Exposing Pytest fixtures

[noirbizarre]

Hi 👋🏼

I have been working on some plugins and I often found myself duplicating the pdm's pytest fixtures that I need to test my plugin.
I already started a branch earlier this year but I didn't submitted it and I wanted to know if it would be accetable and accepted to move most of the fixtures from tests/conftest.py into a reusable pdm/pytest.py fixture module ?
This results in conftest.py only needing this to benefit from all fixtures (especially the invoke fixture)

pytest_plugins = [
    "pdm.pytest",
]

Because I have already done it once, I already know the consequences:

• some fixtures would be splitted between the generic behavior and the one expected by pdm test suite
• a pytest extra (aka. a new entry in project.optionnal-dependencies) would be added for those wanting access to the fixture in their own project
• a few fixtures renaming to be more consistent for usage out of pdm codebase context
• exposed as a module and not a pytest plugin (both are officialy supported way of exposing resulable pytest fixtures) because loading order change when you expose a plugin and this has some sideeffects on PDM test suite.

A legacy version of this is available here: https://github.com/noirbizarre/pdm/tree/feature/pytest (not up to date, still some WIP but gives an overhaul idea of the refactoring)

Should I go further (update it, clean it...) and submit it as PR or do you think this is overengineered and you prefer each plugin to copy-paste the needed fixtures tree ?

[frostming]

Should I go further (update it, clean it...) and submit it as PR or do you think this is overengineered and you prefer each plugin to copy-paste the needed fixtures tree ?

LGTM, it would be nicer to be a PR.