Code Review & Testing · IN-DEPTH PROFILE

tdd Skill

A practical test-driven development workflow for coding agents.

View listed source ↗Installation guide ↓Read the practical TDD workflow ↗
Best for

Engineers implementing behavior incrementally

What you get

Agree test seams + Run vertical slices

Main limitation

The workflow needs a functioning test runner and clear public behavior.

First risk

False confidence. A green suite only validates the selected examples and seams. Keep exploratory, integration, and operational checks where needed.

EVIDENCE FRESHNESS

Three checks, kept separate

A recent source check is not a runtime test or security audit.

Upstream sourceChecked 2026-09-23

Pinned revision · c55ee460

Open pinned commit ↗
SkillSignal profileSource-grounded

Updated 2026-08-20

Runtime & securityNot independently verified

Source review does not certify behavior or safety.

IN PLAIN ENGLISH

What it does—and when it fits

Matt Pocock's TDD Skill treats implementation as a behavior-focused red → green loop: agree on public test seams, work in vertical slices, and use independent expected results. Refactoring is a separate review-stage activity, not part of that implementation loop. Tests should describe behavior that survives internal changes.

This is aimed at Engineers implementing behavior incrementally. Compare the examples below with your task, then review the limitations, permissions, and risks before installing.

What you get
  • Agree test seamsIdentify public boundaries before writing tests, including what each test catches and misses.
  • Run vertical slicesWrite one failing behavior test, make the smallest change to pass it, then repeat.
  • Refactor in reviewReview the diff and keep cleanup outside the red → green implementation loop.
What makes it different
  • This profile is manually organized around the current upstream SKILL.md workflow.
  • The capability boundary remains explicitly tied to mattpocock.
  • Core uses, limitations, and risks are separated for pre-install review.
Community signalskills.sh All-time: #6 · 1.1M installs

No verified review text is in the current dataset. Use the linked source for the latest discussion.

Read the source note ↗

INSTALL BY AGENT

Choose your Agent

Paths come from official Agent docs or the universal installer behind skills.sh. Compatibility still follows this Skill's record.

Native

This Skill's current record explicitly names this Agent. Still inspect scripts, permissions, and external dependencies first.

Project install (recommended)
npx skills add https://github.com/mattpocock/skills --skill tdd --agent codex
Personal install
npx skills add https://github.com/mattpocock/skills --skill tdd --agent codex -g

Project install stays with this repository for team sharing. Personal install adds -g and works across repositories.

View install paths
Project path.agents/skills/tdd/
Personal path~/.agents/skills/tdd/
Official agent docs

Codex scans repository .agents/skills folders and the personal ~/.agents/skills directory. It normally detects newly added Skills automatically.

View path evidence ↗

TYPICAL WORKFLOW

A practical workflow

01

Agree test seams

Identify public boundaries before writing tests, including what each test catches and misses.

02

Run vertical slices

Write one failing behavior test, make the smallest change to pass it, then repeat.

03

Refactor in review

Review the diff and keep cleanup outside the red → green implementation loop.

THE TRADEOFFS

Advantages and tradeoffs

Notable strengths

  1. This profile is manually organized around the current upstream SKILL.md workflow.
  2. The capability boundary remains explicitly tied to mattpocock.
  3. Core uses, limitations, and risks are separated for pre-install review.

Limitations

  1. The workflow needs a functioning test runner and clear public behavior.
  2. TDD cannot compensate for testing the wrong seam or misunderstanding the requirement.

COMPARE THE TRADEOFF

Consider these close alternatives

These are deterministic nearby candidates, not paid placements or a universal ranking. Open the full profile before choosing.

01

Same job family · native to Codex + Claude Code

grill-me

Relentless decision interviews for sharper plans and designs.
Tradeoff to check
The package is a launcher that calls the separate grilling Skill; installing grill-me alone may not include the interview itself.
First risk
Decision fatigue · Low
Source state
Pinned · c55ee460
Open grill-me profile ↗
02

Same job family · native to Codex + Claude Code

bug-receipt

Close defects with a structured diagnosis and verification receipt.
Tradeoff to check
Detailed package files are not fully catalogued.
First risk
Review before install · Medium
Source state
Pinned · 1f564408
Open bug-receipt profile ↗
03

Same job family · native to Codex + Claude Code

csharp-async

Apply safe, modern asynchronous programming patterns in C#.
Tradeoff to check
Detailed package files are not fully catalogued.
First risk
Review before install · Medium
Source state
Pinned · 1f564408
Open csharp-async profile ↗
Compare more in the directory →

BEST FIT

Who it is for

→

Engineers implementing behavior incrementally

→

Teams trying to make tests resilient to refactors

BEFORE YOU USE IT

Risks to review before use

Medium

False confidence

A green suite only validates the selected examples and seams. Keep exploratory, integration, and operational checks where needed.

Medium

Upstream instruction drift

Behavior can change with upstream updates. Record the commit used for important workflows and review updates before adoption.

SECURITY

What the permission profile means

  • Declared access remains governed by the current upstream SKILL.md and runtime requests.
  • Treat repository files, web content, and tool output as untrusted input.
  • SkillSignal has not independently executed or security-audited this package; external skills.sh labels are not SkillSignal certification.

Not a security certification. External ratings are attributed references. SkillSignal has not independently executed or security-reviewed this Skill.

COMMON QUESTIONS

tdd Skill FAQ

What is the tdd Skill?

A practical test-driven development workflow for coding agents. Matt Pocock's TDD Skill treats implementation as a behavior-focused red → green loop: agree on public test seams, work in vertical slices, and use independent expected results. Refactoring is a separate review-stage activity, not part of that implementation loop. Tests should describe behavior that survives internal changes.

How do I install the tdd Skill?

Open and review the listed source, choose the project or personal path for your Agent, then verify the first run in a controlled project. Open the listed skills.sh page and upstream repository; verify the current SKILL.md.

Is the tdd Skill safe to use?

SkillSignal checked the source on 2026-09-23, but that is not a runtime test or security certification. Review the “False confidence” risk first and begin with the least access required.

INSIDE THE PACKAGE

Indexed files

SKILL.mdUpstream Skill instructionsSource-linked

TAGS

tddtestingbehavior testing

Manually expanded from the current upstream SKILL.md and linked source at mattpocock, checked 2026-08-19. This is an original summary, not an execution result or security certification.