diff --git a/ButtonBuilder.php b/ButtonBuilder.php
index ed41b2147d..5e1106ad05 100644
--- a/ButtonBuilder.php
+++ b/ButtonBuilder.php
@@ -27,7 +27,7 @@ class ButtonBuilder implements \IteratorAggregate, FormBuilderInterface
     /**
      * @var bool
      */
-    private $disabled;
+    private $disabled = false;
 
     /**
      * @var ResolvedFormTypeInterface
diff --git a/Extension/Core/Type/ButtonType.php b/Extension/Core/Type/ButtonType.php
index b05dcc018d..ba2f8dfe0e 100644
--- a/Extension/Core/Type/ButtonType.php
+++ b/Extension/Core/Type/ButtonType.php
@@ -26,6 +26,7 @@ class ButtonType extends BaseType implements ButtonTypeInterface
      */
     public function getParent()
     {
+        return null;
     }
 
     /**
diff --git a/Extension/Core/Type/FormType.php b/Extension/Core/Type/FormType.php
index 72b14035e5..a31c171f0e 100644
--- a/Extension/Core/Type/FormType.php
+++ b/Extension/Core/Type/FormType.php
@@ -190,6 +190,7 @@ public function configureOptions(OptionsResolver $resolver)
      */
     public function getParent()
     {
+        return null;
     }
 
     /**
diff --git a/FormError.php b/FormError.php
index 98a1e29a83..078060c9f2 100644
--- a/FormError.php
+++ b/FormError.php
@@ -127,7 +127,7 @@ public function setOrigin(FormInterface $origin)
     /**
      * Returns the form that caused this error.
      *
-     * @return FormInterface The form that caused this error
+     * @return FormInterface|null The form that caused this error
      */
     public function getOrigin()
     {
diff --git a/FormInterface.php b/FormInterface.php
index 5c55bcd795..f8d5c6ea5b 100644
--- a/FormInterface.php
+++ b/FormInterface.php
@@ -31,7 +31,7 @@ interface FormInterface extends \ArrayAccess, \Traversable, \Countable
      * @throws Exception\LogicException            when trying to set a parent for a form with
      *                                             an empty name
      */
-    public function setParent(self $parent = null);
+    public function setParent(FormInterface $parent = null);
 
     /**
      * Returns the parent form.
diff --git a/Test/Traits/ValidatorExtensionTrait.php b/Test/Traits/ValidatorExtensionTrait.php
index 07dd9e0d55..46bd8b7e57 100644
--- a/Test/Traits/ValidatorExtensionTrait.php
+++ b/Test/Traits/ValidatorExtensionTrait.php
@@ -13,6 +13,7 @@
 
 use Symfony\Component\Form\Extension\Validator\ValidatorExtension;
 use Symfony\Component\Form\Test\TypeTestCase;
+use Symfony\Component\Validator\ConstraintViolationList;
 use Symfony\Component\Validator\Mapping\ClassMetadata;
 use Symfony\Component\Validator\Validator\ValidatorInterface;
 
@@ -37,9 +38,9 @@ protected function getValidatorExtension()
         }
 
         $this->validator = $this->getMockBuilder(ValidatorInterface::class)->getMock();
-        $metadata = $this->getMockBuilder(ClassMetadata::class)->disableOriginalConstructor()->setMethods(['addPropertyConstraint'])->getMock();
+        $metadata = $this->getMockBuilder(ClassMetadata::class)->setConstructorArgs([''])->setMethods(['addPropertyConstraint'])->getMock();
         $this->validator->expects($this->any())->method('getMetadataFor')->will($this->returnValue($metadata));
-        $this->validator->expects($this->any())->method('validate')->will($this->returnValue([]));
+        $this->validator->expects($this->any())->method('validate')->will($this->returnValue(new ConstraintViolationList()));
 
         return new ValidatorExtension($this->validator);
     }
diff --git a/Tests/AbstractRequestHandlerTest.php b/Tests/AbstractRequestHandlerTest.php
index f2ee71b342..776c753eca 100644
--- a/Tests/AbstractRequestHandlerTest.php
+++ b/Tests/AbstractRequestHandlerTest.php
@@ -346,7 +346,7 @@ public function getPostMaxSizeFixtures()
             [1024, '1K', false],
             [null, '1K', false],
             [1024, '', false],
-            [1024, 0, false],
+            [1024, '0', false],
         ];
     }
 
diff --git a/Tests/ChoiceList/Factory/CachingFactoryDecoratorTest.php b/Tests/ChoiceList/Factory/CachingFactoryDecoratorTest.php
index b194d65eee..ba4ae7cd19 100644
--- a/Tests/ChoiceList/Factory/CachingFactoryDecoratorTest.php
+++ b/Tests/ChoiceList/Factory/CachingFactoryDecoratorTest.php
@@ -13,7 +13,9 @@
 
 use PHPUnit\Framework\MockObject\MockObject;
 use PHPUnit\Framework\TestCase;
+use Symfony\Component\Form\ChoiceList\ArrayChoiceList;
 use Symfony\Component\Form\ChoiceList\Factory\CachingFactoryDecorator;
+use Symfony\Component\Form\ChoiceList\View\ChoiceListView;
 
 /**
  * @author Bernhard Schussek <bschussek@gmail.com>
@@ -38,7 +40,7 @@ protected function setUp()
 
     public function testCreateFromChoicesEmpty()
     {
-        $list = new \stdClass();
+        $list = new ArrayChoiceList([]);
 
         $this->decoratedFactory->expects($this->once())
             ->method('createListFromChoices')
@@ -54,7 +56,7 @@ public function testCreateFromChoicesComparesTraversableChoicesAsArray()
         // The top-most traversable is converted to an array
         $choices1 = new \ArrayIterator(['A' => 'a']);
         $choices2 = ['A' => 'a'];
-        $list = new \stdClass();
+        $list = new ArrayChoiceList([]);
 
