);
+        Assert.Equal(0, callCount2);
+    }
+
+    [Fact]
+    public void RemoveHandler_NullSourceNonStaticEvent_()
+    {
+        EventHandler<EventArgs> handler = (sender, e) => { };
+        WeakEventManager<ClassWithEvents, EventArgs>.RemoveHandler(null!, nameof(ClassWithEvents.CustomEvent), handler);
+    }
+
+    [Fact]
+    public void RemoveHandler_NullHandler_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("handler", () => WeakEventManager<object, EventArgs>.RemoveHandler(new object(), "EventName", null));
+    }
+
+    [Fact]
+    public void RemoveHandler_NullEventName_ThrowsArgumentNullException()
+    {
+        // TODO: this should throw ArgumentNullException
+        //Assert.Throws<ArgumentNullException>("eventName", () => WeakEventManager<object, EventArgs>.RemoveHandler(new object(), null, (sender, e) => { }));
+        Assert.Throws<NullReferenceException>(() => WeakEventManager<object, EventArgs>.RemoveHandler(new object(), null, (sender, e) => { }));
+    }
+
+    public static IEnumerable<object?[]> RemoveHandler_NoSuchEvent_TestData()
+    {
+        yield return new object?[] { null, "" };
+        yield return new object?[] { null, " " };
+        yield return new object?[] { null, "eventName" };
+        yield return new object?[] { new object(), "" };
+        yield return new object?[] { new object(), " " };
+        yield return new object?[] { new object(), "eventName" };
+        yield return new object?[] { new ClassWithEvents(), nameof(ClassWithEvents.CustomEvent) };
+        yield return new object?[] { new ClassWithEvents(), nameof(ClassWithEvents.StaticEvent1) };
+    }
+
+    [Theory]
+    [MemberData(nameof(RemoveHandler_NoSuchEvent_TestData))]
+    public void RemoveHandler_NoSuchEvent_ThrowsArgumentException(object source, string eventName)
+    {
+        var handler = new EventHandler<EventArgs>((sender, e) => { });
+        // TODO: this should have a paramName.
+        Assert.Throws<ArgumentException>(() => WeakEventManager<object, EventArgs>.RemoveHandler(source, eventName, handler));
+
+        // Call again to test caching.
+        Assert.Throws<ArgumentException>(() => WeakEventManager<object, EventArgs>.RemoveHandler(source, eventName, handler));
+    }
+
+    private class ClassWithEvents
+    {
+        private EventHandler? _event;
+
+        public event EventHandler CustomEvent
+        {
+            add => _event += value;
+            remove => _event -= value;
+        }
+
+        public void OnCustomEvent(object sender, EventArgs e) => _event?.Invoke(sender, e);
+
+        private static EventHandler? _staticEvent1;
+
+        public static event EventHandler StaticEvent1
+        {
+            add => _staticEvent1 += value;
+            remove => _staticEvent1 -= value;
+        }
+
+        public static void OnStaticEvent1(object? sender, EventArgs e) => _staticEvent1?.Invoke(sender, e);
+
+        private static EventHandler? _staticEvent2;
+
+        public static event EventHandler StaticEvent2
+        {
+            add => _staticEvent2 += value;
+            remove => _staticEvent2 -= value;
+        }
+
+        public static void OnStaticEvent2(object? sender, EventArgs e) => _staticEvent2?.Invoke(sender, e);
+    }
+}
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/WeakEventManagerTests.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/WeakEventManagerTests.cs
new file mode 100644
index 00000000000..fab6d3be383
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/System/Windows/WeakEventManagerTests.cs
@@ -0,0 +1,6063 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Reflection;
+using System.Windows.Threading;
+
+namespace System.Windows.Tests;
+
+public class WeakEventManagerTests : WeakEventManager
+{
+    // TODO:
+    // Read/Write lock using RemoteExecutor
+
+    [Fact]
+    public void Ctor_Default()
+    {
+        var manager = new SubWeakEventManager();
+        Assert.NotNull(manager.Dispatcher);
+        Assert.Same(manager.Dispatcher, manager.Dispatcher);
+        Assert.Same(Dispatcher.CurrentDispatcher, manager.Dispatcher);
+        IDisposable readLock = manager.ReadLock;
+        try
+        {
+            Assert.NotNull(readLock);
+        }
+        finally
+        {
+            readLock.Dispose();
+        }
+
+        IDisposable writeLock = manager.WriteLock;
+        try
+        {
+            Assert.NotNull(writeLock);
+        }
+        finally
+        {
+            writeLock.Dispose();
+        }
+    }
+
+    [Fact]
+    public void Item_Get_ReturnsExpected()
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction = (source) => {};
+
+        var source = new object();
+        var listener = new CustomWeakEventListener();
+        manager.ProtectedAddListener(source, listener);
+
+        // Get.
+        SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener, list[0]);
+    }
+
+    public static IEnumerable<object?[]> Item_GetNoSuchSource_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { new object() };
+        yield return new object?[] { 1 };
+    }
+
+    [Theory]
+    [MemberData(nameof(Item_GetNoSuchSource_TestData))]
+    public void Item_GetNoSuchSourceNotEmpty_ReturnsExpected(object source)
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction = (source) => {};
+
+        manager.ProtectedAddListener(new object(), new CustomWeakEventListener());
+        Assert.Null(manager[source]);
+    }
+
+    [Theory]
+    [MemberData(nameof(Item_GetNoSuchSource_TestData))]
+    public void Item_GetNoSuchSourceEmpty_ReturnsExpected(object source)
+    {
+        var manager = new SubWeakEventManager();
+        Assert.Null(manager[source]);
+    }
+
+    public static IEnumerable<object?[]> Item_Set_TestData()
+    {
+        yield return new object?[] { new object(), null };
+        yield return new object?[] { new object(), new object() };
+        yield return new object?[] { new object(), 1 };
+        yield return new object?[] { 1, null };
+        yield return new object?[] { 1, new object() };
+        yield return new object?[] { 1, 1 };
+    }
+
+    [Theory]
+    [MemberData(nameof(Item_Set_TestData))]
+    public void Item_Set_GetReturnsExpected(object source, object value)
+    {
+        var manager = new SubWeakEventManager();
+
+        // Set.
+        manager[source] = value;
+        Assert.Equal(value, manager[source]);
+
+        // Set same.
+        manager[source] = value;
+        Assert.Equal(value, manager[source]);
+    }
+
+    public static IEnumerable<object?[]> Item_SetNullSource_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { new object() };
+        yield return new object?[] { 1 };
+    }
+
+    [Theory]
+    [MemberData(nameof(Item_SetNullSource_TestData))]
+    public void Item_SetNullSource_GetReturnsNull(object value)
+    {
+        var manager = new SubWeakEventManager();
+        object source = null!;
+
+        // Set.
+        manager[source] = value;
+        Assert.Null(manager[source]);
+
+        // Set same.
+        manager[source] = value;
+        Assert.Null(manager[source]);
+    }
+
+    public static IEnumerable<object?[]> DeliverEvent_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { new EventArgs() };
+        yield return new object?[] { EventArgs.Empty };
+    }
+
+    [Theory]
+    [MemberData(nameof(DeliverEvent_TestData))]
+    public void DeliverEvent_InvokeWithListeners_Success(EventArgs args)
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction = (source) => {};
+        var source = new object();
+        var events = new List<string>();
+        var listener1 = new CustomWeakEventListener();
+        listener1.ReceiveWeakEventAction = (t, s, e) =>
+        {
+            Assert.Same(typeof(SubWeakEventManager), t);
+            Assert.Same(source, s);
+            Assert.Same(args, e);
+            events.Add("listener1");
+            return true;
+        };
+        var listener2 = new CustomWeakEventListener();
+        listener2.ReceiveWeakEventAction = (t, s, e) =>
+        {
+            Assert.Same(typeof(SubWeakEventManager), t);
+            Assert.Same(source, s);
+            Assert.Same(args, e);
+            events.Add("listener2");
+            return true;
+        };
+        manager.ProtectedAddListener(source, listener1);
+        manager.ProtectedAddListener(source, listener2);
+
+        manager.DeliverEvent(source, args);
+        Assert.Equal(new string[] { "listener1", "listener2" }, events);
+    }
+
+    [Theory]
+    [MemberData(nameof(DeliverEvent_TestData))]
+    public void DeliverEvent_InvokeWithHandlers_Success(EventArgs args)
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction = (source) => {};
+        var source = new object();
+        var events = new List<string>();
+        var listener1 = new CustomWeakEventListener();
+        listener1.HandlerAction = (s, e) =>
+        {
+            Assert.Same(source, s);
+            Assert.Same(args, e);
+            events.Add("handler1");
+        };
+        var listener2 = new CustomWeakEventListener();
+        listener2.HandlerAction = (s, e) =>
+        {
+            Assert.Same(source, s);
+            Assert.Same(args, e);
+            events.Add("handler2");
+        };
+        Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), listener1, nameof(CustomWeakEventListener.Handler));
+        Delegate handler2 = Delegate.CreateDelegate(typeof(EventHandler), listener2, nameof(CustomWeakEventListener.Handler));
+
+        manager.ProtectedAddHandler(source, handler1);
+        manager.ProtectedAddHandler(source, handler2);
+
+        manager.DeliverEvent(source, args);
+        Assert.Equal(new string[] { "handler1", "handler2" }, events);
+    }
+
+    [Theory]
+    [MemberData(nameof(DeliverEvent_TestData))]
+    public void DeliverEvent_InvokeWithListenersAndHandlers_Success(EventArgs args)
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction = (source) => {};
+        var source = new object();
+        var events = new List<string>();
+        var listener1 = new CustomWeakEventListener();
+        listener1.HandlerAction = (s, e) =>
+        {
+            Assert.Same(source, s);
+            Assert.Same(args, e);
+            events.Add("handler1");
+        };
+        var listener2 = new CustomWeakEventListener();
+        listener2.ReceiveWeakEventAction = (t, s, e) =>
+        {
+            Assert.Same(typeof(SubWeakEventManager), t);
+            Assert.Same(source, s);
+            Assert.Same(args, e);
+            events.Add("listener1");
+            return true;
+        };
+        var listener3 = new CustomWeakEventListener();
+        listener3.HandlerAction = (s, e) =>
+        {
+            Assert.Same(source, s);
+            Assert.Same(args, e);
+            events.Add("handler2");
+        };
+        var listener4 = new CustomWeakEventListener();
+        listener4.ReceiveWeakEventAction = (t, s, e) =>
+        {
+            Assert.Same(typeof(SubWeakEventManager), t);
+            Assert.Same(source, s);
+            Assert.Same(args, e);
+            events.Add("listener2");
+            return true;
+        };
+        Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), listener1, nameof(CustomWeakEventListener.Handler));
+        Delegate handler2 = Delegate.CreateDelegate(typeof(EventHandler), listener3, nameof(CustomWeakEventListener.Handler));
+        manager.ProtectedAddHandler(source, handler1);
+        manager.ProtectedAddListener(source, listener2);
+        manager.ProtectedAddHandler(source, handler2);
+        manager.ProtectedAddListener(source, listener4);
+
+        manager.DeliverEvent(source, args);
+        Assert.Equal(new string[] { "handler1", "listener1", "handler2", "listener2" }, events);
+    }
+
+    [Theory]
+    [MemberData(nameof(DeliverEvent_TestData))]
+    public void DeliverEvent_InvokeMultipleSources_Success(EventArgs args)
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction = (source) => {};
+        var source1 = new object();
+        var source2 = new object();
+        var events = new List<string>();
+        var listener1 = new CustomWeakEventListener();
+        listener1.ReceiveWeakEventAction = (t, s, e) =>
+        {
+            Assert.Same(typeof(SubWeakEventManager), t);
+            Assert.Same(source1, s);
+            Assert.Same(args, e);
+            events.Add("listener1");
+            return true;
+        };
+        var listener2 = new CustomWeakEventListener();
+        listener2.ReceiveWeakEventAction = (t, s, e) =>
+        {
+            Assert.Same(typeof(SubWeakEventManager), t);
+            Assert.Same(source2, s);
+            Assert.Same(args, e);
+            events.Add("listener2");
+            return true;
+        };
+        manager.ProtectedAddListener(source1, listener1);
+        manager.ProtectedAddListener(source2, listener2);
+
+        manager.DeliverEvent(source2, args);
+        Assert.Equal(new string[] { "listener2" }, events);
+        
+        manager.DeliverEvent(source1, args);
+        Assert.Equal(new string[] { "listener2", "listener1" }, events);
+    }
+
+    [Theory]
+    [MemberData(nameof(DeliverEvent_TestData))]
+    public void DeliverEvent_InvokeWithInvalidHandlerAction_ThrowsInvalidCastException(EventArgs args)
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction = (source) => {};
+        var source = new object();
+        Delegate handler = () => {};
+        manager.ProtectedAddHandler(source, handler);
+
+        Assert.Throws<InvalidCastException>(() => manager.DeliverEvent(source, args));
+    }
+
+    [Theory]
+    [MemberData(nameof(DeliverEvent_TestData))]
+    public void DeliverEvent_InvokeWithInvalidHandlerFunc_ThrowsInvalidCastException(EventArgs args)
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction = (source) => {};
+        var source = new object();
+        bool EventHandler(object sender, EventArgs args) => true;
+        manager.ProtectedAddHandler(source, EventHandler);
+
+        Assert.Throws<InvalidCastException>(() => manager.DeliverEvent(source, args));
+    }
+
+    [Theory]
+    [MemberData(nameof(DeliverEvent_TestData))]
+    public void DeliverEvent_InvokeWithInvalidHandlerGenericEventArgs_ThrowsInvalidCastException(EventArgs args)
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction = (source) => {};
+        var source = new object();
+        var target = new CustomWeakEventListener();
+        Delegate handler = Delegate.CreateDelegate(typeof(EventHandler<EventArgs>), target, nameof(CustomWeakEventListener.Handler));
+        manager.ProtectedAddHandler(source, handler);
+
+        Assert.Throws<InvalidCastException>(() => manager.DeliverEvent(source, args));
+    }
+
+    [Theory]
+    [MemberData(nameof(DeliverEvent_TestData))]
+    public void DeliverEvent_InvokeNoSuchSource_Success(EventArgs args)
+    {
+        var manager = new SubWeakEventManager();
+        manager.DeliverEvent(new object(), args);
+        manager.DeliverEvent(null!, args);
+    }
+
+    [Theory]
+    [MemberData(nameof(DeliverEvent_TestData))]
+    public void DeliverEvent_InvokeNotEmptyNoSuchSource_Success(EventArgs args)
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction = (source) => {};
+        var source1 = new object();
+        var events = new List<string>();
+        var listener = new CustomWeakEventListener();
+        listener.ReceiveWeakEventAction = (t, s, e) =>
+        {
+            events.Add("listener1");
+            return true;
+        };
+        manager.ProtectedAddListener(source1, listener);
+
+        var source2 = new object();
+        manager.DeliverEvent(source2, args);
+        Assert.Empty(events);
+        
+        manager.DeliverEvent(null!, args);
+        Assert.Empty(events);
+    }
+
+    [Theory]
+    [MemberData(nameof(DeliverEvent_TestData))]
+    public void DeliverEvent_InvokeEmpty_Success(EventArgs args)
+    {
+        var manager = new SubWeakEventManager();
+        manager.DeliverEvent(new object(), args);
+        manager.DeliverEvent(null!, args);
+    }
+
+    [Theory]
+    [MemberData(nameof(DeliverEvent_TestData))]
+    public void DeliverEvent_SourceNotListenerList_ThrowsInvalidCastException(EventArgs args)
+    {
+        var manager = new SubWeakEventManager();
+        var source = new object();
+        manager[source] = new object();
+
+        Assert.Throws<InvalidCastException>(() => manager.DeliverEvent(source, args));
+    }
+
+    public static IEnumerable<object?[]> DeliverEventToList_TestData()
+    {
+        yield return new object?[] { null, null };
+        yield return new object?[] { new object(), new EventArgs() };
+        yield return new object?[] { new object(), EventArgs.Empty };
+    }
+
+    [Theory]
+    [MemberData(nameof(DeliverEventToList_TestData))]
+    public void DeliverEventToList_InvokeWithListeners_Success(object sender, EventArgs args)
+    {
+        var manager = new SubWeakEventManager();
+
+        var list = new ListenerList();
+        var events = new List<string>();
+        var listener1 = new CustomWeakEventListener();
+        listener1.ReceiveWeakEventAction = (t, s, e) =>
+        {
+            Assert.Equal(typeof(SubWeakEventManager), t);
+            Assert.Same(sender, s);
+            Assert.Same(args, e);
+            events.Add("listener1");
+            return true;
+        };
+        var listener2 = new CustomWeakEventListener();
+        listener2.ReceiveWeakEventAction = (t, s, e) =>
+        {
+            Assert.Equal(typeof(SubWeakEventManager), t);
+            Assert.Same(sender, s);
+            Assert.Same(args, e);
+            events.Add("listener2");
+            return true;
+        };
+        list.Add(listener1);
+        list.Add(listener2);
+
+        manager.DeliverEventToList(sender, args, list);
+        Assert.Equal(new string[] { "listener1", "listener2" }, events);
+    }
+
+    [Theory]
+    [MemberData(nameof(DeliverEventToList_TestData))]
+    public void DeliverEventToList_InvokeWithHandlers_Success(object sender, EventArgs args)
+    {
+        var manager = new SubWeakEventManager();
+
+        var list = new ListenerList();
+        var events = new List<string>();
+        var listener1 = new CustomWeakEventListener();
+        listener1.HandlerAction = (s, e) =>
+        {
+            Assert.Same(sender, s);
+            Assert.Same(args, e);
+            events.Add("handler1");
+        };
+        var listener2 = new CustomWeakEventListener();
+        listener2.HandlerAction = (s, e) =>
+        {
+            Assert.Same(sender, s);
+            Assert.Same(args, e);
+            events.Add("handler2");
+        };
+        Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), listener1, nameof(CustomWeakEventListener.Handler));
+        Delegate handler2 = Delegate.CreateDelegate(typeof(EventHandler), listener2, nameof(CustomWeakEventListener.Handler));
+        list.AddHandler(handler1);
+        list.AddHandler(handler2);
+
+        manager.DeliverEventToList(sender, args, list);
+        Assert.Equal(new string[] { "handler1", "handler2" }, events);
+    }
+
+    [Theory]
+    [MemberData(nameof(DeliverEventToList_TestData))]
+    public void DeliverEventToList_InvokeWithListenersAndHandlers_Success(object sender, EventArgs args)
+    {
+        var manager = new SubWeakEventManager();
+
+        var list = new ListenerList();
+        var events = new List<string>();
+        var listener1 = new CustomWeakEventListener();
+        listener1.HandlerAction = (s, e) =>
+        {
+            Assert.Same(sender, s);
+            Assert.Same(args, e);
+            events.Add("handler1");
+        };
+        var listener2 = new CustomWeakEventListener();
+        listener2.ReceiveWeakEventAction = (t, s, e) =>
+        {
+            Assert.Equal(typeof(SubWeakEventManager), t);
+            Assert.Same(sender, s);
+            Assert.Same(args, e);
+            events.Add("listener1");
+            return true;
+        };
+        var listener3 = new CustomWeakEventListener();
+        listener3.HandlerAction = (s, e) =>
+        {
+            Assert.Same(sender, s);
+            Assert.Same(args, e);
+            events.Add("handler2");
+        };
+        var listener4 = new CustomWeakEventListener();
+        listener4.ReceiveWeakEventAction = (t, s, e) =>
+        {
+            Assert.Equal(typeof(SubWeakEventManager), t);
+            Assert.Same(sender, s);
+            Assert.Same(args, e);
+            events.Add("listener2");
+            return true;
+        };
+        Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), listener1, nameof(CustomWeakEventListener.Handler));
+        Delegate handler2 = Delegate.CreateDelegate(typeof(EventHandler), listener3, nameof(CustomWeakEventListener.Handler));
+        list.AddHandler(handler1);
+        list.Add(listener2);
+        list.AddHandler(handler2);
+        list.Add(listener4);
+
+        manager.DeliverEventToList(sender, args, list);
+        Assert.Equal(new string[] { "handler1", "listener1", "handler2", "listener2" }, events);
+    }
+
+    // TODO: this causes a crash.
+#if false
+    [Theory]
+    [MemberData(nameof(DeliverEventToList_TestData))]
+    public void DeliverEventToList_InvokeWithListenersNotHandled_Success(object sender, EventArgs args)
+    {
+        var manager = new SubWeakEventManager();
+
+        var list = new ListenerList();
+        var events = new List<string>();
+        var listener1 = new CustomWeakEventListener();
+        listener1.ReceiveWeakEventAction = (t, s, e) =>
+        {
+            Assert.Equal(typeof(SubWeakEventManager), t);
+            Assert.Same(sender, s);
+            Assert.Same(args, e);
+            events.Add("listener1");
+            return false;
+        };
+        var listener2 = new CustomWeakEventListener();
+        listener2.ReceiveWeakEventAction = (t, s, e) =>
+        {
+            Assert.Equal(typeof(SubWeakEventManager), t);
+            Assert.Same(sender, s);
+            Assert.Same(args, e);
+            events.Add("listener2");
+            return true;
+        };
+        list.Add(listener1);
+        list.Add(listener2);
+
+        manager.DeliverEventToList(sender, args, list);
+        Assert.Equal(new string[] { "listener1", "listener2" }, events);
+    }
+#endif
+
+    [Theory]
+    [MemberData(nameof(DeliverEventToList_TestData))]
+    public void DeliverEventToList_InvokeWithInvalidHandlerAction_ThrowsInvalidCastException(object sender, EventArgs args)
+    {
+        var manager = new SubWeakEventManager();
+
+        var list = new ListenerList();
+        Delegate handler = () => {};
+        list.AddHandler(handler);
+
+        Assert.Throws<InvalidCastException>(() => manager.DeliverEventToList(sender, args, list));
+    }
+
+    [Theory]
+    [MemberData(nameof(DeliverEventToList_TestData))]
+    public void DeliverEventToList_InvokeWithInvalidHandlerFunc_ThrowsInvalidCastException(object sender, EventArgs args)
+    {
+        var manager = new SubWeakEventManager();
+
+        var list = new ListenerList();
+        bool EventHandler(object sender, EventArgs args) => true;
+        list.AddHandler(EventHandler);
+
+        Assert.Throws<InvalidCastException>(() => manager.DeliverEventToList(sender, args, list));
+    }
+
+    [Theory]
+    [MemberData(nameof(DeliverEventToList_TestData))]
+    public void DeliverEventToList_InvokeWithInvalidHandlerGenericEventArgs_ThrowsInvalidCastException(object sender, EventArgs args)
+    {
+        var manager = new SubWeakEventManager();
+
+        var list = new ListenerList();
+        var target = new CustomWeakEventListener();
+        Delegate handler = Delegate.CreateDelegate(typeof(EventHandler<EventArgs>), target, nameof(CustomWeakEventListener.Handler));
+        list.AddHandler(handler);
+
+        Assert.Throws<InvalidCastException>(() => manager.DeliverEventToList(sender, args, list));
+    }
+
+    [Theory]
+    [MemberData(nameof(DeliverEventToList_TestData))]
+    public void DeliverEventToList_InvokeEmpty_Success(object sender, EventArgs args)
+    {
+        var manager = new SubWeakEventManager();
+
+        var list = new ListenerList();
+        manager.DeliverEventToList(sender, args, list);
+    }
+
+    public static IEnumerable<object?[]> DeliverEventToList_CustomDeliverEvent_TestData()
+    {
+        yield return new object?[] { null, null, true };
+        yield return new object?[] { null, null, false };
+        yield return new object?[] { new object(), new EventArgs(), true };
+        yield return new object?[] { new object(), new EventArgs(), false };
+        yield return new object?[] { new object(), EventArgs.Empty, true };
+        yield return new object?[] { new object(), EventArgs.Empty, false };
+    }
+
+    [Theory]
+    [MemberData(nameof(DeliverEventToList_CustomDeliverEvent_TestData))]
+    public void DeliverEventToList_InvokeCustomDeliverEvent_CallsDeliverEvent(object sender, EventArgs args, bool result)
+    {
+        var manager = new SubWeakEventManager();
+        
+        var list = new CustomListenerList();
+        var events = new List<string>();
+        var listener = new CustomWeakEventListener();
+        listener.ReceiveWeakEventAction = (t, s, e) =>
+        {
+            events.Add("listener1");
+            return true;
+        };
+        list.Add(listener);
+        int deliverEventCallCount = 0;
+        list.DeliverEventAction = (s, a, t) =>
+        {
+            Assert.Same(sender, s);
+            Assert.Same(args, a);
+            Assert.Equal(typeof(SubWeakEventManager), t);
+            deliverEventCallCount++;
+            return result;
+        };
+
+        // Call.
