Exploration Through Example

Example-driven development, Agile testing, context-driven testing, Agile programming, Ruby, and other things of interest to Brian Marick

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Thu, 05 Jun 2003

Configuration Management

Laurent has a post on configuration management. He writes:

... if you ask any experienced developer about SCM, or version control, she will tell you that even if you work by yourself and are interested in none of these things, you would be foolish, verging on suicidal, to start a project without availing yourself of a version control system. It needn't be anything fancy, CVS or SourceSafe will do; but you have to have one.

I agree with this, though I do not go as far as Andy, who apparently puts everything under CM.

But what Laurent made me realize is that I use configuration management very differently for personal work than for paid work. In paid work, I delight in grovelling through CVS logs. I'll do a cvs log to see what change comments the programmers put in, how "churny" different files are (which ones change a lot, so are worth further investigation), etc.

In my own work, I use change control quite differently. I dutifully put in change comments, but I never look at them. All I use CM for is a way to backtrack when I realize I'm caught in a rathole. (And even then, I probably don't use it enough.)

I wonder why the difference? The facile reason is that I know my own code, so I don't need to use indirect means like change logs to start understanding it. But I suspect there's something more going on.

I wish I could watch Andy as he uses change control. I bet I'd learn something.

## Posted at 20:49 in category /misc [permalink] [top]

Rephrasing my message on tests vs. requirements

Earlier, I wrote about an observation in one of Bob Dalgleish's posts. Another one that struck me was this:

On the other hand, a "well written" Requirements Document will [...] make statements about the intended audience that will be impossible to capture in a Test Plan except by inference.

We test-first enthusiasts are sometimes guilty of making it seem that tests do everything that a requirements document does, and that the process of creating tests accomplishes everything that requirements elicitation does. I think we should stop.

Nowadays, I try to be explicit by saying that the goal of test-driven design is to provoke particular programmers to write a program that pleases their customer. That happens also to be a goal of requirements documents. They're different means to the same end. Suppose both tools accomplish that end. You probably don't want to pay for both. Which should you use? Well, the tests actually check that the program does something useful. The requirements don't. They just sit there on paper. So you should pay for tests and not for requirements documents.

Now suppose that tests do not completely achieve the goal. For example, a programmer reading them might not understand the "why" behind them, and that might be a problem. So you'll have to supplement them. Personally, I'd lean toward conversational solutions. Have the original programmer collaborate in the test writing. Make sure programmers work together so that latecomers learn the lore from the old hands. And so forth. But if that wouldn't work, we might want a document explaining the motivation. And that might look something like part of a requirements document.

Even if tests do a perfect job of provoking the programmers, that's not the only goal in a project. Perhaps a requirements document is a better way to achieve some other goal. In that case, you'd keep on creating them. Except I can't believe you'd keep making them the same way. By analogy, take the car: it's a means of transportation. In US culture, it's also a way for teenagers to signal status to each other. If there were no need for transportation, would you invent cars just for signalling status? No. There've got to be cheaper ways. Like clothes, maybe. And if requirements are no longer about instructing programmers, there've got to be cheaper ways to achieve their remaining goals.

So my stance is simultaneously less and more bold. I don't say that tests replace requirement documents. I'm saying that tests are so important and so central that everything else has to adjust itself to fit.

## Posted at 10:06 in category /testing [permalink] [top]