How to test the non-existence of a file with pytest?

Question

I am not a new developer, but I am new to python.

I am modifying an existing routine that checks for a token in an environment variable. I'm modifying it to look in .netrc if the token does not exist in the environment and I want to test it, but I can't figure out how to mock a missing file. The code looks like this.

def _get_path() -> str:;
    """Get personal access token."""
    pat = os.environ["MY_TOKEN"]
    if not pat:
        try:
            pat = netrc.netrc().authenticators('my.site')[2]
        except netrc.NetrcParseError as ne:
            print(f"Parse error in ${ne.filename} at ${ne.lineno}: ${ne.msg})
        else:
            raise ValueError('No PAT found')
     return pat

This defaults to looking for $HOME/.netrc, which exists in my environment but may not in another developers environment. It certainly won't exist in the test environment.

I'm pretty sure I can figure out how to test a bad .netrc but I just can't seem to figure out how to use pytest, mock or mockito to test for a missing $HOME/.netrc regardless of whether or not aa real one exists.

How do I do this?

Edit: To clarify, the testing environment may have the MY_TOKEN variable set and/or may have $HOME/.netrc ... how can I test the non-existence of $HOME/.netrc regardless of whether or not it exists in the testing environment?

Answer 1

This sounds like a good time to use if not os.path.exists(filepath):