Unit-tests you write may require some temporary files or directories. The tempfile module can help you to achieve that. Since temporary stuff usually should be removed after use, tempfile provides context manager as well as plain functions: with tempfile.TemporaryDirectory() as dir_path: open(os.path.join(dir_path, 'a'), 'w').close() open(os.path.join(dir_path, 'b'), 'w').close() open(os.path.join(dir_path, 'c'), 'w').close() assert files_of(dir_path) == ['a', 'b', 'c']