diff --git a/core/lib/Drupal/Core/TypedData/Validation/ExecutionContext.php b/core/lib/Drupal/Core/TypedData/Validation/ExecutionContext.php
index a20fa52..100718e 100644
--- a/core/lib/Drupal/Core/TypedData/Validation/ExecutionContext.php
+++ b/core/lib/Drupal/Core/TypedData/Validation/ExecutionContext.php
@@ -21,7 +21,7 @@
 class ExecutionContext implements ExecutionContextInterface {
 
   /**
-   * @var \Symfony\Component\Validator\ValidatorInterface
+   * @var \Symfony\Component\Validator\Validator\ValidatorInterface
    */
   protected $validator;
 
diff --git a/core/modules/system/tests/modules/theme_test/src/EventSubscriber/ThemeTestSubscriber.php b/core/modules/system/tests/modules/theme_test/src/EventSubscriber/ThemeTestSubscriber.php
index d5f9110..bc8d1d0 100644
--- a/core/modules/system/tests/modules/theme_test/src/EventSubscriber/ThemeTestSubscriber.php
+++ b/core/modules/system/tests/modules/theme_test/src/EventSubscriber/ThemeTestSubscriber.php
@@ -17,7 +17,8 @@ class ThemeTestSubscriber implements EventSubscriberInterface {
   /**
    * The used container.
    *
-   * @var \Symfony\Component\DependencyInjection\IntrospectableContainerInterface
+   * @todo This variable is never initialzed, so we don't know what it is.
+   *   See https://www.drupal.org/node/2721315
    */
   protected $container;
 
diff --git a/core/tests/Drupal/Tests/Component/EventDispatcher/ContainerAwareEventDispatcherTest.php b/core/tests/Drupal/Tests/Component/EventDispatcher/ContainerAwareEventDispatcherTest.php
index dfd12bb..48f7455 100644
--- a/core/tests/Drupal/Tests/Component/EventDispatcher/ContainerAwareEventDispatcherTest.php
+++ b/core/tests/Drupal/Tests/Component/EventDispatcher/ContainerAwareEventDispatcherTest.php
@@ -6,9 +6,10 @@
 use Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher;
 use Symfony\Component\DependencyInjection\Container;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
+use Symfony\Component\DependencyInjection\ContainerInterface;
 use Symfony\Component\EventDispatcher\Tests\CallableClass;
-use Symfony\Component\EventDispatcher\Tests\TestEventListener;
 use Symfony\Component\EventDispatcher\Tests\ContainerAwareEventDispatcherTest as SymfonyContainerAwareEventDispatcherTest;
+use Symfony\Component\EventDispatcher\Tests\TestEventListener;
 
 /**
  * Unit tests for the ContainerAwareEventDispatcher.
@@ -37,7 +38,7 @@ public function testGetListenersWithCallables()
         // When passing in callables exclusively as listeners into the event
         // dispatcher constructor, the event dispatcher must not attempt to
         // resolve any services.
-        $container = $this->getMock('Symfony\Component\DependencyInjection\IntrospectableContainerInterface');
+        $container = $this->getMock(ContainerInterface::class);
         $container->expects($this->never())->method($this->anything());
 
         $firstListener = new CallableClass();
@@ -72,7 +73,7 @@ public function testDispatchWithCallables()
         // When passing in callables exclusively as listeners into the event
         // dispatcher constructor, the event dispatcher must not attempt to
         // resolve any services.
-        $container = $this->getMock('Symfony\Component\DependencyInjection\IntrospectableContainerInterface');
+        $container = $this->getMock(ContainerInterface::class);
         $container->expects($this->never())->method($this->anything());
 
         $firstListener = new CallableClass();
diff --git a/core/tests/Drupal/Tests/Core/Entity/ContentEntityBaseUnitTest.php b/core/tests/Drupal/Tests/Core/Entity/ContentEntityBaseUnitTest.php
index 4c39b4c..cf4acf7 100644
--- a/core/tests/Drupal/Tests/Core/Entity/ContentEntityBaseUnitTest.php
+++ b/core/tests/Drupal/Tests/Core/Entity/ContentEntityBaseUnitTest.php
@@ -9,6 +9,7 @@
 use Drupal\Core\Language\LanguageInterface;
 use Drupal\Tests\UnitTestCase;
 use Drupal\Core\Language\Language;
+use Symfony\Component\Validator\Validator\ValidatorInterface;
 
 /**
  * @coversDefaultClass \Drupal\Core\Entity\ContentEntityBase
@@ -322,7 +323,7 @@ public function testPreSaveRevision() {
    * @covers ::validate
    */
   public function testValidate() {
-    $validator = $this->getMock('\Symfony\Component\Validator\ValidatorInterface');
+    $validator = $this->getMock(ValidatorInterface::class);
     /** @var \Symfony\Component\Validator\ConstraintViolationList|\PHPUnit_Framework_MockObject_MockObject $empty_violation_list */
     $empty_violation_list = $this->getMockBuilder('\Symfony\Component\Validator\ConstraintViolationList')
       ->setMethods(NULL)
@@ -358,7 +359,7 @@ public function testValidate() {
    * @expectedExceptionMessage Entity validation was skipped.
    */
   public function testRequiredValidation() {
-    $validator = $this->getMock('\Symfony\Component\Validator\ValidatorInterface');
+    $validator = $this->getMock(ValidatorInterface::class);
     /** @var \Symfony\Component\Validator\ConstraintViolationList|\PHPUnit_Framework_MockObject_MockObject $empty_violation_list */
     $empty_violation_list = $this->getMockBuilder('\Symfony\Component\Validator\ConstraintViolationList')
       ->setMethods(NULL)