+        manager.DeliverEventToList(sender, args, list);
+        Assert.Equal(1, deliverEventCallCount);
+        Assert.Empty(events);
+
+        // Call again.
+        manager.DeliverEventToList(sender, args, list);
+        Assert.Equal(2, deliverEventCallCount);
+        Assert.Empty(events);
+    }
+
+    [Theory]
+    [MemberData(nameof(DeliverEventToList_CustomDeliverEvent_TestData))]
+    public void DeliverEventToList_SourceNotListenerList_Success(object sender, EventArgs args, bool result)
+    {
+        var manager = new SubWeakEventManager();
+        manager[sender] = new object();
+
+        var list = new CustomListenerList();
+        var events = new List<string>();
+        var listener = new CustomWeakEventListener();
+        listener.ReceiveWeakEventAction = (t, s, e) =>
+        {
+            events.Add("listener1");
+            return true;
+        };
+        list.Add(listener);
+        int deliverEventCallCount = 0;
+        list.DeliverEventAction = (s, a, t) =>
+        {
+            Assert.Same(sender, s);
+            Assert.Same(args, a);
+            Assert.Equal(typeof(SubWeakEventManager), t);
+            deliverEventCallCount++;
+            return result;
+        };
+
+        // Call.
+        manager.DeliverEventToList(sender, args, list);
+        Assert.Equal(1, deliverEventCallCount);
+        Assert.Empty(events);
+
+        // Call again.
+        manager.DeliverEventToList(sender, args, list);
+        Assert.Equal(2, deliverEventCallCount);
+        Assert.Empty(events);
+    }
+
+    [Fact]
+    public void GetCurrentManager_InvokeNoSuchManagerType_ReturnsNull()
+    {
+        Assert.Null(SubWeakEventManager.GetCurrentManager(typeof(SentinelType1)));
+    }
+
+    private class SentinelType1 { }
+
+    [Fact]
+    public void GetCurrentManager_NullSource_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("key", () => SubWeakEventManager.GetCurrentManager(null!));
+    }
+
+    [Fact]
+    public void NewListenerList_Invoke_ReturnsExpected()
+    {
+        var manager = new SubWeakEventManager();
+        SubWeakEventManager.ListenerList list = manager.NewListenerList();
+        Assert.NotNull(list);
+        Assert.Equal(0, list.Count);
+        Assert.True(list.IsEmpty);
+
+        // Invoke again.
+        Assert.NotSame(list, manager.NewListenerList());
+    }
+
+    [Fact]
+    public void ProtectedAddHandler_Invoke_Success()
+    {
+        var manager = new SubWeakEventManager();
+        object? expectedSource = null;
+        int startListeningCallCount = 0;
+        manager.StartListeningAction += (actualSource) =>
+        {
+            Assert.Same(expectedSource, actualSource);
+            startListeningCallCount++;
+        };
+
+        var target1 = new CustomWeakEventListener();
+        Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+        Delegate handler2 = (EventHandler)delegate { };
+        Delegate handler3 = StaticEventHandler;
+        Delegate handler4 = (EventHandler)delegate { };
+
+        // Add new source.
+        var source1 = new object();
+        expectedSource = source1;
+        manager.ProtectedAddHandler(source1, handler1);
+        Assert.Equal(1, startListeningCallCount);
+        SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source1]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(target1, list[0]);
+
+        // Add another listener to first source.
+        manager.ProtectedAddHandler(source1, handler2);
+        Assert.Equal(1, startListeningCallCount);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source1]);
+        Assert.Equal(2, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(target1, list[0]);
+        Assert.Throws<InvalidCastException>(() => list[1]);
+
+        // Add another source.
+        var source2 = new object();
+        expectedSource = source2;
+        manager.ProtectedAddHandler(source2, handler3);
+        Assert.Equal(2, startListeningCallCount);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source1]);
+        Assert.Equal(2, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(target1, list[0]);
+        Assert.Throws<InvalidCastException>(() => list[1]);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source2]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Throws<InvalidCastException>(() => list[0]);
+
+        // Add static source.
+        expectedSource = null;
+        manager.ProtectedAddHandler(null!, handler4);
+        Assert.Equal(3, startListeningCallCount);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source1]);
+        Assert.Equal(2, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(target1, list[0]);
+        Assert.Throws<InvalidCastException>(() => list[1]);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source2]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Throws<InvalidCastException>(() => list[0]);
+        Assert.Null(manager[null!]);
+    }
+
+    [Fact]
+    public void ProtectedAddHandler_InvokeSameTargetMultipleTimes_Success()
+    {
+        var manager = new SubWeakEventManager();
+        
+        object? expectedSource = null;
+        int startListeningCallCount = 0;
+        manager.StartListeningAction += (actualSource) =>
+        {
+            Assert.Same(expectedSource, actualSource);
+            startListeningCallCount++;
+        };
+
+        var source = new object();
+        var target1 = new CustomWeakEventListener();
+        var target2 = new CustomWeakEventListener();
+        Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+        Delegate handler2 = Delegate.CreateDelegate(typeof(EventHandler), target2, nameof(CustomWeakEventListener.Handler));
+        Delegate handler3 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.SecondHandler));
+        Delegate handler4 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+        Delegate handler5 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.SecondHandler));
+        Delegate handler6 = Delegate.CreateDelegate(typeof(EventHandler), target2, nameof(CustomWeakEventListener.SecondHandler));
+        Delegate handler7 = Delegate.CreateDelegate(typeof(EventHandler), target2, nameof(CustomWeakEventListener.Handler));
+
+        // Add first.
+        expectedSource = source;
+        manager.ProtectedAddHandler(source, handler1);
+        Assert.Equal(1, startListeningCallCount);
+        SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(target1, list[0]);
+
+        // Add second.
+        manager.ProtectedAddHandler(source, handler2);
+        Assert.Equal(1, startListeningCallCount);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(2, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(target1, list[0]);
+        Assert.Same(target2, list[1]);
+
+        // Add third.
+        manager.ProtectedAddHandler(source, handler3);
+        Assert.Equal(1, startListeningCallCount);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(3, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(target1, list[0]);
+        Assert.Same(target2, list[1]);
+        Assert.Same(target1, list[2]);
+
+        // Add fourth.
+        manager.ProtectedAddHandler(source, handler4);
+        Assert.Equal(1, startListeningCallCount);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(4, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(target1, list[0]);
+        Assert.Same(target2, list[1]);
+        Assert.Same(target1, list[2]);
+        Assert.Same(target1, list[3]);
+
+        // Add fifth.
+        manager.ProtectedAddHandler(source, handler5);
+        Assert.Equal(1, startListeningCallCount);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(5, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(target1, list[0]);
+        Assert.Same(target2, list[1]);
+        Assert.Same(target1, list[2]);
+        Assert.Same(target1, list[3]);
+        Assert.Same(target1, list[4]);
+
+        // Add sixth.
+        manager.ProtectedAddHandler(source, handler6);
+        Assert.Equal(1, startListeningCallCount);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(6, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(target1, list[0]);
+        Assert.Same(target2, list[1]);
+        Assert.Same(target1, list[2]);
+        Assert.Same(target1, list[3]);
+        Assert.Same(target1, list[4]);
+        Assert.Same(target2, list[5]);
+
+        // Add seventh.
+        manager.ProtectedAddHandler(source, handler6);
+        Assert.Equal(1, startListeningCallCount);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(7, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(target1, list[0]);
+        Assert.Same(target2, list[1]);
+        Assert.Same(target1, list[2]);
+        Assert.Same(target1, list[3]);
+        Assert.Same(target1, list[4]);
+        Assert.Same(target2, list[5]);
+        Assert.Same(target2, list[6]);
+    }
+
+    [Fact]
+    public void ProtectedAddHandler_InvokeStaticSource_Success()
+    {
+        var manager = new SubWeakEventManager();
+
+        FieldInfo actualSourceField = typeof(WeakEventManager).GetField("StaticSource", BindingFlags.NonPublic | BindingFlags.Static)!;
+        Assert.NotNull(actualSourceField);
+        object actualSource = actualSourceField.GetValue(null)!;
+        Assert.Equal("{StaticSource}", actualSource.ToString());
+
+        int startListeningCallCount = 0;
+        manager.StartListeningAction += (source) =>
+        {
+            Assert.Null(source);
+            startListeningCallCount++;
+        };
+
+        Delegate handler1 = (EventHandler)delegate { };
+        Delegate handler2 = (EventHandler)delegate { };
+
+        // Add first listener.
+        manager.ProtectedAddHandler(null!, handler1);
+        Assert.Equal(1, startListeningCallCount);
+        Assert.Null(manager[null!]);
+        SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[actualSource]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Throws<InvalidCastException>(() => list[0]);
+
+        // Add second listener.
+        manager.ProtectedAddHandler(null!, handler2);
+        Assert.Equal(1, startListeningCallCount);
+        Assert.Null(manager[null!]);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[actualSource]);
+        Assert.Equal(2, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Throws<InvalidCastException>(() => list[0]);
+        Assert.Throws<InvalidCastException>(() => list[1]);
+    }
+
+    [Fact]
+    public void ProtectedAddHandler_InvokeWithListeners_Success()
+    {
+        var manager = new SubWeakEventManager();
+        object? expectedSource = null;
+        int startListeningCallCount = 0;
+        manager.StartListeningAction += (actualSource) =>
+        {
+            Assert.Same(expectedSource, actualSource);
+            startListeningCallCount++;
+        };
+
+        var target = new CustomWeakEventListener();
+        Delegate handler = Delegate.CreateDelegate(typeof(EventHandler), target, nameof(CustomWeakEventListener.Handler));
+        var listener = new CustomWeakEventListener();
+
+        // Add listener.
+        var source = new object();
+        expectedSource = source;
+        manager.ProtectedAddListener(source, listener);
+        Assert.Equal(1, startListeningCallCount);
+        SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener, list[0]);
+
+        // Add handler.
+        manager.ProtectedAddHandler(source, handler);
+        Assert.Equal(1, startListeningCallCount);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(2, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener, list[0]);
+        Assert.Same(target, list[1]);
+    }
+
+    [Fact]
+    public void ProtectedAddHandler_InvokeMultipleTimesSameSource_Success()
+    {
+        var manager = new SubWeakEventManager();
+        object? expectedSource = null;
+        int startListeningCallCount = 0;
+        manager.StartListeningAction += (actualSource) =>
+        {
+            Assert.Same(expectedSource, actualSource);
+            startListeningCallCount++;
+        };
+
+        var target = new CustomWeakEventListener();
+        Delegate handler = Delegate.CreateDelegate(typeof(EventHandler), target, nameof(CustomWeakEventListener.Handler));
+
+        // Add first.
+        var source = new object();
+        expectedSource = source;
+        manager.ProtectedAddHandler(source, handler);
+        Assert.Equal(1, startListeningCallCount);
+        SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(target, list[0]);
+
+        // Add second.
+        manager.ProtectedAddHandler(source, handler);
+        Assert.Equal(1, startListeningCallCount);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(2, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(target, list[0]);
+        Assert.Same(target, list[1]);
+    }
+
+    [Fact]
+    public void ProtectedAddHandler_InvokeMultipleTimesDifferentSource_Success()
+    {
+        var manager = new SubWeakEventManager();
+        object? expectedSource = null;
+        int startListeningCallCount = 0;
+        manager.StartListeningAction += (actualSource) =>
+        {
+            Assert.Same(expectedSource, actualSource);
+            startListeningCallCount++;
+        };
+
+        var target = new CustomWeakEventListener();
+        Delegate handler = Delegate.CreateDelegate(typeof(EventHandler), target, nameof(CustomWeakEventListener.Handler));
+
+        // Add first source.
+        var source1 = new object();
+        expectedSource = source1;
+        manager.ProtectedAddHandler(source1, handler);
+        Assert.Equal(1, startListeningCallCount);
+        SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source1]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(target, list[0]);
+
+        // Add second source.
+        var source2 = new object();
+        expectedSource = source2;
+        manager.ProtectedAddHandler(source2, handler);
+        Assert.Equal(2, startListeningCallCount);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source1]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(target, list[0]);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source2]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(target, list[0]);
+    }
+
+    [Fact]
+    public void ProtectedAddHandler_InvokeMultipleSameSourceNotInUse_DoesNotCloneListenerList()
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction += (source) => {};
+
+        var source = new object();
+        var target1 = new CustomWeakEventListener();
+        Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+        var target2 = new CustomWeakEventListener();
+        Delegate handler2 = Delegate.CreateDelegate(typeof(EventHandler), target2, nameof(CustomWeakEventListener.Handler));
+
+        // Add first listener.
+        manager.ProtectedAddHandler(source, handler1);
+        SubWeakEventManager.ListenerList list1 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(1, list1.Count);
+        Assert.False(list1.IsEmpty);
+        Assert.Same(target1, list1[0]);
+
+        // Add second listener.
+        manager.ProtectedAddHandler(source, handler2);
+        SubWeakEventManager.ListenerList list2 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Same(list2, list1);
+        Assert.Equal(2, list2.Count);
+        Assert.False(list2.IsEmpty);
+        Assert.Same(target1, list2[0]);
+        Assert.Same(target2, list2[1]);
+    }
+
+    [Fact]
+    public void ProtectedAddHandler_InvokeMultipleSameSourceInUse_ClonesListenerList()
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction += (source) => {};
+
+        var source = new object();
+        var target1 = new CustomWeakEventListener();
+        Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+        var target2 = new CustomWeakEventListener();
+        Delegate handler2 = Delegate.CreateDelegate(typeof(EventHandler), target2, nameof(CustomWeakEventListener.Handler));
+
+        // Add first listener.
+        manager.ProtectedAddHandler(source, handler1);
+        SubWeakEventManager.ListenerList list1 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(1, list1.Count);
+        Assert.False(list1.IsEmpty);
+        Assert.Same(target1, list1[0]);
+
+        // Begin use.
+        list1.BeginUse();
+
+        // Add second listener.
+        manager.ProtectedAddHandler(source, handler2);
+        SubWeakEventManager.ListenerList list2 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.NotSame(list2, list1);
+        Assert.Equal(1, list1.Count);
+        Assert.False(list1.IsEmpty);
+        Assert.Same(target1, list1[0]);
+        Assert.Equal(2, list2.Count);
+        Assert.False(list2.IsEmpty);
+        Assert.Same(target1, list2[0]);
+        Assert.Same(target2, list2[1]);
+    }
+
+    [Fact]
+    public void ProtectedAddHandler_InvokeMultipleSameSourceNoLongerInUse_DoesNotCloneListenerList()
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction += (source) => {};
+
+        var source = new object();
+        var target1 = new CustomWeakEventListener();
+        Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+        var target2 = new CustomWeakEventListener();
+        Delegate handler2 = Delegate.CreateDelegate(typeof(EventHandler), target2, nameof(CustomWeakEventListener.Handler));
+
+        // Add first listener.
+        manager.ProtectedAddHandler(source, handler1);
+        SubWeakEventManager.ListenerList list1 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(1, list1.Count);
+        Assert.False(list1.IsEmpty);
+        Assert.Same(target1, list1[0]);
+
+        // Begin use.
+        list1.BeginUse();
+
+        // End use.
+        list1.EndUse();
+
+        // Add second listener.
+        manager.ProtectedAddHandler(source, handler2);
+        SubWeakEventManager.ListenerList list2 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Same(list2, list1);
+        Assert.Equal(2, list2.Count);
+        Assert.False(list2.IsEmpty);
+        Assert.Same(target1, list2[0]);
+        Assert.Same(target2, list2[1]);
+    }
+
+    [Theory]
+    [InlineData(1)]
+    [InlineData(3)]
+    [InlineData(4)]
+    [InlineData(6)]
+    [InlineData(7)]
+    public void ProtectedAddHandler_InvokeDifferentSizes_Success(int count)
+    {
+        // Test internal FrugalList implementation.
+        var handlers = new List<Delegate>();
+        for (int i = 0; i < count; i++)
+        {
+            handlers.Add(Delegate.CreateDelegate(typeof(EventHandler), new CustomWeakEventListener(), nameof(CustomWeakEventListener.Handler)));
+        }
+
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction += (source) => {};
+
+        // Add.
+        var source = new object();
+        for (int i = 0; i < count; i++)
+        {
+            manager.ProtectedAddHandler(source, handlers[i]);
+            SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+            Assert.Equal(i + 1, list.Count);
+            Assert.False(list.IsEmpty);
+            for (int j = 0; j <= i; j++)
+            {
+                Assert.Same(handlers[j].Target, list[j]);
+            }
+        }
+    }
+
+    [Fact]
+    public void ProtectedAddHandler_NullHandler_ThrowsArgumentNullException()
+    {
+        var manager = new SubWeakEventManager();
+        var source = new object();
+        Assert.Throws<ArgumentNullException>("handler", () => manager.ProtectedAddHandler(source, null!));
+    }
+
+    [Fact]
+    public void ProtectedAddHandler_SourceNotListenerList_ThrowsInvalidCastException()
+    {
+        var manager = new SubWeakEventManager();
+        var source = new object();
+        manager[source] = new object();
+
+        var target = new CustomWeakEventListener();
+        var handler = Delegate.CreateDelegate(typeof(EventHandler), target, nameof(CustomWeakEventListener.Handler));        
+        Assert.Throws<InvalidCastException>(() => manager.ProtectedAddHandler(source, handler));
+    }
+
+    [Fact]
+    public void ProtectedAddListener_Invoke_Success()
+    {
+        var manager = new SubWeakEventManager();
+        object? expectedSource = null;
+        int startListeningCallCount = 0;
+        manager.StartListeningAction += (actualSource) =>
+        {
+            Assert.Same(expectedSource, actualSource);
+            startListeningCallCount++;
+        };
+
+        var listener1 = new CustomWeakEventListener();
+        var listener2 = new CustomWeakEventListener();
+        var listener3 = new CustomWeakEventListener();
+        var listener4 = new CustomWeakEventListener();
+
+        // Add new source.
+        var source1 = new object();
+        expectedSource = source1;
+        manager.ProtectedAddListener(source1, listener1);
+        Assert.Equal(1, startListeningCallCount);
+        SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source1]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener1, list[0]);
+
+        // Add another listener to first source.
+        manager.ProtectedAddListener(source1, listener2);
+        Assert.Equal(1, startListeningCallCount);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source1]);
+        Assert.Equal(2, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener1, list[0]);
+        Assert.Same(listener2, list[1]);
+
+        // Add another source.
+        var source2 = new object();
+        expectedSource = source2;
+        manager.ProtectedAddListener(source2, listener3);
+        Assert.Equal(2, startListeningCallCount);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source1]);
+        Assert.Equal(2, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener1, list[0]);
+        Assert.Same(listener2, list[1]);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source2]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener3, list[0]);
+
+        // Add static source.
+        expectedSource = null;
+        manager.ProtectedAddListener(null!, listener4);
+        Assert.Equal(3, startListeningCallCount);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source1]);
+        Assert.Equal(2, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener1, list[0]);
+        Assert.Same(listener2, list[1]);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source2]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener3, list[0]);
+        Assert.Null(manager[null!]);
+    }
+
+    [Fact]
+    public void ProtectedAddListener_InvokeStaticSource_Success()
+    {
+        var manager = new SubWeakEventManager();
+
+        FieldInfo actualSourceField = typeof(WeakEventManager).GetField("StaticSource", BindingFlags.NonPublic | BindingFlags.Static)!;
+        Assert.NotNull(actualSourceField);
+        object actualSource = actualSourceField.GetValue(null)!;
+        Assert.Equal("{StaticSource}", actualSource.ToString());
+
+        int startListeningCallCount = 0;
+        manager.StartListeningAction += (source) =>
+        {
+            Assert.Null(source);
+            startListeningCallCount++;
+        };
+
+        var listener1 = new CustomWeakEventListener();
+        var listener2 = new CustomWeakEventListener();
+
+        // Add first listener.
+        manager.ProtectedAddListener(null!, listener1);
+        Assert.Equal(1, startListeningCallCount);
+        Assert.Null(manager[null!]);
+        SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[actualSource]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener1, list[0]);
+
+        // Add second listener.
+        manager.ProtectedAddListener(null!, listener2);
+        Assert.Equal(1, startListeningCallCount);
+        Assert.Null(manager[null!]);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[actualSource]);
+        Assert.Equal(2, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener1, list[0]);
+        Assert.Same(listener2, list[1]);
+    }
+
+    [Fact]
+    public void ProtectedAddListener_InvokeWithHandlers_Success()
+    {
+        var manager = new SubWeakEventManager();
+        object? expectedSource = null;
+        int startListeningCallCount = 0;
+        manager.StartListeningAction += (actualSource) =>
+        {
+            Assert.Same(expectedSource, actualSource);
+            startListeningCallCount++;
+        };
+
+        Delegate handler = () => { };
+        var listener = new CustomWeakEventListener();
+
+        // Add handler.
+        var source = new object();
+        expectedSource = source;
+        manager.ProtectedAddHandler(source, handler);
+        Assert.Equal(1, startListeningCallCount);
+        SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Throws<InvalidCastException>(() => list[0]);
+
+        // Add listener.
+        manager.ProtectedAddListener(source, listener);
+        Assert.Equal(1, startListeningCallCount);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(2, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Throws<InvalidCastException>(() => list[0]);
+        Assert.Same(listener, list[1]);
+    }
+
+    [Fact]
+    public void ProtectedAddListener_InvokeMultipleTimesSameSource_Success()
+    {
+        var manager = new SubWeakEventManager();
+        object? expectedSource = null;
+        int startListeningCallCount = 0;
+        manager.StartListeningAction += (actualSource) =>
+        {
+            Assert.Same(expectedSource, actualSource);
+            startListeningCallCount++;
+        };
+
+        var listener = new CustomWeakEventListener();
+
+        // Add first.
+        var source = new object();
+        expectedSource = source;
+        manager.ProtectedAddListener(source, listener);
+        Assert.Equal(1, startListeningCallCount);
+        SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener, list[0]);
+
+        // Add second.
+        manager.ProtectedAddListener(source, listener);
+        Assert.Equal(1, startListeningCallCount);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(2, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener, list[0]);
+        Assert.Same(listener, list[1]);
+    }
+
+    [Fact]
+    public void ProtectedAddListener_InvokeMultipleTimesDifferentSource_Success()
+    {
+        var manager = new SubWeakEventManager();
+        object? expectedSource = null;
+        int startListeningCallCount = 0;
+        manager.StartListeningAction += (actualSource) =>
+        {
+            Assert.Same(expectedSource, actualSource);
+            startListeningCallCount++;
+        };
+
+        var listener = new CustomWeakEventListener();
+
+        // Add first source.
+        var source1 = new object();
+        expectedSource = source1;
+        manager.ProtectedAddListener(source1, listener);
+        Assert.Equal(1, startListeningCallCount);
+        SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source1]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener, list[0]);
+
+        // Add second source.
+        var source2 = new object();
+        expectedSource = source2;
+        manager.ProtectedAddListener(source2, listener);
+        Assert.Equal(2, startListeningCallCount);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source1]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener, list[0]);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source2]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener, list[0]);
+    }
+
+    [Fact]
+    public void ProtectedAddListener_InvokeMultipleSameSourceNotInUse_DoesNotCloneListenerList()
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction += (source) => {};
+
+        var source = new object();
+        var listener1 = new CustomWeakEventListener();
+        var listener2 = new CustomWeakEventListener();
+
+        // Add first listener.
+        manager.ProtectedAddListener(source, listener1);
+        SubWeakEventManager.ListenerList list1 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(1, list1.Count);
+        Assert.False(list1.IsEmpty);
+        Assert.Same(listener1, list1[0]);
+
+        // Add second listener.
+        manager.ProtectedAddListener(source, listener2);
+        SubWeakEventManager.ListenerList list2 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Same(list2, list1);
+        Assert.Equal(2, list2.Count);
+        Assert.False(list2.IsEmpty);
+        Assert.Same(listener1, list2[0]);
+        Assert.Same(listener2, list2[1]);
+    }
+
+    [Fact]
+    public void ProtectedAddListener_InvokeMultipleSameSourceInUse_ClonesListenerList()
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction += (source) => {};
+
+        var source = new object();
+        var listener1 = new CustomWeakEventListener();
+        var listener2 = new CustomWeakEventListener();
+
+        // Add first listener.
+        manager.ProtectedAddListener(source, listener1);
+        SubWeakEventManager.ListenerList list1 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(1, list1.Count);
+        Assert.False(list1.IsEmpty);
+        Assert.Same(listener1, list1[0]);
+
+        // Begin use.
+        list1.BeginUse();
+
+        // Add second listener.
