I've been retrofitting tests onto legacy code at work as I make some changes to it. (So what's new?) The code has classes that are not really following the singlre responsibility principle. The other day I extracted a class to separate out a responsibility. Once I did that, I could more easily fit tests for that single responsibility onto the newly extracted class. When a class does too many things, its really hard to write tests for it, because you have to configure the universe in order to setup the initial conditions for the test. With a single responsibility the amount of setup is much less and the setup is directly relevant to the test you're trying to write. -- "The Direct3D Graphics Pipeline" -- DirectX 9 draft available for download <http://www.xmission.com/~legalize/book/download/index.html> Legalize Adulthood! <http://blogs.xmission.com/legalize/>