Agent skill

Jest Generator

Generate Jest unit tests for JavaScript/TypeScript with mocking, coverage.

MITAuto-check: notesTesting & QA

Install Jest Generator

skills CLI

$ npx skills add secondsky/claude-skills --skill jest-generator -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI

$ gh skill install secondsky/claude-skills jest-generator --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy

$ git clone --depth 1 https://github.com/secondsky/claude-skills.git skills-src && mkdir -p .claude/skills && cp -r skills-src/plugins/jest-generator/skills/jest-generator .claude/skills/jest-generator && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Paste into Claude Code

Install the "jest-generator" agent skill from https://github.com/secondsky/claude-skills/tree/main/plugins/jest-generator/skills/jest-generator into .claude/skills/jest-generator/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "jest-generator", then confirm the skill loads.

Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

$skill-installer

$skill-installer install https://github.com/secondsky/claude-skills/tree/main/plugins/jest-generator/skills/jest-generator

Type this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.

skills CLI

$ npx skills add secondsky/claude-skills --skill jest-generator -a codex

Project install goes to .agents/skills/; add -g for ~/.codex/skills/.

GitHub CLI

$ gh skill install secondsky/claude-skills jest-generator --agent codex

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/secondsky/claude-skills.git skills-src && mkdir -p .agents/skills && cp -r skills-src/plugins/jest-generator/skills/jest-generator .agents/skills/jest-generator && rm -rf skills-src

Use ~/.agents/skills/ instead of .agents/skills for a personal install.

Codex skills documentation · loads skills from .agents/skills/

Paste into Codex

Install the "jest-generator" agent skill from https://github.com/secondsky/claude-skills/tree/main/plugins/jest-generator/skills/jest-generator into .agents/skills/jest-generator/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "jest-generator", then confirm the skill loads.

Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add secondsky/claude-skills --skill jest-generator -a cursor

Project install goes to .agents/skills/; add -g for ~/.cursor/skills/.

GitHub CLI

$ gh skill install secondsky/claude-skills jest-generator --agent cursor

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/secondsky/claude-skills.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/plugins/jest-generator/skills/jest-generator .cursor/skills/jest-generator && rm -rf skills-src

Use ~/.cursor/skills/ instead of .cursor/skills for a personal install.

Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/

Paste into Cursor

Install the "jest-generator" agent skill from https://github.com/secondsky/claude-skills/tree/main/plugins/jest-generator/skills/jest-generator into .cursor/skills/jest-generator/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "jest-generator", then confirm the skill loads.

Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

gemini skills install

$ gemini skills install https://github.com/secondsky/claude-skills.git --path plugins/jest-generator/skills/jest-generator

--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.

skills CLI

$ npx skills add secondsky/claude-skills --skill jest-generator -a gemini-cli

Project install goes to .agents/skills/; add -g for ~/.gemini/skills/.

GitHub CLI

$ gh skill install secondsky/claude-skills jest-generator --agent gemini-cli

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/secondsky/claude-skills.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/plugins/jest-generator/skills/jest-generator .gemini/skills/jest-generator && rm -rf skills-src

Use ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.

Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/

Paste into Gemini CLI

Install the "jest-generator" agent skill from https://github.com/secondsky/claude-skills/tree/main/plugins/jest-generator/skills/jest-generator into .gemini/skills/jest-generator/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "jest-generator", then confirm the skill loads.

Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

GitHub CLI

$ gh skill install secondsky/claude-skills jest-generator

Installs for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).

skills CLI

$ npx skills add secondsky/claude-skills --skill jest-generator -a github-copilot

Project install goes to .agents/skills/; add -g for ~/.copilot/skills/.

Manual copy

$ git clone --depth 1 https://github.com/secondsky/claude-skills.git skills-src && mkdir -p .github/skills && cp -r skills-src/plugins/jest-generator/skills/jest-generator .github/skills/jest-generator && rm -rf skills-src

Use ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.

GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/

Paste into GitHub Copilot

Install the "jest-generator" agent skill from https://github.com/secondsky/claude-skills/tree/main/plugins/jest-generator/skills/jest-generator into .github/skills/jest-generator/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "jest-generator", then confirm the skill loads.

GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add secondsky/claude-skills --skill jest-generator -a opencode

OpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.

GitHub CLI

$ gh skill install secondsky/claude-skills jest-generator --agent opencode

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/secondsky/claude-skills.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/plugins/jest-generator/skills/jest-generator .opencode/skills/jest-generator && rm -rf skills-src

Use ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.

OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/

Paste into OpenCode

Install the "jest-generator" agent skill from https://github.com/secondsky/claude-skills/tree/main/plugins/jest-generator/skills/jest-generator into .opencode/skills/jest-generator/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "jest-generator", then confirm the skill loads.

OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

Facts

Skill name: jest-generator
GitHub stars: 227
Token cost: ~1.1k tokens
SKILL.md length: 166 words
Files: 1
Skills in repo: 169
Repo updated: Sep 28, 2026
First seen: Oct 7, 2026
Licence: MIT

At a glance

Generate Jest unit tests for JavaScript/TypeScript with mocking, coverage.

Works in 8 steps: Use descriptive test names: should when → Organize with describe blocks → Mock external dependencies only → …
React components
SKILL.md covers Purpose, When to Use, Test File Naming and Running Tests, plus 4 more sections
Calls bun and npm

What it does

Jest Generator is an agent skill from secondsky/claude-skills. Generate Jest unit tests for JavaScript/TypeScript with mocking, coverage. Use for JS/TS modules, React components, test generation, or encountering missing coverage, improper mocking, test structure errors.

Its SKILL.md is about 1.1k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Testing & QA, covering Unit testing and React components. It works with Jest, JavaScript and TypeScript. The repository describes itself as: Production-ready skills for Claude Code CLI - Cloudflare, React, Tailwind v4, and AI integrations. The licence is MIT.

When your agent uses it

React components
Test generation
Encountering missing coverage
Improper mocking

Example prompts

“/jest-generator”

Requirements

Pre-approved tools (allowed-tools): Read, Write, Edit, Bash, Grep, Glob

Workflow steps

8 steps, taken from the first numbered list in SKILL.md.

Use descriptive test names: should when
Organize with describe blocks
Mock external dependencies only
Test user behavior for components
Use test.each for parametrized tests
Keep tests independent
Test error conditions
Aim for 80%+ coverage

What it can do on your machine

Read from SKILL.md and the folder at commit 8837836. It shows what the files ask for, not the result of running them.

Tool permissions
Pre-approves these tools, so the agent can use them without asking each time:
- Read
- Write
- Edit
- Bash
- Grep
- Glob
From allowed-tools in the SKILL.md frontmatter.
Runs code
Shell commands in SKILL.md call:
- bun
- npm
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md. Its commands use npm, which can reach the network depending on how they are called.
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Jest Generator loads about 1.1k tokens when it runs. Until then it costs about 56 tokens; SKILL.md has 166 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it: ~56
When it runs · the whole SKILL.md, loaded when a task matches: ~1.1k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check: notes

The automated check noted patterns worth knowing about, such as sudo or a known installer.

NotePre-approves every shell command (allowed-tools: Bash)SKILL.md
```
allowed-tools: Read, Write, Edit, Bash, Grep, Glob
```

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from secondsky/claude-skills at commit 8837836, republished under its MIT licence (© secondsky). 166 words, ~1,128 tokens.

Download SKILL.mdSave it as .claude/skills/jest-generator/SKILL.md (or your agent's skills folder).

name: jest-generator
description: Generate Jest unit tests for JavaScript/TypeScript with mocking, coverage. Use for JS/TS modules, React components, test generation, or encountering missing coverage, improper mocking, test structure errors.
allowed-tools: Read, Write, Edit, Bash, Grep, Glob
license: MIT

Jest Generator Skill

Purpose

Generate Jest-based unit tests for JavaScript and TypeScript code, following Jest conventions and best practices with proper mocking, describe blocks, and code organization.

