Refactor test_transforms.py into classes

[AnirudhDagar]

This is a follow-up PR as discussed here (#3982 comment) after porting of unittest to pytest. See #3945

@NicolasHug I apologize for the unusually large diff in this single PR, but there is no logical change other than a few that I'll explicitly mark. Please let me know if I can help in getting this reviewed in any possible way.

[AnirudhDagar]

Also just to make sure the tests themselves remain unchanged.

For test_transforms.py,
Before this PR : 886 tests passed 5 skipped.
After this PR : (EDIT) 886 tests passed 5 skipped.

[AnirudhDagar]

@NicolasHug Please take a look whenever you have some time. Thanks :))

[NicolasHug]

Thanks for the PR @AnirudhDagar

I see the value in grouping the "to tensor" and the "to pil" tests into their respective classes.
For other cases though it's not as obvious. For example, it's not obvious whether test_randomresized_params should be in TestResize or in TestRandomX.

Since moving tests around does come with the cost of adding an extra step in the git blame (which isn't negligible when it comes to maintenance), I'd suggest to only keep the TestToTensor and TestToPil classes for now.

Hopefully this will also reduce the size of the PR, making it easier to review. I'm happy to consider further changes in the future (I can't promise they'll be merged though), but I'd suggest to leave that for other PRs.

[AnirudhDagar]

Thanks for the feedback @NicolasHug! I had a similar doubt as well while grouping a few tests. I also understand your very valid point on git blame and maintenance.

As suggested, I'll update the PR to include TestToTensor and TestToPil only for now.

[AnirudhDagar]

@NicolasHug I've made the changes, hopefully now the PR should be manageable for a review. Tests are all green as well! :)

[NicolasHug]

thanks @AnirudhDagar

[NicolasHug]

For the rest I think the only really obvious ones would be to group the test_adjust ones, but even then I don't see a strong incentive to do so, as they all test different transforms after all. So I feel like we can leave the rest as-is.

Thanks a ton for your work @AnirudhDagar !

[AnirudhDagar]

Thanks for your valuable feedback and detailed reviews @NicolasHug ! Let me know if there are any other issues where I can help.

Ps. I'll try to work on re-enabling the broken cpp tests (mnasnet specifically) over the weekend.

[NicolasHug]

If you're interested, #4063 is not taken yet ;)