Fix racing conditions in unit tests. (#496)

diff --git a/tests/mobly/base_test_test.py b/tests/mobly/base_test_test.py
index ead1bf7..f6349ea 100755
--- a/tests/mobly/base_test_test.py
+++ b/tests/mobly/base_test_test.py
@@ -1819,7 +1819,7 @@
         bt_cls.run()
         info1 = bt_cls.results.controller_info[0]
         info2 = bt_cls.results.controller_info[1]
-        self.assertNotEqual(info1.timestamp, info2.timestamp)
+        self.assertNotEqual(info1, info2)
         self.assertEqual(info1.test_class, 'ControllerInfoTest')
         self.assertEqual(info1.controller_name, 'MagicDevice')
         self.assertEqual(info1.controller_info, [{
diff --git a/tests/mobly/test_runner_test.py b/tests/mobly/test_runner_test.py
index 9459f44..0d282ba 100755
--- a/tests/mobly/test_runner_test.py
+++ b/tests/mobly/test_runner_test.py
@@ -107,8 +107,8 @@
                                         expected_info_dict)
         self._assertControllerInfoEqual(tr.results.controller_info[1],
                                         expected_info_dict)
-        self.assertNotEqual(tr.results.controller_info[0].timestamp,
-                            tr.results.controller_info[1].timestamp)
+        self.assertNotEqual(tr.results.controller_info[0],
+                            tr.results.controller_info[1])
 
     def test_summary_file_entries(self):
         """Verifies the output summary's file format.