diff -u b/core/modules/simpletest/lib/Drupal/simpletest/DrupalUnitTestBase.php b/core/modules/simpletest/lib/Drupal/simpletest/DrupalUnitTestBase.php
--- b/core/modules/simpletest/lib/Drupal/simpletest/DrupalUnitTestBase.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/DrupalUnitTestBase.php
@@ -102,12 +102,12 @@
     $this->kernel = new DrupalKernel('unit_testing', drupal_classloader(), FALSE);
     $this->kernel->boot();
 
-    // Create a minimal system.module configuration file so that the list of
+    // Create a minimal system.module configuration object so that the list of
     // enabled modules can be maintained allowing
-    // \Drupal\Core\Config\ConfigInstaller::installDefaultConfig() to work. Not
-    // using configuration factory ensures that events registered by modules
-    // during self::enableModules are registered.
-    \Drupal::service('config.cachedstorage.storage')->write('system.module', array('enabled' => array()));
+    // \Drupal\Core\Config\ConfigInstaller::installDefaultConfig() to work.
+    // Write directly to active storage to avoid early instantiation of
+    // the event dispatcher which can prevent modules from registering events.
+    \Drupal::service('config.storage')->write('system.module', array('enabled' => array()));
 
     // Collect and set a fixed module list.
     $class = get_class($this);
@@ -276,8 +276,8 @@
     $module_handler = $this->container->get('module_handler');
     $module_filenames = $module_handler->getModuleList();
     // Write directly to active storage to avoid early instantiation of
-    // services which can prevent modules from registering events.
-    $active_storage =  \Drupal::service('config.cachedstorage.storage');
+    // the event dispatcher which can prevent modules from registering events.
+    $active_storage =  \Drupal::service('config.storage');
     $system_config = $active_storage->read('system.module');
     foreach ($modules as $module) {
       $module_filenames[$module] = drupal_get_filename('module', $module);