This article is derived from a chapter of the forthcoming book Advanced Principles, Patterns and Process of Software Development, Robert C. Martin, Prentice Hall, 2001. Copyright © 2000 by Robert C. Martin, all rights reserved. Design and programming are human activities; forget that and all is lost. Bjarne Stroustrup, 1991 In order to demonstrate XP (eXtreme Programming) practices, Bob Koss (RSK)