gh-59215: unittest: _top_level_dir is incorrectly persisted

[ZackerySpytz]

Co-Authored-By: Igor Sobreira igor@igorsobreira.com

https://bugs.python.org/issue15010

• Issue: unittest: _top_level_dir is incorrectly persisted between calls to different load_test methods #59215

[tirkarthi]

Is unittest.mock.patch a better option here instead of addCleanup?

def test_discover_should_not_persist_top_level_dir_between_calls(self):
    with unittest.mock.patch('os.path.isfile', return_value=True):
        with unittest.mock.patch('os.path.isdir', return_value=True):
            loader = unittest.TestLoader()
            loader.suiteClass = str
            dir = '/foo/bar'
            top_level_dir = '/foo'

            loader.discover(dir, top_level_dir=top_level_dir)
            self.assertEqual(loader._top_level_dir, None)

            loader._top_level_dir = dir2 = '/previous/dir'
            loader.discover(dir, top_level_dir=top_level_dir)
            self.assertEqual(loader._top_level_dir, dir2)

[encukou]

Nowadays that can be self.enterContext. But, as is, the PR is consistent with other nearby tests; if this needs changing it would be best to change all of them (in a separate PR).

[encukou]

IMO, this is the right solution, even if _top_level_dir isn't perfect.
However, as evidenced by the changed test, this is a change in behaviour. IMO, it needs at least a versionchanged note in the docs, saying that top_level_dir is only stored for the duration of the discover call.

I've sent proposed docs changes as a PR to this PR, here: https://github.com/ZackerySpytz/cpython/pull/39/files [now merged here]
If an unittest expert has time to look over them, that would be great :)

[encukou]

Nowadays that can be self.enterContext. But, as is, the PR is consistent with other nearby tests; if this needs changing it would be best to change all of them (in a separate PR).

[miss-islington-app]

Thanks @ZackerySpytz for the PR, and @encukou for merging it 🌮🎉.. I'm working now to backport this PR to: 3.11, 3.12.
🐍🍒⛏🤖

[bedevere-app]

GH-117508 is a backport of this pull request to the 3.12 branch.

[bedevere-app]

GH-117509 is a backport of this pull request to the 3.11 branch.