         $this->decoratedFactory->expects($this->once())
             ->method('createListFromChoices')
@@ -69,8 +71,8 @@ public function testCreateFromChoicesGroupedChoices()
     {
         $choices1 = ['key' => ['A' => 'a']];
         $choices2 = ['A' => 'a'];
-        $list1 = new \stdClass();
-        $list2 = new \stdClass();
+        $list1 = new ArrayChoiceList([]);
+        $list2 = new ArrayChoiceList([]);
 
         $this->decoratedFactory->expects($this->at(0))
             ->method('createListFromChoices')
@@ -92,7 +94,7 @@ public function testCreateFromChoicesSameChoices($choice1, $choice2)
     {
         $choices1 = [$choice1];
         $choices2 = [$choice2];
-        $list = new \stdClass();
+        $list = new ArrayChoiceList([]);
 
         $this->decoratedFactory->expects($this->once())
             ->method('createListFromChoices')
@@ -110,8 +112,8 @@ public function testCreateFromChoicesDifferentChoices($choice1, $choice2)
     {
         $choices1 = [$choice1];
         $choices2 = [$choice2];
-        $list1 = new \stdClass();
-        $list2 = new \stdClass();
+        $list1 = new ArrayChoiceList([]);
+        $list2 = new ArrayChoiceList([]);
 
         $this->decoratedFactory->expects($this->at(0))
             ->method('createListFromChoices')
@@ -129,7 +131,7 @@ public function testCreateFromChoicesDifferentChoices($choice1, $choice2)
     public function testCreateFromChoicesSameValueClosure()
     {
         $choices = [1];
-        $list = new \stdClass();
+        $list = new ArrayChoiceList([]);
         $closure = function () {};
 
         $this->decoratedFactory->expects($this->once())
@@ -144,8 +146,8 @@ public function testCreateFromChoicesSameValueClosure()
     public function testCreateFromChoicesDifferentValueClosure()
     {
         $choices = [1];
-        $list1 = new \stdClass();
-        $list2 = new \stdClass();
+        $list1 = new ArrayChoiceList([]);
+        $list2 = new ArrayChoiceList([]);
         $closure1 = function () {};
         $closure2 = function () {};
 
@@ -165,7 +167,7 @@ public function testCreateFromChoicesDifferentValueClosure()
     public function testCreateFromLoaderSameLoader()
     {
         $loader = $this->getMockBuilder('Symfony\Component\Form\ChoiceList\Loader\ChoiceLoaderInterface')->getMock();
-        $list = new \stdClass();
+        $list = new ArrayChoiceList([]);
 
         $this->decoratedFactory->expects($this->once())
             ->method('createListFromLoader')
@@ -180,8 +182,8 @@ public function testCreateFromLoaderDifferentLoader()
     {
         $loader1 = $this->getMockBuilder('Symfony\Component\Form\ChoiceList\Loader\ChoiceLoaderInterface')->getMock();
         $loader2 = $this->getMockBuilder('Symfony\Component\Form\ChoiceList\Loader\ChoiceLoaderInterface')->getMock();
-        $list1 = new \stdClass();
-        $list2 = new \stdClass();
+        $list1 = new ArrayChoiceList([]);
+        $list2 = new ArrayChoiceList([]);
 
         $this->decoratedFactory->expects($this->at(0))
             ->method('createListFromLoader')
@@ -199,7 +201,7 @@ public function testCreateFromLoaderDifferentLoader()
     public function testCreateFromLoaderSameValueClosure()
     {
         $loader = $this->getMockBuilder('Symfony\Component\Form\ChoiceList\Loader\ChoiceLoaderInterface')->getMock();
-        $list = new \stdClass();
+        $list = new ArrayChoiceList([]);
         $closure = function () {};
 
         $this->decoratedFactory->expects($this->once())
@@ -214,8 +216,8 @@ public function testCreateFromLoaderSameValueClosure()
     public function testCreateFromLoaderDifferentValueClosure()
     {
         $loader = $this->getMockBuilder('Symfony\Component\Form\ChoiceList\Loader\ChoiceLoaderInterface')->getMock();
-        $list1 = new \stdClass();
-        $list2 = new \stdClass();
+        $list1 = new ArrayChoiceList([]);
+        $list2 = new ArrayChoiceList([]);
         $closure1 = function () {};
         $closure2 = function () {};
 
@@ -236,7 +238,7 @@ public function testCreateViewSamePreferredChoices()
     {
         $preferred = ['a'];
         $list = $this->getMockBuilder('Symfony\Component\Form\ChoiceList\ChoiceListInterface')->getMock();
-        $view = new \stdClass();
+        $view = new ChoiceListView();
 
         $this->decoratedFactory->expects($this->once())
             ->method('createView')
@@ -252,8 +254,8 @@ public function testCreateViewDifferentPreferredChoices()
         $preferred1 = ['a'];
         $preferred2 = ['b'];
         $list = $this->getMockBuilder('Symfony\Component\Form\ChoiceList\ChoiceListInterface')->getMock();
-        $view1 = new \stdClass();
-        $view2 = new \stdClass();
+        $view1 = new ChoiceListView();
+        $view2 = new ChoiceListView();
 
         $this->decoratedFactory->expects($this->at(0))
             ->method('createView')
@@ -272,7 +274,7 @@ public function testCreateViewSamePreferredChoicesClosure()
     {
         $preferred = function () {};
         $list = $this->getMockBuilder('Symfony\Component\Form\ChoiceList\ChoiceListInterface')->getMock();
-        $view = new \stdClass();
+        $view = new ChoiceListView();
 
         $this->decoratedFactory->expects($this->once())
             ->method('createView')
@@ -288,8 +290,8 @@ public function testCreateViewDifferentPreferredChoicesClosure()
         $preferred1 = function () {};
         $preferred2 = function () {};
         $list = $this->getMockBuilder('Symfony\Component\Form\ChoiceList\ChoiceListInterface')->getMock();
-        $view1 = new \stdClass();
-        $view2 = new \stdClass();
+        $view1 = new ChoiceListView();
+        $view2 = new ChoiceListView();
 