When to Use

Generate Jest tests for JavaScript/TypeScript modules
Create test files for React components
Add missing test coverage to existing code
Need Jest-specific patterns (mocks, spies, snapshots)

Test File Naming

Source to Test Mapping:

src/components/Feature.tsx → src/components/Feature.test.tsx
src/utils/validator.ts → src/utils/validator.test.ts
src/models/User.ts → src/models/User.test.ts

Running Tests

bash

# Preferred: Using bun (faster)
bun test

# Run specific file
bun test src/utils/validator.test.ts

# Run with coverage
bun test --coverage

# Watch mode
bun test --watch

# Alternative: Using npm
npm test
npm test -- --coverage

Jest Test Structure

typescript

import { functionToTest, ClassToTest } from './Feature'

jest.mock('./dependency')

describe('ModuleName', () => {
  beforeEach(() => {
    jest.clearAllMocks()
  })

  afterEach(() => {
    jest.restoreAllMocks()
  })

  describe('ClassName', () => {
    let instance: ClassToTest

    beforeEach(() => {
      instance = new ClassToTest()
    })

    it('should return expected result with valid input', () => {
      // Arrange
      const input = { key: 'value' }
      const expected = { processed: true }

      // Act
      const result = instance.method(input)

      // Assert
      expect(result).toEqual(expected)
    })

    it('should throw error with invalid input', () => {
      expect(() => instance.method(null)).toThrow('Invalid input')
    })
  })
})

Jest-Specific Patterns

Mocking

typescript

// Mock entire module
jest.mock('./api', () => ({
  fetchData: jest.fn(),
}))

// Mock with implementation
const mockFn = jest.fn((x: number) => x * 2)

// Spy on method
const spy = jest.spyOn(obj, 'method').mockReturnValue('mocked')
spy.mockRestore()

Async Testing

typescript

it('should resolve with data', async () => {
  const result = await asyncFunction()
  expect(result).toBeDefined()
})

it('should reject with error', async () => {
  await expect(asyncFunction()).rejects.toThrow('Error')
})

Timers

typescript

beforeEach(() => jest.useFakeTimers())
afterEach(() => jest.useRealTimers())

it('should execute after timeout', () => {
  const callback = jest.fn()
  setTimeout(callback, 1000)
  jest.advanceTimersByTime(1000)
  expect(callback).toHaveBeenCalled()
})

Common Matchers

typescript

// Equality
expect(value).toBe(expected)
expect(value).toEqual(expected)

// Truthiness
expect(value).toBeTruthy()
expect(value).toBeNull()
expect(value).toBeDefined()

// Arrays/Objects
expect(array).toContain(item)
expect(obj).toHaveProperty('key')

// Functions/Promises
expect(fn).toThrow('error')
await expect(promise).resolves.toBe(value)

// Mock functions
expect(mockFn).toHaveBeenCalled()
expect(mockFn).toHaveBeenCalledWith(arg)

React Component Testing

typescript

import { render, screen, fireEvent } from '@testing-library/react'
import '@testing-library/jest-dom'
import { Button } from './Button'

describe('Button', () => {
  it('should call onClick when clicked', () => {
    const handleClick = jest.fn()
    render(<Button onClick={handleClick}>Click me</Button>)
    fireEvent.click(screen.getByText('Click me'))
    expect(handleClick).toHaveBeenCalledTimes(1)
  })
})

Quality Checklist

Test file properly named (<module>.test.ts)
All exported functions/classes tested
Happy path and edge cases included
Error conditions tested
External dependencies mocked
Tests organized with describe blocks
beforeEach/afterEach for setup/cleanup
Descriptive test names
Coverage ≥ 80%

Best Practices

Use descriptive test names: should <expected> when <condition>
Organize with describe blocks
Mock external dependencies only
Test user behavior for components
Use test.each for parametrized tests
Keep tests independent
Test error conditions
Aim for 80%+ coverage

Files

Just SKILL.md in plugins/jest-generator/skills/jest-generator of secondsky/claude-skills.

