diff -u b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxFormPageCacheTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxFormPageCacheTest.php
--- b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxFormPageCacheTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxFormPageCacheTest.php
@@ -46,17 +46,16 @@
 
     // Changing the value of a select input element, triggers a AJAX
     // request/response.
-    //
+
     // The callback on the form responds with three AJAX command :-
-    // UpdateBuildIdCommand
-    // HtmlCommand
-    // DataCommand
+    // - UpdateBuildIdCommand
+    // - HtmlCommand
+    // - DataCommand
     $session = $this->getSession();
     $session->getPage()->selectFieldOption('select', 'green');
 
-    // Wait for the DOM to update.
-    // The HtmlCommand will update #ajax_selected_color to reflect the color
-    // change.
+    // Wait for the DOM to update. The HtmlCommand will update
+    // #ajax_selected_color to reflect the color change.
     $green_div = $this->assertSession()->waitForElement('css', "#ajax_selected_color div:contains('green')");
     $this->assertNotNull($green_div, 'DOM update: The selected color DIV is green.');
 
@@ -95,7 +94,8 @@
     $this->assertNotEquals($build_id_from_cache_initial, $build_id_from_cache_first_ajax, 'Build id is changed in the simpletest-DOM on first AJAX submission');
     $this->assertNotEquals($build_id_first_ajax, $build_id_from_cache_first_ajax, 'Build id from first user is not reused');
 
-    // Changing the value of a select input element, triggers a AJAX request/response.
+    // Changing the value of a select input element, triggers a AJAX
+    // request/response.
     $session->getPage()->selectFieldOption('select', 'red');
 
     // Wait for the DOM to update.