+        manager.ProtectedAddListener(source, listener2);
+        SubWeakEventManager.ListenerList list2 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.NotSame(list2, list1);
+        Assert.Equal(1, list1.Count);
+        Assert.False(list1.IsEmpty);
+        Assert.Same(listener1, list1[0]);
+        Assert.Equal(2, list2.Count);
+        Assert.False(list2.IsEmpty);
+        Assert.Same(listener1, list2[0]);
+        Assert.Same(listener2, list2[1]);
+    }
+
+    [Fact]
+    public void ProtectedAddListener_InvokeMultipleSameSourceNoLongerInUse_DoesNotCloneListenerList()
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction += (source) => {};
+
+        var source = new object();
+        var listener1 = new CustomWeakEventListener();
+        var listener2 = new CustomWeakEventListener();
+
+        // Add first listener.
+        manager.ProtectedAddListener(source, listener1);
+        SubWeakEventManager.ListenerList list1 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(1, list1.Count);
+        Assert.False(list1.IsEmpty);
+        Assert.Same(listener1, list1[0]);
+
+        // Begin use.
+        list1.BeginUse();
+
+        // End use.
+        list1.EndUse();
+
+        // Add second listener.
+        manager.ProtectedAddListener(source, listener2);
+        SubWeakEventManager.ListenerList list2 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Same(list2, list1);
+        Assert.Equal(2, list2.Count);
+        Assert.False(list2.IsEmpty);
+        Assert.Same(listener1, list2[0]);
+        Assert.Same(listener2, list2[1]);
+    }
+
+    [Theory]
+    [InlineData(1)]
+    [InlineData(3)]
+    [InlineData(4)]
+    [InlineData(6)]
+    [InlineData(7)]
+    public void ProtectedAddListener_InvokeDifferentSizes_Success(int count)
+    {
+        // Test internal FrugalList implementation.
+        var listeners = new List<CustomWeakEventListener>();
+        for (int i = 0; i < count; i++)
+        {
+            listeners.Add(new CustomWeakEventListener());
+        }
+
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction += (source) => {};
+
+        // Add.
+        var source = new object();
+        for (int i = 0; i < count; i++)
+        {
+            manager.ProtectedAddListener(source, listeners[i]);
+            SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+            Assert.Equal(i + 1, list.Count);
+            Assert.False(list.IsEmpty);
+            for (int j = 0; j <= i; j++)
+            {
+                Assert.Same(listeners[j], list[j]);
+            }
+        }
+    }
+
+    [Fact]
+    public void ProtectedAddListener_NullListener_ThrowsArgumentNullException()
+    {
+        var manager = new SubWeakEventManager();
+        var source = new object();
+        Assert.Throws<ArgumentNullException>("listener", () => manager.ProtectedAddListener(source, null!));
+    }
+
+    [Fact]
+    public void ProtectedAddListener_SourceNotListenerList_ThrowsInvalidCastException()
+    {
+        var manager = new SubWeakEventManager();
+        var source = new object();
+        manager[source] = new object();
+
+        var listener = new CustomWeakEventListener();
+        Assert.Throws<InvalidCastException>(() => manager.ProtectedAddListener(source, listener));
+    }
+
+    [Fact]
+    public void ProtectedRemoveHandler_Invoke_Success()
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction += (source) => {};
+        object? expectedSource = null;
+        int stopListeningCallCount = 0;
+        manager.StopListeningAction += (source) =>
+        {
+            Assert.Same(expectedSource, source);
+            stopListeningCallCount++;
+        };
+
+        var source1 = new object();
+        var source2 = new object();
+        var target1 = new CustomWeakEventListener();
+        Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+        Delegate handler2 = (EventHandler)delegate { };
+        Delegate handler3 = StaticEventHandler;
+        Delegate handler4 = (EventHandler)delegate { };
+        manager.ProtectedAddHandler(source1, handler1);
+        manager.ProtectedAddHandler(source1, handler2);
+        manager.ProtectedAddHandler(source2, handler3);
+        manager.ProtectedAddHandler(source2, handler4);
+        
+        // Remove handler2.
+        manager.ProtectedRemoveHandler(source1, handler2);
+        Assert.Equal(0, stopListeningCallCount);
+        SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source1]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(target1, list[0]);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source2]);
+        Assert.Equal(2, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Throws<InvalidCastException>(() => list[0]);
+        Assert.Throws<InvalidCastException>(() => list[1]);
+        
+        // Remove handler2 again.
+        manager.ProtectedRemoveHandler(source1, handler2);
+        Assert.Equal(0, stopListeningCallCount);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source1]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(target1, list[0]);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source2]);
+        Assert.Equal(2, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Throws<InvalidCastException>(() => list[0]);
+        Assert.Throws<InvalidCastException>(() => list[1]);
+
+        // Remove handler1.
+        expectedSource = source1;
+        manager.ProtectedRemoveHandler(source1, handler1);
+        Assert.Equal(1, stopListeningCallCount);
+        Assert.Null(manager[source1]);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source2]);
+        Assert.Equal(2, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Throws<InvalidCastException>(() => list[0]);
+        Assert.Throws<InvalidCastException>(() => list[1]);
+
+        // Remove handler3.
+        expectedSource = source2;
+        manager.ProtectedRemoveHandler(source2, handler3);
+        Assert.Equal(1, stopListeningCallCount);
+        Assert.Null(manager[source1]);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source2]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Throws<InvalidCastException>(() => list[0]);
+
+        // Remove handler4.
+        expectedSource = source2;
+        manager.ProtectedRemoveHandler(source2, handler4);
+        Assert.Equal(2, stopListeningCallCount);
+        Assert.Null(manager[source1]);
+        Assert.Null(manager[source2]);
+    }
+
+    [Fact]
+    public void ProtectedRemoveHandler_InvokeStaticSource_Success()
+    {
+        var manager = new SubWeakEventManager();
+
+        FieldInfo actualSourceField = typeof(WeakEventManager).GetField("StaticSource", BindingFlags.NonPublic | BindingFlags.Static)!;
+        Assert.NotNull(actualSourceField);
+        object actualSource = actualSourceField.GetValue(null)!;
+        Assert.Equal("{StaticSource}", actualSource.ToString());
+
+        manager.StartListeningAction += (source) => {};
+        int stopListeningCallCount = 0;
+        manager.StopListeningAction += (source) =>
+        {
+            Assert.Null(source);
+            stopListeningCallCount++;
+        };
+
+        Delegate handler1 = (EventHandler)delegate { };
+        Delegate handler2 = (EventHandler)delegate { };
+        manager.ProtectedAddHandler(null!, handler1);
+        manager.ProtectedAddHandler(null!, handler2);
+
+        // Add first handler.
+        manager.ProtectedRemoveHandler(null!, handler1);
+        Assert.Equal(0, stopListeningCallCount);
+        Assert.Null(manager[null!]);
+        SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[actualSource]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Throws<InvalidCastException>(() => list[0]);
+
+        // Add second handler.
+        manager.ProtectedRemoveHandler(null!, handler2);
+        Assert.Equal(1, stopListeningCallCount);
+        Assert.Null(manager[null!]);
+        Assert.Null(manager[actualSource]);
+    }
+
+    [Fact]
+    public void ProtectedRemoveHandler_InvokeSameTargetMultipleTimesSuccess()
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction += (source) => {};
+        object? expectedSource = null;
+        int stopListeningCallCount = 0;
+        manager.StopListeningAction += (source) =>
+        {
+            Assert.Same(expectedSource, source);
+            stopListeningCallCount++;
+        };
+
+        var source = new object();
+        var target1 = new CustomWeakEventListener();
+        var target2 = new CustomWeakEventListener();
+        Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+        Delegate handler2 = Delegate.CreateDelegate(typeof(EventHandler), target2, nameof(CustomWeakEventListener.Handler));
+        Delegate handler3 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.SecondHandler));
+        Delegate handler4 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+        Delegate handler5 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.SecondHandler));
+        Delegate handler6 = Delegate.CreateDelegate(typeof(EventHandler), target2, nameof(CustomWeakEventListener.SecondHandler));
+        Delegate handler7 = Delegate.CreateDelegate(typeof(EventHandler), target2, nameof(CustomWeakEventListener.Handler));
+
+        manager.ProtectedAddHandler(source, handler1);
+        manager.ProtectedAddHandler(source, handler2);
+        manager.ProtectedAddHandler(source, handler3);
+        manager.ProtectedAddHandler(source, handler4);
+        manager.ProtectedAddHandler(source, handler5);
+        manager.ProtectedAddHandler(source, handler6);
+        manager.ProtectedAddHandler(source, handler7);
+
+        // Remove handler1.
+        manager.ProtectedRemoveHandler(source, handler1);
+        Assert.Equal(0, stopListeningCallCount);
+        SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(6, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Equal(target1, list[0]);
+        Assert.Equal(target2, list[1]);
+        Assert.Equal(target1, list[2]);
+        Assert.Equal(target1, list[3]);
+        Assert.Equal(target2, list[4]);
+        Assert.Equal(target2, list[5]);
+
+        // Remove handler2.
+        manager.ProtectedRemoveHandler(source, handler2);
+        Assert.Equal(0, stopListeningCallCount);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(5, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Equal(target1, list[0]);
+        Assert.Equal(target2, list[1]);
+        Assert.Equal(target1, list[2]);
+        Assert.Equal(target1, list[3]);
+        Assert.Equal(target2, list[4]);
+
+        // Remove handler3.
+        manager.ProtectedRemoveHandler(source, handler3);
+        Assert.Equal(0, stopListeningCallCount);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(4, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Equal(target1, list[0]);
+        Assert.Equal(target2, list[1]);
+        Assert.Equal(target1, list[2]);
+        Assert.Equal(target2, list[3]);
+
+        // Remove handler4.
+        manager.ProtectedRemoveHandler(source, handler4);
+        Assert.Equal(0, stopListeningCallCount);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(3, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Equal(target2, list[0]);
+        Assert.Equal(target1, list[1]);
+        Assert.Equal(target2, list[2]);
+        
+        // Remove handler5.
+        manager.ProtectedRemoveHandler(source, handler5);
+        Assert.Equal(0, stopListeningCallCount);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(2, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Equal(target2, list[0]);
+        Assert.Equal(target2, list[1]);
+
+        // Remove handler6.
+        manager.ProtectedRemoveHandler(source, handler6);
+        Assert.Equal(0, stopListeningCallCount);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Equal(target2, list[0]);
+
+        // Remove handler7.
+        expectedSource = source;
+        manager.ProtectedRemoveHandler(source, handler7);
+        Assert.Equal(1, stopListeningCallCount);
+        Assert.Null(manager[source]);
+    }
+
+    [Fact]
+    public void ProtectedRemoveHandler_InvokeWithListeners_Success()
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction += (actualSource) => {};
+        manager.StopListeningAction += (source) => {};
+
+        var source = new object();
+        var listener = new CustomWeakEventListener();
+        Delegate handler = (EventHandler)delegate { };
+        manager.ProtectedAddListener(source, listener);
+        manager.ProtectedAddHandler(source, handler);
+        
+        // Remove handler.
+        manager.ProtectedRemoveHandler(source, handler);
+        SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener, list[0]);
+    }
+
+    [Fact]
+    public void ProtectedRemoveHandler_InvokeMultipleSameSourceNotInUse_DoesNotCloneListenerList()
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction += (source) => {};
+        manager.StopListeningAction += (source) => {};
+
+        var source = new object();
+        var target1 = new CustomWeakEventListener();
+        Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+        var target2 = new CustomWeakEventListener();
+        Delegate handler2 = Delegate.CreateDelegate(typeof(EventHandler), target2, nameof(CustomWeakEventListener.Handler));
+        var target3 = new CustomWeakEventListener();
+        Delegate handler3 = Delegate.CreateDelegate(typeof(EventHandler), target3, nameof(CustomWeakEventListener.Handler));
+        manager.ProtectedAddHandler(source, handler1);
+        manager.ProtectedAddHandler(source, handler2);
+        manager.ProtectedAddHandler(source, handler3);
+
+        // Remove first handler.
+        SubWeakEventManager.ListenerList list1 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        manager.ProtectedRemoveHandler(source, handler1);
+        SubWeakEventManager.ListenerList list2 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Same(list2, list1);
+        Assert.Equal(2, list2.Count);
+        Assert.False(list2.IsEmpty);
+        Assert.Same(target2, list2[0]);
+        Assert.Same(target3, list2[1]);
+        
+        // Remove second handler.
+        manager.ProtectedRemoveHandler(source, handler2);
+        SubWeakEventManager.ListenerList list3 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Same(list3, list1);
+        Assert.Equal(1, list1.Count);
+        Assert.False(list3.IsEmpty);
+        Assert.Same(target3, list3[0]);
+
+        // Remove third handler.
+        manager.ProtectedRemoveHandler(source, handler3);
+        Assert.Null(manager[source]);
+    }
+
+    [Fact]
+    public void ProtectedRemoveHandler_InvokeMultipleSameSourceInUse_ClonesListenerList()
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction += (source) => {};
+        manager.StopListeningAction += (source) => {};
+
+        var source = new object();
+        var target1 = new CustomWeakEventListener();
+        Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+        var target2 = new CustomWeakEventListener();
+        Delegate handler2 = Delegate.CreateDelegate(typeof(EventHandler), target2, nameof(CustomWeakEventListener.Handler));
+        var target3 = new CustomWeakEventListener();
+        Delegate handler3 = Delegate.CreateDelegate(typeof(EventHandler), target3, nameof(CustomWeakEventListener.Handler));
+        manager.ProtectedAddHandler(source, handler1);
+        manager.ProtectedAddHandler(source, handler2);
+        manager.ProtectedAddHandler(source, handler3);
+
+        // Remove first handler.
+        SubWeakEventManager.ListenerList list1 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        manager.ProtectedRemoveHandler(source, handler1);
+        SubWeakEventManager.ListenerList list2 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Same(list2, list1);
+        Assert.Equal(2, list2.Count);
+        Assert.False(list2.IsEmpty);
+        Assert.Same(target2, list2[0]);
+        Assert.Same(target3, list2[1]);
+
+        // Begin use.
+        list1.BeginUse();
+
+        // Remove second handler.
+        manager.ProtectedRemoveHandler(source, handler2);
+        SubWeakEventManager.ListenerList list3 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.NotSame(list3, list1);
+        Assert.Equal(2, list1.Count);
+        Assert.False(list1.IsEmpty);
+        Assert.Same(target2, list1[0]);
+        Assert.Same(target3, list1[1]);
+        Assert.Equal(1, list3.Count);
+        Assert.False(list3.IsEmpty);
+        Assert.Same(target3, list3[0]);
+
+        // Remove third handler.
+        manager.ProtectedRemoveHandler(source, handler3);
+        Assert.Null(manager[source]);
+        Assert.NotSame(list3, list1);
+        Assert.Equal(2, list1.Count);
+        Assert.False(list1.IsEmpty);
+        Assert.Same(target2, list1[0]);
+        Assert.Same(target3, list1[1]);
+        Assert.Equal(0, list3.Count);
+        Assert.True(list3.IsEmpty);
+    }
+
+    [Fact]
+    public void ProtectedRemoveHandler_InvokeMultipleSameSourceNoLongerInUse_DoesNotCloneListenerList()
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction += (source) => {};
+        manager.StopListeningAction += (source) => {};
+
+        var source = new object();
+        var target1 = new CustomWeakEventListener();
+        Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+        var target2 = new CustomWeakEventListener();
+        Delegate handler2 = Delegate.CreateDelegate(typeof(EventHandler), target2, nameof(CustomWeakEventListener.Handler));
+        var target3 = new CustomWeakEventListener();
+        Delegate handler3 = Delegate.CreateDelegate(typeof(EventHandler), target3, nameof(CustomWeakEventListener.Handler));
+        manager.ProtectedAddHandler(source, handler1);
+        manager.ProtectedAddHandler(source, handler2);
+        manager.ProtectedAddHandler(source, handler3);
+
+        // Remove first handler.
+        SubWeakEventManager.ListenerList list1 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        manager.ProtectedRemoveHandler(source, handler1);
+        SubWeakEventManager.ListenerList list2 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Same(list2, list1);
+        Assert.Equal(2, list1.Count);
+        Assert.False(list1.IsEmpty);
+        Assert.Same(target2, list1[0]);
+        Assert.Same(target3, list1[1]);
+
+        // Begin use.
+        list1.BeginUse();
+
+        // End use.
+        list1.EndUse();
+
+        // Remove second handler.
+        manager.ProtectedRemoveHandler(source, handler2);
+        SubWeakEventManager.ListenerList list3 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Same(list3, list1);
+        Assert.Equal(1, list3.Count);
+        Assert.False(list3.IsEmpty);
+        Assert.Same(target3, list3[0]);
+
+        // Remove third handler.
+        manager.ProtectedRemoveHandler(source, handler3);
+        Assert.Null(manager[source]);
+        Assert.Same(list3, list1);
+        Assert.Equal(0, list3.Count);
+        Assert.True(list3.IsEmpty);
+    }
+
+    [Fact]
+    public void ProtectedRemoveHandler_InvokeNoSuchSourceEmpty_Succcess()
+    {
+        var manager = new SubWeakEventManager();
+
+        // Remove.
+        manager.ProtectedRemoveHandler(new object(), (EventHandler)delegate { });
+
+        // Remove again.
+        manager.ProtectedRemoveHandler(new object(), (EventHandler)delegate { });
+    }
+
+    [Fact]
+    public void ProtectedRemoveHandler_InvokeNoSuchSourceNotEmpty_Succcess()
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction += (source) => {};
+        var source = new object();
+        var target = new CustomWeakEventListener();
+        Delegate handler = Delegate.CreateDelegate(typeof(EventHandler), target, nameof(CustomWeakEventListener.Handler));
+        manager.ProtectedAddHandler(source, handler);
+
+        // Remove.
+        manager.ProtectedRemoveHandler(new object(), (EventHandler)delegate { });
+        SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(target, list[0]);
+
+        // Remove again.
+        manager.ProtectedRemoveHandler(new object(), (EventHandler)delegate { });
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(target, list[0]);
+    }
+
+    [Fact]
+    public void ProtectedRemoveHandler_InvokeNoSuchHandler_Success()
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction += (source) => {};
+        var source = new object();
+        var target = new CustomWeakEventListener();
+        Delegate handler = Delegate.CreateDelegate(typeof(EventHandler), target, nameof(CustomWeakEventListener.Handler));
+        manager.ProtectedAddHandler(source, handler);
+
+        // Remove.
+        manager.ProtectedRemoveHandler(source, (EventHandler)delegate { });
+        SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(target, list[0]);
+
+        // Remove again.
+        manager.ProtectedRemoveHandler(source, (EventHandler)delegate { });
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(target, list[0]);
+    }
+
+    [Theory]
+    [InlineData(1, 0)]
+    [InlineData(3, 0)]
+    [InlineData(3, 1)]
+    [InlineData(3, 2)]
+    [InlineData(4, 0)]
+    [InlineData(4, 1)]
+    [InlineData(4, 2)]
+    [InlineData(4, 3)]
+    [InlineData(6, 0)]
+    [InlineData(6, 1)]
+    [InlineData(6, 2)]
+    [InlineData(6, 3)]
+    [InlineData(6, 4)]
+    [InlineData(6, 5)]
+    [InlineData(7, 0)]
+    [InlineData(7, 1)]
+    [InlineData(7, 2)]
+    [InlineData(7, 3)]
+    [InlineData(7, 4)]
+    [InlineData(7, 5)]
+    public void ProtectedRemoveHandler_InvokeDifferentSizes_Success(int count, int removeIndex)
+    {
+        // Test internal FrugalList implementation.
+        var handlers = new List<Delegate>();
+        for (int i = 0; i < count; i++)
+        {
+            handlers.Add(Delegate.CreateDelegate(typeof(EventHandler), new CustomWeakEventListener(), nameof(CustomWeakEventListener.Handler)));
+        }
+
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction += (source) => {};
+        manager.StopListeningAction += (source) => {};
+
+        var source = new object();
+        for (int i = 0; i < handlers.Count; i++)
+        {
+            manager.ProtectedAddHandler(source, handlers[i]);
+        }
+
+        // Remove.
+        manager.ProtectedRemoveHandler(source, handlers[removeIndex]);
+
+        var expectedHandlers = new List<Delegate>(handlers);
+        expectedHandlers.RemoveAt(removeIndex);
+        if (expectedHandlers.Count != 0)
+        {
+            SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+            Assert.Equal(expectedHandlers.Count, list.Count);
+            Assert.False(list.IsEmpty);
+            for (int i = 0; i < expectedHandlers.Count; i++)
+            {
+                Assert.Same(expectedHandlers[i].Target, list[i]);
+            }
+        }
+        else
+        {
+            Assert.Null(manager[source]);
+        }
+
+        // Remove all.
+        for (int i = 0; i < expectedHandlers.Count; i++)
+        {
+            manager.ProtectedRemoveHandler(source, expectedHandlers[i]);
+        }
+
+        Assert.Null(manager[source]);
+    }
+
+    [Fact]
+    public void ProtectedRemoveHandler_NullHandler_ThrowsArgumentNullException()
+    {
+        var manager = new SubWeakEventManager();
+        var source = new object();
+        Assert.Throws<ArgumentNullException>("handler", () => manager.ProtectedRemoveHandler(source, null!));
+    }
+
+    [Fact]
+    public void ProtectedRemoveHandler_SourceNotListenerList_ThrowsInvalidCastException()
+    {
+        var manager = new SubWeakEventManager();
+        var source = new object();
+        manager[source] = new object();
+
+        var target = new CustomWeakEventListener();
+        var handler = Delegate.CreateDelegate(typeof(EventHandler), target, nameof(CustomWeakEventListener.Handler));        
+        Assert.Throws<InvalidCastException>(() => manager.ProtectedRemoveHandler(source, handler));
+    }
+
+    [Fact]
+    public void ProtectedRemoveListener_Invoke_Success()
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction += (source) => {};
+        object? expectedSource = null;
+        int stopListeningCallCount = 0;
+        manager.StopListeningAction += (source) =>
+        {
+            Assert.Same(expectedSource, source);
+            stopListeningCallCount++;
+        };
+
+        var source1 = new object();
+        var source2 = new object();
+        var listener1 = new CustomWeakEventListener();
+        var listener2 = new CustomWeakEventListener();
+        var listener3 = new CustomWeakEventListener();
+        var listener4 = new CustomWeakEventListener();
+        manager.ProtectedAddListener(source1, listener1);
+        manager.ProtectedAddListener(source1, listener2);
+        manager.ProtectedAddListener(source2, listener3);
+        manager.ProtectedAddListener(source2, listener4);
+        
+        // Remove listener2.
+        manager.ProtectedRemoveListener(source1, listener2);
+        Assert.Equal(0, stopListeningCallCount);
+        SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source1]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener1, list[0]);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source2]);
+        Assert.Equal(2, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener3, list[0]);
+        Assert.Same(listener4, list[1]);
+        
+        // Remove listener2 again.
+        manager.ProtectedRemoveListener(source1, listener2);
+        Assert.Equal(0, stopListeningCallCount);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source1]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener1, list[0]);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source2]);
+        Assert.Equal(2, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener3, list[0]);
+        Assert.Same(listener4, list[1]);
+
+        // Remove listener1.
+        expectedSource = source1;
+        manager.ProtectedRemoveListener(source1, listener1);
+        Assert.Equal(1, stopListeningCallCount);
+        Assert.Null(manager[source1]);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source2]);
+        Assert.Equal(2, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener3, list[0]);
+        Assert.Same(listener4, list[1]);
+
+        // Remove listener3.
+        expectedSource = source2;
+        manager.ProtectedRemoveListener(source2, listener3);
+        Assert.Equal(1, stopListeningCallCount);
+        Assert.Null(manager[source1]);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source2]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener4, list[0]);
+
+        // Remove listener4.
+        expectedSource = source2;
+        manager.ProtectedRemoveListener(source2, listener4);
+        Assert.Equal(2, stopListeningCallCount);
+        Assert.Null(manager[source1]);
+        Assert.Null(manager[source2]);
+    }
+
+    [Fact]
+    public void ProtectedRemoveListener_InvokeStaticSource_Success()
+    {
+        var manager = new SubWeakEventManager();
+
+        FieldInfo actualSourceField = typeof(WeakEventManager).GetField("StaticSource", BindingFlags.NonPublic | BindingFlags.Static)!;
+        Assert.NotNull(actualSourceField);
+        object actualSource = actualSourceField.GetValue(null)!;
+        Assert.Equal("{StaticSource}", actualSource.ToString());
+
+        manager.StartListeningAction += (source) => {};
+        int stopListeningCallCount = 0;
+        manager.StopListeningAction += (source) =>
+        {
+            Assert.Null(source);
+            stopListeningCallCount++;
+        };
+
+        var listener1 = new CustomWeakEventListener();
+        var listener2 = new CustomWeakEventListener();
+        manager.ProtectedAddListener(null!, listener1);
+        manager.ProtectedAddListener(null!, listener2);
+
+        // Add first listener.