         $this->decoratedFactory->expects($this->at(0))
             ->method('createView')
@@ -308,7 +310,7 @@ public function testCreateViewSameLabelClosure()
     {
         $labels = function () {};
         $list = $this->getMockBuilder('Symfony\Component\Form\ChoiceList\ChoiceListInterface')->getMock();
-        $view = new \stdClass();
+        $view = new ChoiceListView();
 
         $this->decoratedFactory->expects($this->once())
             ->method('createView')
@@ -324,8 +326,8 @@ public function testCreateViewDifferentLabelClosure()
         $labels1 = function () {};
         $labels2 = function () {};
         $list = $this->getMockBuilder('Symfony\Component\Form\ChoiceList\ChoiceListInterface')->getMock();
-        $view1 = new \stdClass();
-        $view2 = new \stdClass();
+        $view1 = new ChoiceListView();
+        $view2 = new ChoiceListView();
 
         $this->decoratedFactory->expects($this->at(0))
             ->method('createView')
@@ -344,7 +346,7 @@ public function testCreateViewSameIndexClosure()
     {
         $index = function () {};
         $list = $this->getMockBuilder('Symfony\Component\Form\ChoiceList\ChoiceListInterface')->getMock();
-        $view = new \stdClass();
+        $view = new ChoiceListView();
 
         $this->decoratedFactory->expects($this->once())
             ->method('createView')
@@ -360,8 +362,8 @@ public function testCreateViewDifferentIndexClosure()
         $index1 = function () {};
         $index2 = function () {};
         $list = $this->getMockBuilder('Symfony\Component\Form\ChoiceList\ChoiceListInterface')->getMock();
-        $view1 = new \stdClass();
-        $view2 = new \stdClass();
+        $view1 = new ChoiceListView();
+        $view2 = new ChoiceListView();
 
         $this->decoratedFactory->expects($this->at(0))
             ->method('createView')
@@ -380,7 +382,7 @@ public function testCreateViewSameGroupByClosure()
     {
         $groupBy = function () {};
         $list = $this->getMockBuilder('Symfony\Component\Form\ChoiceList\ChoiceListInterface')->getMock();
-        $view = new \stdClass();
+        $view = new ChoiceListView();
 
         $this->decoratedFactory->expects($this->once())
             ->method('createView')
@@ -396,8 +398,8 @@ public function testCreateViewDifferentGroupByClosure()
         $groupBy1 = function () {};
         $groupBy2 = function () {};
         $list = $this->getMockBuilder('Symfony\Component\Form\ChoiceList\ChoiceListInterface')->getMock();
-        $view1 = new \stdClass();
-        $view2 = new \stdClass();
+        $view1 = new ChoiceListView();
+        $view2 = new ChoiceListView();
 
         $this->decoratedFactory->expects($this->at(0))
             ->method('createView')
@@ -416,7 +418,7 @@ public function testCreateViewSameAttributes()
     {
         $attr = ['class' => 'foobar'];
         $list = $this->getMockBuilder('Symfony\Component\Form\ChoiceList\ChoiceListInterface')->getMock();
-        $view = new \stdClass();
+        $view = new ChoiceListView();
 
         $this->decoratedFactory->expects($this->once())
             ->method('createView')
@@ -432,8 +434,8 @@ public function testCreateViewDifferentAttributes()
         $attr1 = ['class' => 'foobar1'];
         $attr2 = ['class' => 'foobar2'];
         $list = $this->getMockBuilder('Symfony\Component\Form\ChoiceList\ChoiceListInterface')->getMock();
-        $view1 = new \stdClass();
-        $view2 = new \stdClass();
+        $view1 = new ChoiceListView();
+        $view2 = new ChoiceListView();
 
         $this->decoratedFactory->expects($this->at(0))
             ->method('createView')
@@ -452,7 +454,7 @@ public function testCreateViewSameAttributesClosure()
     {
         $attr = function () {};
         $list = $this->getMockBuilder('Symfony\Component\Form\ChoiceList\ChoiceListInterface')->getMock();
-        $view = new \stdClass();
+        $view = new ChoiceListView();
 
         $this->decoratedFactory->expects($this->once())
             ->method('createView')
@@ -468,8 +470,8 @@ public function testCreateViewDifferentAttributesClosure()
         $attr1 = function () {};
         $attr2 = function () {};
         $list = $this->getMockBuilder('Symfony\Component\Form\ChoiceList\ChoiceListInterface')->getMock();
-        $view1 = new \stdClass();
-        $view2 = new \stdClass();
+        $view1 = new ChoiceListView();
+        $view2 = new ChoiceListView();
 
         $this->decoratedFactory->expects($this->at(0))
             ->method('createView')
diff --git a/Tests/ChoiceList/Factory/PropertyAccessDecoratorTest.php b/Tests/ChoiceList/Factory/PropertyAccessDecoratorTest.php
index 725a09df08..043989a983 100644
--- a/Tests/ChoiceList/Factory/PropertyAccessDecoratorTest.php
+++ b/Tests/ChoiceList/Factory/PropertyAccessDecoratorTest.php
@@ -13,7 +13,9 @@
 
 use PHPUnit\Framework\MockObject\MockObject;
 use PHPUnit\Framework\TestCase;
+use Symfony\Component\Form\ChoiceList\ArrayChoiceList;
 use Symfony\Component\Form\ChoiceList\Factory\PropertyAccessDecorator;
+use Symfony\Component\Form\ChoiceList\View\ChoiceListView;
 use Symfony\Component\PropertyAccess\PropertyPath;
 
 /**
@@ -45,10 +47,10 @@ public function testCreateFromChoicesPropertyPath()
             ->method('createListFromChoices')
             ->with($choices, $this->isInstanceOf('\Closure'))
             ->willReturnCallback(function ($choices, $callback) {
-                return array_map($callback, $choices);
+                return new ArrayChoiceList(array_map($callback, $choices));
             });
 
