tdd

采用红—绿—重构的测试驱动开发模式。当用户希望以 TDD 方式开发、先编写测试，或说“TDD this”、“test-driven”或“write failing test first”时使用。强制在任何实现之前先编写失败的测试，从而培养严谨的开发习惯。

SKILL.md

--- frontmatter

name: tdd
description: Test-Driven Development with RED-GREEN-REFACTOR cycle. Use when the user wants to develop with TDD, write tests first, or says "TDD this", "test-driven", or "write failing test first". Enforces the discipline of writing a failing test before any implementation.
allowed-tools:
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  - Edit
  - Glob
  - Grep

TDD

RED-GREEN-REFACTOR cycle 驱动开发。

Core Cycle

code

RED → GREEN → REFACTOR → (repeat)

•RED: Write a failing test that describes the desired behavior
•GREEN: Write the MINIMUM code to make it pass
•REFACTOR: Clean up while keeping tests green

Workflow

1. Understand the Requirement

Before writing any test, clarify:

•What behavior is being added or changed?
•What are the inputs and expected outputs?
•What are the edge cases?

2. RED — Write a Failing Test

Write ONE test that captures the next piece of desired behavior.

Rules:

•Test should be specific and focused (test one thing)
•Name should describe the behavior: test_returns_empty_list_when_no_items
•Use the existing test framework and patterns in the project

bash

# Run the test — it MUST fail
[test command]

Show the failure output. If the test passes, something is wrong — the test isn't testing new behavior.

3. GREEN — Minimal Implementation

Write the MINIMUM code to make the failing test pass.

Rules:

•Do not write more code than needed for the current test
•Do not anticipate future requirements
•It's OK to hardcode values if that makes the test pass
•The goal is the shortest path to green

bash

# Run the test — it MUST pass now
[test command]

Show the passing output. Also run the full test suite to ensure nothing broke.

4. REFACTOR — Clean Up

Now that tests are green, improve the code:

•Remove duplication
•Improve naming
•Simplify logic
•Extract common patterns

Rules:

•Do NOT change behavior (tests must stay green)
•Do NOT add new functionality
•Run tests after every change

bash

# Tests must still pass
[test command]

5. Next Cycle

Pick the next piece of behavior and go back to RED.

Guide the user through multiple cycles until the feature is complete.

Detecting the Test Framework

Before starting, detect the project's test setup:

bash

# Check for common test configs
ls package.json pytest.ini setup.cfg pyproject.toml Cargo.toml go.mod 2>/dev/null

Framework	Run Command	File Pattern
Jest	`npx jest`	`.test.ts`, `.spec.ts`
Vitest	`npx vitest run`	`.test.ts`, `.spec.ts`
Pytest	`pytest`	`test_.py`, `_test.py`
Go test	`go test ./...`	`*_test.go`
Cargo test	`cargo test`	inline `#[test]`

Tips

•每个 cycle 不超过 5 分钟的工作量
•如果你发现需要写很多代码才能让测试通过，说明测试粒度太大——拆分
•Refactor 阶段是可选的，不是每个 cycle 都需要
•保持测试快速（< 1s per test）
•当用户说 "just implement it" 时，尊重他们的意愿，跳出 TDD 模式