In the previous three parts, we covered a wide range of techniques for making code easy to understand. In this part, we’re going to apply some of these techniques to two selected topics.

First, we’re going to discuss testing—how to write tests that are effective and readable at the same time.

Then we’re going to walk through the design and implementation of a special-purpose data structure (a “minute/hour counter”) to see an example where performance, good design, and readability interplay.