diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxFormPageCacheTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxFormPageCacheTest.php
index 9358023d9f..4b61a81436 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxFormPageCacheTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxFormPageCacheTest.php
@@ -44,17 +44,32 @@ public function testSimpleAJAXFormValue() {
     $this->assertEquals($this->drupalGetHeader('X-Drupal-Cache'), 'MISS', 'Page was not cached.');
     $build_id_initial = $this->getFormBuildId();
 
-    $session = $this->getSession();
     // 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
+    $session = $this->getSession();
     $session->getPage()->selectFieldOption('select', 'green');
-    $this->assertSession()->assertWaitOnAjaxRequest();
 
+    // 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.');
+
+    // Confirm the operation of the UpdateBuildIdCommand.
     $build_id_first_ajax = $this->getFormBuildId();
     $this->assertNotEquals($build_id_initial, $build_id_first_ajax, 'Build id is changed in the form_build_id element on first AJAX submission');
 
     // Changing the value of a select input element, triggers a AJAX request/response.
     $session->getPage()->selectFieldOption('select', 'red');
-    $this->assertSession()->assertWaitOnAjaxRequest();
+
+    // Wait for the DOM to update.
+    $red_div = $this->assertSession()->waitForElement('css', "#ajax_selected_color div:contains('red')");
+    $this->assertNotNull($red_div, 'DOM update: The selected color DIV is red.');
+
+    // Confirm the operation of the UpdateBuildIdCommand.
     $build_id_second_ajax = $this->getFormBuildId();
     $this->assertNotEquals($build_id_first_ajax, $build_id_second_ajax, 'Build id changes on subsequent AJAX submissions');
 
@@ -67,14 +82,22 @@ public function testSimpleAJAXFormValue() {
 
     // Changing the value of a select input element, triggers a AJAX request/response.
     $session->getPage()->selectFieldOption('select', 'green');
-    $this->assertSession()->assertWaitOnAjaxRequest();
+
+    // Wait for the DOM to update.
+    $green_div2 = $this->assertSession()->waitForElement('css', "#ajax_selected_color div:contains('green')");
+    $this->assertNotNull($green_div2, 'DOM update: After reload - the selected color DIV is green.');
+
     $build_id_from_cache_first_ajax = $this->getFormBuildId();
     $this->assertNotEquals($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.
     $session->getPage()->selectFieldOption('select', 'red');
-    $this->assertSession()->assertWaitOnAjaxRequest();
+
+    // Wait for the DOM to update.
+    $red_div2 = $this->assertSession()->waitForElement('css', "#ajax_selected_color div:contains('red')");
+    $this->assertNotNull($red_div2, 'DOM update: After reload - the selected color DIV is red.');
+
     $build_id_from_cache_second_ajax = $this->getFormBuildId();
     $this->assertNotEquals($build_id_from_cache_first_ajax, $build_id_from_cache_second_ajax, 'Build id changes on subsequent AJAX submissions');