+        manager.ProtectedRemoveListener(null!, listener1);
+        Assert.Equal(0, stopListeningCallCount);
+        Assert.Null(manager[null!]);
+        SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[actualSource]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener2, list[0]);
+
+        // Add second listener.
+        manager.ProtectedRemoveListener(null!, listener2);
+        Assert.Equal(1, stopListeningCallCount);
+        Assert.Null(manager[null!]);
+        Assert.Null(manager[actualSource]);
+    }
+
+    [Fact]
+    public void ProtectedRemoveListener_InvokeWithHandlers_Success()
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction += (actualSource) => {};
+        manager.StopListeningAction += (source) => {};
+
+        var source = new object();
+        Delegate handler = () => { };
+        var listener = new CustomWeakEventListener();
+        manager.ProtectedAddHandler(source, handler);
+        manager.ProtectedAddListener(source, listener);
+        
+        // Remove listener.
+        manager.ProtectedRemoveListener(source, listener);
+        SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Throws<InvalidCastException>(() => list[0]);
+    }
+
+    [Fact]
+    public void ProtectedRemoveListener_InvokeMultipleSameSourceNotInUse_DoesNotCloneListenerList()
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction += (source) => {};
+        manager.StopListeningAction += (source) => {};
+
+        var source = new object();
+        var listener1 = new CustomWeakEventListener();
+        var listener2 = new CustomWeakEventListener();
+        var listener3 = new CustomWeakEventListener();
+        manager.ProtectedAddListener(source, listener1);
+        manager.ProtectedAddListener(source, listener2);
+        manager.ProtectedAddListener(source, listener3);
+
+        // Remove first listener.
+        SubWeakEventManager.ListenerList list1 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        manager.ProtectedRemoveListener(source, listener1);
+        SubWeakEventManager.ListenerList list2 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Same(list2, list1);
+        Assert.Equal(2, list2.Count);
+        Assert.False(list2.IsEmpty);
+        Assert.Same(listener2, list2[0]);
+        Assert.Same(listener3, list2[1]);
+        
+        // Remove second listener.
+        manager.ProtectedRemoveListener(source, listener2);
+        SubWeakEventManager.ListenerList list3 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Same(list3, list1);
+        Assert.Equal(1, list1.Count);
+        Assert.False(list3.IsEmpty);
+        Assert.Same(listener3, list3[0]);
+
+        // Remove third listener.
+        manager.ProtectedRemoveListener(source, listener3);
+        Assert.Null(manager[source]);
+    }
+
+    [Fact]
+    public void ProtectedRemoveListener_InvokeMultipleSameSourceInUse_ClonesListenerList()
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction += (source) => {};
+        manager.StopListeningAction += (source) => {};
+
+        var source = new object();
+        var listener1 = new CustomWeakEventListener();
+        var listener2 = new CustomWeakEventListener();
+        var listener3 = new CustomWeakEventListener();
+        manager.ProtectedAddListener(source, listener1);
+        manager.ProtectedAddListener(source, listener2);
+        manager.ProtectedAddListener(source, listener3);
+
+        // Remove first listener.
+        SubWeakEventManager.ListenerList list1 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        manager.ProtectedRemoveListener(source, listener1);
+        SubWeakEventManager.ListenerList list2 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Same(list2, list1);
+        Assert.Equal(2, list1.Count);
+        Assert.False(list1.IsEmpty);
+        Assert.Same(listener2, list1[0]);
+        Assert.Same(listener3, list1[1]);
+
+        // Begin use.
+        list1.BeginUse();
+
+        // Remove second listener.
+        manager.ProtectedRemoveListener(source, listener2);
+        SubWeakEventManager.ListenerList list3 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.NotSame(list3, list1);
+        Assert.Equal(2, list1.Count);
+        Assert.False(list1.IsEmpty);
+        Assert.Same(listener2, list1[0]);
+        Assert.Same(listener3, list1[1]);
+        Assert.Equal(1, list3.Count);
+        Assert.False(list3.IsEmpty);
+        Assert.Same(listener3, list3[0]);
+
+        // Remove third listener.
+        manager.ProtectedRemoveListener(source, listener3);
+        Assert.Null(manager[source]);
+        Assert.NotSame(list3, list1);
+        Assert.Equal(2, list1.Count);
+        Assert.False(list1.IsEmpty);
+        Assert.Same(listener2, list1[0]);
+        Assert.Same(listener3, list1[1]);
+        Assert.Equal(0, list3.Count);
+        Assert.True(list3.IsEmpty);
+    }
+
+    [Fact]
+    public void ProtectedRemoveListener_InvokeMultipleSameSourceNoLongerInUse_DoesNotCloneListenerList()
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction += (source) => {};
+        manager.StopListeningAction += (source) => {};
+
+        var source = new object();
+        var listener1 = new CustomWeakEventListener();
+        var listener2 = new CustomWeakEventListener();
+        var listener3 = new CustomWeakEventListener();
+        manager.ProtectedAddListener(source, listener1);
+        manager.ProtectedAddListener(source, listener2);
+        manager.ProtectedAddListener(source, listener3);
+
+        // Remove first listener.
+        SubWeakEventManager.ListenerList list1 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        manager.ProtectedRemoveListener(source, listener1);
+        SubWeakEventManager.ListenerList list2 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Same(list2, list1);
+        Assert.Equal(2, list1.Count);
+        Assert.False(list1.IsEmpty);
+        Assert.Same(listener2, list1[0]);
+        Assert.Same(listener3, list1[1]);
+
+        // Begin use.
+        list1.BeginUse();
+
+        // End use.
+        list1.EndUse();
+
+        // Remove second listener.
+        manager.ProtectedRemoveListener(source, listener2);
+        SubWeakEventManager.ListenerList list3 = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Same(list3, list1);
+        Assert.Equal(1, list3.Count);
+        Assert.False(list3.IsEmpty);
+        Assert.Same(listener3, list3[0]);
+
+        // Remove third listener.
+        manager.ProtectedRemoveListener(source, listener3);
+        Assert.Null(manager[source]);
+        Assert.Same(list3, list1);
+        Assert.Equal(0, list3.Count);
+        Assert.True(list3.IsEmpty);
+    }
+
+    [Fact]
+    public void ProtectedRemoveListener_InvokeNoSuchSourceEmpty_Succcess()
+    {
+        var manager = new SubWeakEventManager();
+
+        // Remove.
+        manager.ProtectedRemoveListener(new object(), new CustomWeakEventListener());
+
+        // Remove again.
+        manager.ProtectedRemoveListener(new object(), new CustomWeakEventListener());
+    }
+
+    [Fact]
+    public void ProtectedRemoveListener_InvokeNoSuchSourceNotEmpty_Succcess()
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction += (source) => {};
+        var source = new object();
+        var listener = new CustomWeakEventListener();
+        manager.ProtectedAddListener(source, listener);
+
+        // Remove.
+        manager.ProtectedRemoveListener(new object(), new CustomWeakEventListener());
+        SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener, list[0]);
+
+        // Remove again.
+        manager.ProtectedRemoveListener(new object(), new CustomWeakEventListener());
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener, list[0]);
+    }
+
+    [Fact]
+    public void ProtectedRemoveListener_InvokeNoSuchListener_Success()
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction += (source) => {};
+        var source = new object();
+        var listener = new CustomWeakEventListener();
+        manager.ProtectedAddListener(source, listener);
+
+        // Remove.
+        manager.ProtectedRemoveListener(source, new CustomWeakEventListener());
+        SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener, list[0]);
+
+        // Remove again.
+        manager.ProtectedRemoveListener(source, new CustomWeakEventListener());
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener, list[0]);
+    }
+
+    [Theory]
+    [InlineData(1, 0)]
+    [InlineData(3, 0)]
+    [InlineData(3, 1)]
+    [InlineData(3, 2)]
+    [InlineData(4, 0)]
+    [InlineData(4, 1)]
+    [InlineData(4, 2)]
+    [InlineData(4, 3)]
+    [InlineData(6, 0)]
+    [InlineData(6, 1)]
+    [InlineData(6, 2)]
+    [InlineData(6, 3)]
+    [InlineData(6, 4)]
+    [InlineData(6, 5)]
+    [InlineData(7, 0)]
+    [InlineData(7, 1)]
+    [InlineData(7, 2)]
+    [InlineData(7, 3)]
+    [InlineData(7, 4)]
+    [InlineData(7, 5)]
+    public void ProtectedRemoveListener_InvokeDifferentSizes_Success(int count, int removeIndex)
+    {
+        // Test internal FrugalList implementation.
+        var listeners = new List<CustomWeakEventListener>();
+        for (int i = 0; i < count; i++)
+        {
+            listeners.Add(new CustomWeakEventListener());
+        }
+
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction += (source) => {};
+        manager.StopListeningAction += (source) => {};
+
+        var source = new object();
+        for (int i = 0; i < listeners.Count; i++)
+        {
+            manager.ProtectedAddListener(source, listeners[i]);
+        }
+        
+        // Remove.
+        manager.ProtectedRemoveListener(source, listeners[removeIndex]);
+        
+        var expectedListeners = new List<CustomWeakEventListener>(listeners);
+        expectedListeners.RemoveAt(removeIndex);
+        if (expectedListeners.Count != 0)
+        {
+            SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source]);
+            Assert.Equal(expectedListeners.Count, list.Count);
+            Assert.False(list.IsEmpty);
+            for (int i = 0; i < expectedListeners.Count; i++)
+            {
+                Assert.Equal(expectedListeners[i], list[i]);
+            }
+        }
+        else
+        {
+            Assert.Null(manager[source]);
+        }
+
+        // Remove all.
+        for (int i = 0; i < expectedListeners.Count; i++)
+        {
+            manager.ProtectedRemoveListener(source, expectedListeners[i]);
+        }
+
+        Assert.Null(manager[source]);
+    }
+
+    [Fact]
+    public void ProtectedRemoveListener_NullListener_ThrowsArgumentNullException()
+    {
+        var manager = new SubWeakEventManager();
+        var source = new object();
+        Assert.Throws<ArgumentNullException>("listener", () => manager.ProtectedRemoveListener(source, null!));
+    }
+
+    [Fact]
+    public void ProtectedRemoveListener_SourceNotListenerList_ThrowsInvalidCastException()
+    {
+        var manager = new SubWeakEventManager();
+        var source = new object();
+        manager[source] = new object();
+
+        var listener = new CustomWeakEventListener();
+        Assert.Throws<InvalidCastException>(() => manager.ProtectedRemoveListener(source, listener));
+    }
+
+    public static IEnumerable<object?[]> Purge_Data_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { new object() };
+        yield return new object?[] { new ListenerList() };
+    }
+
+    [Theory]
+    [MemberData(nameof(Purge_Data_TestData))]
+    public void Purge_InvokeNotEmptyPurgeAllWithSource_Success(object data)
+    {
+        var manager = new SubWeakEventManager();
+        object? expectedSource = null;
+        int stopListeningCallCount = 0;
+        manager.StopListeningAction = (source) =>
+        {
+            Assert.Same(expectedSource, source);
+            stopListeningCallCount++;
+        };
+        var source = new object();
+        var value = new object();
+        manager[source] = value;
+        
+        // Purge.
+        expectedSource = source;
+        Assert.False(manager.Purge(source, data, true));
+        Assert.Equal(1, stopListeningCallCount);
+        Assert.Same(value, manager[source]);
+        
+        // Purge again.
+        expectedSource = source;
+        Assert.False(manager.Purge(source, data, true));
+        Assert.Equal(2, stopListeningCallCount);
+        Assert.Same(value, manager[source]);
+    }
+
+    [Fact]
+    public void Purge_InvokeNotEmptyNoPurgeAllNotEmptyListenerListData_ReturnsTrue()
+    {
+        var manager = new SubWeakEventManager();
+        var source = new object();
+        var value = new object();
+        manager[source] = value;
+
+        var list = new ListenerList();
+        var listener = new CustomWeakEventListener();
+        var target = new CustomWeakEventListener();
+        Delegate handler = Delegate.CreateDelegate(typeof(EventHandler), target, nameof(CustomWeakEventListener.Handler));
+        list.Add(listener);
+        list.AddHandler(handler);
+
+        // Purge.
+        Assert.False(manager.Purge(source, list, false));
+        Assert.False(list.IsEmpty);
+        Assert.Equal(2, list.Count);
+        Assert.Same(listener, list[0]);
+        Assert.Same(target, list[1]);
+        Assert.Same(value, manager[source]);
+    }
+
+    [Fact]
+    public void Purge_InvokeNotEmptyNoPurgeAllEmptyListenerListData_ReturnsTrue()
+    {
+        var manager = new SubWeakEventManager();
+        object? expectedSource = null;
+        int stopListeningCallCount = 0;
+        manager.StopListeningAction = (source) =>
+        {
+            Assert.Same(expectedSource, source);
+            stopListeningCallCount++;
+        };
+        var source = new object();
+        var value = new object();
+        manager[source] = value;
+
+        var list = new ListenerList();
+
+        // Purge.
+        expectedSource = source;
+        Assert.True(manager.Purge(source, list, false));
+        Assert.Equal(1, stopListeningCallCount);
+        Assert.True(list.IsEmpty);
+        Assert.Equal(0, list.Count);
+        Assert.Null(manager[source]);
+        
+        // Purge again.
+        expectedSource = source;
+        Assert.True(manager.Purge(source, list, false));
+        Assert.Equal(2, stopListeningCallCount);
+        Assert.True(list.IsEmpty);
+        Assert.Equal(0, list.Count);
+        Assert.Null(manager[source]);
+    }
+
+    [Fact]
+    public void Purge_InvokeNotEmptyNoPurgeAllNullData_ThrowsNullReferenceException()
+    {
+        var manager = new SubWeakEventManager();
+        var source = new object();
+        var value = new object();
+        manager[source] = value;
+
+        // Purge.
+        Assert.Throws<NullReferenceException>(() => manager.Purge(source, null!, false));
+        Assert.Same(value, manager[source]);
+    }
+
+    [Fact]
+    public void Purge_InvokeNotEmptyNoPurgeAllNotListenerListData_ThrowsInvalidCastException()
+    {
+        var manager = new SubWeakEventManager();
+        var source = new object();
+        var value = new object();
+        manager[source] = value;
+
+        // Purge.
+        Assert.Throws<InvalidCastException>(() => manager.Purge(source, new object(), false));
+        Assert.Same(value, manager[source]);
+    }
+
+    [Theory]
+    [MemberData(nameof(Purge_Data_TestData))]
+    public void Purge_InvokeNotEmptyPurgeAllWithNoSource_Success(object data)
+    {
+        var manager = new SubWeakEventManager();
+        var source = new object();
+        var value = new object();
+        manager[source] = value;
+        
+        // Purge.
+        Assert.False(manager.Purge(null!, data, true));
+        Assert.Same(value, manager[source]);
+        
+        // Purge again.
+        Assert.False(manager.Purge(null!, data, true));
+        Assert.Same(value, manager[source]);
+    }
+
+    [Theory]
+    [MemberData(nameof(Purge_Data_TestData))]
+    public void Purge_InvokeNotEmptyNoPurgeAllWithNoSource_Success(object data)
+    {
+        var manager = new SubWeakEventManager();
+        var source = new object();
+        var value = new object();
+        manager[source] = value;
+        
+        // Purge.
+        Assert.False(manager.Purge(null!, data, true));
+        Assert.Same(value, manager[source]);
+        
+        // Purge again.
+        Assert.False(manager.Purge(null!, data, true));
+        Assert.Same(value, manager[source]);
+    }
+
+    [Theory]
+    [MemberData(nameof(Purge_Data_TestData))]
+    public void Purge_InvokeEmptyPurgeAllWithSource_Success(object data)
+    {
+        var manager = new SubWeakEventManager();
+        object? expectedSource = null;
+        int stopListeningCallCount = 0;
+        manager.StopListeningAction = (source) =>
+        {
+            Assert.Same(expectedSource, source);
+            stopListeningCallCount++;
+        };
+        var source = new object();
+        
+        // Purge.
+        expectedSource = source;
+        Assert.False(manager.Purge(source, data, true));
+        Assert.Equal(1, stopListeningCallCount);
+        Assert.Null(manager[source]);
+        
+        // Purge again.
+        expectedSource = source;
+        Assert.False(manager.Purge(source, data, true));
+        Assert.Equal(2, stopListeningCallCount);
+        Assert.Null(manager[source]);
+    }
+
+    [Fact]
+    public void Purge_InvokeEmptyNoPurgeAllNotEmptyListenerListData_ReturnsTrue()
+    {
+        var manager = new SubWeakEventManager();
+        var source = new object();
+
+        var list = new ListenerList();
+        var listener = new CustomWeakEventListener();
+        var target = new CustomWeakEventListener();
+        Delegate handler = Delegate.CreateDelegate(typeof(EventHandler), target, nameof(CustomWeakEventListener.Handler));
+        list.Add(listener);
+        list.AddHandler(handler);
+
+        // Purge.
+        Assert.False(manager.Purge(source, list, false));
+        Assert.False(list.IsEmpty);
+        Assert.Equal(2, list.Count);
+        Assert.Same(listener, list[0]);
+        Assert.Same(target, list[1]);
+        Assert.Null(manager[source]);
+    }
+
+    [Fact]
+    public void Purge_InvokeEmptyNoPurgeAllEmptyListenerListData_ReturnsTrue()
+    {
+        var manager = new SubWeakEventManager();
+        object? expectedSource = null;
+        int stopListeningCallCount = 0;
+        manager.StopListeningAction = (source) =>
+        {
+            Assert.Same(expectedSource, source);
+            stopListeningCallCount++;
+        };
+        var source = new object();
+
+        var list = new ListenerList();
+
+        // Purge.
+        expectedSource = source;
+        Assert.True(manager.Purge(source, list, false));
+        Assert.Equal(1, stopListeningCallCount);
+        Assert.True(list.IsEmpty);
+        Assert.Equal(0, list.Count);
+        Assert.Null(manager[source]);
+        
+        // Purge again.
+        expectedSource = source;
+        Assert.True(manager.Purge(source, list, false));
+        Assert.Equal(2, stopListeningCallCount);
+        Assert.True(list.IsEmpty);
+        Assert.Equal(0, list.Count);
+        Assert.Null(manager[source]);
+    }
+
+    [Fact]
+    public void Purge_InvokeEmptyNoPurgeAllNullData_ThrowsNullReferenceException()
+    {
+        var manager = new SubWeakEventManager();
+        var source = new object();
+
+        // Purge.
+        Assert.Throws<NullReferenceException>(() => manager.Purge(source, null!, false));
+        Assert.Null(manager[source]);
+    }
+
+    [Fact]
+    public void Purge_InvokeEmptyNoPurgeAllNotListenerListData_ThrowsInvalidCastException()
+    {
+        var manager = new SubWeakEventManager();
+        var source = new object();
+
+        // Purge.
+        Assert.Throws<InvalidCastException>(() => manager.Purge(source, new object(), false));
+        Assert.Null(manager[source]);
+    }
+
+    [Theory]
+    [MemberData(nameof(Purge_Data_TestData))]
+    public void Purge_InvokeEmptyPurgeAllWithNoSource_Success(object data)
+    {
+        var manager = new SubWeakEventManager();
+        
+        // Purge.
+        Assert.False(manager.Purge(null!, data, true));
+        
+        // Purge again.
+        Assert.False(manager.Purge(null!, data, true));
+    }
+
+    [Theory]
+    [MemberData(nameof(Purge_Data_TestData))]
+    public void Purge_InvokeEmptyNoPurgeAllWithNoSource_Success(object data)
+    {
+        var manager = new SubWeakEventManager();
+        
+        // Purge.
+        Assert.False(manager.Purge(null!, data, true));
+        
+        // Purge again.
+        Assert.False(manager.Purge(null!, data, true));
+    }
+
+    public static IEnumerable<object?[]> Remove_TestData()
+    {
+        yield return new object?[] { new object() };
+        yield return new object?[] { 1 };
+    }
+
+    [Theory]
+    [MemberData(nameof(Remove_TestData))]
+    public void Remove_Invoke_Success(object source)
+    {
+        var manager = new SubWeakEventManager();
+
+        object listener = new object();
+        manager[source] = listener;
+        Assert.Same(listener, manager[source]);
+
+        // Remove.
+        manager.Remove(source);
+        Assert.Null(manager[source]);
+
+        // Remove again.
+        manager.Remove(source);
+        Assert.Null(manager[source]);
+    }
+
+    public static IEnumerable<object?[]> Remove_NoSuchSource_TestData()
+    {
+        yield return new object?[] { null };
+        yield return new object?[] { new object() };
+        yield return new object?[] { 1 };
+    }
+
+    [Theory]
+    [MemberData(nameof(Remove_NoSuchSource_TestData))]
+    public void Remove_InvokeNoSuchSource_Success(object source)
+    {
+        var manager = new SubWeakEventManager();
+
+        // Remove.
+        manager.Remove(source);
+
+        // Remove again.
+        manager.Remove(source);
+    }
+
+    [Fact]
+    public void SetCurrentManager_Invoke_GetReturnsExpected()
+    {
+        var newManager = new SubWeakEventManager();
+
+        // Set.
+        SubWeakEventManager.SetCurrentManager(typeof(SentinelType2), newManager);
+        Assert.Same(newManager, SubWeakEventManager.GetCurrentManager(typeof(SentinelType2)));
+
+        // Set same.
+        SubWeakEventManager.SetCurrentManager(typeof(SentinelType2), newManager);
+        Assert.Same(newManager, SubWeakEventManager.GetCurrentManager(typeof(SentinelType2)));
+
+        // Set null.
+        SubWeakEventManager.SetCurrentManager(typeof(SentinelType2), null);
+        Assert.Null(SubWeakEventManager.GetCurrentManager(typeof(SentinelType2)));
+    }
+
+    private class SentinelType2 { }
+
+    [Fact]
+    public void SetCurrentManager_NullSource_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>("key", () => SubWeakEventManager.SetCurrentManager(null!, new SubWeakEventManager()));
+    }
+    
+    [Fact]
+    public void ScheduleCleanup_InvokeWithListeners_Success()
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction += (source) => {};
+        
+        var source1 = new object();
+        var source2 = new object();
+        var listener1 = new CustomWeakEventListener();
+        var listener2 = new CustomWeakEventListener();
+        var listener3 = new CustomWeakEventListener();
+        manager.ProtectedAddListener(source1, listener1);
+        manager.ProtectedAddListener(source1, listener2);
+        manager.ProtectedAddListener(source2, listener3);
+
+        // Schedule.
+        manager.ScheduleCleanup();
+        SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source1]);
+        Assert.Equal(2, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener1, list[0]);
+        Assert.Same(listener2, list[1]);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source2]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener3, list[0]);
+
+        // Schedule again.
+        manager.ScheduleCleanup();
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source1]);
+        Assert.Equal(2, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener1, list[0]);
+        Assert.Same(listener2, list[1]);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source2]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener3, list[0]);
+    }
+    
+    [Fact]
+    public void ScheduleCleanup_InvokeWithHandlers_Success()
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction += (source) => {};
+        
+        var source1 = new object();
+        var source2 = new object();
+        var target1 = new CustomWeakEventListener();
+        Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+        Delegate handler2 = (EventHandler)delegate { };
+        Delegate handler3 = StaticEventHandler;
+        manager.ProtectedAddHandler(source1, handler1);
+        manager.ProtectedAddHandler(source1, handler2);
+        manager.ProtectedAddHandler(source2, handler3);
+
+        // Schedule.
+        manager.ScheduleCleanup();
+        SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source1]);
+        Assert.Equal(2, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(target1, list[0]);
+        Assert.Throws<InvalidCastException>(() => list[1]);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source2]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Throws<InvalidCastException>(() => list[0]);
+
+        // Schedule again.
+        manager.ScheduleCleanup();
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source1]);
+        Assert.Equal(2, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(target1, list[0]);
+        Assert.Throws<InvalidCastException>(() => list[1]);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source2]);
+        Assert.Equal(1, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Throws<InvalidCastException>(() => list[0]);
+    }
+    
+    [Fact]
+    public void ScheduleCleanup_InvokeWithListenersAndHandlers_Success()
+    {
+        var manager = new SubWeakEventManager();
+        manager.StartListeningAction += (source) => {};
+        
+        var source1 = new object();
+        var source2 = new object();
+        var listener1 = new CustomWeakEventListener();
+        var listener2 = new CustomWeakEventListener();
+        var listener3 = new CustomWeakEventListener();
+        var target1 = new CustomWeakEventListener();
+        Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+        Delegate handler2 = (EventHandler)delegate { };
+        Delegate handler3 = StaticEventHandler;
+        manager.ProtectedAddListener(source1, listener1);
+        manager.ProtectedAddHandler(source1, handler1);
+        manager.ProtectedAddListener(source1, listener2);
+        manager.ProtectedAddHandler(source1, handler2);
+        manager.ProtectedAddListener(source2, listener3);
+        manager.ProtectedAddHandler(source2, handler3);
+
+        // Schedule.
