We spend most of our time reading code and not writing it. According to some the ratio is 10 to 1. For that reason making sure our Node project is easy to understand is crucial to the success of our team. Documentation is one why to do it but in many cases it is hard to maintain. If you use declarative testing that are structured around the business logic and not your implementation you kill two birds with one stone - you have code that explains what your service should do and it also makes sure it does it!