--- a/testing/marionette/harness/marionette/runner/base.py
+++ b/testing/marionette/harness/marionette/runner/base.py
@@ -4,16 +4,17 @@
 
 from argparse import ArgumentParser
 
 import json
 import mozinfo
 import moznetwork
 import os
 import random
+import re
 import socket
 import sys
 import time
 import traceback
 import unittest
 import warnings
 import mozprofile
 
@@ -776,26 +777,28 @@ setReq.onerror = function() {
                 self.logger.info("starting httpd")
                 self.start_httpd(need_external_ip)
                 self.marionette.baseurl = self.httpd.get_url()
                 self.logger.info("running httpd on %s" % self.marionette.baseurl)
             else:
                 self.marionette.baseurl = self.server_root
                 self.logger.info("using remote content from %s" % self.marionette.baseurl)
 
-
     def _add_tests(self, tests):
         for test in tests:
             self.add_test(test)
 
-        invalid_tests = \
-            [t['filepath'] for t in self.tests
-             if not os.path.basename(t['filepath']).startswith('test_')]
+        pattern = re.compile("^test(((_.+?)+?\.((py)|(js)))|(([A-Z].*?)+?\.js))$")
+        def is_valid(test):
+            filename = os.path.basename(test['filepath'])
+            return pattern.match(filename)
+        invalid_tests = [t['filepath'] for t in self.tests if not is_valid(t)]
         if invalid_tests:
-            raise Exception("Tests file names must start with 'test_'."
+            raise Exception("Test file names must be of the form "
+                            "'test_something.py', 'test_something.js', or 'testSomething.js'."
                             " Invalid test names:\n  %s"
                             % '\n  '.join(invalid_tests))
 
     def _log_skipped_tests(self):
         for test in self.manifest_skipped_tests:
             name = os.path.basename(test['path'])
             self.logger.test_start(name)
             self.logger.test_end(name,

--- a/testing/marionette/harness/marionette/tests/harness_unit/test_marionette_runner.py
+++ b/testing/marionette/harness/marionette/tests/harness_unit/test_marionette_runner.py
@@ -395,11 +395,36 @@ def test_initialize_test_run(mock_runner
     assert "len(tests)" in str(test_exc.traceback[-1].statement)
     with pytest.raises(AssertionError) as hndl_exc:
         mock_runner.test_handlers = []
         mock_runner.run_tests(tests)
     assert "test_handlers" in str(hndl_exc.traceback[-1].statement)
     assert mock_runner.reset_test_stats.call_count == 1
 
 
+def test_add_tests(mock_runner):
+    assert len(mock_runner.tests) == 0
+    fake_tests = ["test_" + i + ".py" for i in "abc"]
+    with patch('marionette.runner.base.mozversion.get_version'):
+        mock_runner.run_tests(fake_tests)
+    assert len(mock_runner.tests) == 3
+    for (test_name, added_test) in zip(fake_tests, mock_runner.tests):
+        assert added_test['filepath'].endswith(test_name)
+
+
+def test_catch_invalid_test_names(runner):
+    good_tests = [u'test_ok.py', u'test_is_ok.py', u'test_is_ok.js', u'testIsOk.js']
+    bad_tests = [u'bad_test.py', u'testbad.py', u'_test_bad.py', u'testBad.notjs',
+                 u'test_bad.notpy', u'test_bad', u'testbad.js', u'badtest.js',
+                 u'test.py', u'test_.py', u'test.js', u'test_.js']
+    with pytest.raises(Exception) as exc:
+        runner._add_tests(good_tests + bad_tests)
+    msg = exc.value.message
+    assert "Test file names must be of the form" in msg
+    for bad_name in bad_tests:
+        assert bad_name in msg
+    for good_name in good_tests:
+        assert good_name not in msg
+
+
 if __name__ == '__main__':
     import sys
     sys.exit(pytest.main(['--verbose', __file__]))