Chapter 5. Testing Principles

Although this book has many specific recipes for testing particular circumstances, several of the techniques may be applied in a wide variety of situations. As with any skill, proficiency comes from learning the mechanics and practicing them. Real expertise comes from understanding the reasons behind the mechanics. This chapter addresses that reasoning.

Applying these principles to your test writing will help you figure out which test patterns are relevant and which particular techniques to use. In the larger scheme, these principles will help you to scale your testing efforts to match the growth of your system without the disproportionate overhead that often occurs.

The principles are presented in order of importance. In general, I would give more weight to the earlier principles than the later ones when making decisions about testing approaches. That said, a solid and clear justification should beat a difference of a couple of places in the order. Ultimately, what is most important is well-reasoned design decisions, not rules.