Programmer Musings

Version Control and Test Driven Development

Almost fifteen years ago, I stumbled across the concept of version control in the form of RCS. I wasn't real sure that this tool was going to be useful for me. After all, it required more work that did not contribute directly to producing code. In order to try it out, I began using RCS to keep up with the source on a few projects I was working on at home. In a few days, I was hooked. I immediately began pushing version control at work despite opposition from the other developer (my boss).

The key to version control for me was a change in my work habits that version control allowed. I have recently come to the realisation that Test Driven Development has had a similar effect on my work habits.

The realisation that drove my use of version control was actually pretty pedestrian. I could experiment with new ideas or designs with almost no risk. If I wanted to see if a new algorithm would work better, I would try it out. If the new idea didn't work out, I could always go back to an earlier version of the code. If I wanted to try out new data structures, I could do the same thing. This was incredibly liberating! I could experiment without worry about messing up code that I had slaved over.

Before I had used RCS, I could do something similar by backing up the old code before trying out my idea. Then, if things didn't work out, I could throw everything away and go back to the old code. But with RCS, I could do backups on small changes and move forward and back through changes with relatively minor effort. Later, I found CVS and my reliance on version control became even stronger.

For the last couple of years, I've been experimenting with unit-test frameworks and Test Driven Development. A lot of the time, the tests really seem to put the fun back in programming. I seem to be moving almost as fast as I did without the tests, but my designs and code appear to be cleaner and more solid.

Although several people have said it different ways before, this is the first time I realised that TDD is giving me the same benefit I first recognised with version control. I can experiment (or refactor) again with almost no cost. If my unit tests are good enough, I can completely refactor my code or re-implement any part of the algorithm with confidence. If I broke anything, the tests will show me. If the tests don't give me the confidence to refactor, my tests aren't complete enough.

This has given me more incentive to work on the TDD way of doing things. It took a little while for me to reach the point of using version control for every project no matter how small. I guess it will probably take a while for me to get to that point with testing as well.