Version Used:

Latest master at commit 69e99a8

Steps to Reproduce:

Run Test.cmd with a non english locale.

Expected Behavior:

All tests pass without errors.

Actual Behavior:

26 out of 41 test assemblies fail with errors. There were already about five failing tests in the past because of localization problems but since the introduction of xlf the situation got unbearable with hundreds of failing tests. I'm not sure but I think PR #23744 is to blame.
Attached you can find the UnitTestResults.zip
In the current situation I'm not able to run all tests locally to find regressions before committing. Maybe xUnit should be forced to use the en-US locale.