+        manager.ScheduleCleanup();
+        SubWeakEventManager.ListenerList list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source1]);
+        Assert.Equal(4, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener1, list[0]);
+        Assert.Same(target1, list[1]);
+        Assert.Same(listener2, list[2]);
+        Assert.Throws<InvalidCastException>(() => list[3]);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source2]);
+        Assert.Equal(2, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener3, list[0]);
+        Assert.Throws<InvalidCastException>(() => list[1]);
+
+        // Schedule again.
+        manager.ScheduleCleanup();
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source1]);
+        Assert.Equal(4, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener1, list[0]);
+        Assert.Same(target1, list[1]);
+        Assert.Same(listener2, list[2]);
+        Assert.Throws<InvalidCastException>(() => list[3]);
+        list = Assert.IsType<SubWeakEventManager.ListenerList>(manager[source2]);
+        Assert.Equal(2, list.Count);
+        Assert.False(list.IsEmpty);
+        Assert.Same(listener3, list[0]);
+        Assert.Throws<InvalidCastException>(() => list[1]);
+    }
+    
+    [Fact]
+    public void ScheduleCleanup_InvokeEmpty_Success()
+    {
+        var manager = new SubWeakEventManager();
+
+        // Schedule
+        manager.ScheduleCleanup();
+
+        // Schedule again.
+        manager.ScheduleCleanup();
+    }
+
+    public class ListenerListTests : WeakEventManager
+    {
+        [Fact]
+        public void Ctor_Default()
+        {
+            var list = new SubListenerList();
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+        }
+
+        [Theory]
+        [InlineData(-1)]
+        [InlineData(0)]
+        [InlineData(1)]
+        [InlineData(2)]
+        [InlineData(3)]
+        [InlineData(4)]
+        [InlineData(5)]
+        [InlineData(6)]
+        [InlineData(7)]
+        public void Ctor_Int(int capacity)
+        {
+            var list = new SubListenerList(capacity);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+        }
+
+        [Fact]
+        public void Empty_Get_Success()
+        {
+            ListenerList list = ListenerList.Empty;
+            Assert.NotNull(list);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+            Assert.Same(list, ListenerList.Empty);
+        }
+
+        [Fact]
+        public void PrepareForWriting_InvokeEmptyInUse_ClonesList()
+        {
+            var originalList = new ListenerList();
+            ListenerList list = originalList;
+
+            // Begin use.
+            list.BeginUse();
+
+            // Invoke.
+            Assert.True(ListenerList.PrepareForWriting(ref list));
+            Assert.NotSame(originalList, list);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+
+            // Invoke again.
+            ListenerList newList = list;
+            Assert.False(ListenerList.PrepareForWriting(ref list));
+            Assert.NotSame(originalList, list);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+        }
+
+        [Fact]
+        public void PrepareForWriting_InvokeEmptyNotInUse_DoesNotCloneList()
+        {
+            var originalList = new ListenerList();
+
+            // Invoke.
+            ListenerList list = originalList;
+            Assert.False(ListenerList.PrepareForWriting(ref list));
+            Assert.Same(originalList, list);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+
+            // Invoke again.
+            ListenerList newList = list;
+            Assert.False(ListenerList.PrepareForWriting(ref list));
+            Assert.Same(originalList, list);
+            Assert.Same(newList, list);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+        }
+
+        [Fact]
+        public void PrepareForWriting_InvokeEmptyNoLongerInUse_DoesNotCloneList()
+        {
+            var originalList = new ListenerList();
+            ListenerList list = originalList;
+
+            // Begin use.
+            list.BeginUse();
+
+            // End use.
+            list.EndUse();
+
+            // Invoke.
+            Assert.False(ListenerList.PrepareForWriting(ref list));
+            Assert.Same(originalList, list);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+
+            // Invoke again.
+            ListenerList newList = list;
+            Assert.False(ListenerList.PrepareForWriting(ref list));
+            Assert.Same(originalList, list);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+        }
+
+        [Fact]
+        public void PrepareForWriting_InvokeNotEmptyNotInUse_DoesNotCloneList()
+        {
+            var originalList = new ListenerList();
+            var listener1 = new CustomWeakEventListener();
+            var listener2 = new CustomWeakEventListener();
+
+            originalList.Add(listener1);
+            originalList.Add(listener2);
+
+            // Invoke.
+            ListenerList list = originalList;
+            Assert.False(ListenerList.PrepareForWriting(ref list));
+            Assert.Same(originalList, list);
+            Assert.Equal(2, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(listener2, list[1]);
+
+            // Invoke again.
+            ListenerList newList = list;
+            Assert.False(ListenerList.PrepareForWriting(ref list));
+            Assert.Same(originalList, list);
+            Assert.Same(newList, list);
+            Assert.Equal(2, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(listener2, list[1]);
+        }
+
+        [Fact]
+        public void PrepareForWriting_InvokeNotEmptyInUse_ClonesList()
+        {
+            var originalList = new ListenerList();
+            var listener1 = new CustomWeakEventListener();
+            var listener2 = new CustomWeakEventListener();
+
+            originalList.Add(listener1);
+            originalList.Add(listener2);
+
+            // Begin use.
+            originalList.BeginUse();
+
+            // Invoke.
+            ListenerList list = originalList;
+            Assert.True(ListenerList.PrepareForWriting(ref list));
+            Assert.NotSame(originalList, list);
+            Assert.Equal(2, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(listener2, list[1]);
+
+            // Invoke again.
+            ListenerList newList = list;
+            Assert.False(ListenerList.PrepareForWriting(ref list));
+            Assert.Same(newList, list);
+            Assert.Equal(2, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(listener2, list[1]);
+        }
+
+        [Fact]
+        public void PrepareForWriting_InvokeNotEmptyNoLongerInUse_DoesNotCloneList()
+        {
+            var originalList = new ListenerList();
+            var listener1 = new CustomWeakEventListener();
+            var listener2 = new CustomWeakEventListener();
+
+            originalList.Add(listener1);
+            originalList.Add(listener2);
+
+            // Begin use.
+            originalList.BeginUse();
+
+            // End use.
+            originalList.EndUse();
+
+            // Invoke.
+            ListenerList list = originalList;
+            Assert.False(ListenerList.PrepareForWriting(ref list));
+            Assert.Same(originalList, list);
+            Assert.Equal(2, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(listener2, list[1]);
+
+            // Invoke again.
+            ListenerList newList = list;
+            Assert.False(ListenerList.PrepareForWriting(ref list));
+            Assert.Same(originalList, list);
+            Assert.Equal(2, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(listener2, list[1]);
+        }
+
+        public static IEnumerable<object?[]> PrepareForWriting_CustomClone_TestData()
+        {
+            yield return new object?[] { null };
+            yield return new object?[] { new SubListenerList() };
+        }
+
+        [Theory]
+        [MemberData(nameof(PrepareForWriting_CustomClone_TestData))]
+        public void PrepareForWriting_CustomCloneInUse_Success(object result)
+        {
+            var originalList = new CustomListenerList();
+            int cloneCallCount = 0;
+            originalList.CloneAction = () =>
+            {
+                cloneCallCount++;
+                return (ListenerList)result;
+            };
+
+            ListenerList list = originalList;
+            list.BeginUse();
+
+            // Invoke.
+            Assert.True(ListenerList.PrepareForWriting(ref list));
+            Assert.NotSame(originalList, list);
+            Assert.Same(result, list);
+            Assert.Equal(1, cloneCallCount);
+        }
+
+        [Fact]
+        public void PrepareForWriting_NullList_ThrowsArgumentNullException()
+        {
+            ListenerList? list = null;
+            // TODO: this should throw ANE.
+            //Assert.Throws<ArgumentNullException>("list", () => ListenerList.PrepareForWriting(ref list));
+            Assert.Throws<NullReferenceException>(() => ListenerList.PrepareForWriting(ref list));
+        }
+
+        [Fact]
+        public void Item_GetListener_ReturnsExpected()
+        {
+            var list = new SubListenerList();
+            var listener1 = new CustomWeakEventListener();
+            list.Add(listener1);
+            Assert.Same(listener1, list[0]);
+        }
+
+        [Fact]
+        public void Item_GetHandlerIWeakEventListenerTarget_ReturnsExpected()
+        {
+            var list = new SubListenerList();
+            var target = new CustomWeakEventListener();
+            Delegate handler = Delegate.CreateDelegate(typeof(EventHandler), target, nameof(CustomWeakEventListener.Handler));
+            Assert.NotNull(handler.Target);
+            Assert.IsAssignableFrom<IWeakEventListener>(handler.Target);
+
+            list.AddHandler(handler);
+            Assert.Same(target, list[0]);
+        }
+
+        [Fact]
+        public void Item_GetHandlerStatic_ThrowsInvalidCastException()
+        {
+            var list = new SubListenerList();
+            static void Handler(object sender, EventArgs e) { }
+            Delegate handler = Handler;
+            Assert.Null(handler.Target);
+
+            list.AddHandler(handler);
+            Assert.Throws<InvalidCastException>(() => list[0]);
+        }
+
+        [Fact]
+        public void Item_GetHandlerNotIWeakEventListenerTarget_ThrowsInvalidCastException()
+        {
+            var list = new SubListenerList();
+            Delegate handler = (EventHandler)delegate { };
+            Assert.NotNull(handler.Target);
+            Assert.False(handler.Target is IWeakEventListener);
+
+            list.AddHandler(handler);
+            Assert.Throws<InvalidCastException>(() => list[0]);
+        }
+
+        [Theory]
+        [InlineData(-1)]
+        [InlineData(0)]
+        [InlineData(1)]
+        [InlineData(2)]
+        [InlineData(3)]
+        [InlineData(4)]
+        [InlineData(5)]
+        [InlineData(6)]
+        [InlineData(7)]
+        public void Item_GetWithCapacity_ReturnsExpected(int capacity)
+        {
+            var list = new SubListenerList(capacity);
+            var listener1 = new CustomWeakEventListener();
+            var listener2 = new CustomWeakEventListener();
+            list.Add(listener1);
+            Assert.Same(listener1, list[0]);
+        }
+
+        [Theory]
+        [InlineData(-1)]
+        [InlineData(0)]
+        [InlineData(1)]
+        public void Item_GetInvalidIndexEmpty_ThrowsArgumentOutOfRangeException(int index)
+        {
+            var list = new SubListenerList();
+            Assert.Throws<ArgumentOutOfRangeException>("index", () => list[index]);
+        }
+
+        [Theory]
+        [InlineData(-1)]
+        [InlineData(0)]
+        [InlineData(1)]
+        [InlineData(2)]
+        [InlineData(3)]
+        [InlineData(4)]
+        [InlineData(5)]
+        [InlineData(6)]
+        [InlineData(7)]
+        public void Item_GetInvalidIndexEmptyWithCapacity_ReturnsExpected(int capacity)
+        {
+            var list = new SubListenerList(capacity);
+            Assert.Throws<ArgumentOutOfRangeException>("index", () => list[-1]);
+            Assert.Throws<ArgumentOutOfRangeException>("index", () => list[0]);
+            Assert.Throws<ArgumentOutOfRangeException>("index", () => list[1]);
+        }
+
+        [Theory]
+        [InlineData(-1)]
+        [InlineData(1)]
+        [InlineData(2)]
+        public void Item_GetInvalidIndexNotEmpty_ThrowsArgumentOutOfRangeException(int index)
+        {
+            var list = new SubListenerList();
+            list.Add(new CustomWeakEventListener());
+            Assert.Throws<ArgumentOutOfRangeException>("index", () => list[index]);
+        }
+
+        [Theory]
+        [InlineData(-1)]
+        [InlineData(0)]
+        [InlineData(1)]
+        [InlineData(2)]
+        [InlineData(3)]
+        [InlineData(4)]
+        [InlineData(5)]
+        [InlineData(6)]
+        [InlineData(7)]
+        public void Item_GetInvalidIndexNotEmptyWithCapacity_ThrowsArgumentOutOfRangeException(int capacity)
+        {
+            var list = new SubListenerList(capacity);
+            list.Add(new CustomWeakEventListener());
+            Assert.Throws<ArgumentOutOfRangeException>("index", () => list[-1]);
+            Assert.Throws<ArgumentOutOfRangeException>("index", () => list[1]);
+            Assert.Throws<ArgumentOutOfRangeException>("index", () => list[2]);
+        }
+
+        [Fact]
+        public void Add_Invoke_Success()
+        {
+            var list = new SubListenerList();
+            var listener1 = new CustomWeakEventListener();
+            var listener2 = new CustomWeakEventListener();
+            var listener3 = new CustomWeakEventListener();
+            var listener4 = new CustomWeakEventListener();
+            var listener5 = new CustomWeakEventListener();
+            var listener6 = new CustomWeakEventListener();
+
+            // Add once.
+            list.Add(listener1);
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+
+            // Add again.
+            list.Add(listener1);
+            Assert.Equal(2, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(listener1, list[1]);
+
+            // Add third.
+            list.Add(null);
+            Assert.Equal(3, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(listener1, list[1]);
+            Assert.Throws<InvalidCastException>(() => list[2]);
+
+            // Add fourth.
+            list.Add(listener2);
+            Assert.Equal(4, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(listener1, list[1]);
+            Assert.Throws<InvalidCastException>(() => list[2]);
+            Assert.Same(listener2, list[3]);
+
+            // Add fifth.
+            list.Add(listener3);
+            Assert.Equal(5, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(listener1, list[1]);
+            Assert.Throws<InvalidCastException>(() => list[2]);
+            Assert.Same(listener2, list[3]);
+            Assert.Same(listener3, list[4]);
+
+            // Add sixth.
+            list.Add(listener4);
+            Assert.Equal(6, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(listener1, list[1]);
+            Assert.Throws<InvalidCastException>(() => list[2]);
+            Assert.Same(listener2, list[3]);
+            Assert.Same(listener3, list[4]);
+            Assert.Same(listener4, list[5]);
+
+            // Add seventh.
+            list.Add(listener5);
+            Assert.Equal(7, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(listener1, list[1]);
+            Assert.Throws<InvalidCastException>(() => list[2]);
+            Assert.Same(listener2, list[3]);
+            Assert.Same(listener3, list[4]);
+            Assert.Same(listener4, list[5]);
+            Assert.Same(listener5, list[6]);
+
+            // Add eighth.
+            list.Add(listener6);
+            Assert.Equal(8, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(listener1, list[1]);
+            Assert.Throws<InvalidCastException>(() => list[2]);
+            Assert.Same(listener2, list[3]);
+            Assert.Same(listener3, list[4]);
+            Assert.Same(listener4, list[5]);
+            Assert.Same(listener5, list[6]);
+            Assert.Same(listener6, list[7]);
+        }
+
+        // TODO: this causes a crash.
+#if false
+        [Fact]
+        public void Add_InvokeInUse_Success()
+        {
+            var list = new SubListenerList();
+            var listener = new SubListener();
+
+            // Begin use.
+            Assert.False(list.BeginUse());
+
+            // Add.
+            list.Add(listener);
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener, list[0]);
+        }
+#endif
+
+        [Fact]
+        public void Add_InvokeNoLongerInUse_Success()
+        {
+            var list = new SubListenerList();
+            var listener = new CustomWeakEventListener();
+
+            // Begin use.
+            Assert.False(list.BeginUse());
+
+            // End use.
+            list.EndUse();
+
+            // Add.
+            list.Add(listener);
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener, list[0]);
+        }
+
+        [Theory]
+        [InlineData(1)]
+        [InlineData(3)]
+        [InlineData(4)]
+        [InlineData(6)]
+        [InlineData(7)]
+        public void Add_InvokeDifferentSizes_Success(int count)
+        {
+            // Test internal FrugalList implementation.
+            var listeners = new List<CustomWeakEventListener>();
+            for (int i = 0; i < count; i++)
+            {
+                listeners.Add(new CustomWeakEventListener());
+            }
+
+            // Add.
+            var list = new SubListenerList();
+            for (int i = 0; i < count; i++)
+            {
+                list.Add(listeners[i]);
+                Assert.Equal(i + 1, list.Count);
+                Assert.False(list.IsEmpty);
+                for (int j = 0; j <= i; j++)
+                {
+                    Assert.Same(listeners[j], list[j]);
+                }
+            }
+        }
+
+        [Fact]
+        public void AddHandler_Invoke_Success()
+        {
+            var list = new SubListenerList();
+            var target1 = new CustomWeakEventListener();
+            var target2 = new CustomWeakEventListener();
+            var target3 = new CustomWeakEventListener();
+            Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+            Delegate handler2 = WeakEventManagerTests.StaticEventHandler;
+            Delegate handler3 = (EventHandler)delegate { };
+            Delegate handler4 = Delegate.CreateDelegate(typeof(EventHandler), target2, nameof(CustomWeakEventListener.Handler));
+            Delegate handler5 = Delegate.CreateDelegate(typeof(EventHandler), target3, nameof(CustomWeakEventListener.Handler));
+
+            // Add once.
+            list.AddHandler(handler1);
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(target1, list[0]);
+
+            // Add again.
+            list.AddHandler(handler1);
+            Assert.Equal(2, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(target1, list[0]);
+            Assert.Same(target1, list[1]);
+
+            // Add third.
+            list.AddHandler(handler2);
+            Assert.Equal(3, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(target1, list[0]);
+            Assert.Same(target1, list[1]);
+            Assert.Throws<InvalidCastException>(() => list[2]);
+
+            // Add again.
+            list.AddHandler(handler2);
+            Assert.Equal(4, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(target1, list[0]);
+            Assert.Same(target1, list[1]);
+            Assert.Throws<InvalidCastException>(() => list[2]);
+            Assert.Throws<InvalidCastException>(() => list[3]);
+
+            // Add fifth.
+            list.AddHandler(handler3);
+            Assert.Equal(5, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(target1, list[0]);
+            Assert.Same(target1, list[1]);
+            Assert.Throws<InvalidCastException>(() => list[2]);
+            Assert.Throws<InvalidCastException>(() => list[3]);
+            Assert.Throws<InvalidCastException>(() => list[4]);
+
+            // Add again.
+            list.AddHandler(handler3);
+            Assert.Equal(6, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(target1, list[0]);
+            Assert.Same(target1, list[1]);
+            Assert.Throws<InvalidCastException>(() => list[2]);
+            Assert.Throws<InvalidCastException>(() => list[3]);
+            Assert.Throws<InvalidCastException>(() => list[4]);
+            Assert.Throws<InvalidCastException>(() => list[5]);
+
+            // Add seventh.
+            list.AddHandler(handler4);
+            Assert.Equal(7, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(target1, list[0]);
+            Assert.Same(target1, list[1]);
+            Assert.Throws<InvalidCastException>(() => list[2]);
+            Assert.Throws<InvalidCastException>(() => list[3]);
+            Assert.Throws<InvalidCastException>(() => list[4]);
+            Assert.Throws<InvalidCastException>(() => list[5]);
+            Assert.Same(target2, list[6]);
+
+            // Add eighth.
+            list.AddHandler(handler5);
+            Assert.Equal(8, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(target1, list[0]);
+            Assert.Same(target1, list[1]);
+            Assert.Throws<InvalidCastException>(() => list[2]);
+            Assert.Throws<InvalidCastException>(() => list[3]);
+            Assert.Throws<InvalidCastException>(() => list[4]);
+            Assert.Throws<InvalidCastException>(() => list[5]);
+            Assert.Same(target2, list[6]);
+            Assert.Same(target3, list[7]);
+        }
+
+        [Fact]
+        public void AddHandler_InvokeSameTargetMultipleTimes_Success()
+        {
+            var list = new SubListenerList();
+
+            var target1 = new CustomWeakEventListener();
+            var target2 = new CustomWeakEventListener();
+            Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+            Delegate handler2 = Delegate.CreateDelegate(typeof(EventHandler), target2, nameof(CustomWeakEventListener.Handler));
+            Delegate handler3 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.SecondHandler));
+            Delegate handler4 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+            Delegate handler5 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.SecondHandler));
+            Delegate handler6 = Delegate.CreateDelegate(typeof(EventHandler), target2, nameof(CustomWeakEventListener.SecondHandler));
+            Delegate handler7 = Delegate.CreateDelegate(typeof(EventHandler), target2, nameof(CustomWeakEventListener.Handler));
+
+            // Add first.
+            list.AddHandler(handler1);
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(target1, list[0]);
+
+            // Add second.
+            list.AddHandler(handler2);
+            Assert.Equal(2, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(target1, list[0]);
+            Assert.Same(target2, list[1]);
+
+            // Add third.
+            list.AddHandler(handler3);
+            Assert.Equal(3, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(target1, list[0]);
+            Assert.Same(target2, list[1]);
+            Assert.Same(target1, list[2]);
+
+            // Add fourth.
+            list.AddHandler(handler4);
+            Assert.Equal(4, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(target1, list[0]);
+            Assert.Same(target2, list[1]);
+            Assert.Same(target1, list[2]);
+            Assert.Same(target1, list[3]);
+
+            // Add fifth.
+            list.AddHandler(handler5);
+            Assert.Equal(5, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(target1, list[0]);
+            Assert.Same(target2, list[1]);
+            Assert.Same(target1, list[2]);
+            Assert.Same(target1, list[3]);
+            Assert.Same(target1, list[4]);
+
+            // Add sixth.
+            list.AddHandler(handler6);
+            Assert.Equal(6, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(target1, list[0]);
+            Assert.Same(target2, list[1]);
+            Assert.Same(target1, list[2]);
+            Assert.Same(target1, list[3]);
+            Assert.Same(target1, list[4]);
+            Assert.Same(target2, list[5]);
+
+            // Add seventh.
+            list.AddHandler(handler7);
+            Assert.Equal(7, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(target1, list[0]);
+            Assert.Same(target2, list[1]);
+            Assert.Same(target1, list[2]);
+            Assert.Same(target1, list[3]);
+            Assert.Same(target1, list[4]);
+            Assert.Same(target2, list[5]);
+            Assert.Same(target2, list[6]);
+        }
+
+        [Fact]
+        public void AddHandler_InvokeMultipleTimesIWeakEventListenerTarget_Success()
+        {
+            var list = new SubListenerList();
+            var target = new CustomWeakEventListener();
+            Delegate handler = Delegate.CreateDelegate(typeof(EventHandler), target, nameof(CustomWeakEventListener.Handler));
+
+            // Add once.
+            list.AddHandler(handler);
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(target, list[0]);
+
+            // Add twice.
+            list.AddHandler(handler);
+            Assert.Equal(2, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(target, list[0]);
+            Assert.Same(target, list[1]);
+
+            // Add three times.
+            list.AddHandler(handler);
+            Assert.Equal(3, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(target, list[0]);
+            Assert.Same(target, list[1]);
+            Assert.Same(target, list[2]);
+        }
+
+        [Fact]
+        public void AddHandler_InvokeMultipleTimesStaticTarget_Success()
+        {
+            var list = new SubListenerList();
+            Delegate handler = WeakEventManagerTests.StaticEventHandler;
+
+            // Add once.
+            list.AddHandler(handler);
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Throws<InvalidCastException>(() => list[0]);
+
+            // Add twice.
+            list.AddHandler(handler);
+            Assert.Equal(2, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Throws<InvalidCastException>(() => list[0]);
+            Assert.Throws<InvalidCastException>(() => list[1]);
+
+            // Add three times.
+            list.AddHandler(handler);
+            Assert.Equal(3, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Throws<InvalidCastException>(() => list[0]);
+            Assert.Throws<InvalidCastException>(() => list[1]);
+            Assert.Throws<InvalidCastException>(() => list[2]);
+        }
+
+        [Fact]
+        public void AddHandler_InvokeMultipleTimesNotIWeakEventListenerTarget_Success()
+        {
+            var list = new SubListenerList();
+            Delegate handler = (EventHandler)delegate { };
+
+            // Add once.
+            list.AddHandler(handler);
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Throws<InvalidCastException>(() => list[0]);
+
+            // Add twice.
+            list.AddHandler(handler);
+            Assert.Equal(2, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Throws<InvalidCastException>(() => list[0]);
+            Assert.Throws<InvalidCastException>(() => list[1]);
+
+            // Add three times.
+            list.AddHandler(handler);
+            Assert.Equal(3, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Throws<InvalidCastException>(() => list[0]);
+            Assert.Throws<InvalidCastException>(() => list[1]);
+            Assert.Throws<InvalidCastException>(() => list[2]);
+        }
+
+        // TODO: this causes a crash.
+#if false
+        [Fact]
+        public void AddHandler_InvokeInUse_Success()
+        {
+            var list = new SubListenerList();
+            Delegate handler = (EventHandler)delegate { };
+
+            // Begin use.
+            Assert.False(list.BeginUse());
+
+            // Add.
