Moar tests!

test/Microsoft.AspNetCore.Hosting.Tests/Internal/MyBadContainerFactory.cs

@@ -0,0 +1,24 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace Microsoft.AspNetCore.Hosting.Tests.Internal
+{
+    public class MyBadContainerFactory : IServiceProviderFactory<MyContainer>
+    {
+        public MyContainer CreateBuilder(IServiceCollection services)
+        {
+            var container = new MyContainer();
+            container.Populate(services);
+            return container;
+        }
+
+        public IServiceProvider CreateServiceProvider(MyContainer containerBuilder)
+        {
+            containerBuilder.Build();
+            return null;
+        }
+    }
+}

test/Microsoft.AspNetCore.Hosting.Tests/Internal/MyContainerFactory.cs

@@ -21,5 +21,4 @@ public IServiceProvider CreateServiceProvider(MyContainer containerBuilder)
             return containerBuilder;
         }
     }
-
 }

test/Microsoft.AspNetCore.Hosting.Tests/StartupManagerTests.cs

@@ -266,6 +266,22 @@ public void CustomServiceProviderFactoryFailsWithOverloadsInStartup()
             Assert.Throws<InvalidOperationException>(() => StartupLoader.LoadMethods(services, typeof(MyContainerStartupWithOverloads), "Development"));
         }
 
+        [Fact]
+        public void BadServiceProviderFactoryFailsThatReturnsNullServiceProviderOverriddenByDefault()
+        {
+            var serviceCollection = new ServiceCollection();
+            serviceCollection.AddSingleton<IServiceProviderFactory<MyContainer>, MyBadContainerFactory>();
+            var services = serviceCollection.BuildServiceProvider();
+
+            var startup = StartupLoader.LoadMethods(services, typeof(MyContainerStartup), "Development");
+
+            var app = new ApplicationBuilder(services);
+            app.ApplicationServices = startup.ConfigureServicesDelegate(serviceCollection);
+
+            Assert.NotNull(app.ApplicationServices);
+            Assert.IsNotType(typeof(MyContainer), app.ApplicationServices);
+        }
+
         public class MyContainerStartupWithOverloads
         {
             public void ConfigureServices(IServiceCollection services)