run pytest in parallel

[shimwell]

Pytest can be run in parallel with another package.

I think the github actions CI has 2 cores

So we could potentially half our CI testing time and reduce local testing time also

pip install pytest-xdist
pytest -n 3

However when running this currently 28 test fail as we have a few race conditions in the tests.

Particular tests look for files while other tests are deleting files.

We have a few cases where a test will do rm *.stp while another test is checking if a stp file exists.

So this is something that we can fix but we need to work through the errors and fix the tests so that they can run in parallel without interfering with each other.

ps on 64 cores the 500 odd tests take about 2 mins :-)

[shimwell]

Here are the tests that fail.
produced with pytest tests -n 63 >tests.txt
tests.txt

[shimwell]

Perhaps the threads argument on the NeutronicsModel.simulate could also be useful