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VIBE-CODING5 MIN READ

Coupon Edge Cases Need the First Failing Test

Choose the test-first action that gives an AI agent a precise target for a checkout edge case.

Promo launch in two hours. What should Leah ask the AI agent to do first? Write the smallest failing checkout test for VIP coupon plus clearance item plus gift card, then implement only enough code to pass it. Right. The test defines the disputed behavior and prevents the model from solving a nearby but wrong coupon problem. Ask the agent to inspect every discount rule and simplify the whole resolver while it is already in the area. Weaker. It violates the small-step discipline of test-first work and turns one edge case into a broad refactor. Change the checkout message first…

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