I recently gave a talk at RailsConf 2007 about testing. During the talk I put several ideas on the table and encouraged the audience to ask questions and challenge my ideas. I thought the presentation went well, but I think examples of each idea could provide a clearer picture. Look for more entries tagged with "Testing Refactorings" in the future.
Alternatively, this link should give the full list: http://blog.jayfields.com/search/label/Testing%20Refactorings