diff --git a/core/core.services.yml b/core/core.services.yml
index f160803..9142a0d 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -7,8 +7,6 @@ services:
   cache.backend.database:
     class: Drupal\Core\Cache\DatabaseBackendFactory
     arguments: ['@database']
-  cache.backend.memory:
-    class: Drupal\Core\Cache\MemoryBackendFactory
   cache.bootstrap:
     class: Drupal\Core\Cache\CacheBackendInterface
     tags:
diff --git a/core/modules/simpletest/lib/Drupal/simpletest/DrupalUnitTestBase.php b/core/modules/simpletest/lib/Drupal/simpletest/DrupalUnitTestBase.php
index 0e40243..f3c220d 100644
--- a/core/modules/simpletest/lib/Drupal/simpletest/DrupalUnitTestBase.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/DrupalUnitTestBase.php
@@ -160,7 +160,7 @@ public function containerBuild(ContainerBuilder $container) {
     $this->container->setParameter('language.default_values', Language::$defaultValues);
 
     $container->register('lock', 'Drupal\Core\Lock\NullLockBackend');
-    $this->settingsSet('cache', array('default' => 'cache.backend.memory'));
+    $container->register('cache_factory', 'Drupal\Core\Cache\MemoryBackendFactory');
 
     $container
       ->register('config.storage', 'Drupal\Core\Config\FileStorage')
diff --git a/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php b/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
index 05195e0..b5c0e34 100644
--- a/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
@@ -743,10 +743,10 @@ protected function setUp() {
         NestedArray::setValue($GLOBALS['conf'], array_merge(array($config_base), explode('.', $name)), $value);
       }
     }
+
     $this->settingsSet('file_public_path', $this->public_files_directory);
     // Execute the non-interactive installer.
     require_once DRUPAL_ROOT . '/core/includes/install.core.inc';
-    $this->settingsSet('cache', array('default' => 'cache.backend.memory'));
     $parameters = $this->installParameters();
     install_drupal($parameters);