diff --git a/core/modules/simpletest/simpletest.module b/core/modules/simpletest/simpletest.module
index 24665c7..f4c2cbc 100644
--- a/core/modules/simpletest/simpletest.module
+++ b/core/modules/simpletest/simpletest.module
@@ -184,14 +184,17 @@ function simpletest_run_tests($test_list) {
  * @param $unescaped_test_classnames
  *   An array of test class names, including full namespaces, to be passed as
  *   a regular expression to PHPUnit's --filter option.
+ * @param int $status
+ *   (optional) The exit status code of the PHPUnit process will be assigned to
+ *   this variable.
  *
  * @return array
  *   The parsed results of PHPUnit's JUnit XML output, in the format of
  *   {simpletest}'s schema.
  */
-function simpletest_run_phpunit_tests($test_id, array $unescaped_test_classnames) {
+function simpletest_run_phpunit_tests($test_id, array $unescaped_test_classnames, &$status = NULL) {
   $phpunit_file = simpletest_phpunit_xml_filepath($test_id);
-  simpletest_phpunit_run_command($unescaped_test_classnames, $phpunit_file);
+  simpletest_phpunit_run_command($unescaped_test_classnames, $phpunit_file, $status);
   return simpletest_phpunit_xml_to_rows($test_id, $phpunit_file);
 }
 
@@ -246,11 +249,14 @@ function simpletest_phpunit_configuration_filepath() {
  *   a regular expression to PHPUnit's --filter option.
  * @param string $phpunit_file
  *   A filepath to use for PHPUnit's --log-junit option.
+ * @param int $status
+ *   (optional) The exit status code of the PHPUnit process will be assigned to
+ *   this variable.
  *
  * @return string
  *  The results as returned by exec().
  */
-function simpletest_phpunit_run_command(array $unescaped_test_classnames, $phpunit_file) {
+function simpletest_phpunit_run_command(array $unescaped_test_classnames, $phpunit_file, &$status = NULL) {
   $phpunit_bin = simpletest_phpunit_command();
 
   $command = array(
@@ -284,7 +290,7 @@ function simpletest_phpunit_run_command(array $unescaped_test_classnames, $phpun
 
   // exec in a subshell so that the environment is isolated when running tests
   // via the simpletest UI.
-  $ret = exec(join($command, " "));
+  $ret = exec(join($command, " "), $output, $status);
   chdir($old_cwd);
   return $ret;
 }
diff --git a/core/scripts/run-tests.sh b/core/scripts/run-tests.sh
index b91a784..f4bc4e8 100755
--- a/core/scripts/run-tests.sh
+++ b/core/scripts/run-tests.sh
@@ -16,7 +16,10 @@
 const SIMPLETEST_SCRIPT_COLOR_PASS = 32; // Green.
 const SIMPLETEST_SCRIPT_COLOR_FAIL = 31; // Red.
 const SIMPLETEST_SCRIPT_COLOR_EXCEPTION = 33; // Brown.
-const SIMPLETEST_SCRIPT_FAILS_OR_ERRORS = 2; // Status code for failed tests.
+
+const SIMPLETEST_SCRIPT_EXIT_SUCCESS = 0;
+const SIMPLETEST_SCRIPT_EXIT_FAILURE = 1;
+const SIMPLETEST_SCRIPT_EXIT_EXCEPTION = 2;
 
 // Set defaults and get overrides.
 list($args, $count) = simpletest_script_parse_args();
@@ -503,8 +506,7 @@ function simpletest_script_setup_database($new = FALSE) {
 function simpletest_script_execute_batch($test_classes) {
   global $args, $test_ids;
 
-  // Keeps track of failures or exceptions during the tests.
-  $has_fails_or_exceptions = FALSE;
+  $total_status = SIMPLETEST_SCRIPT_EXIT_SUCCESS;
 
   // Multi-process execution.
   $children = array();
@@ -522,9 +524,9 @@ function simpletest_script_execute_batch($test_classes) {
       // Process phpunit tests immediately since they are fast and we don't need
       // to fork for them.
       if (is_subclass_of($test_class, 'Drupal\Tests\UnitTestCase')) {
-        $exit_code = simpletest_script_run_phpunit($test_id, $test_class);
-        if ($exit_code) {
-          $has_fails_or_exceptions = TRUE;
+        $phpunit_status = simpletest_script_run_phpunit($test_id, $test_class);
+        if ($phpunit_status > $total_status) {
+          $total_status = $phpunit_status;
         }
         continue;
       }
@@ -556,8 +558,13 @@ function simpletest_script_execute_batch($test_classes) {
       if (empty($status['running'])) {
         // The child exited, unregister it.
         proc_close($child['process']);
-        if ($status['exitcode']) {
-          $has_fails_or_exceptions = TRUE;
+        if ($status['exitcode'] == SIMPLETEST_SCRIPT_EXIT_FAILURE) {
+          if ($status['exitcode'] > $total_status) {
+            $total_status = $status['exitcode'];
+          }
+        }
+        elseif ($status['exitcode']) {
+          $total_status = $status['exitcode'];
           echo 'FATAL ' . $child['class'] . ': test runner returned a non-zero error code (' . $status['exitcode'] . ').' . "\n";
           if ($args['die-on-fail']) {
             list($db_prefix, ) = simpletest_last_test_get($child['test_id']);
@@ -578,16 +585,14 @@ function simpletest_script_execute_batch($test_classes) {
       }
     }
   }
-  if ($has_fails_or_exceptions) {
-    return SIMPLETEST_SCRIPT_FAILS_OR_ERRORS;
-  }
+  return $total_status;
 }
 
 /**
  * Run a group of phpunit tests.
  */
 function simpletest_script_run_phpunit($test_id, $class) {
-  $results = simpletest_run_phpunit_tests($test_id, array($class));
+  $results = simpletest_run_phpunit_tests($test_id, array($class), $status);
   simpletest_process_phpunit_results($results);
 
   // Map phpunit results to a data structure we can pass to
@@ -619,15 +624,10 @@ function simpletest_script_run_phpunit($test_id, $class) {
     }
   }
 
-  $exit_code = 0;
   foreach ($summaries as $class => $summary) {
     simpletest_script_reporter_display_summary($class, $summary);
-
-    if ($summary['#fail'] || $summary['#exception']) {
-      $exit_code = SIMPLETEST_SCRIPT_FAILS_OR_ERRORS;
-    }
   }
-  return($exit_code);
+  return $status;
 }
 
 /**
@@ -644,19 +644,17 @@ function simpletest_script_run_one_test($test_id, $test_class) {
 
     simpletest_script_reporter_display_summary($test_class, $test->results);
 
-
     // Finished, kill this runner.
     if ($test->results['#fail'] || $test->results['#exception']) {
-      exit(SIMPLETEST_SCRIPT_FAILS_OR_ERRORS);
+      exit(SIMPLETEST_SCRIPT_EXIT_FAILURE);
     }
     exit(0);
-
   }
   // DrupalTestCase::run() catches exceptions already, so this is only reached
   // when an exception is thrown in the wrapping test runner environment.
   catch (Exception $e) {
     echo (string) $e;
-    exit(1);
+    exit(SIMPLETEST_SCRIPT_EXIT_EXCEPTION);
   }
 }