+            list.AddHandler(handler);
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Throws<InvalidCastException>(() => list[0]);
+        }
+#endif
+
+        [Fact]
+        public void AddHandler_InvokeNoLongerInUse_Success()
+        {
+            var list = new SubListenerList();
+            Delegate handler = (EventHandler)delegate { };
+
+            // Begin use.
+            Assert.False(list.BeginUse());
+
+            // End use.
+            list.EndUse();
+
+            // Add.
+            list.AddHandler(handler);
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Throws<InvalidCastException>(() => list[0]);
+        }
+
+        [Theory]
+        [InlineData(1)]
+        [InlineData(3)]
+        [InlineData(4)]
+        [InlineData(6)]
+        [InlineData(7)]
+        public void AddHandler_InvokeDifferentSizes_Success(int count)
+        {
+            // Test internal FrugalList implementation.
+            var handlers = new List<Delegate>();
+            for (int i = 0; i < count; i++)
+            {
+                handlers.Add(Delegate.CreateDelegate(typeof(EventHandler), new CustomWeakEventListener(), nameof(CustomWeakEventListener.Handler)));
+            }
+
+            // Add.
+            var list = new SubListenerList();
+            for (int i = 0; i < count; i++)
+            {
+                list.AddHandler(handlers[i]);
+                Assert.Equal(i + 1, list.Count);
+                Assert.False(list.IsEmpty);
+                for (int j = 0; j <= i; j++)
+                {
+                    Assert.Same(handlers[j].Target, list[j]);
+                }
+            }
+        }
+
+        [Fact]
+        public void AddHandler_NullHandler_ThrowsArgumentNullException()
+        {
+            var list = new SubListenerList();
+            // TODO: this should throw ANE.
+            //Assert.Throws<ArgumentNullException>("handler", () => list.AddHandler(null));
+            Assert.Throws<NullReferenceException>(() => list.AddHandler(null));
+        }
+
+        [Fact]
+        public void BeginUse_Invoke_Success()
+        {
+            var list = new SubListenerList();
+
+            // Call once.
+            Assert.False(list.BeginUse());
+
+            // Call again.
+            Assert.True(list.BeginUse());
+        }
+
+        [Fact]
+        public void Clone_InvokeEmptyToEmpty_Success()
+        {
+            var list = new SubListenerList();
+
+            ListenerList newList = Assert.IsType<ListenerList>(list.Clone());
+            Assert.NotSame(list, newList);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+            Assert.Equal(0, newList.Count);
+            Assert.True(newList.IsEmpty);
+        }
+
+        [Fact]
+        public void Clone_NotEmptyWithListenersToEmpty_Success()
+        {
+            var list = new SubListenerList();
+            var listener1 = new CustomWeakEventListener();
+            var listener2 = new CustomWeakEventListener();
+            list.Add(listener1);
+            list.Add(listener2);
+
+            ListenerList newList = Assert.IsType<ListenerList>(list.Clone());
+            Assert.NotSame(list, newList);
+            Assert.Equal(2, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(listener2, list[1]);
+            Assert.Equal(2, newList.Count);
+            Assert.False(newList.IsEmpty);
+            Assert.Same(listener1, newList[0]);
+            Assert.Same(listener2, newList[1]);
+        }
+
+        [Fact]
+        public void Clone_NotEmptyWithHandlersToEmpty_Success()
+        {
+            var list = new SubListenerList();
+            var target1 = new CustomWeakEventListener();
+            Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+            var target2 = new CustomWeakEventListener();
+            Delegate handler2 = Delegate.CreateDelegate(typeof(EventHandler), target2, nameof(CustomWeakEventListener.Handler));
+            Delegate handler3 = (EventHandler)delegate { };
+            Delegate handler4 = WeakEventManagerTests.StaticEventHandler;
+
+            list.AddHandler(handler1);
+            list.AddHandler(handler2);
+            list.AddHandler(handler3);
+            list.AddHandler(handler4);
+
+            ListenerList newList = Assert.IsType<ListenerList>(list.Clone());
+            Assert.NotSame(list, newList);
+            Assert.Equal(4, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(target1, list[0]);
+            Assert.Same(target2, list[1]);
+            Assert.Throws<InvalidCastException>(() => list[2]);
+            Assert.Throws<InvalidCastException>(() => list[3]);
+            Assert.Equal(4, newList.Count);
+            Assert.False(newList.IsEmpty);
+            Assert.Same(target1, newList[0]);
+            Assert.Same(target2, newList[1]);
+            Assert.Throws<InvalidCastException>(() => newList[2]);
+            Assert.Throws<InvalidCastException>(() => newList[3]);
+        }
+
+        [Fact]
+        public void Clone_NotEmptyWithListenersAndHandlersToEmpty_Success()
+        {
+            var list = new SubListenerList();
+            var listener1 = new CustomWeakEventListener();
+            var listener2 = new CustomWeakEventListener();
+            var target1 = new CustomWeakEventListener();
+            Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+            var target2 = new CustomWeakEventListener();
+            Delegate handler2 = Delegate.CreateDelegate(typeof(EventHandler), target2, nameof(CustomWeakEventListener.Handler));
+            Delegate handler3 = (EventHandler)delegate { };
+            Delegate handler4 = WeakEventManagerTests.StaticEventHandler;
+
+            list.Add(listener1);
+            list.AddHandler(handler1);
+            list.Add(listener2);
+            list.AddHandler(handler2);
+            list.AddHandler(handler3);
+            list.AddHandler(handler4);
+
+            ListenerList newList = Assert.IsType<ListenerList>(list.Clone());
+            Assert.NotSame(list, newList);
+            Assert.Equal(6, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(target1, list[1]);
+            Assert.Same(listener2, list[2]);
+            Assert.Same(target2, list[3]);
+            Assert.Throws<InvalidCastException>(() => list[4]);
+            Assert.Throws<InvalidCastException>(() => list[5]);
+            Assert.Equal(6, newList.Count);
+            Assert.False(newList.IsEmpty);
+            Assert.Same(listener1, newList[0]);
+            Assert.Same(target1, newList[1]);
+            Assert.Same(listener2, newList[2]);
+            Assert.Same(target2, newList[3]);
+            Assert.Throws<InvalidCastException>(() => newList[4]);
+            Assert.Throws<InvalidCastException>(() => newList[5]);
+        }
+
+        [Fact]
+        public void CopyTo_InvokeEmptyToEmpty_Success()
+        {
+            var list = new SubListenerList();
+            var newList = new ListenerList();
+
+            list.CopyTo(newList);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+            Assert.Equal(0, newList.Count);
+            Assert.True(newList.IsEmpty);
+        }
+
+        [Fact]
+        public void CopyTo_InvokeEmptyToNotEmptyWithListeners_Success()
+        {
+            var list = new SubListenerList();
+            var newList = new ListenerList();
+            var listener1 = new CustomWeakEventListener();
+            var listener2 = new CustomWeakEventListener();
+
+            newList.Add(listener1);
+            newList.Add(listener2);
+
+            list.CopyTo(newList);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+            Assert.Equal(2, newList.Count);
+            Assert.False(newList.IsEmpty);
+            Assert.Equal(listener1, newList[0]);
+            Assert.Equal(listener2, newList[1]);
+        }
+
+        [Fact]
+        public void CopyTo_InvokeEmptyToNotEmptyWithHandlers_Success()
+        {
+            var list = new SubListenerList();
+            var newList = new ListenerList();
+            var target1 = new CustomWeakEventListener();
+            Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+            var target2 = new CustomWeakEventListener();
+            Delegate handler2 = Delegate.CreateDelegate(typeof(EventHandler), target2, nameof(CustomWeakEventListener.Handler));
+            Delegate handler3 = (EventHandler)delegate { };
+            Delegate handler4 = WeakEventManagerTests.StaticEventHandler;
+
+            newList.AddHandler(handler1);
+            newList.AddHandler(handler2);
+            newList.AddHandler(handler3);
+            newList.AddHandler(handler4);
+
+            list.CopyTo(newList);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+            Assert.Equal(4, newList.Count);
+            Assert.False(newList.IsEmpty);
+            Assert.Equal(target1, newList[0]);
+            Assert.Equal(target2, newList[1]);
+            Assert.Throws<InvalidCastException>(() => newList[2]);
+            Assert.Throws<InvalidCastException>(() => newList[3]);
+        }
+
+        [Fact]
+        public void CopyTo_InvokeEmptyToNotEmptyWithListenersAndHandlers_Success()
+        {
+            var list = new SubListenerList();
+            var newList = new ListenerList();
+            var listener1 = new CustomWeakEventListener();
+            var listener2 = new CustomWeakEventListener();
+            var target1 = new CustomWeakEventListener();
+            Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+            var target2 = new CustomWeakEventListener();
+            Delegate handler2 = Delegate.CreateDelegate(typeof(EventHandler), target2, nameof(CustomWeakEventListener.Handler));
+            Delegate handler3 = (EventHandler)delegate { };
+            Delegate handler4 = WeakEventManagerTests.StaticEventHandler;
+
+            newList.Add(listener1);
+            newList.AddHandler(handler1);
+            newList.Add(listener2);
+            newList.AddHandler(handler2);
+            newList.AddHandler(handler3);
+            newList.AddHandler(handler4);
+
+            list.CopyTo(newList);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+            Assert.Equal(6, newList.Count);
+            Assert.False(newList.IsEmpty);
+            Assert.Same(listener1, newList[0]);
+            Assert.Equal(target1, newList[1]);
+            Assert.Same(listener2, newList[2]);
+            Assert.Equal(target2, newList[3]);
+            Assert.Throws<InvalidCastException>(() => newList[4]);
+            Assert.Throws<InvalidCastException>(() => newList[5]);
+        }
+
+        [Fact]
+        public void CopyTo_InvokeNotEmptyWithListenersToEmpty_Success()
+        {
+            var list = new SubListenerList();
+            var newList = new ListenerList();
+            var listener1 = new CustomWeakEventListener();
+            var listener2 = new CustomWeakEventListener();
+            list.Add(listener1);
+            list.Add(listener2);
+
+            list.CopyTo(newList);
+            Assert.Equal(2, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(listener2, list[1]);
+            Assert.Equal(2, newList.Count);
+            Assert.False(newList.IsEmpty);
+            Assert.Same(listener1, newList[0]);
+            Assert.Same(listener2, newList[1]);
+        }
+
+        [Fact]
+        public void CopyTo_InvokeNotEmptyWithHandlersToEmpty_Success()
+        {
+            var list = new SubListenerList();
+            var newList = new ListenerList();
+            var target1 = new CustomWeakEventListener();
+            Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+            var target2 = new CustomWeakEventListener();
+            Delegate handler2 = Delegate.CreateDelegate(typeof(EventHandler), target2, nameof(CustomWeakEventListener.Handler));
+            Delegate handler3 = (EventHandler)delegate { };
+            Delegate handler4 = WeakEventManagerTests.StaticEventHandler;
+
+            list.AddHandler(handler1);
+            list.AddHandler(handler2);
+            list.AddHandler(handler3);
+            list.AddHandler(handler4);
+
+            list.CopyTo(newList);
+            Assert.Equal(4, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(target1, list[0]);
+            Assert.Same(target2, list[1]);
+            Assert.Throws<InvalidCastException>(() => list[2]);
+            Assert.Throws<InvalidCastException>(() => list[3]);
+            Assert.Equal(4, newList.Count);
+            Assert.False(newList.IsEmpty);
+            Assert.Same(target1, newList[0]);
+            Assert.Same(target2, newList[1]);
+            Assert.Throws<InvalidCastException>(() => newList[2]);
+            Assert.Throws<InvalidCastException>(() => newList[3]);
+        }
+
+        [Fact]
+        public void CopyTo_InvokeNotEmptyWithListenersAndHandlersToEmpty_Success()
+        {
+            var list = new SubListenerList();
+            var newList = new ListenerList();
+            var listener1 = new CustomWeakEventListener();
+            var listener2 = new CustomWeakEventListener();
+            var target1 = new CustomWeakEventListener();
+            Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+            var target2 = new CustomWeakEventListener();
+            Delegate handler2 = Delegate.CreateDelegate(typeof(EventHandler), target2, nameof(CustomWeakEventListener.Handler));
+            Delegate handler3 = (EventHandler)delegate { };
+            Delegate handler4 = WeakEventManagerTests.StaticEventHandler;
+
+            list.Add(listener1);
+            list.AddHandler(handler1);
+            list.Add(listener2);
+            list.AddHandler(handler2);
+            list.AddHandler(handler3);
+            list.AddHandler(handler4);
+
+            list.CopyTo(newList);
+            Assert.Equal(6, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(target1, list[1]);
+            Assert.Same(listener2, list[2]);
+            Assert.Same(target2, list[3]);
+            Assert.Throws<InvalidCastException>(() => list[4]);
+            Assert.Throws<InvalidCastException>(() => list[5]);
+            Assert.Equal(6, newList.Count);
+            Assert.False(newList.IsEmpty);
+            Assert.Same(listener1, newList[0]);
+            Assert.Same(target1, newList[1]);
+            Assert.Same(listener2, newList[2]);
+            Assert.Same(target2, newList[3]);
+            Assert.Throws<InvalidCastException>(() => newList[4]);
+            Assert.Throws<InvalidCastException>(() => newList[5]);
+        }
+
+        [Fact]
+        public void CopyTo_InvokeNotEmptyToNotEmpty_Success()
+        {
+            var list = new SubListenerList();
+            var newList = new ListenerList();
+            var listener1 = new CustomWeakEventListener();
+            var target1 = new CustomWeakEventListener();
+            Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+            var listener2 = new CustomWeakEventListener();
+            var target2 = new CustomWeakEventListener();
+            Delegate handler2 = Delegate.CreateDelegate(typeof(EventHandler), target2, nameof(CustomWeakEventListener.Handler));
+
+            list.Add(listener1);
+            list.AddHandler(handler1);
+            newList.Add(listener2);
+            newList.AddHandler(handler2);
+
+            list.CopyTo(newList);
+            Assert.Equal(2, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(target1, list[1]);
+            Assert.Equal(4, newList.Count);
+            Assert.False(newList.IsEmpty);
+            Assert.Same(listener2, newList[0]);
+            Assert.Same(target2, newList[1]);
+            Assert.Same(listener1, newList[2]);
+            Assert.Same(target1, newList[3]);
+        }
+
+        [Fact]
+        public void CopyTo_InvokeSameNewListEmpty_Success()
+        {
+            var list = new SubListenerList();
+            list.CopyTo(list);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+        }
+
+        [Fact]
+        public void CopyTo_InvokeSameNewListNotEmpty_Success()
+        {
+            var list = new SubListenerList();
+            var listener1 = new CustomWeakEventListener();
+            list.Add(listener1);
+
+            list.CopyTo(list);
+            Assert.Equal(2, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(listener1, list[1]);
+        }
+
+        [Fact]
+        public void CopyTo_NullNewListEmpty_ThrowsArgumentNullException()
+        {
+            var list = new SubListenerList();
+            // TODO: this should throw ANE.
+            //Assert.Throws<ArgumentNullException>("newList", () => list.CopyTo(null!));
+            list.CopyTo(null!);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+        }
+
+        [Fact]
+        public void CopyTo_NullNewListNotEmpty_ThrowsArgumentNullException()
+        {
+            var list = new SubListenerList();
+            var listener1 = new CustomWeakEventListener();
+            list.Add(listener1);
+
+            // TODO: this should throw ANE.
+            //Assert.Throws<ArgumentNullException>("newList", () => list.CopyTo(null!));
+            Assert.Throws<NullReferenceException>(() => list.CopyTo(null!));
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+        }
+
+        public static IEnumerable<object?[]> DeliverEvent_TestData()
+        {
+            yield return new object?[] { null, null, null };
+            yield return new object?[] { new object(), new EventArgs(), typeof(int) };
+            yield return new object?[] { new object(), EventArgs.Empty, typeof(int) };
+        }
+
+        [Theory]
+        [MemberData(nameof(DeliverEvent_TestData))]
+        public void DeliverEvent_InvokeWithListeners_Success(object sender, EventArgs args, Type managerType)
+        {
+            var list = new SubListenerList();
+            var events = new List<string>();
+            var listener1 = new CustomWeakEventListener();
+            listener1.ReceiveWeakEventAction = (t, s, e) =>
+            {
+                Assert.Same(managerType, t);
+                Assert.Same(sender, s);
+                Assert.Same(args, e);
+                events.Add("listener1");
+                return true;
+            };
+            var listener2 = new CustomWeakEventListener();
+            listener2.ReceiveWeakEventAction = (t, s, e) =>
+            {
+                Assert.Same(managerType, t);
+                Assert.Same(sender, s);
+                Assert.Same(args, e);
+                events.Add("listener2");
+                return true;
+            };
+            list.Add(listener1);
+            list.Add(listener2);
+
+            Assert.False(list.DeliverEvent(sender, args, managerType));
+            Assert.Equal(new string[] { "listener1", "listener2" }, events);
+        }
+
+        [Theory]
+        [MemberData(nameof(DeliverEvent_TestData))]
+        public void DeliverEvent_InvokeWithHandlers_Success(object sender, EventArgs args, Type managerType)
+        {
+            var list = new SubListenerList();
+            var events = new List<string>();
+            var listener1 = new CustomWeakEventListener();
+            listener1.HandlerAction = (s, e) =>
+            {
+                Assert.Same(sender, s);
+                Assert.Same(args, e);
+                events.Add("handler1");
+            };
+            var listener2 = new CustomWeakEventListener();
+            listener2.HandlerAction = (s, e) =>
+            {
+                Assert.Same(sender, s);
+                Assert.Same(args, e);
+                events.Add("handler2");
+            };
+            Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), listener1, nameof(CustomWeakEventListener.Handler));
+            Delegate handler2 = Delegate.CreateDelegate(typeof(EventHandler), listener2, nameof(CustomWeakEventListener.Handler));
+            list.AddHandler(handler1);
+            list.AddHandler(handler2);
+
+            Assert.False(list.DeliverEvent(sender, args, managerType));
+            Assert.Equal(new string[] { "handler1", "handler2" }, events);
+        }
+
+        [Theory]
+        [MemberData(nameof(DeliverEvent_TestData))]
+        public void DeliverEvent_InvokeWithListenersAndHandlers_Success(object sender, EventArgs args, Type managerType)
+        {
+            var list = new SubListenerList();
+            var events = new List<string>();
+            var listener1 = new CustomWeakEventListener();
+            listener1.HandlerAction = (s, e) =>
+            {
+                Assert.Same(sender, s);
+                Assert.Same(args, e);
+                events.Add("handler1");
+            };
+            var listener2 = new CustomWeakEventListener();
+            listener2.ReceiveWeakEventAction = (t, s, e) =>
+            {
+                Assert.Same(managerType, t);
+                Assert.Same(sender, s);
+                Assert.Same(args, e);
+                events.Add("listener1");
+                return true;
+            };
+            var listener3 = new CustomWeakEventListener();
+            listener3.HandlerAction = (s, e) =>
+            {
+                Assert.Same(sender, s);
+                Assert.Same(args, e);
+                events.Add("handler2");
+            };
+            var listener4 = new CustomWeakEventListener();
+            listener4.ReceiveWeakEventAction = (t, s, e) =>
+            {
+                Assert.Same(managerType, t);
+                Assert.Same(sender, s);
+                Assert.Same(args, e);
+                events.Add("listener2");
+                return true;
+            };
+            Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), listener1, nameof(CustomWeakEventListener.Handler));
+            Delegate handler2 = Delegate.CreateDelegate(typeof(EventHandler), listener3, nameof(CustomWeakEventListener.Handler));
+            list.AddHandler(handler1);
+            list.Add(listener2);
+            list.AddHandler(handler2);
+            list.Add(listener4);
+
+            Assert.False(list.DeliverEvent(sender, args, managerType));
+            Assert.Equal(new string[] { "handler1", "listener1", "handler2", "listener2" }, events);
+        }
+
+        // TODO: this causes a crash.
+#if false
+        [Theory]
+        [MemberData(nameof(DeliverEvent_TestData))]
+        public void DeliverEvent_InvokeWithListenersNotHandled_Success(object sender, EventArgs args, Type managerType)
+        {
+            var list = new SubListenerList();
+            var events = new List<string>();
+            var listener1 = new CustomWeakEventListener();
+            listener1.ReceiveWeakEventAction = (t, s, e) =>
+            {
+                Assert.Same(managerType, t);
+                Assert.Same(sender, s);
+                Assert.Same(args, e);
+                events.Add("listener1");
+                return false;
+            };
+            var listener2 = new CustomWeakEventListener();
+            listener2.ReceiveWeakEventAction = (t, s, e) =>
+            {
+                Assert.Same(managerType, t);
+                Assert.Same(sender, s);
+                Assert.Same(args, e);
+                events.Add("listener2");
+                return true;
+            };
+            list.Add(listener1);
+            list.Add(listener2);
+
+            Assert.False(list.DeliverEvent(sender, args, managerType));
+            Assert.Equal(new string[] { "listener1", "listener2" }, events);
+        }
+#endif
+
+        [Theory]
+        [MemberData(nameof(DeliverEvent_TestData))]
+        public void DeliverEvent_InvokeWithInvalidHandlerAction_ThrowsInvalidCastException(object sender, EventArgs args, Type managerType)
+        {
+            var list = new SubListenerList();
+            Delegate handler = () => {};
+            list.AddHandler(handler);
+
+            Assert.Throws<InvalidCastException>(() => list.DeliverEvent(sender, args, managerType));
+        }
+
+        [Theory]
+        [MemberData(nameof(DeliverEvent_TestData))]
+        public void DeliverEvent_InvokeWithInvalidHandlerFunc_ThrowsInvalidCastException(object sender, EventArgs args, Type managerType)
+        {
+            var list = new SubListenerList();
+            bool EventHandler(object sender, EventArgs args) => true;
+            list.AddHandler(EventHandler);
+
+            Assert.Throws<InvalidCastException>(() => list.DeliverEvent(sender, args, managerType));
+        }
+
+        [Theory]
+        [MemberData(nameof(DeliverEvent_TestData))]
+        public void DeliverEvent_InvokeWithInvalidHandlerGenericEventHandler_ThrowsInvalidCastException(object sender, EventArgs args, Type managerType)
+        {
+            var list = new SubListenerList();
+            var target = new CustomWeakEventListener();
+            Delegate handler = Delegate.CreateDelegate(typeof(EventHandler<EventArgs>), target, nameof(CustomWeakEventListener.Handler));
+            list.AddHandler(handler);
+
+            Assert.Throws<InvalidCastException>(() => list.DeliverEvent(sender, args, managerType));
+        }
+
+        [Theory]
+        [MemberData(nameof(DeliverEvent_TestData))]
+        public void DeliverEvent_InvokeEmpty_ReturnsFalse(object sender, EventArgs args, Type managerType)
+        {
+            var list = new SubListenerList();
+            Assert.False(list.DeliverEvent(sender, args, managerType));
+        }
+
+        [Fact]
+        public void EndUse_InvokeBegan_Success()
+        {
+            var list = new SubListenerList();
+
+            // Begin.
+            Assert.False(list.BeginUse());
+
+            // End.
+            list.EndUse();
+
+            // Begin.
+            Assert.False(list.BeginUse());
+
+            // Begin.
+            Assert.True(list.BeginUse());
+        }
+
+        [Fact]
+        public void EndUse_InvokeNotBegan_Success()
+        {
+            var list = new SubListenerList();
+
+            // Call once.
+            list.EndUse();
+
+            // Call again.
+            list.EndUse();
+
+            // Begin.
+            Assert.True(list.BeginUse());
+
+            // Begin.
+            Assert.True(list.BeginUse());
+
+            // Begin.
+            Assert.False(list.BeginUse());
+
+            // Begin.
+            Assert.True(list.BeginUse());
+        }
+
+        [Fact]
+        public void Purge_InvokeEmpty_Success()
+        {
+            var list = new SubListenerList();
+
+            Assert.False(list.Purge());
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+        }
+
+        // TODO: this causes a crash.
