XP involves as one team, in a sustainable process without imposed overtime, developers working in pairs who truly enjoy their work, and an informed and available customer to whom they regularly deliver releases. The system's design is clearly described for all by a forceful metaphor, driven by a comprehensive suite of developer and customer tests, and kept simple and understandable by constant refactoring and coding to uniform standards under the team's collective responsibility. This turns out to be a lot of fun and counter-intuitively effective.
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