def test_fail_existing_file(mocker):
mocker.patch("os.path.isfile", return_value=False)
with pytest.raises(argparse.ArgumentTypeError, match="No file called"):
parser.existing_file("any")
def test_existing_file(mocker):
mocker.patch("os.path.isfile", return_value=True)
assert os.path.abspath("any") == parser.existing_file("any")