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@repobuddy/jest

@repobuddy/jest replaces a hand-written Jest config with one preset line. Pick the preset that matches the language, the module format, and the test environment of the project. The package also exports the pieces each preset is built from, a toSatisfies matcher, and a function that lists the packages a Jest config needs.

Install

Section titled “Install”
Terminal window
# npm
npm install -D @repobuddy/jest


# yarn
yarn add -D @repobuddy/jest


# pnpm
pnpm add -D @repobuddy/jest


# rush
rush add -p @repobuddy/jest --dev

Then install the peers your preset needs:

Package Peer range Optional peer Needed by
jest >=29.5.0 no every preset
@swc/jest ^0.2.31 no ts-esm, jsdom-ts-esm, and ts / jsdom-ts in an ESM package
ts-jest ^29 yes ts-cjs, jsdom-ts-cjs, and ts / jsdom-ts in a CommonJS package
jest-esm-transformer-2 ^1 yes ts-cjs, jsdom-ts-cjs, js-cjs
jest-watch-suspend ^1 || ^2 yes watch and every -watch preset
jest-watch-toggle-config ^3 yes watch and every -watch preset
jest-watch-typeahead ^3.0.0 yes watch and every -watch preset
identity-obj-proxy ^3.0.0 yes fields.knownModuleNameMappers.cssAll only

@swc/jest itself needs @swc/core (its own peer dependency). The jsdom presets also need jest-environment-jsdom, which @repobuddy/jest does not declare. Each preset page lists the exact packages it references.

To list what a config needs, run buddy check-deps or call extract.extractPackages().

Use a preset

Section titled “Use a preset”
jest.config.mjs
export default {
  preset: '@repobuddy/jest/presets/ts-watch',
}

ESM presets need Jest’s ESM support. Run Jest with NODE_OPTIONS=--experimental-vm-modules, as the TypeScript with ESM guide shows.

Choose a preset

Section titled “Choose a preset”
Language Module format Environment Preset Transform
TypeScript from package.json type Node.js ts as ts-esm or ts-cjs
TypeScript ESM Node.js ts-esm @swc/jest
TypeScript CommonJS Node.js ts-cjs ts-jest, jest-esm-transformer-2 for JS
JavaScript ESM Node.js js-esm Jest’s default (babel-jest)
JavaScript CommonJS Node.js js-cjs jest-esm-transformer-2
TypeScript from package.json type jsdom jsdom-ts as jsdom-ts-esm or jsdom-ts-cjs
TypeScript ESM jsdom jsdom-ts-esm @swc/jest
TypeScript CommonJS jsdom jsdom-ts-cjs ts-jest, jest-esm-transformer-2 for JS
any any any watch none: watch plugins only, for the root of a multi-project config

Every preset except watch has a -watch variant (ts-watch, jsdom-ts-cjs-watch, and so on) that adds five watch plugins. See watch for the list. The presets index has every name.

Support

Section titled “Support”
Area Support Source
Jest jest >=29.5.0 (peer). This repository tests with Jest 30. packages/jest/package.json
Node.js No engines field. Node-version test files cover Node.js 14 up to the running major. packages/jest/src/configs/node.ts
Package format ESM (esm/) and CommonJS (cjs/) builds of every entry. packages/jest/package.json exports
Project module format ESM (-esm presets) and CommonJS (-cjs presets). ts and jsdom-ts choose from package.json type. packages/jest/src/presets/
Environments node (node and js presets) and jsdom (jsdom presets). packages/jest/src/configs/node.ts, jsdom.ts
TypeScript transforms @swc/jest for ESM, ts-jest with isolatedModules: true for CommonJS. ts-jest for ESM through fields.knownTransforms.tsJestEsm(). packages/jest/src/configs/typescript.ts, src/fields/transform.ts
ESM dependencies in CommonJS jest-esm-transformer-2 with transformIgnorePatterns: [] transforms ESM packages in node_modules. packages/jest/src/configs/typescript.ts, javascript.ts
Source folder First of src, source, ts, js that exists in the working directory; src otherwise. packages/jest/src/configs/source.ts
Monorepo Run Jest in each package, or use projects with one preset per project and watch at the root. Detection runs in the working directory: see the monorepo guide. packages/jest/src/presets/watch/jest-preset.ts

Not supported

Section titled “Not supported”
  • JavaScript in jsdom. Every jsdom preset is a TypeScript preset. Compose configs.jsdom with configs.jsEsm or configs.jsCjs yourself (see customize a preset).
  • Other environments, such as happy-dom or a real browser. The package knows only node and jsdom.
  • A Babel preset. No preset configures Babel. js-esm sets no transform, so Jest’s default babel-jest stays in place.
  • ts-jest for ESM as a preset. The ESM presets use @swc/jest. Build the ts-jest variant from configs and fields.
  • Per-project detection in a multi-project config. Each preset reads the source folder and package.json type from the directory Jest runs in, not from each project’s rootDir.
  • A @repobuddy/jest/resolver entry. The resolver is reachable only as resolver from the main entry (see resolver).
  • Load tests in the jsdom presets. *.load.* files run only through configs.nodeLoad.

Next steps

Section titled “Next steps”