+#if false
+        [Fact]
+        public void Purge_InvokeEmptyInUse_Success()
+        {
+            var list = new SubListenerList();
+            Assert.False(list.BeginUse());
+
+            Assert.False(list.Purge());
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+        }
+#endif
+
+        [Fact]
+        public void Purge_InvokeNotEmptyWithListeners_Success()
+        {
+            var list = new SubListenerList();
+            var listener1 = new CustomWeakEventListener();
+            var listener2 = new CustomWeakEventListener();
+            list.Add(listener1);
+            list.Add(listener2);
+
+            Assert.False(list.Purge());
+            Assert.Equal(2, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(listener2, list[1]);
+        }
+        
+        [Fact]
+        public void Purge_InvokeNotEmptyWithHandlers_Success()
+        {
+            var list = new SubListenerList();
+            var target1 = new CustomWeakEventListener();
+            Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+            Delegate handler2 = (EventHandler)delegate { };
+            Delegate handler3 = WeakEventManagerTests.StaticEventHandler;
+            list.AddHandler(handler1);
+            list.AddHandler(handler2);
+            list.AddHandler(handler3);
+
+            Assert.False(list.Purge());
+            Assert.Equal(3, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Equal(target1, list[0]);
+            Assert.Same(target1, list[0]);
+            Assert.Throws<InvalidCastException>(() => list[1]);
+            Assert.Throws<InvalidCastException>(() => list[2]);
+        }
+
+        [Fact]
+        public void Purge_InvokeNotEmptyWithListenersAndHandlers_Success()
+        {
+            var list = new SubListenerList();
+            var listener1 = new CustomWeakEventListener();
+            var listener2 = new CustomWeakEventListener();
+            var target1 = new CustomWeakEventListener();
+            Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+            Delegate handler2 = (EventHandler)delegate { };
+            Delegate handler3 = WeakEventManagerTests.StaticEventHandler;
+            list.Add(listener1);
+            list.AddHandler(handler1);
+            list.Add(listener2);
+            list.AddHandler(handler2);
+            list.AddHandler(handler3);
+
+            Assert.False(list.Purge());
+            Assert.Equal(5, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(target1, list[1]);
+            Assert.Same(listener2, list[2]);
+            Assert.Throws<InvalidCastException>(() => list[3]);
+            Assert.Throws<InvalidCastException>(() => list[4]);
+        }
+
+        // TODO: this causes a crash.
+#if false
+        [Fact]
+        public void Purge_InvokeNotEmptyInUse_Success()
+        {
+            var list = new SubListenerList();
+            var listener1 = new SubListener();
+            list.Add(listener1);
+            Assert.False(list.BeginUse());
+
+            Assert.False(list.Purge());
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+        }
+#endif
+
+
+        [Fact]
+        public void Remove_InvokeEmptyList_Success()
+        {
+            var list = new SubListenerList();
+            var listener = new CustomWeakEventListener();
+
+            list.Remove(listener);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+        }
+
+        [Fact]
+        public void Remove_InvokeOneItemList_Success()
+        {
+            var list = new SubListenerList();
+            var listener1 = new CustomWeakEventListener();
+            var listener2 = new CustomWeakEventListener();
+
+            list.Add(listener1);
+
+            // Remove none.
+            list.Remove(listener2);
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+
+            // Remove last.
+            list.Remove(listener1);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+
+            // Remove again.
+            list.Remove(listener1);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+        }
+
+        [Fact]
+        public void Remove_InvokeOneItemListWithNull_Success()
+        {
+            var list = new SubListenerList();
+            var listener1 = new CustomWeakEventListener();
+
+            list.Add(null);
+
+            // Remove none.
+            list.Remove(listener1);
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Throws<InvalidCastException>(() => list[0]);
+
+            // Remove last.
+            list.Remove(null);
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Throws<InvalidCastException>(() => list[0]);
+
+            // Remove again.
+            list.Remove(null);
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Throws<InvalidCastException>(() => list[0]);
+        }
+
+        [Fact]
+        public void Remove_InvokeThreeItemList_Success()
+        {
+            var list = new SubListenerList();
+            var listener1 = new CustomWeakEventListener();
+            var listener2 = new CustomWeakEventListener();
+            var listener3 = new CustomWeakEventListener();
+            var listener4 = new CustomWeakEventListener();
+
+            list.Add(listener1);
+            list.Add(listener2);
+            list.Add(listener3);
+
+            // Remove none.
+            list.Remove(listener4);
+            Assert.Equal(3, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(listener2, list[1]);
+            Assert.Same(listener3, list[2]);
+
+            // Remove last.
+            list.Remove(listener3);
+            Assert.Equal(2, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(listener2, list[1]);
+
+            // Remove first.
+            list.Remove(listener1);
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener2, list[0]);
+
+            // Remove last.
+            list.Remove(listener2);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+
+            // Remove again.
+            list.Remove(listener2);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+        }
+
+        [Fact]
+        public void Remove_InvokeThreeItemListWithNull_Success()
+        {
+            var list = new SubListenerList();
+            var listener1 = new CustomWeakEventListener();
+            var listener2 = new CustomWeakEventListener();
+            var listener3 = new CustomWeakEventListener();
+
+            list.Add(listener1);
+            list.Add(null);
+            list.Add(listener2);
+
+            // Remove none.
+            list.Remove(listener3);
+            Assert.Equal(3, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Throws<InvalidCastException>(() => list[1]);
+            Assert.Same(listener2, list[2]);
+
+            // Remove last.
+            list.Remove(listener2);
+            Assert.Equal(2, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Throws<InvalidCastException>(() => list[1]);
+
+            // Remove first.
+            list.Remove(listener1);
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Throws<InvalidCastException>(() => list[0]);
+
+            // Remove null.
+            list.Remove(null);
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Throws<InvalidCastException>(() => list[0]);
+
+            // Remove again.
+            list.Remove(null);
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Throws<InvalidCastException>(() => list[0]);
+        }
+
+        [Fact]
+        public void Remove_InvokeFourItemList_Success()
+        {
+            var list = new SubListenerList();
+            var listener1 = new CustomWeakEventListener();
+            var listener2 = new CustomWeakEventListener();
+            var listener3 = new CustomWeakEventListener();
+            var listener4 = new CustomWeakEventListener();
+            var listener5 = new CustomWeakEventListener();
+
+            list.Add(listener1);
+            list.Add(listener2);
+            list.Add(listener3);
+            list.Add(listener4);
+
+            // Remove none.
+            list.Remove(listener5);
+            Assert.Equal(4, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(listener2, list[1]);
+            Assert.Same(listener3, list[2]);
+            Assert.Same(listener4, list[3]);
+
+            // Remove last.
+            list.Remove(listener4);
+            Assert.Equal(3, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(listener2, list[1]);
+            Assert.Same(listener3, list[2]);
+
+            // Remove middle.
+            list.Remove(listener2);
+            Assert.Equal(2, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(listener3, list[1]);
+
+            // Remove first.
+            list.Remove(listener1);
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener3, list[0]);
+
+            // Remove last.
+            list.Remove(listener3);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+
+            // Remove again.
+            list.Remove(listener3);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+        }
+
+        [Fact]
+        public void Remove_InvokeFourItemListWithNull_Success()
+        {
+            var list = new SubListenerList();
+            var listener1 = new CustomWeakEventListener();
+            var listener2 = new CustomWeakEventListener();
+            var listener3 = new CustomWeakEventListener();
+            var listener4 = new CustomWeakEventListener();
+
+            list.Add(listener1);
+            list.Add(null);
+            list.Add(listener2);
+            list.Add(listener3);
+
+            // Remove none.
+            list.Remove(listener4);
+            Assert.Equal(4, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Throws<InvalidCastException>(() => list[1]);
+            Assert.Same(listener2, list[2]);
+
+            // Remove last.
+            list.Remove(listener3);
+            Assert.Equal(3, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Throws<InvalidCastException>(() => list[1]);
+            Assert.Same(listener2, list[2]);
+
+            // Remove first.
+            list.Remove(listener1);
+            Assert.Equal(2, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Throws<InvalidCastException>(() => list[0]);
+            Assert.Same(listener2, list[1]);
+
+            // Remove null.
+            list.Remove(null);
+            Assert.Equal(2, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Throws<InvalidCastException>(() => list[0]);
+            Assert.Same(listener2, list[1]);
+
+            // Remove last.
+            list.Remove(listener2);
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Throws<InvalidCastException>(() => list[0]);
+
+            // Remove again.
+            list.Remove(listener2);
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Throws<InvalidCastException>(() => list[0]);
+        }
+
+        [Fact]
+        public void Remove_InvokeSixItemList_Success()
+        {
+            var list = new SubListenerList();
+            var listener1 = new CustomWeakEventListener();
+            var listener2 = new CustomWeakEventListener();
+            var listener3 = new CustomWeakEventListener();
+            var listener4 = new CustomWeakEventListener();
+            var listener5 = new CustomWeakEventListener();
+            var listener6 = new CustomWeakEventListener();
+            var listener7 = new CustomWeakEventListener();
+
+            list.Add(listener1);
+            list.Add(listener2);
+            list.Add(listener3);
+            list.Add(listener4);
+            list.Add(listener5);
+            list.Add(listener6);
+
+            // Remove none.
+            list.Remove(listener7);
+            Assert.Equal(6, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(listener2, list[1]);
+            Assert.Same(listener3, list[2]);
+            Assert.Same(listener4, list[3]);
+            Assert.Same(listener5, list[4]);
+            Assert.Same(listener6, list[5]);
+
+            // Remove last.
+            list.Remove(listener6);
+            Assert.Equal(5, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(listener2, list[1]);
+            Assert.Same(listener3, list[2]);
+            Assert.Same(listener4, list[3]);
+            Assert.Same(listener5, list[4]);
+
+            // Remove middle.
+            list.Remove(listener2);
+            Assert.Equal(4, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(listener3, list[1]);
+            Assert.Same(listener4, list[2]);
+            Assert.Same(listener5, list[3]);
+
+            // Remove first.
+            list.Remove(listener1);
+            Assert.Equal(3, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener3, list[0]);
+            Assert.Same(listener4, list[1]);
+            Assert.Same(listener5, list[2]);
+
+            // Remove all.
+            list.Remove(listener3);
+            list.Remove(listener4);
+            list.Remove(listener5);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+
+            // Remove again.
+            list.Remove(listener5);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+        }
+
+        [Fact]
+        public void Remove_InvokeSixItemListWithNull_Success()
+        {
+            var list = new SubListenerList();
+            var listener1 = new CustomWeakEventListener();
+            var listener2 = new CustomWeakEventListener();
+            var listener3 = new CustomWeakEventListener();
+            var listener4 = new CustomWeakEventListener();
+            var listener5 = new CustomWeakEventListener();
+            var listener6 = new CustomWeakEventListener();
+
+            list.Add(listener1);
+            list.Add(null);
+            list.Add(listener2);
+            list.Add(listener3);
+            list.Add(listener4);
+            list.Add(listener5);
+
+            // Remove none.
+            list.Remove(listener6);
+            Assert.Equal(6, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Throws<InvalidCastException>(() => list[1]);
+            Assert.Same(listener2, list[2]);
+            Assert.Same(listener3, list[3]);
+            Assert.Same(listener4, list[4]);
+            Assert.Same(listener5, list[5]);
+
+            // Remove last.
+            list.Remove(listener5);
+            Assert.Equal(5, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Throws<InvalidCastException>(() => list[1]);
+            Assert.Same(listener2, list[2]);
+            Assert.Same(listener3, list[3]);
+            Assert.Same(listener4, list[4]);
+
+            // Remove middle.
+            list.Remove(listener2);
+            Assert.Equal(4, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Throws<InvalidCastException>(() => list[1]);
+            Assert.Same(listener3, list[2]);
+            Assert.Same(listener4, list[3]);
+
+            // Remove first.
+            list.Remove(listener1);
+            Assert.Equal(3, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Throws<InvalidCastException>(() => list[0]);
+            Assert.Same(listener3, list[1]);
+            Assert.Same(listener4, list[2]);
+
+            // Remove null.
+            list.Remove(null);
+            Assert.Equal(3, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Throws<InvalidCastException>(() => list[0]);
+            Assert.Same(listener3, list[1]);
+            Assert.Same(listener4, list[2]);
+
+            // Remove all.
+            list.Remove(listener3);
+            list.Remove(listener4);
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Throws<InvalidCastException>(() => list[0]);
+
+            // Remove again.
+            list.Remove(listener4);
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Throws<InvalidCastException>(() => list[0]);
+        }
+
+        [Fact]
+        public void Remove_InvokeSevenItemList_Success()
+        {
+            var list = new SubListenerList();
+            var listener1 = new CustomWeakEventListener();
+            var listener2 = new CustomWeakEventListener();
+            var listener3 = new CustomWeakEventListener();
+            var listener4 = new CustomWeakEventListener();
+            var listener5 = new CustomWeakEventListener();
+            var listener6 = new CustomWeakEventListener();
+            var listener7 = new CustomWeakEventListener();
+            var listener8 = new CustomWeakEventListener();
+
+            list.Add(listener1);
+            list.Add(listener2);
+            list.Add(listener3);
+            list.Add(listener4);
+            list.Add(listener5);
+            list.Add(listener6);
+            list.Add(listener7);
+
+            // Remove none.
+            list.Remove(listener8);
+            Assert.Equal(7, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(listener2, list[1]);
+            Assert.Same(listener3, list[2]);
+            Assert.Same(listener4, list[3]);
+            Assert.Same(listener5, list[4]);
+            Assert.Same(listener6, list[5]);
+            Assert.Same(listener7, list[6]);
+
+            // Remove last.
+            list.Remove(listener7);
+            Assert.Equal(6, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(listener2, list[1]);
+            Assert.Same(listener3, list[2]);
+            Assert.Same(listener4, list[3]);
+            Assert.Same(listener5, list[4]);
+            Assert.Same(listener6, list[5]);
+
+            // Remove middle.
+            list.Remove(listener2);
+            Assert.Equal(5, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(listener3, list[1]);
+            Assert.Same(listener4, list[2]);
+            Assert.Same(listener5, list[3]);
+            Assert.Same(listener6, list[4]);
+
+            // Remove first.
+            list.Remove(listener1);
+            Assert.Equal(4, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener3, list[0]);
+            Assert.Same(listener4, list[1]);
+            Assert.Same(listener5, list[2]);
+            Assert.Same(listener6, list[3]);
+
+            // Remove all.
+            list.Remove(listener3);
+            list.Remove(listener4);
+            list.Remove(listener5);
+            list.Remove(listener6);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+
+            // Remove again.
+            list.Remove(listener6);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+        }
+
+        [Fact]
+        public void Remove_InvokeSevenItemListWithNull_Success()
+        {
+            var list = new SubListenerList();
+            var listener1 = new CustomWeakEventListener();
+            var listener2 = new CustomWeakEventListener();
+            var listener3 = new CustomWeakEventListener();
+            var listener4 = new CustomWeakEventListener();
+            var listener5 = new CustomWeakEventListener();
+            var listener6 = new CustomWeakEventListener();
+            var listener7 = new CustomWeakEventListener();
+
+            list.Add(listener1);
+            list.Add(null);
+            list.Add(listener2);
+            list.Add(listener3);
+            list.Add(listener4);
+            list.Add(listener5);
+            list.Add(listener6);
+
+            // Remove none.
+            list.Remove(listener7);
+            Assert.Equal(7, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Throws<InvalidCastException>(() => list[1]);
+            Assert.Same(listener2, list[2]);
+            Assert.Same(listener3, list[3]);
+            Assert.Same(listener4, list[4]);
+            Assert.Same(listener5, list[5]);
+            Assert.Same(listener6, list[6]);
+
+            // Remove last.
+            list.Remove(listener6);
+            Assert.Equal(6, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Throws<InvalidCastException>(() => list[1]);
+            Assert.Same(listener2, list[2]);
+            Assert.Same(listener3, list[3]);
+            Assert.Same(listener4, list[4]);
+            Assert.Same(listener5, list[5]);
+
+            // Remove middle.
+            list.Remove(listener2);
+            Assert.Equal(5, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Throws<InvalidCastException>(() => list[1]);
+            Assert.Same(listener3, list[2]);
+            Assert.Same(listener4, list[3]);
+            Assert.Same(listener5, list[4]);
+
+            // Remove first.
+            list.Remove(listener1);
+            Assert.Equal(4, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Throws<InvalidCastException>(() => list[0]);
+            Assert.Same(listener3, list[1]);
+            Assert.Same(listener4, list[2]);
+            Assert.Same(listener5, list[3]);
+
+            // Remove null.
+            list.Remove(null);
+            Assert.Equal(4, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Throws<InvalidCastException>(() => list[0]);
+            Assert.Same(listener3, list[1]);
+            Assert.Same(listener4, list[2]);
+            Assert.Same(listener5, list[3]);
+
+            // Remove all.
+            list.Remove(listener3);
+            list.Remove(listener4);
+            list.Remove(listener5);
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Throws<InvalidCastException>(() => list[0]);
+
+            // Remove again.
+            list.Remove(listener5);
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Throws<InvalidCastException>(() => list[0]);
+        }
+
+        // TODO: this causes a crash.
+#if false
+        [Fact]
+        public void Remove_InvokeInUse_Success()
+        {
+            var list = new SubListenerList();
+            var listener = new SubListener();
+            list.Add(listener);
+
+            // Begin use.
+            Assert.False(list.BeginUse());
+
+            // Add.
+            list.Remove(listener);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+        }
+#endif
+
+        [Fact]
+        public void Remove_InvokeNoLongerInUse_Success()
+        {
+            var list = new SubListenerList();
+            var listener = new CustomWeakEventListener();
+            list.Add(listener);
+
+            // Begin use.
+            Assert.False(list.BeginUse());
+
+            // End use.
+            list.EndUse();
+
+            // Add.
+            list.Remove(listener);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+        }
+        
+        [Fact]
+        public void Remove_InvokeNoSuchListenerEmpty_Success()
+        {
+            var list = new SubListenerList();
+
+            // Remove.
+            list.Remove(new CustomWeakEventListener());
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+            
+            // Remove again.
+            list.Remove(new CustomWeakEventListener());
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+
+            // Remove null.
+            list.Remove(null);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+        }
+        
+        [Fact]
+        public void Remove_InvokeNoSuchListenerNotEmpty_Success()
+        {
+            var list = new SubListenerList();
+            var listener = new CustomWeakEventListener();
+            list.Add(listener);
+
+            // Remove.
+            list.Remove(new CustomWeakEventListener());
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener, list[0]);
+
+            // Remove again.
+            list.Remove(new CustomWeakEventListener());
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener, list[0]);
+
+            // Remove null.
+            list.Remove(null);
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener, list[0]);
+        }
+
+        [Theory]
+        [InlineData(1, 0)]
+        [InlineData(3, 0)]
+        [InlineData(3, 1)]
+        [InlineData(3, 2)]
+        [InlineData(4, 0)]
+        [InlineData(4, 1)]
+        [InlineData(4, 2)]
+        [InlineData(4, 3)]
+        [InlineData(6, 0)]
+        [InlineData(6, 1)]
+        [InlineData(6, 2)]
+        [InlineData(6, 3)]
+        [InlineData(6, 4)]
+        [InlineData(6, 5)]
+        [InlineData(7, 0)]
+        [InlineData(7, 1)]
+        [InlineData(7, 2)]
+        [InlineData(7, 3)]
+        [InlineData(7, 4)]
+        [InlineData(7, 5)]
+        public void Remove_InvokeDifferentSizes_Success(int count, int removeIndex)
+        {
+            // Test internal FrugalList implementation.
+            var listeners = new List<CustomWeakEventListener>();
+            for (int i = 0; i < count; i++)
+            {
+                listeners.Add(new CustomWeakEventListener());
+            }
+
+            var list = new SubListenerList();
+            for (int i = 0; i < listeners.Count; i++)
+            {
+                list.Add(listeners[i]);
+            }
+
+            // Remove.
+            list.Remove(listeners[removeIndex]);
+
+            var expectedListeners = new List<CustomWeakEventListener>(listeners);
+            expectedListeners.RemoveAt(removeIndex);
+            Assert.Equal(expectedListeners.Count, list.Count);
+            Assert.Equal(expectedListeners.Count == 0, list.IsEmpty);
+            for (int i = 0; i < expectedListeners.Count; i++)
+            {
+                Assert.Equal(expectedListeners[i], list[i]);
+            }
+
+            // Remove all.
+            for (int i = 0; i < expectedListeners.Count; i++)
+            {
+                list.Remove(expectedListeners[i]);
+            }
+
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+        }
+
+        [Fact]
+        public void RemoveHandler_Invoke_Success()
+        {
+            var list = new SubListenerList();
+            var target1 = new CustomWeakEventListener();
+            Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+            var target2 = new CustomWeakEventListener();
+            Delegate handler2 = Delegate.CreateDelegate(typeof(EventHandler), target2, nameof(CustomWeakEventListener.Handler));
+            var target3 = new CustomWeakEventListener();
+            Delegate handler3 = Delegate.CreateDelegate(typeof(EventHandler), target3, nameof(CustomWeakEventListener.SecondHandler));
+
+            list.AddHandler(handler1);
+            list.AddHandler(handler2);
+            list.AddHandler(handler3);
+
+            // Remove handler2.
+            list.RemoveHandler(handler2);
+            Assert.Equal(2, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Equal(target1, list[0]);
+            Assert.Equal(target3, list[1]);
+
+            // Remove again.
+            list.RemoveHandler(handler2);
+            Assert.Equal(2, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.False(list.IsEmpty);
+            Assert.Equal(target1, list[0]);
+            Assert.Equal(target3, list[1]);
+
+            // Remove handler3.
+            list.RemoveHandler(handler3);
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Equal(target1, list[0]);
+
+            // Remove handler1.
+            list.RemoveHandler(handler1);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+        }
+
+        [Fact]
+        public void Remove_InvokeSameTargetMultipleTimesSuccess()
+        {
+            var list = new SubListenerList();
+
+            var target1 = new CustomWeakEventListener();
+            var target2 = new CustomWeakEventListener();
+            Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+            Delegate handler2 = Delegate.CreateDelegate(typeof(EventHandler), target2, nameof(CustomWeakEventListener.Handler));
+            Delegate handler3 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.SecondHandler));
+            Delegate handler4 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+            Delegate handler5 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.SecondHandler));
+            Delegate handler6 = Delegate.CreateDelegate(typeof(EventHandler), target2, nameof(CustomWeakEventListener.SecondHandler));
+            Delegate handler7 = Delegate.CreateDelegate(typeof(EventHandler), target2, nameof(CustomWeakEventListener.Handler));
+
+            list.AddHandler(handler1);
+            list.AddHandler(handler2);
+            list.AddHandler(handler3);
+            list.AddHandler(handler4);
+            list.AddHandler(handler5);
+            list.AddHandler(handler6);
+            list.AddHandler(handler7);
+
+            // Remove handler1.
+            list.RemoveHandler(handler1);
+            Assert.Equal(6, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Equal(target1, list[0]);
+            Assert.Equal(target2, list[1]);
+            Assert.Equal(target1, list[2]);
+            Assert.Equal(target1, list[3]);
+            Assert.Equal(target2, list[4]);
+            Assert.Equal(target2, list[5]);
+
+            // Remove handler2.
+            list.RemoveHandler(handler2);
+            Assert.Equal(5, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Equal(target1, list[0]);
+            Assert.Equal(target2, list[1]);
+            Assert.Equal(target1, list[2]);
+            Assert.Equal(target1, list[3]);
+            Assert.Equal(target2, list[4]);
+
+            // Remove handler3.
+            list.RemoveHandler(handler3);
+            Assert.Equal(4, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Equal(target1, list[0]);
+            Assert.Equal(target2, list[1]);
+            Assert.Equal(target1, list[2]);
+            Assert.Equal(target2, list[3]);
+
+            // Remove handler4.
+            list.RemoveHandler(handler4);
+            Assert.Equal(3, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Equal(target2, list[0]);
+            Assert.Equal(target1, list[1]);
+            Assert.Equal(target2, list[2]);
+            
+            // Remove handler5.
+            list.RemoveHandler(handler5);
+            Assert.Equal(2, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Equal(target2, list[0]);
+            Assert.Equal(target2, list[1]);
+
+            // Remove handler6.
+            list.RemoveHandler(handler6);
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Equal(target2, list[0]);
+
+            // Remove handler7.
+            list.RemoveHandler(handler7);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+        }
+
+        // TODO: this causes a crash.
+#if false
+        [Fact]
+        public void RemoveHandler_InvokeInUse_Success()
+        {
+            var list = new SubListenerList();
+            var target = new CustomWeakEventListener();
+            Delegate handler = Delegate.CreateDelegate(typeof(EventHandler), target, nameof(CustomWeakEventListener.Handler));
+            list.AddHandler(handler);
+
+            // Begin use.
+            Assert.False(list.BeginUse());
+
+            // Add.
+            list.RemoveHandler(handler);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+        }
+#endif
+
+        [Fact]
+        public void RemoveHandler_InvokeNoLongerInUse_Success()
+        {
+            var list = new SubListenerList();
+            var target = new CustomWeakEventListener();
+            Delegate handler = Delegate.CreateDelegate(typeof(EventHandler), target, nameof(CustomWeakEventListener.Handler));
+            list.AddHandler(handler);
+
+            // Begin use.
+            Assert.False(list.BeginUse());
+
+            // End use.
+            list.EndUse();
+
+            // Add.