-        $this->assertSame(['value'], $this->factory->createListFromChoices($choices, 'property'));
+        $this->assertSame(['value' => 'value'], $this->factory->createListFromChoices($choices, 'property')->getChoices());
     }
 
     public function testCreateFromChoicesPropertyPathInstance()
@@ -59,10 +61,10 @@ public function testCreateFromChoicesPropertyPathInstance()
             ->method('createListFromChoices')
             ->with($choices, $this->isInstanceOf('\Closure'))
             ->willReturnCallback(function ($choices, $callback) {
-                return array_map($callback, $choices);
+                return new ArrayChoiceList(array_map($callback, $choices));
             });
 
-        $this->assertSame(['value'], $this->factory->createListFromChoices($choices, new PropertyPath('property')));
+        $this->assertSame(['value' => 'value'], $this->factory->createListFromChoices($choices, new PropertyPath('property'))->getChoices());
     }
 
     /**
@@ -88,10 +90,10 @@ public function testCreateFromLoaderPropertyPath()
             ->method('createListFromLoader')
             ->with($loader, $this->isInstanceOf('\Closure'))
             ->willReturnCallback(function ($loader, $callback) {
-                return $callback((object) ['property' => 'value']);
+                return new ArrayChoiceList((array) $callback((object) ['property' => 'value']));
             });
 
-        $this->assertSame('value', $this->factory->createListFromLoader($loader, 'property'));
+        $this->assertSame(['value' => 'value'], $this->factory->createListFromLoader($loader, 'property')->getChoices());
     }
 
     /**
@@ -118,10 +120,10 @@ public function testCreateFromChoicesAssumeNullIfValuePropertyPathUnreadable()
             ->method('createListFromChoices')
             ->with($choices, $this->isInstanceOf('\Closure'))
             ->willReturnCallback(function ($choices, $callback) {
-                return array_map($callback, $choices);
+                return new ArrayChoiceList(array_map($callback, $choices));
             });
 
-        $this->assertSame([null], $this->factory->createListFromChoices($choices, 'property'));
+        $this->assertSame([null], $this->factory->createListFromChoices($choices, 'property')->getChoices());
     }
 
     // https://github.com/symfony/symfony/issues/5494
@@ -133,10 +135,10 @@ public function testCreateFromChoiceLoaderAssumeNullIfValuePropertyPathUnreadabl
             ->method('createListFromLoader')
             ->with($loader, $this->isInstanceOf('\Closure'))
             ->willReturnCallback(function ($loader, $callback) {
-                return $callback(null);
+                return new ArrayChoiceList((array) $callback(null));
             });
 
-        $this->assertNull($this->factory->createListFromLoader($loader, 'property'));
+        $this->assertSame([], $this->factory->createListFromLoader($loader, 'property')->getChoices());
     }
 
     public function testCreateFromLoaderPropertyPathInstance()
@@ -147,10 +149,10 @@ public function testCreateFromLoaderPropertyPathInstance()
             ->method('createListFromLoader')
             ->with($loader, $this->isInstanceOf('\Closure'))
             ->willReturnCallback(function ($loader, $callback) {
-                return $callback((object) ['property' => 'value']);
+                return new ArrayChoiceList((array) $callback((object) ['property' => 'value']));
             });
 
-        $this->assertSame('value', $this->factory->createListFromLoader($loader, new PropertyPath('property')));
+        $this->assertSame(['value' => 'value'], $this->factory->createListFromLoader($loader, new PropertyPath('property'))->getChoices());
     }
 
     public function testCreateViewPreferredChoicesAsPropertyPath()
@@ -161,13 +163,10 @@ public function testCreateViewPreferredChoicesAsPropertyPath()
             ->method('createView')
             ->with($list, $this->isInstanceOf('\Closure'))
             ->willReturnCallback(function ($list, $preferred) {
-                return $preferred((object) ['property' => true]);
+                return new ChoiceListView((array) $preferred((object) ['property' => true]));
             });
 
-        $this->assertTrue($this->factory->createView(
-            $list,
-            'property'
-        ));
+        $this->assertSame([true], $this->factory->createView($list, 'property')->choices);
     }
 
     /**
@@ -196,13 +195,10 @@ public function testCreateViewPreferredChoicesAsPropertyPathInstance()
             ->method('createView')
             ->with($list, $this->isInstanceOf('\Closure'))
             ->willReturnCallback(function ($list, $preferred) {
-                return $preferred((object) ['property' => true]);
+                return new ChoiceListView((array) $preferred((object) ['property' => true]));
             });
 
-        $this->assertTrue($this->factory->createView(
-            $list,
-            new PropertyPath('property')
-        ));
+        $this->assertSame([true], $this->factory->createView($list, 'property')->choices);
     }
 
     // https://github.com/symfony/symfony/issues/5494
@@ -214,13 +210,10 @@ public function testCreateViewAssumeNullIfPreferredChoicesPropertyPathUnreadable
             ->method('createView')
             ->with($list, $this->isInstanceOf('\Closure'))
             ->willReturnCallback(function ($list, $preferred) {
-                return $preferred((object) ['category' => null]);
+                return new ChoiceListView((array) $preferred((object) ['category' => null]));
             });
 
-        $this->assertFalse($this->factory->createView(
-            $list,
-            'category.preferred'
-        ));
+        $this->assertSame([false], $this->factory->createView($list, 'category.preferred')->choices);
     }
 
     public function testCreateViewLabelsAsPropertyPath()
@@ -231,14 +224,10 @@ public function testCreateViewLabelsAsPropertyPath()
             ->method('createView')
             ->with($list, null, $this->isInstanceOf('\Closure'))
             ->willReturnCallback(function ($list, $preferred, $label) {
-                return $label((object) ['property' => 'label']);
+                return new ChoiceListView((array) $label((object) ['property' => 'label']));
             });
 
-        $this->assertSame('label', $this->factory->createView(
-            $list,
-            null, // preferred choices
-            'property'
-        ));
+        $this->assertSame(['label'], $this->factory->createView($list, null, 'property')->choices);
     }
 
