make tests runnable without specifying subdirectory

                break

    if proc.poll() is None:

        if test_dir is None:

            test_dir = ""

            test_dir = "test"

        suite = unittest.TestLoader().discover(test_dir, pattern="*_test.py", top_level_dir="test")

        result = unittest.TextTestRunner(verbosity=2).run(suite)

        return len(result.failures) + len(result.errors)