Test-Driven Development

测试类

Use before implementing any feature or fixing a bug, before writing implementation code.

Quick Start

Understand in 30 Seconds

Write test first. Watch it fail. Write minimal code to pass.

Core Principle: If you haven't seen the test fail, you don't know it tests the right thing.

When to Use

• New features
• Bug fixes
• Refactoring
• Behavior changes

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Complete Guide

Iron Law

No production code without a failing test first

RED-GREEN-REFACTOR Cycle

RED - Write Failing Test

• One behavior
• Clear name
• Real code

Verify RED - Watch It Fail

Must execute. Never skip.

GREEN - Minimal Coding

Write the simplest code to pass the test.

Verify GREEN - Watch It Pass

Must execute.

REFACTOR - Cleanup

Only after GREEN: eliminate duplication, improve naming, extract helpers

Red Flags

• Writing code before tests
• Writing tests after implementation
• Tests pass immediately
• Cannot explain why test fails

All of these mean: Delete the code. Start over with TDD.

Related Skills

Prerequisite Skills

• brainstorming - Understand what to build

Follow-up Skills

• verification-before-completion - Verify before completion