Presets

The presets

ts-jest comes with several presets, covering most of the project's base configuration:

Preset name	Description
ts-jest/presets/default or ts-jest	TypeScript files (.ts, .tsx) will be transformed by ts-jest to CommonJS syntax, leaving JavaScript files (.js, jsx) as-is.
ts-jest/presets/js-with-ts	TypeScript and JavaScript files (.ts, .tsx, .js, .jsx) will be transformed by ts-jest to CommonJS syntax. You'll need to set allowJs to true in your tsconfig.json file.
ts-jest/presets/js-with-babel	TypeScript files (.ts, .tsx) will be transformed by ts-jest to CommonJS syntax, and JavaScript files (.js, jsx) will be transformed by babel-jest.

Basic usage

In most cases, simply setting the preset key to the desired preset name in your Jest config should be enough to start using TypeScript with Jest (assuming you added ts-jest to your dev. dependencies of course):

// jest.config.js
module.exports = {
  // [...]
  // Replace `ts-jest` with the preset you want to use
  // from the above list
  preset: 'ts-jest',
}

// package.json
{
  // [...]
  "jest": {
    // Replace `ts-jest` with the preset you want to use
    // from the above list
    "preset": "ts-jest"
  }
}

Note: presets use testMatch, like Jest does in its defaults. If you want to use testRegex instead in your configuration, you MUST set testMatch to null or Jest will bail.

Advanced

Any preset can also be used with other options. If you're already using another preset, you might want only some specific settings from the chosen ts-jest preset. In this case you'll need to use the JavaScript version of Jest config (comment/uncomment according to your use-case):

// jest.config.js
const { defaults: tsjPreset } = require('ts-jest/presets')
// const { jsWithTs: tsjPreset } = require('ts-jest/presets')
// const { jsWithBabel: tsjPreset } = require('ts-jest/presets')

module.exports = {
  // [...]
  transform: {
    ...tsjPreset.transform,
    // [...]
  },
}

Or through TypeScript (if ts-node is installed):

// jest.config.ts
import type { InitialOptionsTsJest } from 'ts-jest/dist/types'
import { defaults as tsjPreset } from 'ts-jest/presets'
// import { jsWithTs as tsjPreset } from 'ts-jest/presets'
// import { jsWithBabel as tsjPreset } from 'ts-jest/presets'
const config: InitialOptionsTsJest = {
  // [...]
  transform: {
    ...tsjPreset.transform,
    // [...]
  },
}
export default config