It's sad, but
Unit testing books don't get
alot of respect on the market, and it seems to me, when people write them, they don't write them with love. The books I've seen have been riddled with typos and code errors. I can deal with the typos, but errors in code is unacceptable.
Having said that the two books that deal with Cactus that I've used as references are:
Tools for XP Programming and
Jakarta Pitfalls, including Cactus The latter is pretty good for Cactus. I think you'll find both of these books give you some good ideas, but might not give you the depth you're looking for. But then again, a good book shows you how to use the tools - it's up to you to decide what it is you will craft from them.
Happy Unit Testing!
-Cameron McKenzie