How to test opened files in argparse using nose

So I'm trying to test my parser using nose. I have few arguments that are used for handling files using type=argparse.FileType().

When I print out my parser's parser_args() function, my filename argument is of course specified, looks like this:

Namespace(command_name='edit', filename=[<open file 'filename.p', mode 'r' at 0x108d4e1e0>])

Now I want to test this using nose testing framework, specifically checking if the correct filename was indeed opened but I don't know exactly how.

When I do this (test_sys_args is modified sys.argv list for testing purposes):

test_parser = test_parser_output(test_sys_args) assert_equal(test_parser.filename, "[<open file 'filename.p', mode 'r' at 0x108d4e1e0>]")

It doesn't work. I know I'm not doing this right because the memory address might be different each time the test is run and I'm also not sure if I can pass the filename object as a string like that.

Solution

Try:

assert_equal(test_parser.filename.name, 'filename.p')
assert_equal(test_parser.filename.mode, 'r')

Here's part of the section of the test_argparse.py file (from a recent development download):

class RFile(object):
    seen = {}

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

    def __eq__(self, other):
        if other in self.seen:
            text = self.seen[other]
        else:
            text = self.seen[other] = other.read()
            other.close()
        if not isinstance(text, str):
            text = text.decode('ascii')
        return self.name == other.name == text


class TestFileTypeR(TempDirMixin, ParserTestCase):
    """Test the FileType option/argument type for reading files"""

    def setUp(self):
        super(TestFileTypeR, self).setUp()
        for file_name in ['foo', 'bar']:
            file = open(os.path.join(self.temp_dir, file_name), 'w')
            file.write(file_name)
            file.close()
        self.create_readonly_file('readonly')

    argument_signatures = [
        Sig('-x', type=argparse.FileType()),
        Sig('spam', type=argparse.FileType('r')),
    ]
    failures = ['-x', '', 'non-existent-file.txt']
    successes = [
        ('foo', NS(x=None, spam=RFile('foo'))),
        ('-x foo bar', NS(x=RFile('foo'), spam=RFile('bar'))),
        ('bar -x foo', NS(x=RFile('foo'), spam=RFile('bar'))),
        ('-x - -', NS(x=sys.stdin, spam=sys.stdin)),
        ('readonly', NS(x=None, spam=RFile('readonly'))),
    ]

There's a lot of testing framework that I'm not showing, but you should get the idea. The full file is at https://hg.python.org/cpython/file/ba5d7041e2f5/Lib/test/test_argparse.py