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Using unittest to test argparse - exit errors

Disabling Greg Haskin answered in this question , I tried to do unittest to check that argparse gives the corresponding error when I pass it some arguments that are not present in choices. However, it unittestgenerates a false positive value using the instructions try/exceptbelow.

In addition, when I do a test using only the operator with assertRaises, it argparseforces me to exit the system, and the program no longer runs the tests.

I would like to be able to verify this, but maybe it is superfluous, given that argparseit fails with an error?

#!/usr/bin/env python3

import argparse
import unittest

class sweep_test_case(unittest.TestCase):
    """Tests that the merParse class works correctly"""

    def setUp(self):
        self.parser=argparse.ArgumentParser()
        self.parser.add_argument(
            "-c", "--color",
            type=str,
            choices=["yellow", "blue"],
            required=True)

    def test_required_unknown_TE(self):
        """Try to perform sweep on something that isn't an option.
        Should return an attribute error if it fails.
        This test incorrectly shows that the test passed, even though that must
        not be true."""
        args = ["--color", "NADA"]
        try:
            self.assertRaises(argparse.ArgumentError, self.parser.parse_args(args))
        except SystemExit:
            print("should give a false positive pass")

    def test_required_unknown(self):
        """Try to perform sweep on something that isn't an option.
        Should return an attribute error if it fails.
        This test incorrectly shows that the test passed, even though that must
        not be true."""
        args = ["--color", "NADA"]
        with self.assertRaises(argparse.ArgumentError):
            self.parser.parse_args(args)

if __name__ == '__main__':
    unittest.main()

Errors:

Usage: temp.py [-h] -c {yellow,blue}
temp.py: error: argument -c/--color: invalid choice: 'NADA' (choose from 'yellow', 'blue')
E
usage: temp.py [-h] -c {yellow,blue}
temp.py: error: argument -c/--color: invalid choice: 'NADA' (choose from 'yellow', 'blue')
should give a false positive pass
.
======================================================================
ERROR: test_required_unknown (__main__.sweep_test_case)
Try to perform sweep on something that isn't an option.
----------------------------------------------------------------------
Traceback (most recent call last): #(I deleted some lines)
  File "/Users/darrin/anaconda/lib/python3.5/argparse.py", line 2310, in _check_value
    raise ArgumentError(action, msg % args)
argparse.ArgumentError: argument -c/--color: invalid choice: 'NADA' (choose from 'yellow', 'blue')

During handling of the above exception, another exception occurred:

Traceback (most recent call last): #(I deleted some lines)
  File "/anaconda/lib/python3.5/argparse.py", line 2372, in exit
    _sys.exit(status)
SystemExit: 2
+4
4

ArgumentError , parser.error parse.exit. , sys.exit(2).

, asssertRaises argparse. unittest test/test_argparse.py , ArgumentParser, error .

parser.parse_known_args ( parse_args) :

    try:
        namespace, args = self._parse_known_args(args, namespace)
        if hasattr(namespace, _UNRECOGNIZED_ARGS_ATTR):
            args.extend(getattr(namespace, _UNRECOGNIZED_ARGS_ATTR))
            delattr(namespace, _UNRECOGNIZED_ARGS_ATTR)
        return namespace, args
    except ArgumentError:
        err = _sys.exc_info()[1]
        self.error(str(err))

=================

( test_argparse.py:

import argparse
import unittest

class ErrorRaisingArgumentParser(argparse.ArgumentParser):
    def error(self, message):
        #print(message)
        raise ValueError(message)  # reraise an error

class sweep_test_case(unittest.TestCase):
    """Tests that the Parse class works correctly"""

    def setUp(self):
        self.parser=ErrorRaisingArgumentParser()
        self.parser.add_argument(
            "-c", "--color",
            type=str,
            choices=["yellow", "blue"],
            required=True)

    def test_required_unknown(self):
        """Try to perform sweep on something that isn't an option.
        Should pass"""
        args = ["--color", "NADA"]
        with self.assertRaises(ValueError) as cm:
            self.parser.parse_args(args)
        print('msg:',cm.exception)
        self.assertIn('invalid choice', str(cm.exception))

if __name__ == '__main__':
    unittest.main()

:

1931:~/mypy$ python3 stack39028204.py 
msg: argument -c/--color: invalid choice: 'NADA' (choose from 'yellow', 'blue')
.
----------------------------------------------------------------------
Ran 1 test in 0.002s

OK
+3

, , a argparse.ArgumentError , AttributeError. :

