It’s taking best practices to the extreme…

• Long iterations become short iterations with early experience
• Long, irregular meetings become frequent stand up meetings
• Back-end testing becomes unit testing
• Specification artifacts become stories and a full-time customer (proxy)
• Enforced deadlines become developer-derived estimates
• Code reviews become pair programming

The XP Values

• Communication
• Feedback
• Simplicity
• Courage

The Tenets of Extreme Programming & Refactoring

• Establish a guiding vision, or “metaphor,” and then design as you go, with no big, up-front design.
• Do the simplest thing that works, at first, and then refactor as needed.
• No “Spec Gen” (speculative generality). Rely on refactoring to add features only as they actually become required.
• No speculative performance tuning. Rely on refactoring to introduce performance tuning later.
• Code in small iterations and fast release cycles.
• Put unit and functional testing at the core of the project goal posts, not as an optional add-on. In fact, write the tests before you write the code to be tested. You cannot rely on refactoring without a complete baseline of unit tests.
• Do not refactor and add functionality at the same time. Alternate between them.
• Coding standards should have buy-in by all team members and call for the least amount of work possible.
• Work directly with an on-site customer and/or user and make them a part of the programming team.
• The customer determines the priorities, not the developers.
• Developers provide the estimates, not the customer.
• “Spikes” are written when preliminary research is required to provide a confident estimate.
• The entire development team has collective ownership of the entire project. It is not portioned-out code to individual experts.
• Program in pairs to assure quality and stay on track.
• Use stand-up meetings to stay on track.
• Stick to a 40-hour workweek, sleep well and lead a balanced, healthy lifestyle.

Getting Started

1. Kent Beck’s “Extreme Programming Explained” (second edition) is the seminal work in the field. It’s an easy read and it paints a good overall picture.
2. Martin Fowler’s “Refactoring: Improving the Design of Existing Code” is a must-read. The first 100 pages describes refactoring (and a bit about test-driven development). The remaining pages are a catalog of refactorings — essentially a cookbook of step-by-step recipes.
3. Robert Martin’s “Agile Software Development” has also been recommended as a good starting point, though it’s not primarily about XP.