Right, seems like the issues it that you need to specify an OS of 17.0.1 instead of 17.0, so I solved that problem.
So the results - TLDR; compile times seem to be improved, test times are improved but still unacceptably slow.
A few comparisons - I am only comparing successful jobs:
Xcode 14:
- Core package, build-for-testing - 3m 41s
- Core package, test-without-building (445 tests) - 1m 8s
- Release build (no tests, entire job) - 7m 28s
Xcode 15:
- Core package, build-for-testing - 5m 32s
- Core package, test-without-building (445 tests) - 42m 17s (!!!)
- Release build (no tests, entire job) - 9m 2s
Xcode 15.1 b1:
- Core package, build-for-testing - 3m 50s
- Core package, test-without-building (445 tests) - 19m 11s
- Release build (no tests, entire job) - 9m 21s
So as you can see, compile times when building without testing are almost back to what they were with Xcode 14, which is good. The release build is still a bit slower but that could be due to changes in Swift 5.9 or the compiler itself.
Test time has halved from 15.0 but it’s still 19x slower than Xcode 14 and not an acceptable amount of time. I note that the job is still hitting a ceiling of 98% CPU usage and 83% memory usage once the tests start.
I will retest with the yeetd script above.