diff --git a/core/modules/config_translation/tests/modules/config_translation_test/src/EventSubscriber/ConfigTranslationTestSubscriber.php b/core/modules/config_translation/tests/modules/config_translation_test/src/EventSubscriber/ConfigTranslationTestSubscriber.php
index 9d875a4..45db5ce 100644
--- a/core/modules/config_translation/tests/modules/config_translation_test/src/EventSubscriber/ConfigTranslationTestSubscriber.php
+++ b/core/modules/config_translation/tests/modules/config_translation_test/src/EventSubscriber/ConfigTranslationTestSubscriber.php
@@ -1,18 +1,35 @@
 <?php
 
+/**
+ * @file
+ * Contains \Drupal\config_translation_test\EventSubscriber\ConfigTranslationTestSubscriber.
+ */
+
 namespace Drupal\config_translation_test\EventSubscriber;
 
 use Drupal\config_translation\Event\ConfigMapperEvent;
 use Drupal\config_translation\Event\ConfigTranslationEvents;
 use Symfony\Component\EventDispatcher\EventSubscriberInterface;
 
-
+/**
+ * Adds configuration names to configuration mapper on POPULATE_MAPPER event.
+ */
 class ConfigTranslationTestSubscriber implements EventSubscriberInterface {
+
+  /**
+   * {@inheritdoc}
+   */
   static function getSubscribedEvents() {
     $events[ConfigTranslationEvents::POPULATE_MAPPER][] = ['addConfigNames'];
     return $events;
   }
 
+  /**
+   * Reacts to the population of a configuration mapper.
+   *
+   * @param \Drupal\config_translation\Event\ConfigMapperEvent $event
+   *   The configuration mapper event.
+   */
   public function addConfigNames(ConfigMapperEvent $event) {
     $mapper = $event->getMapper();
     if ($mapper->getBaseRouteName() === 'system.site_information_settings' && $mapper->getLangcode() === 'en') {