Issue #1597888 by Niklas Fiekas, sun: Fixed Cache NullBackend is entirely...

Issue #1597888 by Niklas Fiekas, sun: Fixed Cache NullBackend is entirely broken, does not implement CacheBackendInterface.

core/lib/Drupal/Core/Cache/NullBackend.php

@@ -42,7 +42,7 @@ function getMultiple(&$cids) {
   /**
    * Implements Drupal\Core\Cache\CacheBackendInterface::set().
    */
-  function set($cid, $data, $expire = CACHE_PERMANENT) {}
+  function set($cid, $data, $expire = CACHE_PERMANENT, array $tags = array()) {}
 
   /**
    * Implements Drupal\Core\Cache\CacheBackendInterface::delete().
@@ -74,6 +74,11 @@ function expire() {}
    */
   function garbageCollection() {}
 
+  /**
+   * Implements Drupal\Core\Cache\CacheBackendInterface::invalidateTags().
+   */
+  public function invalidateTags(array $tags) {}
+
   /**
    * Implements Drupal\Core\Cache\CacheBackendInterface::isEmpty().
    */

core/modules/system/lib/Drupal/system/Tests/Cache/NullBackendTest.php

+<?php
+
+/**
+ * @file
+ * Definition of Drupal\system\Tests\Cache\NullBackendTest.
+ */
+
+namespace Drupal\system\Tests\Cache;
+
+use Drupal\Core\Cache\NullBackend;
+use Drupal\simpletest\UnitTestBase;
+
+/**
+ * Tests the cache NullBackend.
+ */
+class NullBackendTest extends UnitTestBase {
+  public static function getInfo() {
+    return array(
+      'name' => 'Cache NullBackend test',
+      'description' => 'Tests the cache NullBackend.',
+      'group' => 'Cache',
+    );
+  }
+
+  /**
+   * Tests that the NullBackend does not actually store variables.
+   */
+  function testNullBackend() {
+    $null_cache = new NullBackend('test');
+
+    $key = $this->randomName();
+    $value = $this->randomName();
+
+    $null_cache->set($key, $value);
+    $this->assertTrue($null_cache->isEmpty());
+    $this->assertFalse($null_cache->get($key));
+  }
+}