diff --git a/core/tests/Drupal/Tests/Core/Entity/EntityTypeManagerTest.php b/core/tests/Drupal/Tests/Core/Entity/EntityTypeManagerTest.php
index 300a4bfc1e3..170157d0635 100644
--- a/core/tests/Drupal/Tests/Core/Entity/EntityTypeManagerTest.php
+++ b/core/tests/Drupal/Tests/Core/Entity/EntityTypeManagerTest.php
@@ -243,8 +243,8 @@ class EntityTypeManagerTest extends UnitTestCase {
 
     $apple_form = $this->entityTypeManager->getFormObject('apple', 'default');
     $this->assertInstanceOf(TestEntityForm::class, $apple_form);
-    $this->assertAttributeInstanceOf(ModuleHandlerInterface::class, 'moduleHandler', $apple_form);
-    $this->assertAttributeInstanceOf(TranslationInterface::class, 'stringTranslation', $apple_form);
+    $this->assertInstanceOf(ModuleHandlerInterface::class, $apple_form->moduleHandler);
+    $this->assertInstanceOf(TranslationInterface::class, $apple_form->stringTranslation);
 
     $banana_form = $this->entityTypeManager->getFormObject('banana', 'default');
     $this->assertInstanceOf(TestEntityFormInjected::class, $banana_form);
@@ -272,7 +272,7 @@ class EntityTypeManagerTest extends UnitTestCase {
    * @covers ::getHandler
    */
   public function testGetHandler() {
-    $class = $this->getTestHandlerClass();
+    $class = get_class($this->getMockForAbstractClass(TestEntityHandlerBase::class));
     $apple = $this->prophesize(EntityTypeInterface::class);
     $apple->getHandlerClass('storage')->willReturn($class);
 
@@ -282,8 +282,8 @@ class EntityTypeManagerTest extends UnitTestCase {
 
     $apple_controller = $this->entityTypeManager->getHandler('apple', 'storage');
     $this->assertInstanceOf($class, $apple_controller);
-    $this->assertAttributeInstanceOf(ModuleHandlerInterface::class, 'moduleHandler', $apple_controller);
-    $this->assertAttributeInstanceOf(TranslationInterface::class, 'stringTranslation', $apple_controller);
+    $this->assertInstanceOf(ModuleHandlerInterface::class, $apple_controller->moduleHandler);
+    $this->assertInstanceOf(TranslationInterface::class, $apple_controller->stringTranslation);
   }
 
   /**
@@ -312,8 +312,8 @@ class EntityTypeManagerTest extends UnitTestCase {
 
     $apple_route_provider = $this->entityTypeManager->getRouteProviders('apple');
     $this->assertInstanceOf(TestRouteProvider::class, $apple_route_provider['default']);
-    $this->assertAttributeInstanceOf(ModuleHandlerInterface::class, 'moduleHandler', $apple_route_provider['default']);
-    $this->assertAttributeInstanceOf(TranslationInterface::class, 'stringTranslation', $apple_route_provider['default']);
+    $this->assertInstanceOf(ModuleHandlerInterface::class, $apple_route_provider['default']->moduleHandler);
+    $this->assertInstanceOf(TranslationInterface::class, $apple_route_provider['default']->stringTranslation);
   }
 
   /**
@@ -396,6 +396,26 @@ class EntityTypeManagerTest extends UnitTestCase {
 
 }
 
+/**
+ * Provides a test entity handler.
+ */
+abstract class TestEntityHandlerBase extends EntityHandlerBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public $moduleHandler;
+
+  /**
+   * {@inheritdoc}
+   */
+  public $stringTranslation;
+
+}
+
+/**
+ * Provides a test entity type manager.
+ */
 class TestEntityTypeManager extends EntityTypeManager {
 
   /**
@@ -415,6 +435,16 @@ class TestEntityTypeManager extends EntityTypeManager {
  */
 class TestEntityForm extends EntityHandlerBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  public $moduleHandler;
+
+  /**
+   * {@inheritdoc}
+   */
+  public $stringTranslation;
+
   /**
    * The entity type manager.
    *
@@ -496,4 +526,14 @@ class TestEntityFormInjected extends TestEntityForm implements ContainerInjectio
  */
 class TestRouteProvider extends EntityHandlerBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  public $moduleHandler;
+
+  /**
+   * {@inheritdoc}
+   */
+  public $stringTranslation;
+
 }
diff --git a/core/tests/Drupal/Tests/Traits/PHPUnit8Warnings.php b/core/tests/Drupal/Tests/Traits/PHPUnit8Warnings.php
index be0f3f1929e..1e3e9041705 100644
--- a/core/tests/Drupal/Tests/Traits/PHPUnit8Warnings.php
+++ b/core/tests/Drupal/Tests/Traits/PHPUnit8Warnings.php
@@ -26,7 +26,6 @@ trait PHPUnit8Warnings {
     'readAttribute() is deprecated and will be removed in PHPUnit 9.',
     'getObjectAttribute() is deprecated and will be removed in PHPUnit 9.',
     'assertAttributeEquals() is deprecated and will be removed in PHPUnit 9.',
-    'assertAttributeInstanceOf() is deprecated and will be removed in PHPUnit 9.',
   ];
 
   /**