Testing SHOULD

There are three levels of requirement in the CSS specs

MUST - the behavior is required
SHOULD/RECOMMENDED - the behavior is required unless there's a
                      good reason not to do it
MAY - the behavior is allowed

We're testing as many MUST requirements as we can, of course,
but it would be useful to also test SHOULD requirements. However,
we should distinguish these tests somehow from the MUST tests.
I was thinking to have a flag for SHOULD tests. Not sure what
to call it... optional? should? recommend?

Comments?

~fantasai