some errors in TEST.groups and ProblemList are hard to find, e.g. if a test group mentions a non-existent test, jtreg will fail only when one this test group is used, if someone made a typo in problem list file, jtreg will just ignore this line and won't exclude a test from execution.

it'd be nice to have a test suite validate mechanism -- a special execution mode of jtreg, in which it will report all such errors, so it will be much easier to find and fix them.