Make sure we use different cache directories every time we run the tests (#205)

* Make sure we use different cache directories every time we run the tests

* Renamed variable

Author: Nyholm

Tests/Resources/app/AppKernel.php

@@ -11,6 +11,11 @@ class AppKernel extends Kernel
 {
     use MicroKernelTrait;
 
+    /**
+     * @var string
+     */
+    private static $cacheDir;
+
     /**
      * {@inheritdoc}
      */
@@ -55,7 +60,10 @@ protected function configureRoutes(RouteCollectionBuilder $routes)
      */
     public function getCacheDir()
     {
-        return sys_get_temp_dir().'/httplug-bundle/cache';
+        if (null === self::$cacheDir) {
+            self::$cacheDir = uniqid('cache');
+        }
+        return sys_get_temp_dir().'/httplug-bundle/'.self::$cacheDir;
     }
 
     /**