Support updating test durations when running for a single group

It would be useful to add support for calculating test durations while using the parameters --splits and group. To clarify, this is currently possible but it runs the full test suite, not just the tests for that particular group. Instead, users can calculate the test_durations for each group and then combine the results.

Happy to send a merge request your way if you think this makes sense!

[jerry-git]

This was done in https://github.com/jerry-git/pytest-split/pull/14

[sondrelg]

Ok so to summarize:

• Leave --store-durations as a required argument for triggering any caching
• Write durations data to .test_durations by default, unless the existing --durations-path argument is passed
• Change from list of list to saving the cache data as a dictionary

I agree we probably don’t need to involve the .pytest_cache - I can just put the .test_durations file in my own .gitignore and get the same result 🙂

Otherwise people would easily start committing .test_durations file unintentionally.

Yeah I agree 👍