     /**
@@ -268,14 +257,10 @@ public function testCreateViewLabelsAsPropertyPathInstance()
             ->method('createView')
             ->with($list, null, $this->isInstanceOf('\Closure'))
             ->willReturnCallback(function ($list, $preferred, $label) {
-                return $label((object) ['property' => 'label']);
+                return new ChoiceListView((array) $label((object) ['property' => 'label']));
             });
 
-        $this->assertSame('label', $this->factory->createView(
-            $list,
-            null, // preferred choices
-            new PropertyPath('property')
-        ));
+        $this->assertSame(['label'], $this->factory->createView($list, null, new PropertyPath('property'))->choices);
     }
 
     public function testCreateViewIndicesAsPropertyPath()
@@ -286,15 +271,10 @@ public function testCreateViewIndicesAsPropertyPath()
             ->method('createView')
             ->with($list, null, null, $this->isInstanceOf('\Closure'))
             ->willReturnCallback(function ($list, $preferred, $label, $index) {
-                return $index((object) ['property' => 'index']);
+                return new ChoiceListView((array) $index((object) ['property' => 'index']));
             });
 
-        $this->assertSame('index', $this->factory->createView(
-            $list,
-            null, // preferred choices
-            null, // label
-            'property'
-        ));
+        $this->assertSame(['index'], $this->factory->createView($list, null, null, 'property')->choices);
     }
 
     /**
@@ -325,15 +305,10 @@ public function testCreateViewIndicesAsPropertyPathInstance()
             ->method('createView')
             ->with($list, null, null, $this->isInstanceOf('\Closure'))
             ->willReturnCallback(function ($list, $preferred, $label, $index) {
-                return $index((object) ['property' => 'index']);
+                return new ChoiceListView((array) $index((object) ['property' => 'index']));
             });
 
-        $this->assertSame('index', $this->factory->createView(
-            $list,
-            null, // preferred choices
-            null, // label
-            new PropertyPath('property')
-        ));
+        $this->assertSame(['index'], $this->factory->createView($list, null, null, new PropertyPath('property'))->choices);
     }
 
     public function testCreateViewGroupsAsPropertyPath()
@@ -344,16 +319,10 @@ public function testCreateViewGroupsAsPropertyPath()
             ->method('createView')
             ->with($list, null, null, null, $this->isInstanceOf('\Closure'))
             ->willReturnCallback(function ($list, $preferred, $label, $index, $groupBy) {
-                return $groupBy((object) ['property' => 'group']);
+                return new ChoiceListView((array) $groupBy((object) ['property' => 'group']));
             });
 
-        $this->assertSame('group', $this->factory->createView(
-            $list,
-            null, // preferred choices
-            null, // label
-            null, // index
-            'property'
-        ));
+        $this->assertSame(['group'], $this->factory->createView($list, null, null, null, 'property')->choices);
     }
 
     /**
@@ -385,16 +354,10 @@ public function testCreateViewGroupsAsPropertyPathInstance()
             ->method('createView')
             ->with($list, null, null, null, $this->isInstanceOf('\Closure'))
             ->willReturnCallback(function ($list, $preferred, $label, $index, $groupBy) {
-                return $groupBy((object) ['property' => 'group']);
+                return new ChoiceListView((array) $groupBy((object) ['property' => 'group']));
             });
 
-        $this->assertSame('group', $this->factory->createView(
-            $list,
-            null, // preferred choices
-            null, // label
-            null, // index
-            new PropertyPath('property')
-        ));
+        $this->assertSame(['group'], $this->factory->createView($list, null, null, null, new PropertyPath('property'))->choices);
     }
 
     // https://github.com/symfony/symfony/issues/5494
@@ -406,16 +369,10 @@ public function testCreateViewAssumeNullIfGroupsPropertyPathUnreadable()
             ->method('createView')
             ->with($list, null, null, null, $this->isInstanceOf('\Closure'))
             ->willReturnCallback(function ($list, $preferred, $label, $index, $groupBy) {
-                return $groupBy((object) ['group' => null]);
+                return new ChoiceListView((array) $groupBy((object) ['group' => null]));
             });
 
-        $this->assertNull($this->factory->createView(
-            $list,
-            null, // preferred choices
-            null, // label
-            null, // index
-            'group.name'
-        ));
+        $this->assertSame([], $this->factory->createView($list, null, null, null, 'group.name')->choices);
     }
 
     public function testCreateViewAttrAsPropertyPath()
@@ -426,17 +383,10 @@ public function testCreateViewAttrAsPropertyPath()
             ->method('createView')
             ->with($list, null, null, null, null, $this->isInstanceOf('\Closure'))
             ->willReturnCallback(function ($list, $preferred, $label, $index, $groupBy, $attr) {
-                return $attr((object) ['property' => 'attr']);
+                return new ChoiceListView((array) $attr((object) ['property' => 'attr']));
             });
 
-        $this->assertSame('attr', $this->factory->createView(
-            $list,
-            null, // preferred choices
-            null, // label
-            null, // index
-            null, // groups
-            'property'
-        ));
+        $this->assertSame(['attr'], $this->factory->createView($list, null, null, null, null, 'property')->choices);
     }
 
     /**
@@ -469,16 +419,9 @@ public function testCreateViewAttrAsPropertyPathInstance()
             ->method('createView')
             ->with($list, null, null, null, null, $this->isInstanceOf('\Closure'))
             ->willReturnCallback(function ($list, $preferred, $label, $index, $groupBy, $attr) {
-                return $attr((object) ['property' => 'attr']);
+                return new ChoiceListView((array) $attr((object) ['property' => 'attr']));
             });
 
-        $this->assertSame('attr', $this->factory->createView(
-            $list,
-            null, // preferred choices
-            null, // label
-            null, // index
-            null, // groups
-            new PropertyPath('property')
-        ));
+        $this->assertSame(['attr'], $this->factory->createView($list, null, null, null, null, new PropertyPath('property'))->choices);
     }
 }
diff --git a/Tests/ChoiceList/LazyChoiceListTest.php b/Tests/ChoiceList/LazyChoiceListTest.php
index 5888038370..aa6b6b5d49 100644
--- a/Tests/ChoiceList/LazyChoiceListTest.php
+++ b/Tests/ChoiceList/LazyChoiceListTest.php
@@ -56,10 +56,10 @@ public function testGetChoiceLoadersLoadsLoadedListOnFirstCall()
         // The same list is returned by the loader
         $this->loadedList->expects($this->exactly(2))
             ->method('getChoices')
-            ->willReturn('RESULT');
+            ->willReturn(['RESULT']);
 
