Python unittest with argparse

Question

I am trying to use unittest with a program that uses the argparse module and having some difficulties. I referenced this helpful post as a starting point but I'm clearly still missing something.

Here is the basic program:

#arg_test.py
import sys
import argparse


class Thingy:
    def __init__(self, name):
        self.name = name

    def parse_args(args):
        parser = argparse.ArgumentParser(description='description here')
        parser.add_argument('-v', '--version', action='version', version='%(prog)s 0.1')
        parser.add_argument('-a', '--arg1', required=True, help='this is for arg1')
        parser.add_argument('-b', '--arg2', required=True, help='this is for arg2')
        return parser.parse_args()


def main():
    parser = Thingy.parse_args(sys.argv[1:])
    print('the args are: {}'.format(parser))
    if parser.arg1:
        print('the value of arg1 is : {}'.format(parser.arg1))
    if parser.arg2:
        print('the value of arg2 is : {}'.format(parser.arg2))


if __name__ == '__main__':
    main()

Running this:

python arg_test.py --arg1 asdf --arg2 qwer

Results in the expected output of:

the args are: Namespace(arg1='asdf', arg2='qwer')
the value of arg1 is : asdf
the value of arg2 is : qwer

Now here is the simple unittest program:

#test/test_arg_test.py
import unittest
from arg_test import Thingy


def test_parser(self):
    parser = Thingy.parse_args(['--arg1'])
    self.assertTrue(parser.arg1,'asdf')


if __name__ == '__main__':
    main()

Running this:

python -m unittest -v test/test_arg_test.py --arg1 asdf --arg2 qwer

Results in this:

python -m unittest -v test/test_arg_test.py --arg1 asdf --arg2 qwer
usage: python -m unittest [-h] [-v] [-q] [--locals] [-f] [-c] [-b]
                          [tests [tests ...]]
python -m unittest: error: unrecognized arguments: --arg1 asdf --arg2 qwer

Can someone please point me in the right direction on how to run these tests?

Thanks.

Update #1

Here is the updated unittest program based on the helpful recommendations below but something is still missing.

#import unittest
from arg_test import Thingy

class TestThingys(unittest.TestCase):
    def test_isupper(self):
        self.assertTrue('FOO'.isupper())
        self.assertFalse('Foo'.isupper())

    def test_parser(self):
        argv1 = ['--arg1', 'asdf', '--arg2', 'qwer']
        parser = Thingy().parse_args(argv1)
        self.assertTrue(parser.arg1,'asdf')

if __name__ == '__main__':
    main()

Running this:

python -m unittest -v test/test_arg_test.py

Results in this:

test_isupper (test.test_arg_test.TestThingys) ... ok
test_parser (test.test_arg_test.TestThingys) ... ERROR

======================================================================
ERROR: test_parser (test.test_arg_test.TestThingys)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/username/scripts/python/arg_test/test/test_arg_test.py", line 12, in test_parser
    parser = Thingy().parse_args(argv1)
TypeError: __init__() missing 1 required positional argument: 'name'

----------------------------------------------------------------------
Ran 2 tests in 0.001s

FAILED (errors=1)

Update #2

#test/test_arg_test.py
import unittest
from arg_test import Thingy

class TestThingys(unittest.TestCase):
    def test_isupper(self):
        self.assertTrue('FOO'.isupper())
        self.assertFalse('Foo'.isupper())

    def test_parser(self):
        argv1 = ['--arg1', 'asdf', '--arg2', 'qwer']
        parser = Thingy('name').parse_args(argv1)
        self.assertEquals(parser.arg1,'asdf')

if __name__ == '__main__':
    main()

Running this:

python -m unittest -v test/test_arg_test.py

Results in this:

test_isupper (test.test_arg_test.TestThingys) ... ok
test_parser (test.test_arg_test.TestThingys) ... ERROR

======================================================================
ERROR: test_parser (test.test_arg_test.TestThingys)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/username/scripts/python/arg_test/test/test_arg_test.py", line 12, in test_parser
    parser = Thingy('name').parse_args(argv1)
TypeError: parse_args() takes 1 positional argument but 2 were given

----------------------------------------------------------------------
Ran 2 tests in 0.001s

FAILED (errors=1)

Answer 1

use argv inside class TestThingy

def test_parser(self):
    argv1 = ['--arg1', 'asdf', '--arg2', 'qwer']
    parser = Thingy('name').parse_args(argv1)
    self.assertEquals(parser.arg1,'asdf')

    argv2 = ['--trigger_exception`, 'asdf`]
    with self.assertRaise(Exception):
        parser = Thingy('name').parse_args(argv2)