speed up tests with pytest-xdist

[EtayLivne]

Hi,

As I've been working on pull request #113, I've noticed that the tests are quite compute intensive and take a while to run.

I've added in pytest-xdist to see if it helps any, and on my 16 core machine it reduces test execution time from 1m46s to 1m, roughly 45% faster.
It's a "breaking change" in the sense that anyone who already has a local env installed will need to install pytest-xdist to run tests.

It's a small change that'll help the repo remain more manageable as it grows, so I thought to suggest it here :)

[SamDuffield]

Agree that the tests can be sped up, so thanks for thinking about this.

I'm not very familiar with pytest-xdist but I'm a tad hesitant to automatically use up parallel resources by default since often developers want to run the tests in the background without interfering with other running threads. Ofc let me know if my caution here is unfounded.

Maybe there is a way to make this optional for the user but not default (but we can use xdist for the github actions runs)?

[EtayLivne]

Great point - I was imagining that someone running the test is likely doing it on a personal PC and is unlikely to have background workloads, but it's always good to be conservative with resource demand!

As you suggested, I disabled the automatic multithreading when running tests locally (anyone can still opt in by adding the "-n auto" arg when they invoke the tests), and added automatic multithreading the the github tests action.

[SamDuffield]

Great stuff, and we can see the tests action ran successfully here https://github.com/normal-computing/posteriors/actions/runs/11531612977/job/32102755647?pr=114