I really liked it, and I will probably use it as documentation for newcomers in my team. However there is one point that I don't really agree: "it can be diffi

I really liked it, and I will probably use it as documentation for newcomers in my team. However there is one point that I don't really agree: "it can be difficult to add tests to a large application that has been developed entirely without testing. And that is why testing should be first on your mind when building serious software." I've being doing it all my life. Join a new project, without any test, and start to add test code, while getting used with the code base. Actually, I would say that "adding tests" for a code base is the easiest and safest way to get used with the code base itself.