Following is a few links to RoR Testing tutorials:
Not a bad introduction
http://blog.new-bamboo.co.uk/articles/2006/08/01/rails-tdd-you-never-know-when-the-brakes-might-fail
In depth testing walk through. Long.
http://grayproductions.net/ruby/first_steps.html
Another walk through. Not Rails. Long also.
http://www.rubycentral.com/articles/pink/index.html
ActiveTest. Looks interesting but not so interesting that I would use it.
http://www.mathewabonyi.com/articles/2006/08/14/activetest-rails-style-testing
Autotest (and Zentest). Very useful for hard core tdd.
http://nubyonrails.com/articles/2006/04/19/autotest-rails
Code coverage tool. This is a must and is dead easy. There is no reason why you shouldn’t use this.
http://eigenclass.org/hiki.rb?rcov
Testing cheat sheet. Big list o’ asserts http://nubyonrails.com/articles/2006/08/24/ruby-rails-test-rails-cheat-sheet
Misc stuff…
Coloured test output
http://errtheblog.com/post/15
Several articles about ruby-prof on this blog http://on-ruby.blogspot.com/
Memory Leak Testing.
http://scottstuff.net/blog/articles/2006/08/17/memory-leak-profiling-with-rails
Kent Beck Podcast. Worth a listen.
http://www.itconversations.com/shows/detail301.html
exceptionz 