Testing: Pay in Advance or Afterwards?

In a recent post, I talked about people ignoring the cost of some decision. In his blog “Joel on Software”, they talk about the same thing: How easy it is to fall into the “we must have strict rules” trap to protect ourselves against some vague  fear of failure. Only, humans are really bad at sticking to rules. Or are they? Maybe it’s just that reality doesn’t care so much about rules because things change. If you built your castle on the belief how well strong walls will protect you, the swamp around the basement is not going to care. You’re going down, chummer.

So we end up with a lot of rules which make exactly one thing simple: To assign blame. I’ve been working for a big company where we have a strict process how projects were to be set up. There were lots of documents and forms and comittees how to start a project and a lot of documents describing how to end it (put it into production, what documents to file, who to inform, you name it). It was a great process (in the sense of “big”, mind). The actual writing of the code was explained in a document which contained a single page. On that single page, they talked on how they would strive to write excellent, error free code and that they would use a proven strategy, the waterfall model.

They built a huge, shiny castle on nothing.

If you go to a bank and tell them you have lots of $$$ and you need to pay some big bill somewhere in the future, their first question will be: How you want to make that money work for you in the meantime? Just letting it rot under your desk is not very smart, right? You should invest it somewhere, so you will have $$$$$ or even $$$$$$$ when it comes to pay the bill. Which makes sense. Contrary to that, when we write software, we tend to spend our money first instead of parking it in a safe place where it can return some revenue, being ever vigilant to be able to pay as the bills show up. Which is harder than just sitting back and relying on some mythical process someone else has written on a piece of paper a long time ago.

So when you ask: “Should I write tests for all my classes? For every line of code? How should I spend my money?” Then my answer will be: I don’t know. How can I? I know nothing about your project. But I can give you some ideas how to figure it out yourself.

“Should I write tests for all my classes?” That depends on what these classes are meant for. The more low-level the code, the more tests you should have. Rule of thumb: Tests yield more result in the basement. Make sure the ground you’re building on is sound. And behaves as you expect. The upper levels are mostly built from lego bricks. They are easy to take apart and reshape. They are exchangable, so you can get away with fewer tests. But every bug in the foundation will cripple anything above it.

“For every line of code?” No. Never. 1. It’s not possible. 2. Maintaining the tests will cost more than the real code. 3. Tests are more simple than the real code but you still make a constant amount of mistakes per lines of code. So this will only drive the number of bugs through the roof. 4. Strict, fixed rules never work (note the paradox).

“How should I spend my money?” One word: Wisely. Wisely means to think about your specific problem and find the unique solution. Do you know in advance how much each piece will cost? No. So the best you can do is a staggered approach: Invest a bit of money, check how it plays out. If it works well, spend more. If it doesn’t, scratch it, learn, try something else. Which you will be able to do since you didn’t put all your money on a single horse.

So what if your three month venture into agile development didn’t really work out? All you lost is three months. Other projects are deemed a “success” after going over budget by 100%, using twice the time that was estimated (and none of them were shorter than a year). But you will still have learned something. You paid for it, that wisdom is yours.

Use it wisely.

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