Issue #2553661 by claudiu.cristea, geertvd, dawehner, Xano, neclimdul: KernelTestBase fails to set up FileCache

core/lib/Drupal/Component/FileCache/FileCache.php

@@ -153,4 +153,13 @@ class FileCache implements FileCacheInterface {
     }
   }
 
+  /**
+   * Resets the static cache.
+   *
+   * @todo Replace this once https://www.drupal.org/node/2260187 is in.
+   */
+  public static function reset() {
+    static::$cached = [];
+  }
+
 }

core/modules/system/tests/src/Kernel/Extension/ModuleHandlerTest.php

@@ -7,6 +7,7 @@
 
 namespace Drupal\Tests\system\Kernel\Extension;
 
+use Drupal\Component\FileCache\FileCacheFactory;
 use Drupal\Core\DependencyInjection\ContainerBuilder;
 use \Drupal\Core\Extension\ModuleUninstallValidatorException;
 use Drupal\KernelTests\KernelTestBase;
@@ -18,6 +19,11 @@ use Drupal\KernelTests\KernelTestBase;
  */
 class ModuleHandlerTest extends KernelTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = ['system'];
+
   /**
    * {@inheritdoc}
    */
@@ -48,7 +54,7 @@ class ModuleHandlerTest extends KernelTestBase {
    * The basic functionality of retrieving enabled modules.
    */
   function testModuleList() {
-    $module_list = array();
+    $module_list = ['system'];
 
     $this->assertModuleList($module_list, 'Initial');
 

core/tests/Drupal/KernelTests/KernelTestBase.php

@@ -7,6 +7,9 @@
 
 namespace Drupal\KernelTests;
 
+use Drupal\Component\FileCache\ApcuFileCacheBackend;
+use Drupal\Component\FileCache\FileCache;
+use Drupal\Component\FileCache\FileCacheFactory;
 use Drupal\Component\Utility\Html;
 use Drupal\Component\Utility\SafeMarkup;
 use Drupal\Core\Config\ConfigImporter;
@@ -214,6 +217,7 @@ abstract class KernelTestBase extends \PHPUnit_Framework_TestCase implements Ser
     parent::setUp();
 
     $this->root = static::getDrupalRoot();
+    $this->initFileCache();
     $this->bootEnvironment();
     $this->bootKernel();
   }
@@ -487,6 +491,32 @@ abstract class KernelTestBase extends \PHPUnit_Framework_TestCase implements Ser
     return $container;
   }
 
+  /**
+   * Initializes the FileCache component.
+   *
+   * We can not use the Settings object in a component, that's why we have to do
+   * it here instead of \Drupal\Component\FileCache\FileCacheFactory.
+   */
+  protected function initFileCache() {
+    $configuration = Settings::get('file_cache');
+
+    // Provide a default configuration, if not set.
+    if (!isset($configuration['default'])) {
+      $configuration['default'] = [
+        'class' => FileCache::class,
+        'cache_backend_class' => NULL,
+        'cache_backend_configuration' => [],
+      ];
+      // @todo Use extension_loaded('apcu') for non-testbot
+      //  https://www.drupal.org/node/2447753.
+      if (function_exists('apc_fetch')) {
+        $configuration['default']['cache_backend_class'] = ApcuFileCacheBackend::class;
+      }
+    }
+    FileCacheFactory::setConfiguration($configuration);
+    FileCacheFactory::setPrefix(Settings::getApcuPrefix('file_cache', $this->root));
+  }
+
   /**
    * Returns Extension objects for $modules to enable.
    *
@@ -633,6 +663,9 @@ abstract class KernelTestBase extends \PHPUnit_Framework_TestCase implements Ser
       }
     }
 
+    // Clean FileCache cache.
+    FileCache::reset();
+
     // Clean up statics, container, and settings.
     if (function_exists('drupal_static_reset')) {
       drupal_static_reset();

core/tests/Drupal/KernelTests/KernelTestBaseTest.php

@@ -7,6 +7,7 @@
 
 namespace Drupal\KernelTests;
 
+use Drupal\Component\FileCache\FileCacheFactory;
 use Drupal\Core\Database\Database;
 use org\bovigo\vfs\vfsStream;
 use org\bovigo\vfs\visitor\vfsStreamStructureVisitor;
@@ -91,6 +92,8 @@ class KernelTestBaseTest extends KernelTestBase {
       $this->assertEquals('on', $database->query("SHOW standard_conforming_strings")->fetchField());
       $this->assertEquals('escape', $database->query("SHOW bytea_output")->fetchField());
     }
+
+    $this->assertNotNull(FileCacheFactory::getPrefix());
   }
 
   /**