When I first looked up Spring Test-related content, most of them used something called mock, @SpringTest, or something like that, and used various annotations. Wow... Is this kind of testing meaningful? Is it right to use annotations that set up all the injections declared in the bean? How do you set up null values? I had many thoughts like this, and I became curious about how everyone tests. So I looked for lectures and saw a way to test without mocks or h2, and I thought, "Huh?!?" But at first, I thought, "If you want to test without mocks or h2, you have to abstract a lot, and it's just as annoying to create a fake class." (To be honest, I still have some of that. It's not so much a problem as it's that you have to do all the tests.) And because there are so many abstractions, when I try to follow along with my existing project, it doesn't work well. It was done in a layered architecture format! However, while listening to explanations about good architecture, good tests, and good design processes, I thought, "Oh, that's why everyone does it this way." Ah~ I realized that this direction would be good, so I thought it was a really good lecture. I learned a lot because it didn't just teach me about testing, but also taught me how to design for easy and good testing. Thank you!