feat: add tests_dir to config

[souradeep-das]

Overview

closes #368

Changes

Adds test_dir to the config, allowing specific tests to be run

Notes

The logic has been added to each high level method, instead of PytestRunner.execute_pytest thinking about fine-grained control. Do lmk if that needs to be changed

[Otto-AA]

Hi @souradeep-das , thanks for this PR! I tested it out and it looks good :)

One thing that we should change is to support a list of directories (eg tests_dir = [ "tests/" ] in pyproject.toml), rather than only a single directory.

It would also be good to have an E2E test for this. If you want to do this: in e2e_projects/config you could create two test directories (e.g. move test_main.py to tests/main/test_main.py and create a new tests/ignored/test_ignored.py) and then add tests_dir=[ "tests/main" ] in this pyproject.toml. The test_ignored.py should test some function that is not tested by test_main.py (maybe you need to create this function), so we can verify that the tests got ignored and the mutants are reported as untested (code 33). See CONTRIBUTING.rst on how to run the tests and update the snapshots.

I can also add the E2E test if you want.

Apart from that, a small nitpick: instead of getattr(mutmut.config, 'tests_dir', None) we can directly use mutmut.config.tests_dir. The typing is wrong, but the config should always be loaded.

[souradeep-das]

Thanks for the review and comments @Otto-AA! Updated the code and the e2e tests. Do lmk if there needs to be any other changes. :)

[Otto-AA]

Awesome, thanks for the E2E test and the list fix!