Adding timestamps to the beginning of every test file in run_test

Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/12994

Reviewed By: anderspapitto

Differential Revision: D10515291

Pulled By: pjh5

fbshipit-source-id: 191054cdacff308b63e9063d22d62314398e4f88
diff --git a/test/run_test.py b/test/run_test.py
index 1f5a337..0b888b1 100644
--- a/test/run_test.py
+++ b/test/run_test.py
@@ -3,6 +3,7 @@
 from __future__ import print_function
 
 import argparse
+from datetime import datetime
 import os
 import shlex
 import shutil
@@ -371,7 +372,8 @@
         test_name = 'test_{}'.format(test)
         test_module = parse_test_module(test)
 
-        print_to_stderr('Running {} ...'.format(test_name))
+        # Printing the date here can help diagnose which tests are slow
+        print_to_stderr('Running {} ... [{}]'.format(test_name, datetime.now()))
         handler = CUSTOM_HANDLERS.get(test_module, run_test)
         return_code = handler(python, test_name, test_directory, options)
         assert isinstance(return_code, int) and not isinstance(