Testing

When you create a class, you are probably pretty sure that it works. You will, after all, have put it through its paces during development. You'll also have run your system with the component in place, checking that it integrates well, and your new functionality is available and performing as expected.

Can you be sure that your class will carry on working as expected though? That might seem like a silly question. After all, you've checked your code once; why should it stop working arbitrarily? Well, of course it won't; nothing happens arbitrarily, and if you never add another line of code to your system, you can probably breathe easy. If, on the other hand your project is active, then it's inevitable that your component's context will change, and highly likely that the component itself will be altered in any number of ways.