If you are interested in building unit tested websites, check out
NARF:

http://narf-lib.sourceforge.net/doc/

NARF is a cgi api designed to facilitate unit testing of cgi scripts
w/out a web server.  In addition to using get / post / mod_ruby ways
of setting state, there are also programmatic shortcuts to set things
like parameters, cookies, the output stream, etc.

The goal is to make testing cgis in a black box manner as easy as
possible.  Given these inputs, the following output is returned, etc. 
We test cgi's from the lowest possible level, so that in larger
applications the appropriate framework can evolve.

NARF is currently tagged as alpha.  If you want to experiment give it
a try and let us know what you think!

~ Patrick May