Since my last post I have tried using VS2005's testing framework and NUnit with our actual code base. Yesterday I checked in the first tests (totalling 38 test methods for a single class) to our source code control. I had picked the class under test quite randomly but hit a sweet spot with my choice - one of the tests found a bug in a method that was written more than three years ago. And I actually tried to write the tests to match existing code... Perhaps the method is not used very much, since no one had noticed the bug before. (It should have turned up by now, because the method generates a short part of an SQL statement, and with one valid input it returned SQL that is not valid in any DBMS.) There was also at least one method where a null parameter was not considered a special case.
"The other guy" tried checking out the tests and running them, and everything went smoothly. He also thought the tests were a good example of finding small bugs in existing code. Since everything had worked, I updated my paper and added some technical details about running the tests.
Today I finished writing it (at 19 pages) and checked it in. I also wrote tests for another of our basic classes and checked them in as well. This time writing 24 test methods took a lot less time than the previous ones.
So far no one has commented on the work - except for the guy who wrote the method with the bug I found. I went to check if it was ok that I used his method as an example of hard-to-see bugs that could be found easily with testing. He was just browsing through my paper and was pretty impressed. Although no one else has given any feedback, I feel pretty confident. I actually think I'm changing things here.
Let's see if I'm just fooling myself or if my colleagues also start writing some tests.