Test-Driven Development

Write the failing test first, then the code.

From Superpowers. Before your agent implements a feature or a bug fix, it writes a test that fails, then the code that makes it pass.

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npx skills add https://github.com/obra/superpowers --skill test-driven-development

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Claude Code
Run this in your project
npx skills add https://github.com/obra/superpowers --skill test-driven-development -a claude-code
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Or ask Claude Code to do it
Install the "test-driven-development" skill from https://github.com/obra/superpowers for Claude Code. Copy the skill folder (the one containing SKILL.md, with any scripts or reference files next to it) into .claude/skills/ in this project. Before copying, show me the SKILL.md and list any scripts it includes, and wait for me to confirm.
Or copy the folder yourself
Unzip the download into .claude/skills/ for this project, or ~/.claude/skills/ for all your projects.
Picked up in the current session, no restart needed.
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Claude.ai
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1. In Settings > Capabilities, turn on Code execution and file creation.
2. Go to Customize > Skills, press +, then Create skill.
3. Choose Upload a skill and pick the ZIP you downloaded.
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ChatGPT
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1. Open Skills in ChatGPT and select Create.
2. Select Upload from your computer and pick the ZIP you downloaded.
3. Wait for ChatGPT's safety scan. A skill marked Needs Review asks you to check it before use.
Skills that rely on scripts or a terminal may not work unchanged in ChatGPT.
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Codex
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npx skills add https://github.com/obra/superpowers --skill test-driven-development -a codex
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Or ask Codex to do it
Install the "test-driven-development" skill from https://github.com/obra/superpowers for Codex. Copy the skill folder (the one containing SKILL.md, with any scripts or reference files next to it) into .agents/skills/ in this project. Before copying, show me the SKILL.md and list any scripts it includes, and wait for me to confirm.
Or copy the folder yourself
Unzip the download into .agents/skills/ for this project, or ~/.agents/skills/ for all your projects.
Restart Codex if the skill does not show up.
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Cursor
Run this in your project
npx skills add https://github.com/obra/superpowers --skill test-driven-development -a cursor
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Or ask Cursor to do it
Install the "test-driven-development" skill from https://github.com/obra/superpowers for Cursor. Copy the skill folder (the one containing SKILL.md, with any scripts or reference files next to it) into .cursor/skills/ in this project. Before copying, show me the SKILL.md and list any scripts it includes, and wait for me to confirm.
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Unzip the download into .cursor/skills/ for this project, or ~/.cursor/skills/ for all your projects.
Run it by typing / and the skill name in chat.
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GitHub Copilot
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npx skills add https://github.com/obra/superpowers --skill test-driven-development -a github-copilot
Add -g to install it for every project instead.
Or ask GitHub Copilot to do it
Install the "test-driven-development" skill from https://github.com/obra/superpowers for GitHub Copilot. Copy the skill folder (the one containing SKILL.md, with any scripts or reference files next to it) into .github/skills/ in this project. Before copying, show me the SKILL.md and list any scripts it includes, and wait for me to confirm.
Or copy the folder yourself
Unzip the download into .github/skills/ for this project, or ~/.copilot/skills/ for all your projects.
Works in Copilot CLI, the cloud agent and agent mode in VS Code and JetBrains.
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Antigravity
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npx skills add https://github.com/obra/superpowers --skill test-driven-development -a antigravity
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Or ask Antigravity to do it
Install the "test-driven-development" skill from https://github.com/obra/superpowers for Antigravity. Copy the skill folder (the one containing SKILL.md, with any scripts or reference files next to it) into .agents/skills/ in this project. Before copying, show me the SKILL.md and list any scripts it includes, and wait for me to confirm.
Or copy the folder yourself
Unzip the download into .agents/skills/ for this project, or ~/.gemini/config/skills/ for all your projects.
Antigravity skills docs
Gemini CLI
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npx skills add https://github.com/obra/superpowers --skill test-driven-development -a gemini-cli
Add -g to install it for every project instead.
Or ask Gemini CLI to do it
Install the "test-driven-development" skill from https://github.com/obra/superpowers for Gemini CLI. Copy the skill folder (the one containing SKILL.md, with any scripts or reference files next to it) into .gemini/skills/ in this project. Before copying, show me the SKILL.md and list any scripts it includes, and wait for me to confirm.
Or copy the folder yourself
Unzip the download into .gemini/skills/ for this project, or ~/.gemini/skills/ for all your projects.
Run /skills to check it was found.
Gemini CLI skills docs

Installs: 225.2K via skills.sh
GitHub: 286.3K stars ↗
Last updated: 12 Sept 2026
Licence: MIT

Security checks

Run by independent scanners and published on skills.sh. Their results, not a Viberation review.