+            list.RemoveHandler(handler);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+        }
+
+        [Fact]
+        public void RemoveHandler_InvokeNoSuchHandlerEmpty_Success()
+        {
+            var list = new SubListenerList();
+            var target = new CustomWeakEventListener();
+            Delegate handler = Delegate.CreateDelegate(typeof(EventHandler), target, nameof(CustomWeakEventListener.Handler));
+
+            // Remove.
+            list.RemoveHandler(handler);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+
+            // Remove again.
+            list.RemoveHandler(handler);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+        }
+        
+        [Fact]
+        public void RemoveHandler_InvokeNoSuchHandlerNotEmpty_Success()
+        {
+            var list = new SubListenerList();
+            var target = new CustomWeakEventListener();
+            Delegate handler = Delegate.CreateDelegate(typeof(EventHandler), target, nameof(CustomWeakEventListener.Handler));
+            list.AddHandler(handler);
+
+            // Remove.
+            list.RemoveHandler(Delegate.CreateDelegate(typeof(EventHandler), target, nameof(CustomWeakEventListener.SecondHandler)));
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Equal(target, list[0]);
+
+            // Remove again.
+            list.RemoveHandler(Delegate.CreateDelegate(typeof(EventHandler), target, nameof(CustomWeakEventListener.SecondHandler)));
+            Assert.Equal(1, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Equal(target, list[0]);
+        }
+
+        [Theory]
+        [InlineData(1, 0)]
+        [InlineData(3, 0)]
+        [InlineData(3, 1)]
+        [InlineData(3, 2)]
+        [InlineData(4, 0)]
+        [InlineData(4, 1)]
+        [InlineData(4, 2)]
+        [InlineData(4, 3)]
+        [InlineData(6, 0)]
+        [InlineData(6, 1)]
+        [InlineData(6, 2)]
+        [InlineData(6, 3)]
+        [InlineData(6, 4)]
+        [InlineData(6, 5)]
+        [InlineData(7, 0)]
+        [InlineData(7, 1)]
+        [InlineData(7, 2)]
+        [InlineData(7, 3)]
+        [InlineData(7, 4)]
+        [InlineData(7, 5)]
+        public void RemoveHandler_InvokeDifferentSizes_Success(int count, int removeIndex)
+        {
+            // Test internal FrugalList implementation.
+            var handlers = new List<Delegate>();
+            for (int i = 0; i < count; i++)
+            {
+                handlers.Add(Delegate.CreateDelegate(typeof(EventHandler), new CustomWeakEventListener(), nameof(CustomWeakEventListener.Handler)));
+            }
+
+            var list = new SubListenerList();
+            for (int i = 0; i < count; i++)
+            {
+                list.AddHandler(handlers[i]);
+            }
+
+            // Remove.
+            list.RemoveHandler(handlers[removeIndex]);
+
+            var expectedHandlers = new List<Delegate>(handlers);
+            expectedHandlers.RemoveAt(removeIndex);
+            Assert.Equal(expectedHandlers.Count, list.Count);
+            Assert.Equal(expectedHandlers.Count == 0, list.IsEmpty);
+            for (int i = 0; i < expectedHandlers.Count; i++)
+            {
+                Assert.Same(expectedHandlers[i].Target, list[i]);
+            }
+
+            // Remove all.
+            for (int i = 0; i < expectedHandlers.Count; i++)
+            {
+                list.RemoveHandler(expectedHandlers[i]);
+            }
+
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+        }
+
+        [Fact]
+        public void RemoveHandler_NullHandler_ThrowsArgumentNullException()
+        {
+            var list = new SubListenerList();
+            // TODO: this should throw ANE.
+            //Assert.Throws<ArgumentNullException>("handler", () => list.RemoveHandler(null));
+            Assert.Throws<NullReferenceException>(() => list.RemoveHandler(null));
+        }
+
+        private class SubListenerList : ListenerList
+        {
+            public SubListenerList() : base()
+            {
+            }
+
+            public SubListenerList(int capacity) : base(capacity)
+            {
+            }
+
+            public new void CopyTo(ListenerList newList) => base.CopyTo(newList);
+        }
+
+        protected override void StartListening(object source) => throw new NotImplementedException();
+
+        protected override void StopListening(object source) => throw new NotImplementedException();
+    }
+
+    public class ListenerListTEventArgsTests : WeakEventManager
+    {
+        [Fact]
+        public void Ctor_Default()
+        {
+            var list = new SubListenerList<EventArgs>();
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+        }
+
+        [Theory]
+        [InlineData(-1)]
+        [InlineData(0)]
+        [InlineData(1)]
+        [InlineData(2)]
+        [InlineData(3)]
+        [InlineData(4)]
+        [InlineData(5)]
+        [InlineData(6)]
+        [InlineData(7)]
+        public void Ctor_Int(int capacity)
+        {
+            var list = new SubListenerList<EventArgs>(capacity);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+        }
+
+        [Fact]
+        public void Clone_InvokeEmptyToEmpty_Success()
+        {
+            var list = new SubListenerList<EventArgs>();
+
+            ListenerList newList = Assert.IsType<ListenerList<EventArgs>>(list.Clone());
+            Assert.NotSame(list, newList);
+            Assert.Equal(0, list.Count);
+            Assert.True(list.IsEmpty);
+            Assert.Equal(0, newList.Count);
+            Assert.True(newList.IsEmpty);
+        }
+
+        [Fact]
+        public void Clone_NotEmptyWithListenersToEmpty_Success()
+        {
+            var list = new SubListenerList<EventArgs>();
+            var listener1 = new CustomWeakEventListener();
+            var listener2 = new CustomWeakEventListener();
+            list.Add(listener1);
+            list.Add(listener2);
+
+            ListenerList newList = Assert.IsType<ListenerList<EventArgs>>(list.Clone());
+            Assert.NotSame(list, newList);
+            Assert.Equal(2, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(listener2, list[1]);
+            Assert.Equal(2, newList.Count);
+            Assert.False(newList.IsEmpty);
+            Assert.Same(listener1, newList[0]);
+            Assert.Same(listener2, newList[1]);
+        }
+
+        [Fact]
+        public void Clone_NotEmptyWithHandlersToEmpty_Success()
+        {
+            var list = new SubListenerList<EventArgs>();
+            var target1 = new CustomWeakEventListener();
+            Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+            var target2 = new CustomWeakEventListener();
+            Delegate handler2 = Delegate.CreateDelegate(typeof(EventHandler), target2, nameof(CustomWeakEventListener.Handler));
+            Delegate handler3 = (EventHandler)delegate { };
+            Delegate handler4 = WeakEventManagerTests.StaticEventHandler;
+
+            list.AddHandler(handler1);
+            list.AddHandler(handler2);
+            list.AddHandler(handler3);
+            list.AddHandler(handler4);
+
+            ListenerList newList = Assert.IsType<ListenerList<EventArgs>>(list.Clone());
+            Assert.NotSame(list, newList);
+            Assert.Equal(4, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(target1, list[0]);
+            Assert.Same(target2, list[1]);
+            Assert.Throws<InvalidCastException>(() => list[2]);
+            Assert.Throws<InvalidCastException>(() => list[3]);
+            Assert.Equal(4, newList.Count);
+            Assert.False(newList.IsEmpty);
+            Assert.Same(target1, newList[0]);
+            Assert.Same(target2, newList[1]);
+            Assert.Throws<InvalidCastException>(() => newList[2]);
+            Assert.Throws<InvalidCastException>(() => newList[3]);
+        }
+
+        [Fact]
+        public void Clone_NotEmptyWithListenersAndHandlersToEmpty_Success()
+        {
+            var list = new SubListenerList<EventArgs>();
+            var listener1 = new CustomWeakEventListener();
+            var listener2 = new CustomWeakEventListener();
+            var target1 = new CustomWeakEventListener();
+            Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler), target1, nameof(CustomWeakEventListener.Handler));
+            var target2 = new CustomWeakEventListener();
+            Delegate handler2 = Delegate.CreateDelegate(typeof(EventHandler), target2, nameof(CustomWeakEventListener.Handler));
+            Delegate handler3 = (EventHandler)delegate { };
+            Delegate handler4 = WeakEventManagerTests.StaticEventHandler;
+
+            list.Add(listener1);
+            list.AddHandler(handler1);
+            list.Add(listener2);
+            list.AddHandler(handler2);
+            list.AddHandler(handler3);
+            list.AddHandler(handler4);
+
+            ListenerList newList = Assert.IsType<ListenerList<EventArgs>>(list.Clone());
+            Assert.NotSame(list, newList);
+            Assert.Equal(6, list.Count);
+            Assert.False(list.IsEmpty);
+            Assert.Same(listener1, list[0]);
+            Assert.Same(target1, list[1]);
+            Assert.Same(listener2, list[2]);
+            Assert.Same(target2, list[3]);
+            Assert.Throws<InvalidCastException>(() => list[4]);
+            Assert.Throws<InvalidCastException>(() => list[5]);
+            Assert.Equal(6, newList.Count);
+            Assert.False(newList.IsEmpty);
+            Assert.Same(listener1, newList[0]);
+            Assert.Same(target1, newList[1]);
+            Assert.Same(listener2, newList[2]);
+            Assert.Same(target2, newList[3]);
+            Assert.Throws<InvalidCastException>(() => newList[4]);
+            Assert.Throws<InvalidCastException>(() => newList[5]);
+        }
+
+        public static IEnumerable<object?[]> DeliverEvent_TestData()
+        {
+            yield return new object?[] { null, null, null };
+            yield return new object?[] { new object(), new EventArgs(), typeof(int) };
+            yield return new object?[] { new object(), EventArgs.Empty, typeof(int) };
+        }
+
+        [Theory]
+        [MemberData(nameof(DeliverEvent_TestData))]
+        public void DeliverEvent_InvokeWithListeners_Success(object sender, EventArgs args, Type managerType)
+        {
+            var list = new SubListenerList<EventArgs>();
+            var events = new List<string>();
+            var listener1 = new CustomWeakEventListener();
+            listener1.ReceiveWeakEventAction = (t, s, e) =>
+            {
+                Assert.Same(managerType, t);
+                Assert.Same(sender, s);
+                Assert.Same(args, e);
+                events.Add("listener1");
+                return true;
+            };
+            var listener2 = new CustomWeakEventListener();
+            listener2.ReceiveWeakEventAction = (t, s, e) =>
+            {
+                Assert.Same(managerType, t);
+                Assert.Same(sender, s);
+                Assert.Same(args, e);
+                events.Add("listener2");
+                return true;
+            };
+            list.Add(listener1);
+            list.Add(listener2);
+
+            Assert.False(list.DeliverEvent(sender, args, managerType));
+            Assert.Equal(new string[] { "listener1", "listener2" }, events);
+        }
+
+        [Theory]
+        [MemberData(nameof(DeliverEvent_TestData))]
+        public void DeliverEvent_InvokeWithHandlers_Success(object sender, EventArgs args, Type managerType)
+        {
+            var list = new SubListenerList<EventArgs>();
+            var events = new List<string>();
+            var listener1 = new CustomWeakEventListener();
+            listener1.HandlerAction = (s, e) =>
+            {
+                Assert.Same(sender, s);
+                Assert.Same(args, e);
+                events.Add("handler1");
+            };
+            var listener2 = new CustomWeakEventListener();
+            listener2.HandlerAction = (s, e) =>
+            {
+                Assert.Same(sender, s);
+                Assert.Same(args, e);
+                events.Add("handler2");
+            };
+            var listener3 = new CustomWeakEventListener();
+            listener3.HandlerAction = (s, e) =>
+            {
+                Assert.Same(sender, s);
+                Assert.Same(args, e);
+                events.Add("handler3");
+            };
+            Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler<EventArgs>), listener1, nameof(CustomWeakEventListener.Handler));
+            Delegate handler2 = Delegate.CreateDelegate(typeof(EventHandler<EventArgs>), listener2, nameof(CustomWeakEventListener.Handler));
+            Delegate handler3 = Delegate.CreateDelegate(typeof(EventHandler<EventArgs>), listener3, nameof(CustomWeakEventListener.Handler));
+            list.AddHandler(handler1);
+            list.AddHandler(handler2);
+            list.AddHandler(handler3);
+
+            Assert.False(list.DeliverEvent(sender, args, managerType));
+            Assert.Equal(new string[] { "handler1", "handler2", "handler3" }, events);
+        }
+
+        [Theory]
+        [MemberData(nameof(DeliverEvent_TestData))]
+        public void DeliverEvent_InvokeWithListenersAndHandlers_Success(object sender, EventArgs args, Type managerType)
+        {
+            var list = new SubListenerList<EventArgs>();
+            var events = new List<string>();
+            var listener1 = new CustomWeakEventListener();
+            listener1.HandlerAction = (s, e) =>
+            {
+                Assert.Same(sender, s);
+                Assert.Same(args, e);
+                events.Add("handler1");
+            };
+            var listener2 = new CustomWeakEventListener();
+            listener2.ReceiveWeakEventAction = (t, s, e) =>
+            {
+                Assert.Same(managerType, t);
+                Assert.Same(sender, s);
+                Assert.Same(args, e);
+                events.Add("listener1");
+                return true;
+            };
+            var listener3 = new CustomWeakEventListener();
+            listener3.HandlerAction = (s, e) =>
+            {
+                Assert.Same(sender, s);
+                Assert.Same(args, e);
+                events.Add("handler2");
+            };
+            var listener4 = new CustomWeakEventListener();
+            listener4.ReceiveWeakEventAction = (t, s, e) =>
+            {
+                Assert.Same(managerType, t);
+                Assert.Same(sender, s);
+                Assert.Same(args, e);
+                events.Add("listener2");
+                return true;
+            };
+            var listener5 = new CustomWeakEventListener();
+            listener5.HandlerAction = (s, e) =>
+            {
+                Assert.Same(sender, s);
+                Assert.Same(args, e);
+                events.Add("handler3");
+            };
+            Delegate handler1 = Delegate.CreateDelegate(typeof(EventHandler<EventArgs>), listener1, nameof(CustomWeakEventListener.Handler));
+            Delegate handler2 = Delegate.CreateDelegate(typeof(EventHandler<EventArgs>), listener3, nameof(CustomWeakEventListener.Handler));
+            Delegate handler3 = Delegate.CreateDelegate(typeof(EventHandler<EventArgs>), listener5, nameof(CustomWeakEventListener.Handler));
+            list.AddHandler(handler1);
+            list.Add(listener2);
+            list.AddHandler(handler2);
+            list.Add(listener4);
+            list.AddHandler(handler3);
+
+            Assert.False(list.DeliverEvent(sender, args, managerType));
+            Assert.Equal(new string[] { "handler1", "listener1", "handler2", "listener2", "handler3" }, events);
+        }
+
+        // TODO: this causes a crash.
+#if false
+        [Theory]
+        [MemberData(nameof(DeliverEvent_TestData))]
+        public void DeliverEvent_InvokeWithListenersNotHandled_Success(object sender, EventArgs args, Type managerType)
+        {
+            var list = new SubListenerList<EventArgs>();
+            var events = new List<string>();
+            var listener1 = new CustomWeakEventListener();
+            listener1.ReceiveWeakEventAction = (t, s, e) =>
+            {
+                Assert.Same(managerType, t);
+                Assert.Same(sender, s);
+                Assert.Same(args, e);
+                events.Add("listener1");
+                return false;
+            };
+            var listener2 = new CustomWeakEventListener();
+            listener2.ReceiveWeakEventAction = (t, s, e) =>
+            {
+                Assert.Same(managerType, t);
+                Assert.Same(sender, s);
+                Assert.Same(args, e);
+                events.Add("listener2");
+                return true;
+            };
+            list.Add(listener1);
+            list.Add(listener2);
+
+            Assert.False(list.DeliverEvent(sender, args, managerType));
+            Assert.Equal(new string[] { "listener1", "listener2" }, events);
+        }
+#endif
+
+        [Theory]
+        [MemberData(nameof(DeliverEvent_TestData))]
+        public void DeliverEvent_InvokeWithInvalidHandlerAction_ThrowsInvalidCastException(object sender, EventArgs args, Type managerType)
+        {
+            var list = new SubListenerList<EventArgs>();
+            Delegate handler = () => {};
+            list.AddHandler(handler);
+
+            Assert.Throws<InvalidCastException>(() => list.DeliverEvent(sender, args, managerType));
+        }
+
+        [Theory]
+        [MemberData(nameof(DeliverEvent_TestData))]
+        public void DeliverEvent_InvokeWithInvalidHandlerFunc_ThrowsInvalidCastException(object sender, EventArgs args, Type managerType)
+        {
+            var list = new SubListenerList<EventArgs>();
+            bool EventHandler(object sender, EventArgs args) => true;
+            list.AddHandler(EventHandler);
+
+            Assert.Throws<InvalidCastException>(() => list.DeliverEvent(sender, args, managerType));
+        }
+
+        [Theory]
+        [MemberData(nameof(DeliverEvent_TestData))]
+        public void DeliverEvent_InvokeWithInvalidHandlerEventHandler_ThrowsInvalidCastException(object sender, EventArgs args, Type managerType)
+        {
+            var list = new SubListenerList<EventArgs>();
+            var target = new CustomWeakEventListener();
+            Delegate handler = Delegate.CreateDelegate(typeof(EventHandler), target, nameof(CustomWeakEventListener.Handler));
+            list.AddHandler(handler);
+
+            Assert.Throws<InvalidCastException>(() => list.DeliverEvent(sender, args, managerType));
+        }
+
+        [Theory]
+        [MemberData(nameof(DeliverEvent_TestData))]
+        public void DeliverEvent_InvokeEmpty_ReturnsFalse(object sender, EventArgs args, Type managerType)
+        {
+            var list = new SubListenerList<EventArgs>();
+            Assert.False(list.DeliverEvent(sender, args, managerType));
+        }
+
+        private class SubListenerList<TEventArgs> : ListenerList<TEventArgs> where TEventArgs : EventArgs
+        {
+            public SubListenerList() : base()
+            {
+            }
+            
+            public SubListenerList(int capacity) : base(capacity)
+            {
+            }
+        }
+
+        protected override void StartListening(object source) => throw new NotImplementedException();
+
+        protected override void StopListening(object source) => throw new NotImplementedException();
+    }
+
+    private static void StaticEventHandler(object sender, EventArgs e)
+    {
+    }
+
+    private class CustomListenerList : ListenerList
+    {
+        public Func<ListenerList>? CloneAction { get; set; }
+
+        public override ListenerList Clone() => CloneAction!.Invoke();
+
+        public Func<object, EventArgs, Type, bool>? DeliverEventAction { get; set; }
+
+        public override bool DeliverEvent(object sender, EventArgs e, Type managerType)
+        {
+            if (DeliverEventAction is null)
+            {
+                return base.DeliverEvent(sender, e, managerType);
+            }
+
+            return DeliverEventAction(sender, e, managerType);
+        }
+    }
+
+    private class CustomWeakEventListener : IWeakEventListener
+    {
+        public Func<Type, object, EventArgs, bool>? ReceiveWeakEventAction { get; set; }
+
+        public bool ReceiveWeakEvent(Type managerType, object sender, EventArgs e)
+        {
+            if (ReceiveWeakEventAction is null)
+            {
+                throw new NotImplementedException();
+            }
+
+            return ReceiveWeakEventAction(managerType, sender, e);
+        }
+
+        public Action<object, EventArgs>? HandlerAction { get; set; }
+
+        public void Handler(object sender, EventArgs e)
+        {
+            if (HandlerAction is null)
+            {
+                throw new NotImplementedException();
+            }
+
+            HandlerAction(sender, e);
+        }
+        
+        public void SecondHandler(object sender, EventArgs e) => throw new NotImplementedException();
+    }
+
+    private class SubWeakEventManager : WeakEventManager
+    {
+        public SubWeakEventManager()
+        {
+        }
+
+        public new IDisposable ReadLock => base.ReadLock;
+
+        public new IDisposable WriteLock => base.WriteLock;
+
+        public new object this[object source]
+        {
+            get => base[source];
+            set => base[source] = value;
+        }
+
+        public new void DeliverEvent(object sender, EventArgs args) => base.DeliverEvent(sender, args);
+
+        public new void DeliverEventToList(object sender, EventArgs args, ListenerList list) => base.DeliverEventToList(sender, args, list);
+
+        public new static WeakEventManager GetCurrentManager(Type managerType) => WeakEventManager.GetCurrentManager(managerType);
+
+        public new ListenerList NewListenerList() => base.NewListenerList();
+
+        public new void ProtectedAddHandler(object source, Delegate handler) => base.ProtectedAddHandler(source, handler);
+
+        public new void ProtectedAddListener(object source, IWeakEventListener listener) => base.ProtectedAddListener(source, listener);
+
+        public new void ProtectedRemoveHandler(object source, Delegate handler) => base.ProtectedRemoveHandler(source, handler);
+
+        public new void ProtectedRemoveListener(object source, IWeakEventListener listener) => base.ProtectedRemoveListener(source, listener);
+
+        public new bool Purge(object source, object data, bool purgeAll) => base.Purge(source, data, purgeAll);
+
+        public new void Remove(object source) => base.Remove(source);
+
+        public new static void SetCurrentManager(Type managerType, WeakEventManager? newManager) => WeakEventManager.SetCurrentManager(managerType, newManager);
+
+        public new void ScheduleCleanup() => base.ScheduleCleanup();
+
+        public Action<object>? StartListeningAction { get; set; }
+
+        protected override void StartListening(object source)
+        {
+            if (StartListeningAction is null)
+            {
+                throw new NotImplementedException();
+            }
+
+            StartListeningAction(source);
+        }
+
+        public Action<object>? StopListeningAction { get; set; }
+
+        protected override void StopListening(object source)
+        {
+            if (StopListeningAction is null)
+            {
+                throw new NotImplementedException();
+            }
+
+            StopListeningAction(source);
+        }
+    }
+
+    protected override void StartListening(object source) => throw new NotImplementedException();
+
+    protected override void StopListening(object source) => throw new NotImplementedException();
+}
\ No newline at end of file
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/Tests to Add.md b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/Tests to Add.md
new file mode 100644
index 00000000000..71583514a63
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/Tests to Add.md	
@@ -0,0 +1,25 @@
+# Tests to add
+- System.ComponentModel.DependencyPropertyDescriptor
+- System.IO.Packaging.EncryptedPackageEnvelope
+- System.IO.Packaging.PackageDigitalSignature
+- System.IO.Packaging.PackageDigitalSignatureManager
+- System.IO.Packaging.RightsManagementInformation
+- System.Security.RightsManagement.CryptoProvider
+- System.Security.RightsManagement.PublishLicense
+- System.Security.RightsManagement.SecureEnvironment
+- System.Security.RightsManagement.UnsignedPublishLicense
+- System.Security.RightsManagement.UseLicense
+- System.Windows.Interop.ComponentDispatcher
+- System.Windows.Threading.Dispatcher
+- System.Windows.Threading.DispatcherEventArgs
+- System.Windows.Threading.DispatcherUnhandledExceptionEventArgs
+- System.Windows.Threading.DispatcherUnhandledExceptionFilterEventArgs
+- System.Windows.Threading.DispatcherFrame
+- System.Windows.Threading.DispatcherHooks
+- System.Windows.Threading.DispatcherOperation
+- System.Windows.Threading.DispatcherSynchronizationContext
+- System.Windows.Threading.DispatcherTimer
+- System.Windows.AttachedPropertyBrowsableForTypeAttribute
+- System.Windows.AttachedPropertyBrowsableWhenAttributePresentAttribute
+- System.Windows.DependencyProperty
+- System.Windows.SplashScreen
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/Usings.cs b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/Usings.cs
new file mode 100644
index 00000000000..9dc6920eea2
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/Usings.cs
@@ -0,0 +1,6 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+global using System.Collections.Generic;
+global using Xunit;
diff --git a/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/WindowsBase.Tests.csproj b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/WindowsBase.Tests.csproj
new file mode 100644
index 00000000000..e0408eecb93
--- /dev/null
+++ b/src/Microsoft.DotNet.Wpf/tests/UnitTests/WindowsBase.Tests/WindowsBase.Tests.csproj
@@ -0,0 +1,23 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <AssemblyName>WindowsBase.Tests</AssemblyName>
+    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+    <GenerateRuntimeConfigurationFiles>true</GenerateRuntimeConfigurationFiles>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="$(WpfSourceDir)System.Xaml\System.Xaml.csproj" />
+    <ProjectReference Include="$(WpfSourceDir)WindowsBase\WindowsBase.csproj" />
+    <ProjectReference Include="$(WpfSourceDir)PresentationCore\PresentationCore.csproj" />
+    <ProjectReference Include="$(WpfSourceDir)PresentationFramework\PresentationFramework.csproj" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="$(SystemIOPackagingPackage)" Version="$(SystemIOPackagingVersion)" />
+    <PackageReference Include="Moq" Version="$(MoqPackageVersion)" />
+    <PackageReference Include="coverlet.msbuild" Version="$(CoverletMSBuildPackageVersion)" />
+  </ItemGroup>
+
+</Project>