Why I Think XP Works
I gave a talk at PyGTA last night on what we’re doing to integrate Python into the undergraduate curriculum at the University of Toronto, and what I’ll be doing with my PSF grant to promote Python in science and engineering. I was pleased at how many people turned out, given the weather, and thought everything went well…
…someone asked what I thought about Extreme Programming (XP). It was late, I was tired, so I ran off at the mouth a little. (I do that.) Here’s what I should have said:
- I’ve never used XP on a real project, so take my opinions with a large grain of salt.
- That said, I’m sceptical of the claims made about it, partly because they fly in the face of my personal experience, but also because the Scot in me instinctively mistrusts anything that’s hyped as hard as XP has been.
- Most importantly, I don’t think that the particular practices that make up XP (pair programming, on-site customer, stand-up meetings, etc.) are the real reason it’s successful. The reason is that teams that adopt diametrically opposed methodologies, like CleanRoom, also see their productivity go up. One possible explanation is that common practice is the worst of all possible worlds, and any change at all would be an improvement. (There are days when I believe this.) A more likely explanation is that what really matters is deciding that you want to be a better programmer. If you make a sincere commitment to that, then exactly how you get there is a detail. It’s kind of like dieting: Atkins, South Beach, macrobiotic, seasonal, or fruitarian is secondary to being sincere about eating better and exercising more.
This hearkens back to a point I made a couple of times during my talk. It’s easy to make students jump through hoops in a course. What’s hard is convincing them that jumping through those hoops after the course is over really will make their lives better. The best way I’ve found so far is to bring in experienced programmers who are doing exciting things, and have them say, “Comments, version control, test-driven development…” I’d be interested in hearing what other people do to make the case.
Steve McConnell has been preaching for years that one of the most common software engineering process is the code-and-fix paradigm, which, incidentally, is also the worst. Adding insult to injury, code-and-fix is also a really slow way to learn anything. One makes the same mistakes again and again and, slowly, learns from them. Some sort of feeback, be it defect analysis or, say, unit tests in the form of test-driven development, makes it much easier to learn from one’s mistakes and actually become a better programmer. The hard part about unit tests is that you need to learn how to make good and effective test cases, which is far from trivial.
By the way, the commenting system does not allow one to give an URL in the URL field. It says that ‘Your comment could not be submitted due to questionable content: ‘. I had to leave out the actual message, because it complains about even if it is in the comment content. It’s not that I desperately wanted to add it, but that it’s a bit silly to have a input field that you cannot use.
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