pytest argparse test case does not work - python-3.x

Question

I'm using Python 3.4.6.
Here is the factory:
def create_parser():
""" Create argument parser """
# Input configuration parameters
_parser = argparse.ArgumentParser(description='Segments Engine')
# Application only parameters
_parser.add_argument(
'-V', '--version', version='%(prog)s ' + __version__,
action='version')
_pasrser.add_argument(
'-d', '--debug', action='store_true')
return _parser
The test case is as follows:
class TestCli(unittest.TestCase):
""" Test the cli.py module """
def __init__(self, *args, **kwargs):
""" Initialize Unit Test """
super(TestCli, self).__init__(*args, **kwargs)
def setup(self):
""" Setup before each test case """
setup_config(app)
setup_logging(app)
def teardown(self):
""" Tear down after each test case """
pass
def test_version(self):
parser = create_parser()
with pytest.raises(SystemExit):
args = vars(parser.parse_args(['', '-V']))
assert args.version == __version__
def test_debug(self):
parser = create_parser()
args = parser.parse_args(['-d'])
assert args.debug
Then I execute as follows:
pytest tests/test_cli.py
I get the following errors, what am I doing wrong?
======================================================================================= test session starts =========================================================================================
platform darwin -- Python 3.4.6, pytest-3.1.3, py-1.4.34, pluggy-0.4.0
rootdir: /Users/francisco.benavides/Documents/src/segments-engine, inifile:
collected 1 item s
tests/test_cli.py F
self = <tests.test_cli.TestCli testMethod=test_version>
def test_version(self):
parser = create_parser()
> args = vars(parser.parse_args(['', '-V']))
tests/test_cli.py:29:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
../../../.pyenv/versions/3.4.6/lib/python3.4/argparse.py:1728: in parse_args
args, argv = self.parse_known_args(args, namespace)
../../../.pyenv/versions/3.4.6/lib/python3.4/argparse.py:1760: in parse_known_args
namespace, args = self._parse_known_args(args, namespace)
../../../.pyenv/versions/3.4.6/lib/python3.4/argparse.py:1966: in _parse_known_args
start_index = consume_optional(start_index)
../../../.pyenv/versions/3.4.6/lib/python3.4/argparse.py:1906: in consume_optional
take_action(action, args, option_string)
../../../.pyenv/versions/3.4.6/lib/python3.4/argparse.py:1834: in take_action
action(self, namespace, argument_values, option_string)
../../../.pyenv/versions/3.4.6/lib/python3.4/argparse.py:1043: in __call__
parser.exit()
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
self = ArgumentParser(prog='pytest', usage=None, description='Segments Engine', formatter_class=<class 'argparse.HelpFormatter'>, conflict_handler='error', add_help=True), status = 0, message = None
def exit(self, status=0, message=None):
if message:
self._print_message(message, _sys.stderr)
> _sys.exit(status)
E SystemExit: 0
../../../.pyenv/versions/3.4.6/lib/python3.4/argparse.py:2373: SystemExit
---------------------------------------------------------------------------------------- Captured stdout call ----------------------------------------------------------------------------------------
pytest 0.0.1
I have tried several ways I found googling, but so far nothing has helped me.

Answer 1

Just a guess since you haven't shown us your create_parser implementation:
-V is a "version" type command (?), if you read the docs version is to
"[print] version information and [exit] when invoked".
You'll want to capture the exit, here's one way:
with pytest.raises(SystemExit):
parser.parse_args(['', '-V'])
# maybe use `capsys` to verify that the version was printed
out, err = capsys.readouterr()
# ...