diff --git a/core/modules/system/tests/common.test b/core/modules/system/tests/common.test
index 500ec02..4456bf5 100644
--- a/core/modules/system/tests/common.test
+++ b/core/modules/system/tests/common.test
@@ -1424,13 +1424,14 @@ class CommonJavaScriptTestCase extends DrupalWebTestCase {
   }
 
   /**
-   * Test that JavaScript aggregation is not affected by ordering in
-   * different groups.
+   * Tests JavaScript aggregation when files are added to a different scope.
    */
   function testAggregationOrder() {
+    // Enable JavaScript aggregation.
     config('system.performance')->set('preprocess_js', 1)->save();
     drupal_static_reset('drupal_add_js');
 
+    // Add two JavaScript files to the current request and build the cache.
     drupal_add_js('core/misc/ajax.js');
     drupal_add_js('core/misc/autocomplete.js');
 
@@ -1440,25 +1441,28 @@ class CommonJavaScriptTestCase extends DrupalWebTestCase {
       'core/misc/autocomplete.js' => $js_items['core/misc/autocomplete.js']
     ));
 
+    // Store the expected key for the first item in the cache.
     $cache = array_keys(variable_get('drupal_js_cache_files', array()));
     $expected_key = $cache[0];
 
+    // Reset variables and add a file in a different scope first.
     variable_del('drupal_js_cache_files');
     drupal_static_reset('drupal_add_js');
     drupal_add_js('some/custom/javascript_file.js', array('scope' => 'footer'));
     drupal_add_js('core/misc/ajax.js');
     drupal_add_js('core/misc/autocomplete.js');
 
+    // Rebuild the cache.
     $js_items = drupal_add_js();
     drupal_build_js_cache(array(
       'core/misc/ajax.js' => $js_items['core/misc/ajax.js'],
       'core/misc/autocomplete.js' => $js_items['core/misc/autocomplete.js']
     ));
 
+    // Compare the expected key for the first file to the current one.
     $cache = array_keys(variable_get('drupal_js_cache_files', array()));
     $key = $cache[0];
-
-    $this->assertEqual($key, $expected_key, t('JavaScript aggregation is not affected by ordering in different groups.'));
+    $this->assertEqual($key, $expected_key, 'JavaScript aggregation is not affected by ordering in different scopes.');
   }
 
   /**