#!/usr/bin/env python3

import argparse
import unittest
from argparse import ArgumentError

class sweep_test_case(unittest.TestCase):
    """Tests that the merParse class works correctly"""

    def setUp(self):
        self.parser=argparse.ArgumentParser()
        self.parser.add_argument(
            "-c", "--color",
            type=str,
            choices=["yellow", "blue"],
            required=True)

    def test_required_unknown_TE(self):
        """Try to perform sweep on something that isn't an option.
        Should return an attribute error if it fails.
        This test incorrectly shows that the test passed, even though that must
        not be true."""
        args = ["--color", "NADA"]
        try:
            self.assertRaises(ArgumentError, self.parser.parse_args(args))
        except SystemExit:
            print("should give a false positive pass")

    def test_required_unknown(self):
        """Try to perform sweep on something that isn't an option.
        Should return an attribute error if it fails.
        This test incorrectly shows that the test passed, even though that must
        not be true."""
        args = ["--color", "NADA"]
        with self.assertRaises(ArgumentError):
            self.parser.parse_args(args)

if __name__ == '__main__':
    unittest.main()
+1

argparse, argparse.py, 1732 ( python - 3.5.1), ArgumentParser, parse_known_args. :

# parse the arguments and exit if there are any errors
try:
    namespace, args = self._parse_known_args(args, namespace)
    if hasattr(namespace, _UNRECOGNIZED_ARGS_ATTR):
        args.extend(getattr(namespace, _UNRECOGNIZED_ARGS_ATTR))
        delattr(namespace, _UNRECOGNIZED_ARGS_ATTR)
    return namespace, args
except ArgumentError:
    err = _sys.exc_info()[1]
    self.error(str(err))

, ArgumentError argparse . , , , - sys.exc_info.

+1

- SystemExit ArgumentError. , SystemExit:

#!/usr/bin/env python3

import argparse
import unittest

class SweepTestCase(unittest.TestCase):
    """Tests that the merParse class works correctly"""

    def setUp(self):
        self.parser=argparse.ArgumentParser()
        self.parser.add_argument(
            "-c", "--color",
            type=str,
            choices=["yellow", "blue"],
            required=True)

    def test_required_unknown(self):
        """ Try to perform sweep on something that isn't an option. """
        args = ["--color", "NADA"]
        with self.assertRaises(SystemExit):
            self.parser.parse_args(args)

if __name__ == '__main__':
    unittest.main()

, :

$ python scratch.py
usage: scratch.py [-h] -c {yellow,blue}
scratch.py: error: argument -c/--color: invalid choice: 'NADA' (choose from 'yellow', 'blue')
.
----------------------------------------------------------------------
Ran 1 test in 0.001s

OK

, , . , " ".

, sys.stderr:

#!/usr/bin/env python3

import argparse
import unittest
from io import StringIO
from unittest.mock import patch


class SweepTestCase(unittest.TestCase):
    """Tests that the merParse class works correctly"""

    def setUp(self):
        self.parser=argparse.ArgumentParser()
        self.parser.add_argument(
            "-c", "--color",
            type=str,
            choices=["yellow", "blue"],
            required=True)

    @patch('sys.stderr', new_callable=StringIO)
    def test_required_unknown(self, mock_stderr):
        """ Try to perform sweep on something that isn't an option. """
        args = ["--color", "NADA"]
        with self.assertRaises(SystemExit):
            self.parser.parse_args(args)
        self.assertRegexpMatches(mock_stderr.getvalue(), r"invalid choice")


if __name__ == '__main__':
    unittest.main()

:

$ python scratch.py
.
----------------------------------------------------------------------
Ran 1 test in 0.002s

OK

pytest , .

import argparse

import pytest


def test_required_unknown():
    """ Try to perform sweep on something that isn't an option. """
    parser=argparse.ArgumentParser()
    parser.add_argument(
        "-c", "--color",
        type=str,
        choices=["yellow", "blue"],
        required=True)
    args = ["--color", "NADA"]

    with pytest.raises(SystemExit):
        parser.parse_args(args)

Pytest stdout/stderr , .

$ pytest scratch.py
================================== test session starts ===================================
platform linux -- Python 3.6.7, pytest-3.5.0, py-1.7.0, pluggy-0.6.0
rootdir: /home/don/.PyCharm2018.3/config/scratches, inifile:
collected 1 item                                                                         

scratch.py .                                                                       [100%]

================================ 1 passed in 0.01 seconds ================================

stdout/stderr pytest:

import argparse

import pytest


def test_required_unknown(capsys):
    """ Try to perform sweep on something that isn't an option. """
    parser=argparse.ArgumentParser()
    parser.add_argument(
        "-c", "--color",
        type=str,
        choices=["yellow", "blue"],
        required=True)
    args = ["--color", "NADA"]

    with pytest.raises(SystemExit):
        parser.parse_args(args)

    stderr = capsys.readouterr().err
    assert 'invalid choice' in stderr

, , pytest , .

0

Source: https://habr.com/ru/post/1651723/

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