diff --git a/core/modules/system/src/Tests/Form/ElementsLabelsTest.php b/core/modules/system/src/Tests/Form/ElementsLabelsTest.php
index 766386a..98721bf 100644
--- a/core/modules/system/src/Tests/Form/ElementsLabelsTest.php
+++ b/core/modules/system/src/Tests/Form/ElementsLabelsTest.php
@@ -96,7 +96,7 @@ function testFormLabels() {
   }
 
   /**
-   * Test description of form elements with different placement options.
+   * Tests different display options for form element descriptions.
    */
   function testFormDescriptions() {
     $test = $this->drupalGet('form_test/form-descriptions');
@@ -113,10 +113,13 @@ function testFormDescriptions() {
     $elements = $this->xpath('//input[@id="' . $field_id . '" and @aria-describedby="' . $description_id . '"]/preceding-sibling::div[@id="' . $description_id . '"]');
     $this->assertTrue(isset($elements[0]), t('Properly places the #description element before the form item.'));
 
-    // Check #description placement with #description_display='invisible'.
+    // Check if the class is 'visually-hidden' on the form element description
+    // for the option with #description_display='invisible' and also check that
+    // the description is placed after the form element.
     $field_id = 'edit-form-textfield-test-description-invisible';
     $description_id = $field_id . '--description';
     $elements = $this->xpath('//input[@id="' . $field_id . '" and @aria-describedby="' . $description_id . '"]/following-sibling::div[contains(@class, "visually-hidden")]');
     $this->assertTrue(isset($elements[0]), t('Properly renders the #description element visually-hidden.'));
   }
+
 }
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestDescriptionForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestDescriptionForm.php
index 65df1e6..1b500bb 100644
--- a/core/modules/system/tests/modules/form_test/src/Form/FormTestDescriptionForm.php
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestDescriptionForm.php
@@ -12,7 +12,9 @@
 use Symfony\Component\HttpFoundation\JsonResponse;
 
 /**
- * Form for testing the different positions of the description in an element.
+ * Defines a form for testing form element description display options.
+ *
+ * @see \Drupal\system\Tests\Form\ElementsLabelsTest::testFormDescriptions()
  */
 class FormTestDescriptionForm extends FormBase {
 
@@ -27,35 +29,35 @@ public function getFormId() {
    * {@inheritdoc}
    */
   public function buildForm(array $form, FormStateInterface $form_state) {
-  $form['form_textfield_test_description_before'] = array(
-    '#type' =>'textfield',
-    '#title' => 'Textfield test for description before element',
-    '#description' => 'Textfield test for description before element',
-    '#description_display' => 'before',
-  );
-
-  $form['form_textfield_test_description_after'] = array(
-    '#type' =>'textfield',
-    '#title' => 'Textfield test for description after element',
-    '#description' => 'Textfield test for description after element',
-    '#description_display' => 'after',
-  );
-
-  $form['form_textfield_test_description_invisible'] = array(
-    '#type' =>'textfield',
-    '#title' => 'Textfield test for visually-hidden description',
-    '#description' => 'Textfield test for visually-hidden description',
-    '#description_display' => 'invisible',
-  );
-
-  return $form;
+    $form['form_textfield_test_description_before'] = array(
+      '#type' => 'textfield',
+      '#title' => 'Textfield test for description before element',
+      '#description' => 'Textfield test for description before element',
+      '#description_display' => 'before',
+    );
+
+    $form['form_textfield_test_description_after'] = array(
+      '#type' => 'textfield',
+      '#title' => 'Textfield test for description after element',
+      '#description' => 'Textfield test for description after element',
+      '#description_display' => 'after',
+    );
+
+    $form['form_textfield_test_description_invisible'] = array(
+      '#type' => 'textfield',
+      '#title' => 'Textfield test for visually-hidden description',
+      '#description' => 'Textfield test for visually-hidden description',
+      '#description_display' => 'invisible',
+    );
+
+    return $form;
   }
 
   /**
    * {@inheritdoc}
    */
   public function submitForm(array &$form, FormStateInterface $form_state) {
-
+    // The test that uses this form does not submit the form so this is empty.
   }
 
 }