Is the Test-Driven Development (Addy Osmani) skill free?

Yes. The skill itself is free from kevinnft/ai-agent-skills. SkillProof publishes the install command and an independent test verdict at no cost.

What is the Test-Driven Development (Addy Osmani) SkillProof Score?

8.4/10 — installs cleanly 4/5, triggers reliably 5/5, output vs. baseline 9/10, docs & honesty 3/5.

How do I install Test-Driven Development (Addy Osmani)?

Copy the install command from this page, run it in your terminal, and restart Claude Code. Skills live in ~/.claude/skills/ (global) or .claude/skills/ inside a project.

Can I use Test-Driven Development (Addy Osmani) with Cursor, Copilot, Gemini CLI, Codex or other AI tools?

The SKILL.md format is native to Claude (Claude Code, Desktop, claude.ai). The instructions inside adapt to other assistants: Cursor rules, GitHub Copilot instructions, Windsurf rules, Custom GPTs, AGENTS.md for OpenAI Codex, and GEMINI.md for Google Gemini CLI — our conversion guides cover each, and the free converter on the tools page does the wrapping for you.

Test-Driven Development (Addy Osmani)

Enforces RED-GREEN-REFACTOR and a test-first 'Prove-It Pattern' for every bug fix or behavior change.

by kevinnft · kevinnft/ai-agent-skills

Works with setup

Install — copy the command Download source ↗

Test report

Verdict: Works with setup
Score: 8.4/10
Tested: Jul 16, 2026
Environment: Claude Code 2.x (agent harness)
Upstream re-checked: Jul 16, 2026

⚠ This skill is no longer available upstream. Our re-check on Aug 10, 2026 couldn't find it any more (SKILL.md not found in repo tree). The test below is what we measured on Jul 16, 2026 and we're leaving it up as a record — but there is nothing left to install, so we've removed the command.

Actually ran the Prove-It Pattern on a planted discount-calculator bug in Node: the reproduction tests failed 3/3 against the buggy implementation ($100 at 20% returned 20 instead of 80) before the fix, then passed 3/3 after — a genuinely stronger, evidence-backed artifact than the baseline's silent patch-and-done. Docked to 'setup' because the SKILL.md points to `references/testing-patterns.md` for detailed patterns, but that file returns a 404 and doesn't exist anywhere in the repo, and the referenced 'browser-testing-with-devtools' companion is a sibling skill folder a verbatim per-skill copy won't carry along.

Scored on four weighted criteria — install, triggering, output vs. baseline, docs. How scoring works

Installs cleanly 4/5
Triggers reliably 5/5
Output vs. baseline 9/10
Docs & honesty 3/5

What Test-Driven Development (Addy Osmani) does

Requires a failing test before any new logic or bug fix, walks through RED/GREEN/REFACTOR with worked TypeScript examples, and reproduces bugs with a failing test before attempting a fix. Also covers the test pyramid, DAMP-over-DRY, real-implementation-over-mocks, and a pre-completion verification checklist. Triggers when implementing logic, fixing a bug, or modifying existing behavior; explicitly skips pure config/doc-only changes.

How to install Test-Driven Development (Addy Osmani)

Nothing to install: the source repository no longer has this skill. If the author brings it back, our daily re-check will pick it up and the command will reappear here.

Commands — how to trigger Test-Driven Development (Addy Osmani)

/addyosmani-tdd Enforces RED-GREEN-REFACTOR and a test-first 'Prove-It Pattern' for every bug fix or behavior change.

It also activates on plain-language prompts like these:

Write a failing test before you fix this discount calculator bug
Walk me through red-green-refactor for this new checkout feature
Reproduce this reported bug with a test before we attempt a patch

Frequently asked questions

Is the Test-Driven Development (Addy Osmani) skill free?: Yes. The skill itself is free from kevinnft/ai-agent-skills. SkillProof publishes the install command and an independent test verdict at no cost.
Does Test-Driven Development (Addy Osmani) work with Claude Code?: We tested it with Claude Code 2.x (agent harness) on Jul 16, 2026. Verdict: Works with setup. Actually ran the Prove-It Pattern on a planted discount-calculator bug in Node: the reproduction tests failed 3/3 against the buggy implementation ($100 at 20% returned 20 instead of 80) before the fix, then passed 3/3 after — a genuinely stronger, evidence-backed artifact than the baseline's silent patch-and-done. Docked to 'setup' because the SKILL.md points to `references/testing-patterns.md` for detailed patterns, but that file returns a 404 and doesn't exist anywhere in the repo, and the referenced 'browser-testing-with-devtools' companion is a sibling skill folder a verbatim per-skill copy won't carry along.
What is the Test-Driven Development (Addy Osmani) SkillProof Score?: 8.4/10 — installs cleanly 4/5, triggers reliably 5/5, output vs. baseline 9/10, docs & honesty 3/5.
How do I install Test-Driven Development (Addy Osmani)?: Copy the install command from this page, run it in your terminal, and restart Claude Code. Skills live in ~/.claude/skills/ (global) or .claude/skills/ inside a project.
Can I use Test-Driven Development (Addy Osmani) with Cursor, Copilot, Gemini CLI, Codex or other AI tools?: The SKILL.md format is native to Claude (Claude Code, Desktop, claude.ai). The instructions inside adapt to other assistants: Cursor rules, GitHub Copilot instructions, Windsurf rules, Custom GPTs, AGENTS.md for OpenAI Codex, and GEMINI.md for Google Gemini CLI — our conversion guides cover each, and the free converter on the tools page does the wrapping for you.