https://drafts.csswg.org/css-cascade-3/ has a Test Suite: link to http://test.csswg.org/suites/css-cascade-3_dev/nightly-unstable/ which as far as I can tell is not in any respository anywhere (e.g. not in web-platform-tests), so there’s no way to report issues on the tests, nor submit patches for the tests.
There is https://github.com/w3c/web-platform-tests/tree/master/css/css-cascade which appears to have a few of the test files, e.g.:
However there are only 8 such test files in web-platform-tests/tree/master/css/css-cascade whereas there appear to be over 100 in http://test.csswg.org/suites/css-cascade-3_dev/nightly-unstable/html/toc.htm
This should be considered a CR-exit blocker (PR blocker), since there is no obvious way for implementers to file issues on (and submit corrections for) the tests which implementations must pass in order to demonstrate interop to exit CR.
E.g. I would file an issue for this test https://test.csswg.org/suites/css-cascade-3_dev/nightly-unstable/html/cascade-import-002.htm, specifically, tests g,h,q,r, are wrong because they depend on implementation of meta http-equiv=link which was officially removed from HTML in 2010! (See: https://www.w3.org/Bugs/Public/show_bug.cgi?id=9797)
Labels: css-cascade, css-cascade-3, Needs review of Test Case(s), PR blocker