diff --git a/core/tests/Drupal/Tests/Component/Annotation/AnnotatedClassDiscoveryCachedTest.php b/core/tests/Drupal/Tests/Component/Annotation/AnnotatedClassDiscoveryCachedTest.php
new file mode 100644
index 0000000000..ef839c9075
--- /dev/null
+++ b/core/tests/Drupal/Tests/Component/Annotation/AnnotatedClassDiscoveryCachedTest.php
@@ -0,0 +1,63 @@
+<?php
+
+namespace Drupal\Tests\Component\Annotation;
+
+use Drupal\Component\Annotation\Plugin\Discovery\AnnotatedClassDiscovery;
+use Drupal\Component\FileCache\FileCacheFactory;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * @coversDefaultClass \Drupal\Component\Annotation\Plugin\Discovery\AnnotatedClassDiscovery
+ * @group Annotation
+ */
+class AnnotatedClassDiscoveryCachedTest extends TestCase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+    // Ensure that FileCacheFactory has a prefix.
+    FileCacheFactory::setPrefix('prefix');
+  }
+
+  /**
+   * Test that getDefinitions() retrieves the file cache correctly.
+   *
+   * @covers ::getDefinitions
+   */
+  public function testGetDefinitions() {
+    // Path to the classes which we'll discover and parse annotation.
+    $discovery_path  = __DIR__ . '/Fixtures';
+    // File path that should be discovered within that directory.
+    $file_path = $discovery_path . '/PluginNamespace/DiscoveryTest1.php';
+
+    $discovery = new AnnotatedClassDiscovery(['com\example' => [$discovery_path]]);
+    $this->assertEquals([
+      'discovery_test_1' => [
+        'id' => 'discovery_test_1',
+        'class' => 'com\example\PluginNamespace\DiscoveryTest1',
+      ],
+    ], $discovery->getDefinitions());
+
+    // Gain access to the file cache so we can change it.
+    $ref_file_cache = new \ReflectionProperty($discovery, 'fileCache');
+    $ref_file_cache->setAccessible(TRUE);
+    /* @var $file_cache \Drupal\Component\FileCache\FileCacheInterface */
+    $file_cache = $ref_file_cache->getValue($discovery);
+    // The file cache is keyed by the file path, and we'll add some known
+    // content to test against.
+    $file_cache->set($file_path, [
+      'id' => 'wrong_id',
+      'content' => serialize(['an' => 'array']),
+    ]);
+
+    // Now perform the same query and check for the cached results.
+    $this->assertEquals([
+      'wrong_id' => [
+        'an' => 'array',
+      ],
+    ], $discovery->getDefinitions());
+  }
+
+}
diff --git a/core/tests/Drupal/Tests/Component/Annotation/AnnotatedClassDiscoveryTest.php b/core/tests/Drupal/Tests/Component/Annotation/AnnotatedClassDiscoveryTest.php
index 333a2514f2..85c6f010f3 100644
--- a/core/tests/Drupal/Tests/Component/Annotation/AnnotatedClassDiscoveryTest.php
+++ b/core/tests/Drupal/Tests/Component/Annotation/AnnotatedClassDiscoveryTest.php
@@ -4,13 +4,26 @@
 
 use Drupal\Component\Annotation\Plugin;
 use Drupal\Component\Annotation\Plugin\Discovery\AnnotatedClassDiscovery;
-use Drupal\Tests\UnitTestCase;
+use Drupal\Component\FileCache\FileCacheFactory;
+use PHPUnit\Framework\TestCase;
 
 /**
  * @coversDefaultClass \Drupal\Component\Annotation\Plugin\Discovery\AnnotatedClassDiscovery
  * @group Annotation
  */
-class AnnotatedClassDiscoveryTest extends UnitTestCase {
+class AnnotatedClassDiscoveryTest extends TestCase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+    // Ensure that the NullFileCache implementation is used for the FileCache as
+    // unit tests should not be relying on caches implicitly.
+    FileCacheFactory::setConfiguration([FileCacheFactory::DISABLE_CACHE => TRUE]);
+    // Ensure that FileCacheFactory has a prefix.
+    FileCacheFactory::setPrefix('prefix');
+  }
 
