diff --git a/core/modules/simpletest/simpletest.install b/core/modules/simpletest/simpletest.install
index 78830c79aa69ea1b753a4ae74e42cefccb90ef16..373876807bd7532a3bca580049aa3f8943105eb3 100644
--- a/core/modules/simpletest/simpletest.install
+++ b/core/modules/simpletest/simpletest.install
@@ -22,6 +22,12 @@
 function simpletest_requirements($phase) {
   $requirements = [];
 
+  $requirements['deprecation'] = [
+    'title' => t('Testing (SimpleTest)'),
+    'value' => t('The <em>Testing</em> (SimpleTest) module is deprecated for removal in Drupal 9. It should not be enabled on production sites. Read <a href="https://www.drupal.org/node/3091784">The Drupal core SimpleTest module is deprecated</a> for alternative ways to run tests during development.'),
+    'severity' => $phase === 'runtime' ? REQUIREMENT_WARNING : REQUIREMENT_INFO,
+  ];
+
   $has_phpunit = class_exists(TestCase::class);
   $has_curl = function_exists('curl_init');
 
diff --git a/core/modules/system/tests/src/Functional/Update/UpdatePathRC1TestBaseFilledTest.php b/core/modules/system/tests/src/Functional/Update/UpdatePathRC1TestBaseFilledTest.php
index c0fcdf4f58149023046b0ead7149e745b2fdf81c..0b59c4b6f4fbe80cd6733d0d934c36bbcbb26a55 100644
--- a/core/modules/system/tests/src/Functional/Update/UpdatePathRC1TestBaseFilledTest.php
+++ b/core/modules/system/tests/src/Functional/Update/UpdatePathRC1TestBaseFilledTest.php
@@ -384,7 +384,6 @@ public function testUpdatedSite() {
       'search',
       'serialization',
       'shortcut',
-      'simpletest',
       'statistics',
       'syslog',
       'system',
diff --git a/core/modules/system/tests/src/Functional/Update/UpdatePathTestBaseFilledTest.php b/core/modules/system/tests/src/Functional/Update/UpdatePathTestBaseFilledTest.php
index e03073f00bde337e42b6a88568364c85c17038ea..05c112055d2bf98082bfb78776da92930ce2bf61 100644
--- a/core/modules/system/tests/src/Functional/Update/UpdatePathTestBaseFilledTest.php
+++ b/core/modules/system/tests/src/Functional/Update/UpdatePathTestBaseFilledTest.php
@@ -386,7 +386,6 @@ public function testUpdatedSite() {
       'search',
       'serialization',
       'shortcut',
-      'simpletest',
       'statistics',
       'syslog',
       'system',