As far as testing goes, I have a simple approach. If I just wrote some code and had to poke at it in a REPL with some different inputs to check if it works, th

As far as testing goes, I have a simple approach. If I just wrote some code and had to poke at it in a REPL with some different inputs to check if it works, then I should take whatever I did and turn it into a test. With a good testing framework, like the one built into Clojure (formerly clojure.contrib.test-is and now clojure.test), it's really easy. I just copy from my REPL and paste it into the appropriate test file, along with the expected results. If I find a bug, I fix it, write a test for it, and also copy whatever I did to check my work from the REPL into a test file. That's it. I routinely change code around with all the confidence TDD advocates claim. I don't test trivialities. I don't test if my database connection was correctly established --- but I will test database connection loss error handling if I put any non-trivial logic in there. I'll often write a little snippet of sample code for an API I'm working on, but I never write a full formal test in advance. It makes letting the actual API evolve as it grows too cumbersome.