   /**
    * @covers ::__construct
diff --git a/core/tests/Drupal/Tests/Component/Annotation/AnnotationBaseTest.php b/core/tests/Drupal/Tests/Component/Annotation/AnnotationBaseTest.php
index 80c8988984..91d5ae28c3 100644
--- a/core/tests/Drupal/Tests/Component/Annotation/AnnotationBaseTest.php
+++ b/core/tests/Drupal/Tests/Component/Annotation/AnnotationBaseTest.php
@@ -3,13 +3,13 @@
 namespace Drupal\Tests\Component\Annotation;
 
 use Drupal\Component\Annotation\AnnotationBase;
-use Drupal\Tests\UnitTestCase;
+use PHPUnit\Framework\TestCase;
 
 /**
  * @coversDefaultClass \Drupal\Component\Annotation\AnnotationBase
  * @group Annotation
  */
-class AnnotationBaseTest extends UnitTestCase {
+class AnnotationBaseTest extends TestCase {
 
   /**
    * @covers ::getProvider
diff --git a/core/tests/Drupal/Tests/Component/Annotation/MockFileFinderTest.php b/core/tests/Drupal/Tests/Component/Annotation/MockFileFinderTest.php
index 157f5a5335..697551c33a 100644
--- a/core/tests/Drupal/Tests/Component/Annotation/MockFileFinderTest.php
+++ b/core/tests/Drupal/Tests/Component/Annotation/MockFileFinderTest.php
@@ -3,13 +3,13 @@
 namespace Drupal\Tests\Component\Annotation;
 
 use Drupal\Component\Annotation\Reflection\MockFileFinder;
-use Drupal\Tests\UnitTestCase;
+use PHPUnit\Framework\TestCase;
 
 /**
  * @coversDefaultClass \Drupal\Component\Annotation\Reflection\MockFileFinder
  * @group Annotation
  */
-class MockFileFinderTest extends UnitTestCase {
+class MockFileFinderTest extends TestCase {
 
   /**
    * @covers ::create
diff --git a/core/tests/Drupal/Tests/Component/Annotation/PluginIdTest.php b/core/tests/Drupal/Tests/Component/Annotation/PluginIdTest.php
index 2c00c0c0e3..f115de34f1 100644
--- a/core/tests/Drupal/Tests/Component/Annotation/PluginIdTest.php
+++ b/core/tests/Drupal/Tests/Component/Annotation/PluginIdTest.php
@@ -3,25 +3,25 @@
 namespace Drupal\Tests\Component\Annotation;
 
 use Drupal\Component\Annotation\PluginID;
-use Drupal\Tests\UnitTestCase;
+use PHPUnit\Framework\TestCase;
 
 /**
  * @coversDefaultClass \Drupal\Component\Annotation\PluginId
  * @group Annotation
  */
-class PluginIdTest extends UnitTestCase {
+class PluginIdTest extends TestCase {
 
   /**
    * @covers ::get
    */
   public function testGet() {
     // Assert plugin starts empty regardless of constructor.
-    $plugin = new PluginId([
+    $plugin = new PluginID([
       'foo' => 'bar',
       'biz' => [
         'baz' => 'boom',
       ],
-      'nestedAnnotation' => new PluginId([
+      'nestedAnnotation' => new PluginID([
         'foo' => 'bar',
       ]),
       'value' => 'biz',
@@ -47,7 +47,7 @@ public function testGet() {
    * @covers ::getId
    */
   public function testGetId() {
-    $plugin = new PluginId([]);
+    $plugin = new PluginID([]);
     $plugin->value = 'example';
     $this->assertEquals('example', $plugin->getId());
   }
diff --git a/core/tests/Drupal/Tests/Component/Annotation/PluginTest.php b/core/tests/Drupal/Tests/Component/Annotation/PluginTest.php
index 84f99859f2..d942764005 100644
--- a/core/tests/Drupal/Tests/Component/Annotation/PluginTest.php
+++ b/core/tests/Drupal/Tests/Component/Annotation/PluginTest.php
@@ -3,13 +3,13 @@
 namespace Drupal\Tests\Component\Annotation;
 
 use Drupal\Component\Annotation\Plugin;
-use Drupal\Tests\UnitTestCase;
+use PHPUnit\Framework\TestCase;
 
 /**
  * @coversDefaultClass \Drupal\Component\Annotation\Plugin
  * @group Annotation
  */
-class PluginTest extends UnitTestCase {
+class PluginTest extends TestCase {
 
   /**
    * @covers ::__construct