I've updgraded to Xcode 10, and the tests for my project run and pass perfectly.
However I'm trying to debug a CI crash that only seems to happen with Xcode 9.4.1, yet when I try to run my tests in 9.4.1, I get the following error:
Could not attach to PID {number}
It's pretty bizarre. I've tried all the obvious steps (clearing derived data, restarting everything, cleaning, investigating certificate issues, uninstalling Xcode 10, holding a seance....)