TDD and software archaeology

Can you tell by looking at the unit test cases whether the code’s author wrote the tests first? During a TDD class I taught last week, one of the participants suggested that you can’t tell. Completed code and unit tests would look the same regardless of which had been written first. At the time I didn’t give the comment much thought.

I returned to the team I was working with at another client on Thursday, the last day of their iteration cycle. I picked up a small story so I could contribute something before the end of the day. It was a bug fix for JavaScript input validation logic in a webapp. Like many applications, this one uses date ranges to activate and deactivate certain data values that drive functionality. In this case, the input validation function neglected to ensure the expiration date was later than the effective date. Continue reading