Frequent manual testing is too impractical for any but the smallest systems. The only way around this is the use of automated tests. They are the only effective method to reduce the time and cost of building, deploying, and maintaining applications. In order to effectively manage applications, it is of the utmost importance that both the implementation and test codes are as simple as possible. Simplicity is one of the core extreme programming (XP) values (http://www.extremeprogramming.org/rules/simple.html) and the key to TDD and programming in general. It is most often accomplished through division into small units. In Java, units are methods. Being the smallest, the feedback loop they provide is the fastest so we spend most of our time thinking and working on them. As a counterpart to implementation methods, unit tests should constitute by far the biggest percentage of all tests.