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ts-cjs

ts-cjs runs TypeScript tests as CommonJS in the node environment. ts-jest transforms TypeScript, and jest-esm-transformer-2 transforms JavaScript, including ESM packages in node_modules.

Usage

Section titled “Usage”
jest.config.js
module.exports = {
  preset: '@repobuddy/jest/presets/ts-cjs',
}

Options

Section titled “Options”

None. A preset takes no options.

Effective config

Section titled “Effective config”

Printed from the built preset with Node.js 26, in a directory that has a src folder:

{
  transform: {
    '^.+\\.(ts|tsx|cts|mts)$': ['ts-jest', { isolatedModules: true }],
    '\\.m?jsx?$': 'jest-esm-transformer-2',
  },
  transformIgnorePatterns: [],
  collectCoverageFrom: [
    '<rootDir>/src/**/*.{js,jsx,cjs,mjs,ts,tsx,cts,mts}',
    '!<rootDir>/src/**/*.stories.*',
  ],
  roots: ['<rootDir>/src'],
  coveragePathIgnorePatterns: [
    '\\.(spec|test|unit|accept|integrate|learning|system|perf|stress|load)(\\..*)?\\.(js|jsx|cjs|mjs|ts|tsx|cts|mts)$',
  ],
  testEnvironment: 'node',
  testRegex: [
    '\\.(spec|test|unit|accept|integrate|learning|system|perf|stress)(\\.node)?\\.(js|jsx|cjs|mjs|ts|tsx|cts|mts)$',
    '\\.(spec|test|unit|accept|integrate|learning|system|perf|stress)\\.node14\\.(js|jsx|cjs|mjs|ts|tsx|cts|mts)$',
    // one entry per Node.js major, from 15 up to the running major
  ],
}

It is built from configs.tsCjs, configs.configSource(), and configs.node.

Packages it needs

Section titled “Packages it needs”

extract.extractPackages() on the preset returns:

['jest-environment-node', 'jest-esm-transformer-2', 'ts-jest']

ts-jest also needs typescript.

Behavior

Section titled “Behavior”
  • transformIgnorePatterns: [] makes Jest transform files in node_modules too. jest-esm-transformer-2 turns ESM-only packages into CommonJS, so import chalk from 'chalk' works with chalk 6 in the ts-cjs fixture.
  • The .js, .jsx, .mjs files of the project also go through jest-esm-transformer-2.
  • ts-jest reads the project’s tsconfig.json. The preset passes only isolatedModules: true, which skips type checking.
  • With ts-jest 29.4.14, the run prints a warning that the isolatedModules option of ts-jest is deprecated in favor of isolatedModules: true in tsconfig.json. The tests still run.
  • Test file names: see test file names.

ts-cjs-watch variant

Section titled “ts-cjs-watch variant”

@repobuddy/jest/presets/ts-cjs-watch is ts-cjs plus the watch plugins of the watch preset.

Examples

Section titled “Examples”
jest.config.js
module.exports = {
  preset: '@repobuddy/jest/presets/ts-cjs-watch',
}

Pass your own ts-jest options. Your transform pattern is the same as the preset’s, so it replaces that entry and keeps jest-esm-transformer-2:

jest.config.js
const { fields } = require('@repobuddy/jest')


module.exports = {
  preset: '@repobuddy/jest/presets/ts-cjs',
  transform: fields.knownTransforms.tsJestCjs({ tsconfig: 'tsconfig.test.json' }),
}
Section titled “Related”