Open the folder on GitHubat commit 8837836

Compare with similar skills

Jest Generator next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Jest Generator compared with similar skills
Skill	Stars	Used in	Tokens	Auto-check	Licence	Repo updated
Jest Generator this skillsecondsky/claude-skills	227	—	~1.1k	Automated safety check: Notes	MIT	9 days ago
Jest Skillsickn33/agentic-awesome-skills	47k	1 repos	~1.4k	Automated safety check: Pass	MIT	yesterday
Typescript Rulessoftspark/ai-toolkit	179	—	~2.7k	Automated safety check: Notes	Apache-2.0	today
React Testinggetsentry/sentry	45k	—	~2.2k	Automated safety check: Pass	Custom licence	today
Vitest Skillsickn33/agentic-awesome-skills	47k	1 repos	~1.2k	Automated safety check: Pass	MIT	yesterday
Javascript Typescript Jestgithub/awesome-copilot	40k	1 repos	~559	Automated safety check: Pass	MIT	today

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Works with

Questions about Jest Generator

What does Jest Generator do?

Generate Jest unit tests for JavaScript/TypeScript with mocking, coverage. Jest Generator is an agent skill from secondsky/claude-skills. Generate Jest unit tests for JavaScript/TypeScript with mocking, coverage.

When should I use Jest Generator?

Jest Generator fits situations like: React components; test generation; encountering missing coverage; improper mocking.

How do I install Jest Generator in Claude Code?

Run `npx skills add secondsky/claude-skills --skill jest-generator -a claude-code`. Or copy the skill folder (plugins/jest-generator/skills/jest-generator in secondsky/claude-skills) into .claude/skills/jest-generator in your project. Claude Code loads it when a task matches its description.

How do I install Jest Generator in Codex?

Run `npx skills add secondsky/claude-skills --skill jest-generator -a codex`. Or copy the skill folder (plugins/jest-generator/skills/jest-generator in secondsky/claude-skills) into .agents/skills/jest-generator in your project. Codex loads it when a task matches its description.

Can I use Jest Generator in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add secondsky/claude-skills --skill jest-generator -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/jest-generator, .gemini/skills/jest-generator, .github/skills/jest-generator and .opencode/skills/jest-generator in your project.

What does Jest Generator need to run?

Going by SKILL.md and its folder, Jest Generator needs the command-line tools its instructions call (bun and npm). Its frontmatter pre-approves these tools: Read, Write, Edit, Bash, Grep, Glob.

Does Jest Generator access the network?

SKILL.md contains no URLs. Its commands use npm, which can reach the network depending on how they are called. This is read from the text; nothing was executed.

Is Jest Generator safe to install?

Our automated static check of SKILL.md found notes only (pre-approves every shell command (allowed-tools: bash)), nothing it rates as a warning. It is not a guarantee. Review the folder before installing.

What licence does Jest Generator use?

Jest Generator is published under the MIT licence (declared in SKILL.md). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Jest Generator use?

About 1.1k tokens (SKILL.md is roughly 4.5k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Jest Generator?

Skills that share tags, products or a category with Jest Generator: Jest Skill (sickn33/agentic-awesome-skills, 47k stars), Typescript Rules (softspark/ai-toolkit, 179 stars), React Testing (getsentry/sentry, 45k stars) and Vitest Skill (sickn33/agentic-awesome-skills, 47k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Jest Generator?

secondsky (a GitHub user) maintains it in secondsky/claude-skills, which has 227 GitHub stars. The repository holds 169 skills in this directory. The repository was last updated on September 28, 2026.

Source: secondsky/claude-skills on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.

Install Jest Generator

Facts

At a glance

What it does

When your agent uses it

Example prompts

Requirements

Workflow steps

What it can do on your machine

Tool permissions

Runs code

Network

Credentials

Context cost

Safety

SKILL.md

Jest Generator Skill

Purpose

When to Use

Test File Naming

Running Tests

Jest Test Structure

Jest-Specific Patterns

Mocking

Async Testing

Timers

Common Matchers

React Component Testing

Quality Checklist

Best Practices

Files

Compare with similar skills

Similar skills

More from secondsky/claude-skills

Related

Questions about Jest Generator