diff --git a/core/modules/simpletest/lib/Drupal/simpletest/Form/SimpletestTestForm.php b/core/modules/simpletest/lib/Drupal/simpletest/Form/SimpletestTestForm.php
index 2113c2b..f6dd55c 100644
--- a/core/modules/simpletest/lib/Drupal/simpletest/Form/SimpletestTestForm.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/Form/SimpletestTestForm.php
@@ -123,7 +123,7 @@ public function buildForm(array $form, array &$form_state) {
 
       // Cycle through each test within the current group.
       foreach ($tests as $class => $info) {
-        $test_class_id = 'edit-' . strtolower(trim(preg_replace("/[^\w\d]/", '', $class)));
+        $test_class_id = 'edit-' . drupal_html_id($class);
         $current_js['testNames'][] = $test_class_id;
 
         // Test name is used to determine what tests to run.