I just revised our entry-level testing overview tutorial at: http://wiki.ros.org/UnitTesting . Please have a look, and make any corrections necessary, or complain here to me. Also, share it with all your collaborators, who you think, do not test enough!
This is a part of a larger effort that we started to overhaul, extend and complete ROS QA resources, to encourage industrial use of ROS. We code name it “Quality Hub”: http://wiki.ros.org/Quality. For now there is very little, but we hope that others will jump on it, and we will improve the situation substantially, creating a handbook for professional use of ROS for high quality long lasting systems.
I was considering moving this tutorial to http://wiki.ros.og/Quality/Tutorials/UnitTesting (possibly with a redirect, I hope that moin wiki has some mechanism for that). This would help the centralization and navigation of quality resources. But this article is so old originally, that I am a bit hesitant to do it, without a broader opinion. So please comment on the idea of moving with a redirect as well.
PS. If you wonder what changes I did: I made the writing a bit slower, so that it provides more context, added a broader analysis of benefits, discussed costs, added an example, and provided a few more guidelines, and more links to other resources (some still dangling, but we are working on them).