Gen Agent Trust Hub Pass
This skill provides comprehensive instructions for implementing Test-Driven Development (TDD) and avoiding testing anti-patterns. No malicious patterns were detected. A low-risk finding regarding indirect prompt injection is noted due to the skill's nature of processing user-provided code and executing tests.
17 Feb 2026
Socket Pass
No alerts
18 Mar 2026
Snyk Pass
Risk: LOW · No issues
17 Feb 2026
Runlayer Pass
2 files scanned · No issues
26 Feb 2026
ZeroLeaks Pass
Score: 93/100 · 2 sections analyzed
16 Apr 2026

What's inside (2 files)

SKILL.md9K chars
writing-good-tests.md8.2K chars

SKILL.md, first part. Shown as plain text.

---
name: test-driven-development
description: Use when implementing any feature or bugfix, before writing implementation code
---

# Test-Driven Development (TDD)

## Overview

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

**Core principle:** If you didn't watch the test fail, you don't know if it tests the right thing.

**Violating the letter of the rules is violating the spirit of the rules.**

## When to Use

**Always:**
- New features
- Bug fixes
- Refactoring
- Behavior changes

**Exceptions (ask your human partner):**
- Throwaway prototypes
- Generated code
- Configuration files

Thinking "skip TDD just this once"? Stop. That's rationalization.

## The Iron Law

```
NO PRODUCTION CODE WITHOUT A FAILING TEST FIRST
```

Write code before the test? Delete it. Start over.

**No exceptions:**
- Don't keep it as "reference"
- Don't "adapt" it while writing tests
- Don't look at it
- Delete means delete

Implement fresh from tests. Period.

## Red-Green-Refactor

```dot
digraph tdd_cycle {
    rankdir=LR;
    red [label="RED\nWrite failing test", shape=box, style=filled, fillcolor="#ffcccc"];
    verify_red [label="Verify fails\ncorrectly", shape=diamond];
    green [label="GREEN\nMinimal code", shape=box, style=filled, fillcolor="#ccffcc"];
    verify_green [label="Verify passes\nAll green", shape=diamond];
    refactor [label="REFACTOR\nClean up", shape=box, style=filled, fillcolor="#ccccff"];
    next [label="Next", shape=ellipse];

    red -> verify_red;
    verify_red -> green [label="yes"];
    verify_red -> red [label="wrong\nfailure"];
    green -> verify_green;
    verify_green -> refactor [label="yes"];
    verify_green -> green [label="no"];
    refactor -> verify_green [label="stay\ngreen"];
    verify_green -> next;
    next -> red;
}
```

### RED - Write Failing Test

Write one minimal test showing what should happen.

<Good>
```typescript
test('retries failed operations 3 times', async () => {
  let attempts = 0;
  const operation = () => {
    attempts++;
    if (attempts < 3) throw new Error('fail');
    return 'success';
  };

  const result = await retryOperation(operation);

  expect(result).toBe('success');
  expect(attempts).toBe(3);
});
```
Clear name, tests real behavior, one thing
</Good>

<Bad>
```typescript
test('retry works', async () => {
  const mock = jest.fn()
    .mockRejectedValueOnce(new Error())
    .mockRejectedValueOnce(new Error())
    .mockResolvedValueOnce('success');
  await retryOperation(mock);
  expect(mock).toHaveBeenCalledTimes(3);
});
```
Vague name, tests mock not code
</Bad>

**Requirements:**
- One behavior
- Clear name
- Real code (no mocks unless unavoidable)

### Verify RED - Watch It Fail

**MANDATORY. Never skip.**

```bash
npm test path/to/test.test.ts
```

Confirm:
- Test fails (not errors)
- Failure message is expected
- Fails because feature missing (not typos)

**Test passes?** You're testing existing behavior. Fix test.

**Test errors?** Fix error, re-run until it fails correctly.

### GREEN - Minimal Code

Write simplest code to pass the test.

<Good>
```typescript
async function retryOperation<T>(fn: () => Promise<T>): Promise<T> {
  for (let i = 0; i < 3; i++) {
    try {
      return await fn();
    } catch (e) {
      if (i === 2) throw e;
    }
  }
  throw new Error('unreachable');
}
```
Just enough to pass
</Good>

<Bad>
```typescript
async function retryOperation<T>(
  fn: () => Promise<T>,
  options?: {
    maxRetries?: number;
    backoff?: 'linear' | 'exponential';
    onRetry?: (attempt: number) => void;
  }
): Promise<T> {
  // YAGNI
}
```
Over-engineered
</Bad>

Don't add features, refactor other code, or "improve" beyond the test.

### Verify GREEN - Watch It Pass

**MANDATORY.**

```bash
npm test path/to/test.test.ts
```

Confirm:
- Test passes
- Other tests still pass
- Output pristine (no errors, warnings)

**Test fails?** Fix code, not test.

**Other tests fail?** Fix now.

### REFACTOR - Clean Up

After green only:
- Remove du

Key info

Pricing: Open source
Category: Skills

Test-Driven Development

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