diff -u b/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
--- b/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -2401,9 +2401,9 @@
  * @see Drupal\Core\DrupalKernel
  *
  * @param $new_container
- *   A new container instance to reset the Drupal container to.
- * @param $load
- *   Whether to create a new container.
+ *   A new container instance to store.
+ * @param $reset
+ *   Set to TRUE to create a new bare essentials container.
  *
  * @return Symfony\Component\DependencyInjection\Container
  *   The instance of the Container used to set up and maintain object
diff -u b/core/includes/file.inc b/core/includes/file.inc
--- b/core/includes/file.inc
+++ b/core/includes/file.inc
@@ -2025,6 +2025,8 @@
 
   $options['key'] = in_array($options['key'], array('uri', 'filename', 'name')) ? $options['key'] : 'uri';
   $files = array();
+  // Avoid warnings when opendir does not have the permissions to open a
+  // directory.
   if (is_dir($dir) && $handle = @opendir($dir)) {
     while (FALSE !== ($filename = readdir($handle))) {
       if (!preg_match($options['nomask'], $filename) && $filename[0] != '.') {
diff -u b/core/lib/Drupal/Core/DrupalKernel.php b/core/lib/Drupal/Core/DrupalKernel.php
--- b/core/lib/Drupal/Core/DrupalKernel.php
+++ b/core/lib/Drupal/Core/DrupalKernel.php
@@ -28,6 +28,18 @@
 class DrupalKernel extends Kernel {
 
   /**
+   * @var string The name of the container class.
+   */
+  protected $containerClassName;
+
+  public function __construct($environment, $debug, $containerClassName = NULL) {
+    parent::__construct($environment, $debug);
+    if ($containerClassName) {
+      $this->containerClassName = $containerClassName;
+    }
+  }
+
+  /**
    * Overrides Kernel::init().
    */
   public function init() {
@@ -63,39 +75,30 @@
    * Initializes the service container.
    */
   protected function initializeContainer() {
-    $class = $this->getContainerClass();
+    $class = $this->containerClassName ? $this->containerClassName : $this->getContainerClass();
     $cache_file = $class . '.php';
 
     $storage = drupal_php_storage('service_container');
-    if (!$storage->exists($cache_file)) {
-      $container = $this->buildContainer();
-      $this->dumpDrupalContainer($cache_file, $container, $class, $this->getContainerBaseClass(), $storage);
+    // First, try to load.
+    if (!class_exists($class)) {
+      $storage->load($cache_file);
+    }
+    // If the load succeeded or the class already existed, use it.
+    if (class_exists($class)) {
+      $this->container = new $class;
+    }
+    else {
+      $this->container = $this->buildContainer();
+      if ($storage->writeable()) {
+        $this->dumpDrupalContainer($cache_file, $this->container, $class, $this->getContainerBaseClass(), $storage);
+      }
     }
-
-    $storage->load($cache_file);
-
-    $this->container = new $class();
     $this->container->set('kernel', $this);
 
     drupal_container($this->container);
   }
 
   /**
-   * Gets the container class.
-   *
-   * @return string
-   */
-  protected function getContainerClass() {
-    $class = parent::getContainerClass();
-    $class_original = $class;
-    $prefix = 0;
-    while (class_exists($class)) {
-      $class = $class_original . $prefix++;
-    }
-    return $class;
-  }
-
-  /**
    * Builds the service container.
    *
    * @return ContainerBuilder The compiled service container
diff -u b/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php b/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
--- b/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
@@ -663,6 +663,7 @@
     ))->fetchField();
     if ($install_profile_module_exists) {
       module_enable(array($this->profile), FALSE);
+      $modules[] = $this->profile;
     }
 
     // Create a new DrupalKernel for testing purposes, now that all required
@@ -671,7 +672,7 @@
     // restores the original container.
     // @see Drupal\Core\DrupalKernel::initializeContainer()
     drupal_container(NULL, TRUE);
-    $this->kernel = new DrupalKernel('testing', FALSE);
+    $this->kernel = new DrupalKernel('testing', FALSE, hash('sha256', implode(',', $modules)));
     // Booting the kernel is necessary to initialize the new DIC. While
     // normally the kernel gets booted on demand in
     // Symfony\Component\HttpKernel\handle(), this kernel needs manual booting
only in patch2:
unchanged:
--- a/core/lib/Drupal/Component/PhpStorage/FileReadOnlyStorage.php
+++ b/core/lib/Drupal/Component/PhpStorage/FileReadOnlyStorage.php
@@ -69,4 +69,11 @@ class FileReadOnlyStorage implements PhpStorageInterface {
   protected function getFullPath($name) {
     return $this->directory . '/' . $name;
   }
+
+  /**
+   * Implements Drupal\Component\PhpStorage\PhpStorageInterface::writeable().
+   */
+  function writeable() {
+    return FALSE;
+  }
 }
only in patch2:
unchanged:
--- a/core/lib/Drupal/Component/PhpStorage/FileStorage.php
+++ b/core/lib/Drupal/Component/PhpStorage/FileStorage.php
@@ -71,4 +71,11 @@ class FileStorage implements PhpStorageInterface {
   protected function getFullPath($name) {
     return $this->directory . '/' . $name;
   }
+
+  /**
+   * Implements Drupal\Component\PhpStorage\PhpStorageInterface::writeable().
+   */
+  function writeable() {
+    return TRUE;
+  }
 }
only in patch2:
unchanged:
--- a/core/lib/Drupal/Component/PhpStorage/PhpStorageInterface.php
+++ b/core/lib/Drupal/Component/PhpStorage/PhpStorageInterface.php
@@ -57,6 +57,13 @@ interface PhpStorageInterface {
   public function save($name, $code);
 
   /**
+   * Whether this is a writeable storage.
+   *
+   * @return bool
+   */
+  public function writeable();
+
+  /**
    * Deletes PHP code from storage.
    *
    * @param string $name