diff --git a/core/modules/system/lib/Drupal/system/Tests/Menu/LocalTasksTest.php b/core/modules/system/lib/Drupal/system/Tests/Menu/LocalTasksTest.php
index 28ccb5d..729b4f6 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Menu/LocalTasksTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Menu/LocalTasksTest.php
@@ -199,9 +199,11 @@ public function testPluginLocalTask() {
     $this->assertEqual($definitions['menu_local_task_test_tasks_settings_sub2']['provider'], 'menu_test');
     $this->assertEqual($definitions['menu_local_task_test_tasks_settings_sub3']['provider'], 'menu_test');
 
+    // Create an entity which will be used in the following upcasting tests.
     $entity = \Drupal::entityManager()->getStorageController('entity_test')->create(array('bundle' => 'test'));
     $entity->save();
 
+    // Check the sub1 tab is the only active tab.
     $this->drupalGet('menu-local-task-test-upcasting/1/sub1');
 
     $tasks = array(
@@ -211,9 +213,11 @@ public function testPluginLocalTask() {
     $this->assertLocalTasks($tasks, 0);
 
     $result = $this->xpath('//ul[contains(@class, "tabs")]//li[contains(@class, "active")]');
-    $this->assertEqual(1, count($result), 'There are tabs active on both levels.');
-    $this->assertEqual('upcasting sub1', (string) $result[0]->a, 'The settings tab is active.');
+    $this->assertEqual(1, count($result), 'There is just a single active tab.');
+    $this->assertEqual('upcasting sub1', (string) $result[0]->a, 'The sub1 tab is active.');
 
+    // Switch tabs to check that the sub1 tab is no longer active and that the
+    // sub2 tab is the only active tab.
     $this->drupalGet('menu-local-task-test-upcasting/1/sub2');
 
     $tasks = array(
@@ -223,8 +227,8 @@ public function testPluginLocalTask() {
     $this->assertLocalTasks($tasks, 0);
 
     $result = $this->xpath('//ul[contains(@class, "tabs")]//li[contains(@class, "active")]');
-    $this->assertEqual(1, count($result), 'There are tabs active on both levels.');
-    $this->assertEqual('upcasting sub2', (string) $result[0]->a, 'The settings tab is active.');
+    $this->assertEqual(1, count($result), 'There is just a single active tab.');
+    $this->assertEqual('upcasting sub2', (string) $result[0]->a, 'The sub2 tab is active.');
   }
 
 }