Matt Pocock 工程方法论 - tdd

tdd：mattpocock/skills 方法论: engineering/tdd，适用于工程实践、代码质量与开发流程优化。

Skill Documentation

Matt Pocock 工程方法论 - tdd

摘要

tdd：mattpocock/skills 方法论: engineering/tdd，适用于工程实践、代码质量与开发流程优化。

> 来源: mattpocock/skills (141k stars) — Total TypeScript 创始人 Matt Pocock

> 类目: 工程方法论

> 原文件: skills/engineering/tdd/SKILL.md

> 模型推荐: gpt-4.1 (代码工程)

这个 skill 是干嘛的

Matt Pocock (Total TypeScript, 141k stars) 沉淀下来的"日常代码工程动作"skill 模板。

每一个对应一个具体动作(代码评审 / TDD / 重构 / 文档对齐 / 任务交接),不是工具,是"该怎么干这件事"的工作流模板。

michael 强调"skill 要有相应的指导功能,指导用户使用",所以这里加了下面两节让 Agent 和用户对接。

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🤖 Agent 使用说明

1. 接到任务后先按这个 skill 的检查清单走一遍

2. 清单里如果出现"先做 X 才能做 Y"的红线 → 必须先完成 X

3. 跑完清单后开始动手(改代码 / 写文档 / 评审)

4. 完工前用 `verification-before-completion`(superpowers) 或 `verification` 类 step 自检

5. 任务量大时考虑用 `dispatching-parallel-agents`(superpowers) 或 `wayfinder`(mattpocock) 拆解

👤 用户需要做什么?

1. 告诉 Agent 你要做什么(一句话即可)

2. Agent 跑 skill 清单时不要打断 — 它可能在收集上下文

3. 如果 Agent 主动问你"代码评审要不要安排一个 reviewer"等决策点 → 直接回答

4. 完工后让 Agent 跑一遍自检再交回

5. 整个过程 Agent 自动化,不需要手工介入

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原 skill 内容(mattpocock/skills/engineering/tdd/SKILL.md)

---

name: tdd

description: Test-driven development. Use when the user wants to build features or fix bugs test-first, mentions "red-green-refactor", or wants integration tests.

---

Test-Driven Development

TDD is the red → green loop. This skill is the reference that makes that loop produce tests worth keeping: what a good test is, where tests go, the anti-patterns, and the rules of the loop. Every section applies on every cycle — consult them before and during the loop, not after.

When exploring the codebase, read `CONTEXT.md` (if it exists) so test names and interface vocabulary match the project's domain language, and respect ADRs in the area you're touching.

What a good test is

Tests verify behavior through public interfaces, not implementation details. Code can change entirely; tests shouldn't. A good test reads like a specification — "user can checkout with valid cart" tells you exactly what capability exists — and survives refactors because it doesn't care about internal structure.

See [tests.md](tests.md) for examples and [mocking.md](mocking.md) for mocking guidelines.

Seams — where tests go

A **seam** is the public boundary you test at: the interface where you observe behavior without reaching inside. Tests live at seams, never against internals.

**Test only at pre-agreed seams.** Before writing any test, write down the seams under test and confirm them with the user. No test is written at an unconfirmed seam. You can't test everything — agreeing the seams up front is how testing effort lands on the critical paths and complex logic instead of every edge case.

Ask: "What's the public interface, and which seams should we test?"

When the shape of that interface is itself in question — how deep the module is, where the seam belongs, what the interface should expose — call the Skill tool with "codebase-design" for the vocabulary. It is the shared source of the module, interface, depth, seam, adapter, leverage and locality terms, and it is a reference to consult, not a session to run.

Anti-patterns

• **Implementation-coupled** — mocks internal collaborators, tests private methods, or verifies through a side channel (querying the database instead of using the interface). The tell: the test breaks when you refactor but behavior hasn't changed.
• **Tautological** — the assertion recomputes the expected value the way the code does (`expect(add(a, b)).toBe(a + b)`, a snapshot derived by hand the same way, a constant asserted equal to itself), so it passes by construction and can never disagree with the code. Expected values must come from an independent source of truth — a known-good literal, a worked example, the spec.
• **Horizontal slicing** — writing all tests first, then all implementation. Bulk tests verify _imagined_ behavior: you test the _shape_ of things rather than user-facing behavior, the tests go insensitive to real changes, and you commit to test structure before understanding the implementation. Work in **vertical slices** instead — one test → one implementation → repeat, each test a **tracer bullet** that responds to what the last cycle taught you.

Rules of the loop

• **Red before green.** Write the failing test first, then only enough code to pass it. Don't anticipate future tests or add speculative features.
• **One slice at a time.** One seam, one test, one minimal implementation per cycle.
• **Refactoring is not part of the loop.** It belongs to the review stage (see the `code-review` skill), not the red → green implementation cycle.

常见问题（FAQ）

使用「tdd」这个 skill 能解决什么问题?

本 skill 专注于tdd，mattpocock/skills 方法论: engineering/tdd。它将相关流程标准化，帮助用户更快拿到可靠结果，减少重复手工操作。

什么情况下适合使用「tdd」?

当你需要在tdd相关工作中获得稳定、可复用的产出时最适合——无论是单次任务还是纳入日常工作流，都能直接调用。

使用「tdd」前需要准备什么?

需要一个具体的项目或任务上下文，最好带有代码仓库或需求文档。