diff -u b/core/modules/system/lib/Drupal/system/Tests/Plugin/CacheDecoratorTest.php b/core/modules/system/lib/Drupal/system/Tests/Plugin/CacheDecoratorTest.php
--- b/core/modules/system/lib/Drupal/system/Tests/Plugin/CacheDecoratorTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Plugin/CacheDecoratorTest.php
@@ -7,7 +7,8 @@
 
 namespace Drupal\system\Tests\Plugin;
 
-use Drupal\Core\Flood\MemoryBackend;
+use Drupal\Core\Cache\MemoryBackendFactory;
+use Drupal\Core\Cache\MemoryBackend;
 use Drupal\system\Tests\Plugin\Discovery\DiscoveryTestBase;
 use Drupal\Component\Plugin\Discovery\StaticDiscovery;
 use Drupal\Core\Plugin\Discovery\CacheDecorator;
@@ -47,7 +48,7 @@
     // Use a non-db cache backend, so that we can use DiscoveryTestBase (which
     // extends UnitTestBase).
     // @todo switch to injecting the MemoryBackend http://drupal.org/node/1903346
-    drupal_container()->set("cache.$this->cacheBin", new MemoryBackend());
+    drupal_container()->set("cache.$this->cacheBin", new MemoryBackend($this->cacheBin));
 
     // Create discovery objects to test.
     $this->emptyDiscovery = new StaticDiscovery();