@jacobtylerwalls Thank you for your work and patience on this one 🌟

I have replied to the outstanding comment: I wanted to push a solution myself, after attempting a rebase and squash, which resulted in many conflicts.

Do you think you'd have some time to squash all commits into one and see if you have some ideas for the comment above?

@jacobtylerwalls Thank you for the latest work, the PR looks in great shape.

I was thinking whether considering some unification for all the duplicated (new) tests make sense. Have you given this a thought? I can't decide whether the extra helper would make sense or be worth it. I toyed with this idea and came up with this option, but would like to know your thoughts:

from io import StringIO
from unittest import mock


class AssertFormatterFailedToLaunch:

    def __init__(self, test):
        self.out = StringIO()
        self.err = StringIO()
        self.test = test

    def __enter__(self):
        self.mocker = mock.patch("django.core.management.utils.shutil.which", return_value="nonexistent")
        self.mocker.start()
        return self

    def __exit__(self, exc_type, exc_value, traceback):
        self.mocker.stop()
        self.test.assertIn("Formatters failed to launch", self.err.getvalue())

Then each new test would be:

from user_commands.utils import AssertFormatterFailedToLaunch

    def test_failure_to_format(self):
        with AssertFormatterFailedToLaunch(self) as f:
            call_command(
                "startapp", "mynewapp", directory=self.test_dir, stdout=f.out, stderr=f.err
            )

That's interesting, and thanks for raising it. I did have a feeling this was too repetitive.

Four of the tests are already in a MigrationTestBase providing specialized assertions, so I just pushed a possibility that tries to blend in.

I do need to be aware of the temporary migration module handling, so folding that in seemed nice, and then leaving one single test for startapp without a helper assertion didn't feel too verbose. I'm open to alternatives. How does this look to you?

That's interesting, and thanks for raising it. I did have a feeling this was too repetitive.

Four of the tests are already in a MigrationTestBase providing specialized assertions, so I just pushed a possibility that tries to blend in.

I do need to be aware of the temporary migration module handling, so folding that in seemed nice, and then leaving one single test for startapp without a helper assertion didn't feel too verbose. I'm open to alternatives. How does this look to you?

I loved this proposal. Since you were on board, I doubled down on this mixing the two approaches. I like the result, so I'm pushing these changes, and if you don't object, I'll be merging this when CI is green.

Thank you for indulging me!