-        $this->assertSame('RESULT', $this->list->getChoices());
-        $this->assertSame('RESULT', $this->list->getChoices());
+        $this->assertSame(['RESULT'], $this->list->getChoices());
+        $this->assertSame(['RESULT'], $this->list->getChoices());
     }
 
     /**
@@ -96,10 +96,10 @@ public function testGetValuesLoadsLoadedListOnFirstCall()
         // The same list is returned by the loader
         $this->loadedList->expects($this->exactly(2))
             ->method('getValues')
-            ->willReturn('RESULT');
+            ->willReturn(['RESULT']);
 
-        $this->assertSame('RESULT', $this->list->getValues());
-        $this->assertSame('RESULT', $this->list->getValues());
+        $this->assertSame(['RESULT'], $this->list->getValues());
+        $this->assertSame(['RESULT'], $this->list->getValues());
     }
 
     public function testGetStructuredValuesLoadsLoadedListOnFirstCall()
@@ -112,10 +112,10 @@ public function testGetStructuredValuesLoadsLoadedListOnFirstCall()
         // The same list is returned by the loader
         $this->loadedList->expects($this->exactly(2))
             ->method('getStructuredValues')
-            ->willReturn('RESULT');
+            ->willReturn(['RESULT']);
 
-        $this->assertSame('RESULT', $this->list->getStructuredValues());
-        $this->assertSame('RESULT', $this->list->getStructuredValues());
+        $this->assertSame(['RESULT'], $this->list->getStructuredValues());
+        $this->assertSame(['RESULT'], $this->list->getStructuredValues());
     }
 
     public function testGetOriginalKeysLoadsLoadedListOnFirstCall()
@@ -128,10 +128,10 @@ public function testGetOriginalKeysLoadsLoadedListOnFirstCall()
         // The same list is returned by the loader
         $this->loadedList->expects($this->exactly(2))
             ->method('getOriginalKeys')
-            ->willReturn('RESULT');
+            ->willReturn(['RESULT']);
 
-        $this->assertSame('RESULT', $this->list->getOriginalKeys());
-        $this->assertSame('RESULT', $this->list->getOriginalKeys());
+        $this->assertSame(['RESULT'], $this->list->getOriginalKeys());
+        $this->assertSame(['RESULT'], $this->list->getOriginalKeys());
     }
 
     public function testGetChoicesForValuesForwardsCallIfListNotLoaded()
@@ -139,10 +139,10 @@ public function testGetChoicesForValuesForwardsCallIfListNotLoaded()
         $this->loader->expects($this->exactly(2))
             ->method('loadChoicesForValues')
             ->with(['a', 'b'])
-            ->willReturn('RESULT');
+            ->willReturn(['RESULT']);
 
-        $this->assertSame('RESULT', $this->list->getChoicesForValues(['a', 'b']));
-        $this->assertSame('RESULT', $this->list->getChoicesForValues(['a', 'b']));
+        $this->assertSame(['RESULT'], $this->list->getChoicesForValues(['a', 'b']));
+        $this->assertSame(['RESULT'], $this->list->getChoicesForValues(['a', 'b']));
     }
 
     public function testGetChoicesForValuesUsesLoadedList()
@@ -160,13 +160,13 @@ public function testGetChoicesForValuesUsesLoadedList()
         $this->loadedList->expects($this->exactly(2))
             ->method('getChoicesForValues')
             ->with(['a', 'b'])
-            ->willReturn('RESULT');
+            ->willReturn(['RESULT']);
 
         // load choice list
         $this->list->getChoices();
 
-        $this->assertSame('RESULT', $this->list->getChoicesForValues(['a', 'b']));
-        $this->assertSame('RESULT', $this->list->getChoicesForValues(['a', 'b']));
+        $this->assertSame(['RESULT'], $this->list->getChoicesForValues(['a', 'b']));
+        $this->assertSame(['RESULT'], $this->list->getChoicesForValues(['a', 'b']));
     }
 
     /**
@@ -198,12 +198,12 @@ public function testGetValuesForChoicesUsesLoadedList()
         $this->loadedList->expects($this->exactly(2))
             ->method('getValuesForChoices')
             ->with(['a', 'b'])
-            ->willReturn('RESULT');
+            ->willReturn(['RESULT']);
 
         // load choice list
         $this->list->getChoices();
 
-        $this->assertSame('RESULT', $this->list->getValuesForChoices(['a', 'b']));
-        $this->assertSame('RESULT', $this->list->getValuesForChoices(['a', 'b']));
+        $this->assertSame(['RESULT'], $this->list->getValuesForChoices(['a', 'b']));
+        $this->assertSame(['RESULT'], $this->list->getValuesForChoices(['a', 'b']));
     }
 }
diff --git a/Tests/Extension/Csrf/Type/FormTypeCsrfExtensionTest.php b/Tests/Extension/Csrf/Type/FormTypeCsrfExtensionTest.php
index 232fd52b46..ea7fc5ff50 100644
--- a/Tests/Extension/Csrf/Type/FormTypeCsrfExtensionTest.php
+++ b/Tests/Extension/Csrf/Type/FormTypeCsrfExtensionTest.php
@@ -142,7 +142,7 @@ public function testGenerateCsrfTokenUsesFormNameAsIntentionByDefault()
         $this->tokenManager->expects($this->once())
             ->method('getToken')
             ->with('FORM_NAME')
-            ->willReturn('token');
+            ->willReturn(new CsrfToken('TOKEN_ID', 'token'));
 
