I found three xctest.dll files in various subdirectories but picked the directory below:
C:\Users\roger\AppData\Local\Programs\Swift\Platforms\6.0.0\Windows.platform\Developer\Library\XCTest-development\usr\bin64\
added it to the PATH environment variable, rebooted, and it works - thank you! I'll watch for the next update and see if that can be removed from that PATH after installing it.
One more follow-up about the new Testing framework. Yes, I realize I can the Testing package as a dependency, but is there support for running and debugging those tests in VSCode or just the old XCTests. I'll give it a quick try but I think I tried it before (when I could only run but not debug code) and I got the "import Testing" line to compile, but the tests didn't run. Again, I'm ok with using XCTests but just thought I'd use the new Testing framework if it's supported rather than teach them an old style of testing.