Hello Thomas,
Right now this discussion is not about unit tests (parallel running).
This discussion is about Integration tests, runner for Horizon integration tests and using Pytest in general. - Specifically for Watcher.
As for pytest vs stestr, again, Horizon never used stestr as a test runner and I am still waiting if someone - who is here longer than me and maybe was the part of the historical decisions - why nosetests, why Django built-in test runner, why Pytest and NEVER stestr. If I do not get an answer here I will try to directly ping longer active members of Horizon or will dig into some old meeting notes, etc. But now I am still hearing from you why we should use stestr and why it is required but I do not hear why Horizon NEVER used it for integration tests. So I am not arguing we should not use it, but I am really curious why it is so important as you are saying and why it was never used for Horizon Integration tests.
I understand that there are gaps in Horizon and now this thread appeared and you are using it to share all things that you are not satisfied with and although I am trying to answer them all, we should stick here with the original topic and you can come to discuss the others (unit tests parallel running, oslo.config, etc.) on our weekly meetings or PTG.
But to very briefly answer your question: Oslo.config was discussed on previous (Flamingo) PTG as something that would be nice to have:
https://etherpad.opendev.org/p/horizon-flamingo-ptg#L85 but as there are still higher priority topics, the current state is that the team is not working on it but also we did not give-up. We know about it, we would like to complete this topic but it is waiting for its time.
Thank you
Jan