         $view = $this->factory
             ->createNamed('FORM_NAME', 'Symfony\Component\Form\Extension\Core\Type\FormType', null, [
@@ -160,7 +160,7 @@ public function testGenerateCsrfTokenUsesTypeClassAsIntentionIfEmptyFormName()
         $this->tokenManager->expects($this->once())
             ->method('getToken')
             ->with('Symfony\Component\Form\Extension\Core\Type\FormType')
-            ->willReturn('token');
+            ->willReturn(new CsrfToken('TOKEN_ID', 'token'));
 
         $view = $this->factory
             ->createNamed('', 'Symfony\Component\Form\Extension\Core\Type\FormType', null, [
diff --git a/Tests/Extension/DataCollector/FormDataExtractorTest.php b/Tests/Extension/DataCollector/FormDataExtractorTest.php
index 6d897c711f..4b61223773 100644
--- a/Tests/Extension/DataCollector/FormDataExtractorTest.php
+++ b/Tests/Extension/DataCollector/FormDataExtractorTest.php
@@ -16,6 +16,7 @@
 use Symfony\Component\Form\CallbackTransformer;
 use Symfony\Component\Form\Exception\TransformationFailedException;
 use Symfony\Component\Form\Extension\DataCollector\FormDataExtractor;
+use Symfony\Component\Form\Extension\Core\Type\HiddenType;
 use Symfony\Component\Form\FormBuilder;
 use Symfony\Component\Form\FormError;
 use Symfony\Component\Form\FormView;
@@ -57,7 +58,7 @@ public function testExtractConfiguration()
         $type = $this->getMockBuilder('Symfony\Component\Form\ResolvedFormTypeInterface')->getMock();
         $type->expects($this->any())
             ->method('getInnerType')
-            ->willReturn(new \stdClass());
+            ->willReturn(new HiddenType());
 
         $form = $this->createBuilder('name')
             ->setType($type)
@@ -66,7 +67,7 @@ public function testExtractConfiguration()
         $this->assertSame([
             'id' => 'name',
             'name' => 'name',
-            'type_class' => 'stdClass',
+            'type_class' => HiddenType::class,
             'synchronized' => true,
             'passed_options' => [],
             'resolved_options' => [],
@@ -78,7 +79,7 @@ public function testExtractConfigurationSortsPassedOptions()
         $type = $this->getMockBuilder('Symfony\Component\Form\ResolvedFormTypeInterface')->getMock();
         $type->expects($this->any())
             ->method('getInnerType')
-            ->willReturn(new \stdClass());
+            ->willReturn(new HiddenType());
 
         $options = [
             'b' => 'foo',
@@ -96,7 +97,7 @@ public function testExtractConfigurationSortsPassedOptions()
         $this->assertSame([
             'id' => 'name',
             'name' => 'name',
-            'type_class' => 'stdClass',
+            'type_class' => HiddenType::class,
             'synchronized' => true,
             'passed_options' => [
                 'a' => 'bar',
@@ -112,7 +113,7 @@ public function testExtractConfigurationSortsResolvedOptions()
         $type = $this->getMockBuilder('Symfony\Component\Form\ResolvedFormTypeInterface')->getMock();
         $type->expects($this->any())
             ->method('getInnerType')
-            ->willReturn(new \stdClass());
+            ->willReturn(new HiddenType());
 
         $options = [
             'b' => 'foo',
@@ -127,7 +128,7 @@ public function testExtractConfigurationSortsResolvedOptions()
         $this->assertSame([
             'id' => 'name',
             'name' => 'name',
-            'type_class' => 'stdClass',
+            'type_class' => HiddenType::class,
             'synchronized' => true,
             'passed_options' => [],
             'resolved_options' => [
@@ -143,7 +144,7 @@ public function testExtractConfigurationBuildsIdRecursively()
         $type = $this->getMockBuilder('Symfony\Component\Form\ResolvedFormTypeInterface')->getMock();
         $type->expects($this->any())
             ->method('getInnerType')
-            ->willReturn(new \stdClass());
+            ->willReturn(new HiddenType());
 
         $grandParent = $this->createBuilder('grandParent')
             ->setCompound(true)
@@ -163,7 +164,7 @@ public function testExtractConfigurationBuildsIdRecursively()
         $this->assertSame([
             'id' => 'grandParent_parent_name',
             'name' => 'name',
-            'type_class' => 'stdClass',
+            'type_class' => HiddenType::class,
             'synchronized' => true,
             'passed_options' => [],
             'resolved_options' => [],
diff --git a/Tests/FormFactoryTest.php b/Tests/FormFactoryTest.php
index ddd5b4bb72..79421be635 100644
--- a/Tests/FormFactoryTest.php
+++ b/Tests/FormFactoryTest.php
@@ -14,6 +14,7 @@
 use PHPUnit\Framework\MockObject\MockObject;
 use PHPUnit\Framework\TestCase;
 use Symfony\Component\Form\FormFactory;
+use Symfony\Component\Form\FormInterface;
 use Symfony\Component\Form\FormTypeGuesserChain;
 use Symfony\Component\Form\Guess\Guess;
 use Symfony\Component\Form\Guess\TypeGuess;
@@ -193,11 +194,13 @@ public function testCreateUsesBlockPrefixIfTypeGivenAsString()
             ->method('buildForm')
             ->with($this->builder, $resolvedOptions);
 
+        $form = $this->createMock(FormInterface::class);
+
         $this->builder->expects($this->once())
             ->method('getForm')
-            ->willReturn('FORM');
+            ->willReturn($form);
 
-        $this->assertSame('FORM', $this->factory->create('TYPE', null, $options));
+        $this->assertSame($form, $this->factory->create('TYPE', null, $options));
     }
 
     public function testCreateNamed()
@@ -224,11 +227,13 @@ public function testCreateNamed()
             ->method('buildForm')
             ->with($this->builder, $resolvedOptions);
 
+        $form = $this->createMock(FormInterface::class);
+
         $this->builder->expects($this->once())
             ->method('getForm')
-            ->willReturn('FORM');
+            ->willReturn($form);
 
