I was attending a workshop at XP/Agile Universe in 2002 when the phrase 'Specification By Example' struck me as a way to describe one of roles of testing in XP. (These days it's terribly unfashionable to talk about Test Driven Development (TDD) having anything to do with testing, but like Jon I do think that having a comprehensive automated test suite is more valuable than the term 'side-effect' i