In this chapter, you looked at the importance of learning as early as possible from your user's behavior. You also learned how to organize a usability testing session and get quality feedback to improve your product before building it. This ensures that you only build a product when you are confident enough that you are moving in the right direction.
This is the last chapter that describes the stages of the design process. However, you should understand that the process is not a set of linear steps. Testing is just another step that may complete one more iteration; depending on the results, it can lead you to any of the previous stages to learn more from your users, explore new ideas, prototype different approaches, or adjust the test script. Design is a never ending process; what is important is to serve your users better on each iteration.