Chapter 11. Error Condition Verification

You can tell a well-written piece of software as much by the way it handles failures as by the way it implements its primary functionality. Software failures stimulate an inordinate proportion of the support requests against and, perhaps more importantly for your product’s reputation, the blog posts, forum comments, and tweets about your product. Yet error paths are often the least tested part of the code.

This chapter focuses on testing your failure paths. It relies heavily on the material from the previous chapters. In fact, it adds little in the way of new techniques for verification and injection of behavior. Rather, it shows you how to apply the previous techniques to the problem of inducing and verifying the failures possible in your code.

Along the way, you will see ways to improve your error-handling approaches to make them more valuable and testable. The last section summarizes a number of design concerns toward that end.