Sounds like a Big Can of Worms™ to me. I would simply
enforce that all changes be committed to a CVS system so
that in case a designer breaks the interface you can roll
back. Also, you have two webservers ... one in-house
development server and a live production server. All
changes are made to the devel server and nothing is rolled
out until it has been tested and is correct.
Also, i think that writing test cases of expected
HTML output is a waste of time as well.* Hell, is it even practical?
I mean, i envision a case where a designer needs to
reposition the data. Are you going to require that (s)he
get a back-end coder to change the test suite just so the
template will check out? Better to test that data is correct
and let the designer put it where ever they need. And if
they screw up, you simply back out an older revision from
CVS.
CVS and a seperate development server are what we use here
at work. Sure, a test suite that ensures modifications won't
break would be nice, but the time it takes to develop and
keep it up to date surely is not worth the time
you will have to invest.