jest-config-generator_skill

Overview

This skill generates complete, ready-to-use Jest configuration files for JavaScript and TypeScript projects. It produces jest.config.js, jest.config.ts, or jest.config.json with sensible defaults for coverage, transforms, module resolution, and environment-specific settings. Use it to quickly bootstrap testing configs for Node APIs, React apps, Next.js, monorepos, or packages.

How this skill works

On request it detects the project type (TypeScript Node, React/Vite/CRA, Next.js, API backend, monorepo, or single package) and returns a tailored Jest configuration file. Each template includes testEnvironment, transforms (ts-jest or babel-jest), moduleNameMapper for common path aliases and asset mocks, coverage settings and thresholds, setup files, and performance/timeouts. It also flags missing setup files or mismatched tsconfig path aliases so you can adjust before saving.

When to use it

• Bootstrapping tests for a new TypeScript Node API
• Adding Jest to a React app using Vite or CRA with React Testing Library
• Creating a Next.js-compatible Jest config (App Router supported)
• Standardizing Jest configs across a monorepo or multiple packages
• Generating project-specific coverage and mock rules quickly

Best practices

• Match testEnvironment to runtime: 'node' for backends, 'jsdom' for frontend DOM tests
• Keep transforms aligned with your build tool: ts-jest for TS, babel-jest for JS/JSX when using Babel
• Sync moduleNameMapper with tsconfig paths to avoid unresolved imports in tests
• Exclude generated, story, and type files from coverage to get meaningful metrics
• Add setupFilesAfterEnv for global mocks (e.g., jest-dom, IntersectionObserver) and note required files if missing

Example use cases

• Create Jest config for a TypeScript Node.js API with ts-jest, coverage, and path aliases
• Generate a React app config with jsdom, CSS and file mocks, and RTL setup file
• Produce a Next.js Jest config using next/jest and app-router-aware settings
• Create a root monorepo Jest config that references per-package jest.config.js files
• Generate a package-level jest.config.js with displayName and preset for shared libraries