@swc/jest
To make your Jest tests run faster, you can swap out the default JavaScript-based runner (ts-jest) for a drop-in Rust replacement using SWC.
Installation
pnpm
pnpm i -D jest @swc/core @swc/jestUsage
Inside jest.config.js, configure Jest to use SWC:
jest.config.js
module.exports = {
transform: {
'^.+\\.(t|j)sx?$': '@swc/jest',
},
}It will load the SWC configuration from .swcrc by default. You also can customize it:
jest.config.js
const fs = require('fs')
const config = JSON.parse(fs.readFileSync(`${__dirname}/.swcrc`, 'utf-8'))
module.exports = {
transform: {
'^.+\\.(t|j)sx?$': ['@swc/jest', { ...config, /* custom configuration in Jest */ }],
},
}Q & A
Q: Jest uses CommonJS by default. But I want to use ESM
A: Setup Jest following this Guide .
For JavaScript, edit package.json as follows:
package.json
{
// ...
"type": "module"
}For TypeScript, edit jest.config.js as follows:
jest.config.js
module.exports = {
// ...
extensionsToTreatAsEsm: ['.ts', '.tsx'],
}Run test with --experimental-vm-modules:
cross-env NODE_OPTIONS=--experimental-vm-modules jest
# or
node --experimental-vm-modules ./node_modules/jest/bin/jest.jsQ: What ECMAScript target is set by jsc.target?
A: By default, the version supported by your Node runtime.
| Node version | Default jsc.target |
|---|---|
| 12 | ’es2018’ |
| 13 | ’es2019’ |
| 14 | ’es2020’ |
| 15 | ’es2021’ |
| 16 | ’es2021’ |
| 17 | ’es2022’ |
You can customize this by setting an explicit version in jest.config.js:
jest.config.js
module.exports = {
transform: {
"^.+\\.(t|j)sx?$": [
"@swc/jest",
{
jsc: {
target: "es2021",
},
},
],
},
}Last updated on