It was an opportunity to understand the concept of TDD and actually implement it, and especially, it was very helpful that I could practice it through nodejs. The regrettable thing is that if I try to follow the sample, I think it would be better if each sample was structured a bit more so that I could look up the sample and recall what I learned after taking the class. Since it is updated as I progress with one sample, only the final code remains, making it difficult to review the learning content. And the explanation of the describe structure and before, done is a bit lacking, so I had no choice but to just follow it. It would be good to have a general explanation of the various options and various usages.