Jest config generator — jest.config.js with ts-jest and coverage

How to use the Jest config generator

1. Choose the Test environment: Node or jsdom (browser-like).
2. Keep TypeScript via ts-jest ticked for .ts tests, or untick it for plain JavaScript.
3. Tick Collect coverage and set Coverage threshold %; 0 means no minimum.
4. Optionally fill in Test roots (comma-separated folders) and a Setup file after environment, such as jest.setup.ts.
5. Tick Stub CSS imports if components import style files, pick the Module format, then copy the config and run the install command.

What it does and when to use it

Jest runs without any config, but real projects soon need one: TypeScript compilation, a browser-like DOM, a setup file for test helpers, or a coverage gate in CI. This tool writes those settings in one go and lists the packages they depend on, which is where hand-written configs usually go wrong.

If you skip ts-jest, the Babel config generator gives Jest a way to read modern syntax and TypeScript. The tsconfig generator sets up the compiler options ts-jest reads, and the GitHub Actions generator can run npm test on every push so the coverage threshold actually blocks bad merges.

How it works

The file opens with a type comment so editors offer autocomplete, then adds only what you chose:

• preset: 'ts-jest' and the TypeScript packages when ts-jest is on;
• testEnvironment, plus jest-environment-jsdom for jsdom;
• roots and setupFilesAfterEnv, with <rootDir>/ added in front of each path;
• a moduleNameMapper that sends .css, .less, .scss and .sass imports to identity-obj-proxy;
• coverage with the V8 provider, gathered from src/**, and a global threshold for branches, functions, lines and statements.

clearMocks: true resets mock calls between tests. Option names match the Jest configuration docs; the tool targets Jest 30.

Worked examples

Defaults: Node, ts-jest, 80% coverage, roots src.

  preset: 'ts-jest',
  testEnvironment: 'node',
  roots: ['<rootDir>/src'],
  collectCoverage: true,
  coverageDirectory: 'coverage',
  coverageProvider: 'v8',
  collectCoverageFrom: ['src/**/*.{ts,tsx}', '!src/**/*.d.ts'],

followed by global: { branches: 80, functions: 80, lines: 80, statements: 80 },. Install: npm install --save-dev jest ts-jest @types/jest typescript.

A JavaScript component library. jsdom, no ts-jest, no coverage, CSS stubs on, ES module, setup file ./jest.setup.js, roots cleared. The config gains setupFilesAfterEnv: ['<rootDir>/jest.setup.js'], and ends with export default config;. Install: npm install --save-dev jest jest-environment-jsdom identity-obj-proxy.

Limits and tips

• Coverage is always collected from src/. Edit collectCoverageFrom if your code lives elsewhere.
• Path aliases such as @/ need their own moduleNameMapper entry.
• The setup file is only referenced. Create it yourself, for example to import @testing-library/jest-dom.