diff -u b/core/tests/Drupal/KernelTests/Core/Routing/RouteProviderTest.php b/core/tests/Drupal/KernelTests/Core/Routing/RouteProviderTest.php
--- b/core/tests/Drupal/KernelTests/Core/Routing/RouteProviderTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Routing/RouteProviderTest.php
@@ -83,7 +83,7 @@
   protected function setUp() {
     parent::setUp();
     $this->fixtures = new RoutingFixtures();
-    $this->state = new State(new KeyValueMemoryFactory(), new MemoryBackend('test'), new NullLockBackend());
+    $this->state = new State(new KeyValueMemoryFactory(), new MemoryBackend(new PhpSerialize()), new NullLockBackend());
     $this->currentPath = new CurrentPathStack(new RequestStack());
     $this->cache = new MemoryBackend(new PhpSerialize());
     $this->pathProcessor = \Drupal::service('path_processor_manager');
diff -u b/core/tests/Drupal/Tests/Core/Render/RendererBubblingTest.php b/core/tests/Drupal/Tests/Core/Render/RendererBubblingTest.php
--- b/core/tests/Drupal/Tests/Core/Render/RendererBubblingTest.php
+++ b/core/tests/Drupal/Tests/Core/Render/RendererBubblingTest.php
@@ -505,7 +505,7 @@
     $this->setupMemoryCache();
 
     // Mock the State service.
-    $memory_state = new State(new KeyValueMemoryFactory(), new MemoryBackend('test'), new NullLockBackend());
+    $memory_state = new State(new KeyValueMemoryFactory(), new MemoryBackend(new PhpSerialize()), new NullLockBackend());
     \Drupal::getContainer()->set('state', $memory_state);
     $this->controllerResolver->expects($this->any())
       ->method('getControllerFromDefinition')
only in patch2:
unchanged:
--- a/core/tests/Drupal/KernelTests/Core/Routing/MatcherDumperTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Routing/MatcherDumperTest.php
@@ -2,6 +2,7 @@
 
 namespace Drupal\KernelTests\Core\Routing;
 
+use Drupal\Component\Serialization\PhpSerialize;
 use Drupal\Core\Cache\MemoryBackend;
 use Drupal\Core\KeyValueStore\KeyValueMemoryFactory;
 use Drupal\Core\Lock\NullLockBackend;
@@ -38,7 +39,7 @@ protected function setUp() {
     parent::setUp();
 
     $this->fixtures = new RoutingFixtures();
-    $this->state = new State(new KeyValueMemoryFactory(), new MemoryBackend('test'), new NullLockBackend());
+    $this->state = new State(new KeyValueMemoryFactory(), new MemoryBackend(new PhpSerialize()), new NullLockBackend());
   }
 
   /**
only in patch2:
unchanged:
--- a/core/tests/Drupal/Tests/Core/Extension/ThemeHandlerTest.php
+++ b/core/tests/Drupal/Tests/Core/Extension/ThemeHandlerTest.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\Tests\Core\Extension;
 
+use Drupal\Component\Serialization\PhpSerialize;
 use Drupal\Core\Cache\MemoryBackend;
 use Drupal\Core\Extension\Extension;
 use Drupal\Core\Extension\InfoParser;
@@ -80,7 +81,7 @@ protected function setUp() {
       ),
     ));
     $this->moduleHandler = $this->getMock('Drupal\Core\Extension\ModuleHandlerInterface');
-    $this->state = new State(new KeyValueMemoryFactory(), new MemoryBackend('test'), new NullLockBackend());
+    $this->state = new State(new KeyValueMemoryFactory(), new MemoryBackend(new PhpSerialize()), new NullLockBackend());
     $this->infoParser = $this->getMock('Drupal\Core\Extension\InfoParserInterface');
     $this->extensionDiscovery = $this->getMockBuilder('Drupal\Core\Extension\ExtensionDiscovery')
       ->disableOriginalConstructor()