diff -u b/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php b/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
--- b/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
@@ -176,7 +176,7 @@
    * Internal helper: stores the assert.
    *
    * @param $status
-   *   Can be 'pass', 'fail', 'exception'.
+   *   Can be 'pass', 'fail', 'exception', 'debug'.
    *   TRUE is a synonym for 'pass', FALSE for 'fail'.
    * @param $message
    *   (optional) A message to display with the assertion. Do not translate
@@ -232,7 +232,7 @@
       return TRUE;
     }
     else {
-      if ($this->dieOnFail) {
+      if ($this->dieOnFail && ($status == 'fail' || $status == 'exception')) {
         exit(1);
       }
       return FALSE;
diff -u b/core/scripts/run-tests.sh b/core/scripts/run-tests.sh
--- b/core/scripts/run-tests.sh
+++ b/core/scripts/run-tests.sh
@@ -366,7 +366,9 @@
             $public_files = variable_get('file_public_path', conf_path() . '/files');
             $test_directory = $public_files . '/simpletest/' . substr($db_prefix, 10);
             echo 'Simpletest database and files kept and test exited immediately on fail so should be reproducible if you change settings.php to use the database prefix '. $db_prefix . ' and config directories in '. $test_directory . "\n";
-            exit();
+            $args['keep-results'] = TRUE;
+            // Exit repeat loop immediately.
+            $args['repeat'] = -1;
           }
         }
         // Free-up space by removing any potentially created resources.