diff --git a/core/modules/simpletest/simpletest.permissions.yml b/core/modules/simpletest/simpletest.permissions.yml
index a23e8c8548..a88524d562 100644
--- a/core/modules/simpletest/simpletest.permissions.yml
+++ b/core/modules/simpletest/simpletest.permissions.yml
@@ -1,3 +1,2 @@
 administer unit tests:
   title: 'Administer tests'
-  restrict access: true
diff --git a/core/modules/system/system.install b/core/modules/system/system.install
index db361f3971..611e4794ed 100644
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -74,6 +74,19 @@ function system_requirements($phase) {
         'severity' => REQUIREMENT_WARNING,
       ];
     }
+
+    // Warn if Testing/simpletest is enabled. Users should not have simpletest
+    // enabled on production sites.
+    $requirements['simpletest_enabled'] = [
+      'title' => t('Testing module'),
+      'value' => t('Not enabled'),
+      'description' => t('The Testing/simpletest module should not be enabled on production sites, because it represents a security risk.'),
+      'severity' => REQUIREMENT_OK,
+    ];
+    if (array_key_exists('simpletest', $enabled_modules)) {
+      $requirements['simpletest_enabled']['value'] = t('Enabled');
+      $requirements['simpletest_enabled']['severity'] = REQUIREMENT_WARNING;
+    }
   }
 
   // Web server information.