Summary

... instead of creating a new process for each

From #31070 (comment) and following

One thing that might be worth looking into is finding a way to batch tests into a single subprocess call, but I fear that will spiral to a level of complexity of pytest-xdist.

possibly I‘m thinking too simple, but couldn’t we create a permanent process through a session-scoped fixture. Then dispatch the respective test code into that process?

Maybe it is that easy, I have some concerns about making sure we manage to move failures back correctly and reliably (the current scheme does text processing on stdout).

This should wait until we have figured out the subprocess timeout issues on CI. #30851

Related: #30883