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TDD wasn't a novel invention but a rediscovery: Kent mapped a forgotten input-tape trick from an old payroll-programming book onto his SUnit testing framework, writing tests before the code existed, and found it dissolved his programming anxiety.

Kent Beck recounts rediscovering TDD by recalling a tape-era programming book technique and applying it to his SUnit framework, which unexpectedly calmed his anxiety about coding. ✦ AI generated

Kent Beck · The Pragmatic Engineer · 2026-07-01 · original ↗

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Years later, Kent built SUnit, a small testing framework, and randomly remembered the input-tape trick, so mapped it onto SUnit. If he followed the pattern, he’d write the test before the code. He laughed out loud at this because it seemed like such a stupid idea: why write a test that’s guaranteed to fail, when the classes and methods aren’t even defined yet?

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✳ SUnit ✳ TDD ◉ Kent Beck

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