In previous recipes, we purposefully simplified the examples to a reasonable degree to highlight the specific topics. The code was correct but the recipes did not have any unit tests, because the topic had not yet been addressed. The first thing you are likely to notice in the recipes in this chapter is that we are adding additional structure to the code; for example, each function has its own directory and files and we have also added some lightweight layering to the code. This structure is intended to facilitate the testing process by making it easier to isolate the unit that is under test. So, let's now dig deeper into the tools and structure that have been added.
The first tool that is called in the npm test script is ...
