How to default tests to run on one worker and then opt in case by case

[pauldambra]

We have a large test suite and it won't be straight-forward to convert to running in parallel but it's getting very slow 😅

Since conversion won't be straight-forward I'd like to set all tests to run on one worker and then opt files/classes in to running on multiple workers.

Is this possible?

[RonnyPfannschmidt]

Currently there's no affinity mechanism

[pauldambra]

It looked to me like any code I added to the pytest_collection_modifyitems hook wasn't affecting xdist.

I'd like to add a marker to any test that doesn't already have one so I can default all tests into one group. Is that right? Is there an equivalent hook in xdist?

[nicoddemus]

pytest_collection_modifyitems works with xdist, the only catch is that it only runs on the workers, not on master.

[pauldambra]

Ah, that should be fine for me... I was splitting my attention and probably did something silly. I'll check again. Thank you 🙏

[RonnyPfannschmidt]

Workers don't decide about scheduling,so the hook can't help your case

[pauldambra]

My current thought is that I set xdist_group to a default value if it isn't present. Then all tests would run on one worker until we opt then into a different group