diff --git a/core/scripts/run-tests.sh b/core/scripts/run-tests.sh
index f9076f4..d136e7b 100755
--- a/core/scripts/run-tests.sh
+++ b/core/scripts/run-tests.sh
@@ -72,9 +72,15 @@
 simpletest_script_reporter_init();
 
 // Execute tests.
+$bench = array();
 for ($i = 0; $i < $args['repeat']; $i++) {
   simpletest_script_execute_batch($test_list);
 }
+echo "\n", 'Most expensive tests:', "\n\n";
+arsort($bench);
+foreach ($bench as $class => $time) {
+  echo sprintf('%8.3fs %s', $time, $class), "\n";
+}
 
 // Stop the timer.
 simpletest_script_reporter_timer_stop();
@@ -615,6 +621,7 @@ function simpletest_script_execute_batch($test_classes) {
         'test_id' => $test_id,
         'class' => $test_class,
         'pipes' => $pipes,
+        'start' => microtime(TRUE),
       );
     }
 
@@ -625,9 +632,14 @@ function simpletest_script_execute_batch($test_classes) {
     foreach ($children as $cid => $child) {
       $status = proc_get_status($child['process']);
       if (empty($status['running'])) {
+        // Record total time of test class.
+        $GLOBALS['bench'][$child['class']] = microtime(TRUE) - $child['start'];
+
+        // Print stdout of the subprocess (TestBase::bench() output).
         echo 'Bench: ', $child['class'], "\n";
         echo stream_get_contents($child['pipes'][1]);
         fclose($child['pipes'][1]);
+
         // The child exited, unregister it.
         proc_close($child['process']);
         if ($status['exitcode']) {