I read Younghan's book as an annual event and moved on, but I felt like I couldn't put it off any longer..(I have practical experience ㅠㅠ) I am listening to the lecture and gaining strength, and I am diligently creating test code while applying it. In particular, the concept of related subjects and practical references will be especially helpful. This felt like an uneasy infinite loop, but I completely understood it after watching the lecture.