Are self-describing reftests required?

Hey all,

There was some discussion on #whatwg this morning about where to go for
documentation on writing CSS3 tests that will be accepted. Looking at the
links on these pages:

http://www.w3.org/Style/CSS/Test/
http://wiki.csswg.org/test

I see a page on writing reftests, but none of the other pages say much about
them. The only mention of reftests I could find was the match/mismatch
metadata. In particular, there's nothing that requires a submitted test be a
self-describing reftest. I am under the impression that self-describing
reftests are vastly preferred, if not outright required.

Are reftests a requirement, a strong preference, or something less? If it's
one of the first two, shouldn't the test suite documentation and test
writing guidelines mention them?

Thanks,

Alan