@swc/jest

@swc/jest

SWC binding for Jest.

Installation

# if you use npm
npm i -D jest @swc/core @swc/jest
# if you use yarn
yarn add -D jest @swc/core @swc/jest

Usage

jest.config.js:

module.exports = {
  transform: {
    '^.+\\.(t|j)sx?$': '@swc/jest',
  },
}

It will load the SWC configuration from .swcrc by default. You also can customize it:

const fs = require('fs')

const config = JSON.parse(fs.readFileSync(`${__dirname}/.swcrc`, 'utf-8'))

module.exports = {
  transform: {
    '^.+\\.(t|j)sx?$': ['@swc/jest', { ...config, /* custom configuration in Jest */ }],
  },
}

Q & A

Q: Jest uses CommonJS by default. But I want to use ESM.

A: Setup Jest following this Guide.

For JavaScript, edit package.json as follows:

{
  // ...
  "type": "module"
}

For TypeScript, edit jest.config.js as follows:

module.exports = {
  // ...
  extensionsToTreatAsEsm: ['.ts', '.tsx'],
}

Run test with --experimental-vm-modules:

cross-env NODE_OPTIONS=--experimental-vm-modules jest

# or
node --experimental-vm-modules ./node_modules/jest/bin/jest.js

Q: What ECMAScript target is set by jsc.target?

A: By default, the version supported by your Node runtime.

Node version	Default jsc.target
12	'es2018'
13	'es2019'
14	'es2020'
15	'es2021'
16	'es2021'
17	'es2022'
18	'es2023'
19	'es2023'
20	'es2023'

You can customize this by setting an explicit version in jest.config.js:

module.exports = {
    transform: {
        "^.+\\.(t|j)sx?$": [
            "@swc/jest",
            {
                jsc: {
                    target: "es2021",
                },
            },
        ],
    },
}

License

MIT

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