-        $this->assertSame('FORM', $this->factory->createNamed('name', 'type', null, $options));
+        $this->assertSame($form, $this->factory->createNamed('name', 'type', null, $options));
     }
 
     public function testCreateBuilderForPropertyWithoutTypeGuesser()
@@ -242,11 +247,11 @@ public function testCreateBuilderForPropertyWithoutTypeGuesser()
         $factory->expects($this->once())
             ->method('createNamedBuilder')
             ->with('firstName', 'Symfony\Component\Form\Extension\Core\Type\TextType', null, [])
-            ->willReturn('builderInstance');
+            ->willReturn($this->builder);
 
         $this->builder = $factory->createBuilderForProperty('Application\Author', 'firstName');
 
-        $this->assertEquals('builderInstance', $this->builder);
+        $this->assertSame($this->builder, $this->builder);
     }
 
     public function testCreateBuilderForPropertyCreatesFormWithHighestConfidence()
@@ -274,11 +279,11 @@ public function testCreateBuilderForPropertyCreatesFormWithHighestConfidence()
         $factory->expects($this->once())
             ->method('createNamedBuilder')
             ->with('firstName', 'Symfony\Component\Form\Extension\Core\Type\PasswordType', null, ['attr' => ['maxlength' => 7]])
-            ->willReturn('builderInstance');
+            ->willReturn($this->builder);
 
         $this->builder = $factory->createBuilderForProperty('Application\Author', 'firstName');
 
-        $this->assertEquals('builderInstance', $this->builder);
+        $this->assertSame($this->builder, $this->builder);
     }
 
     public function testCreateBuilderCreatesTextFormIfNoGuess()
@@ -293,11 +298,11 @@ public function testCreateBuilderCreatesTextFormIfNoGuess()
         $factory->expects($this->once())
             ->method('createNamedBuilder')
             ->with('firstName', 'Symfony\Component\Form\Extension\Core\Type\TextType')
-            ->willReturn('builderInstance');
+            ->willReturn($this->builder);
 
         $this->builder = $factory->createBuilderForProperty('Application\Author', 'firstName');
 
-        $this->assertEquals('builderInstance', $this->builder);
+        $this->assertSame($this->builder, $this->builder);
     }
 
     public function testOptionsCanBeOverridden()
@@ -316,7 +321,7 @@ public function testOptionsCanBeOverridden()
         $factory->expects($this->once())
             ->method('createNamedBuilder')
             ->with('firstName', 'Symfony\Component\Form\Extension\Core\Type\TextType', null, ['attr' => ['class' => 'foo', 'maxlength' => 11]])
-            ->willReturn('builderInstance');
+            ->willReturn($this->builder);
 
         $this->builder = $factory->createBuilderForProperty(
             'Application\Author',
@@ -325,7 +330,7 @@ public function testOptionsCanBeOverridden()
             ['attr' => ['maxlength' => 11]]
         );
 
-        $this->assertEquals('builderInstance', $this->builder);
+        $this->assertSame($this->builder, $this->builder);
     }
 
     public function testCreateBuilderUsesMaxLengthIfFound()
@@ -351,14 +356,14 @@ public function testCreateBuilderUsesMaxLengthIfFound()
         $factory->expects($this->once())
             ->method('createNamedBuilder')
             ->with('firstName', 'Symfony\Component\Form\Extension\Core\Type\TextType', null, ['attr' => ['maxlength' => 20]])
-            ->willReturn('builderInstance');
+            ->willReturn($this->builder);
 
         $this->builder = $factory->createBuilderForProperty(
             'Application\Author',
             'firstName'
         );
 
-        $this->assertEquals('builderInstance', $this->builder);
+        $this->assertSame($this->builder, $this->builder);
     }
 
     public function testCreateBuilderUsesMaxLengthAndPattern()
@@ -384,7 +389,7 @@ public function testCreateBuilderUsesMaxLengthAndPattern()
         $factory->expects($this->once())
             ->method('createNamedBuilder')
             ->with('firstName', 'Symfony\Component\Form\Extension\Core\Type\TextType', null, ['attr' => ['maxlength' => 20, 'pattern' => '.{5,}', 'class' => 'tinymce']])
-            ->willReturn('builderInstance');
+            ->willReturn($this->builder);
 
         $this->builder = $factory->createBuilderForProperty(
             'Application\Author',
@@ -393,7 +398,7 @@ public function testCreateBuilderUsesMaxLengthAndPattern()
             ['attr' => ['class' => 'tinymce']]
         );
 
-        $this->assertEquals('builderInstance', $this->builder);
+        $this->assertSame($this->builder, $this->builder);
     }
 
     public function testCreateBuilderUsesRequiredSettingWithHighestConfidence()
@@ -419,14 +424,14 @@ public function testCreateBuilderUsesRequiredSettingWithHighestConfidence()
         $factory->expects($this->once())
             ->method('createNamedBuilder')
             ->with('firstName', 'Symfony\Component\Form\Extension\Core\Type\TextType', null, ['required' => false])
-            ->willReturn('builderInstance');
+            ->willReturn($this->builder);
 
         $this->builder = $factory->createBuilderForProperty(
             'Application\Author',
             'firstName'
         );
 
-        $this->assertEquals('builderInstance', $this->builder);
+        $this->assertSame($this->builder, $this->builder);
     }
 
     public function testCreateBuilderUsesPatternIfFound()
@@ -452,14 +457,14 @@ public function testCreateBuilderUsesPatternIfFound()
         $factory->expects($this->once())
             ->method('createNamedBuilder')
             ->with('firstName', 'Symfony\Component\Form\Extension\Core\Type\TextType', null, ['attr' => ['pattern' => '[a-zA-Z]']])
-            ->willReturn('builderInstance');
+            ->willReturn($this->builder);
 
         $this->builder = $factory->createBuilderForProperty(
             'Application\Author',
             'firstName'
         );
 
-        $this->assertEquals('builderInstance', $this->builder);
+        $this->assertSame($this->builder, $this->builder);
     }
 
     private function getMockFactory(array $methods = [])