--- a/testing/marionette/harness/marionette/tests/harness_unit/test_marionette_runner.py
+++ b/testing/marionette/harness/marionette/tests/harness_unit/test_marionette_runner.py
@@ -392,11 +392,25 @@ def test_reset_test_stats(runner):
     runner.failed = 1
     runner.failures.append(['TEST-UNEXPECTED-FAIL'])
     assert not reset_successful(runner)
     with pytest.raises(Exception):
         runner.run_tests([u'test_fake_thing.py'])
     assert reset_successful(runner)
 
 
+def test_initialize_test_run(runner_mock):
+    tests = [u'test_fake_thing.py']
+    with patch('marionette.runner.base.mozversion.get_version'):
+        runner_mock.run_tests(tests)
+    assert runner_mock.start_time and type(runner_mock.start_time) is float
+    with pytest.raises(AssertionError) as test_exc:
+        runner_mock.run_tests([])
+    assert "len(tests)" in str(test_exc.traceback[-1].statement)
+    with pytest.raises(AssertionError) as hndl_exc:
+        runner_mock.test_handlers = []
+        runner_mock.run_tests(tests)
+    assert "test_handlers" in str(hndl_exc.traceback[-1].statement)
+
+
 if __name__ == '__main__':
     import sys
     sys.exit(pytest.main(['--verbose', __file__]))