diff -u b/core/modules/comment/tests/Drupal/comment/Tests/Entity/CommentLockTest.php b/core/modules/comment/tests/Drupal/comment/Tests/Entity/CommentLockTest.php
--- b/core/modules/comment/tests/Drupal/comment/Tests/Entity/CommentLockTest.php
+++ b/core/modules/comment/tests/Drupal/comment/Tests/Entity/CommentLockTest.php
@@ -33,6 +33,7 @@
    */
   public function testLocks() {
     $container = new ContainerBuilder();
+    $container->set('module_handler', $this->getMock('Drupal\Core\Extension\ModuleHandlerInterface'));
     $container->set('current_user', $this->getMock('Drupal\Core\Session\AccountInterface'));
     $container->register('request', 'Symfony\Component\HttpFoundation\Request');
     $lock = $this->getMock('Drupal\Core\Lock\LockBackendInterface');