python unittest for argparse

Question

I have a function inside a module that creates an argparse:

def get_options(prog_version='1.0', prog_usage='', misc_opts=None):
     options = [] if misc_opts is None else misc_opts
     parser = ArgumentParser(usage=prog_usage) if prog_usage else ArgumentParser()
     parser.add_argument('-v', '--version', action='version', version='%(prog)s {}'.format(prog_version))
     parser.add_argument('-c', '--config', dest='config', required=True, help='the path to the configuration file')

    for option in options:
        if 'option' in option and 'destination' in option:
            parser.add_argument(option['option'],
                                dest=option.get('destination', ''),
                                default=option.get('default', ''),
                                help=option.get('description', ''),
                                action=option.get('action', 'store'))

    return parser.parse_args()

A sample myapp.py would be:

my_options = [
    {
        "option": "-s",
        "destination": "remote_host",
        "default": "127.0.0.1",
        "description": "The remote server name or IP address",
        "action": "store"
    },
]

# Get Command Line Options
options = get_options(misc_opts=my_options)
print options.config
print options.remote_host

and this will be called as:

$> python myapp.py -c config.yaml
$> config.yaml
   127.0.0.1

Now, I am trying to create a unit test for this function but my problem is that I can't pass command line parameters via test code.

# mytest.py
import unittest
from mymodule import get_options

class argParseTestCase(unittest.TestCase):
     def test_parser(self):
         options = get_options()
         # ...pass the command line arguments...
         self.assertEquals('config.yaml', options.config) # ofcourse this fails because I don't know how I will pass the command line arguments

My problem is that I need to pass the command line arguments to get_options() but I don't know how to do it properly.

Expected proper call: python mytest.py (-c config.yaml should be passed inside the test code somehow.)

What is "working"/not working right now:

1. python mytest.py -c config.yaml is also not working. Returns AttributeError: 'module' object has no attribute 'config' since it expects me to call argParseTestCase instead. In other words, python mytest.py -c argParseTestCase "works" but would ofcourse be an return AssertionError: 'config.yaml' != 'argParseTestCase'

2. python mytest.py -v to run the unit test in verbose mode also fails. It returns:

   test_parser (main.argParseTestCase) ... mytest.py 1.0 ERROR ERROR: test_parser (main.argParseTestCase)
   Traceback (most recent call last): File "tests/unit_tests/mytest.py", line 376, in test_parser options = get_options() File "/root/test/lib/python2.7/site-packages/mymodule.py", line 61, in get_options return parser.parse_args()
   File "/usr/local/lib/python2.7/argparse.py", line 1701, in parse_args args, argv = self.parse_known_args(args, namespace)
   File "/usr/local/lib/python2.7/argparse.py", line 1733, in parse_known_args namespace, args = self._parse_known_args(args, namespace)
   File "/usr/local/lib/python2.7/argparse.py", line 1939, in _parse_known_args start_index = consume_optional(start_index)
   File "/usr/local/lib/python2.7/argparse.py", line 1879, in consume_optional take_action(action, args, option_string)
   File "/usr/local/lib/python2.7/argparse.py", line 1807, in take_action action(self, namespace, argument_values, option_string)
   File "/usr/local/lib/python2.7/argparse.py", line 1022, in call parser.exit(message=formatter.format_help())
   File "/usr/local/lib/python2.7/argparse.py", line 2362, in exit _sys.exit(status) SystemExit: 0

Answer 1

我更喜欢显式传递参数，而不是依赖全局可用的属性，例如sys.argv（parser.parse_args()在内部执行）。因此，我通常argparse通过自己传递参数列表来使用（到main()和随后get_options()以及您需要它们的任何地方）：

def get_options(args, prog_version='1.0', prog_usage='', misc_opts=None):
    # ...
    return parser.parse_args(args)

然后传入参数

def main(args):
    get_options(args)

if __name__ == "__main__":
    main(sys.argv[1:])

这样我就可以替换和测试我喜欢的任何参数列表

options = get_options(['-c','config.yaml'])
self.assertEquals('config.yaml', options.config)