Create lightning_utilities.testing subpackage

[akihironitta]

🚀 Feature

Collect common classes, functions, e.g.

• RunIf: https://github.com/Lightning-AI/lightning/blob/95374440ce9b4f499f83b0e6b8cee0bc715aa18b/tests/tests_pytorch/helpers/runif.py#L55
• no_warning_call: https://github.com/Lightning-AI/lightning/blob/95374440ce9b4f499f83b0e6b8cee0bc715aa18b/tests/tests_pytorch/helpers/utils.py#L92
• ...

Motivation

Prevents duplication across repositories.

[Borda]

@carmocca still thinking about having the RunIf as a prototype with some simple functionality which would be extended/inherit in particular projects like PL

[carmocca]

What simple functionality? Only min_python and skip_windows don't require any packages. And the code deduplication will be almost nothing because each repo will need to rewrite its own.

[carmocca]

I added #55 but haven't updated the projects to use it.

[Borda]

I found with cutting strategies and accelerators that I am always coping with GPU, standalone, min torch, etc.

[carmocca]

What's the issue with copying it? It's very simple infrastructure. If you wanted to share code, then it should be done through fabric or pytorch lightning, which do install torch