Phase 3: The Generate-Validate Loop · 45 min · Claude Code · Python

Test-Driven AI Generation

Write the tests before the agent writes the code, and 'what did you mean' stops being a question anyone has to guess at.

Real-world application: Encoding requirements as failing tests before prompting generation is concrete evidence of test-driven discipline applied to AI work, not just a claim that you 'write tests.'

What you will learn

Explain why writing failing tests before generation prevents the 'AI guessed what I meant' problem
Apply the red-green-refactor loop to AI-assisted development
Encode a spec's acceptance criteria as concrete, runnable test cases before prompting for an implementation
Use passing tests as a safety net while refactoring generated code

Introduction

Test-Driven AI Generation

Objective

Run a real red-green-refactor loop: confirm tests fail against a stub, confirm they pass against a working implementation, then confirm they still pass after refactoring.

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You've read the first 2 sections. The rest of this lesson covers The Problem, The Concept, Build, Check Yourself, Key Terms & Next — plus a hands-on lab, quiz, and project artifact.

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Key terms in this lesson

Agent