Five quick points about unit tests that will reduce your defect rates.
- Always stop to add that simple unit test. You will be amazed how often this discovers a bug or unexplored corner case.
- Never develop from a main method, find a way to turn it into a test. Main driven development is horrible, they are not part of the continuous development cycle so once finished they get forgotten.
- Make all tests run in the continuous integration environment. A test that does not run is a dark test. Tests that are not continually run are probably broken. Same goes for main method development.
- Expend effort getting the time from commit to all project tests passing tests as small as possible. If I could check in, and see the results 1 second later there is little chance of me holding someone else up. Aim for less than 15 mins with current technology. Parallelism is the key. Separate the build, many small suits that run in parallel. Why not build a cloud just for running parallel test suits in?
- Do as much testing as possible using simple unit tests. Unit tests are cheap to write, run fast and are easier to maintain. Test as much as possible with them, resort to higher level tests only to test integration. Good unit level coverage will also mean the higher levels have less to do.
If you just did the above you would be doing very well indeed.
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