A Jest runner that runs tests directly in bare Node.js, without virtualizing the environment.
MIT License
A Jest runner that runs tests directly in bare Node.js, without virtualizing the environment.
This approach is way faster than the default Jest runner (it more than doubled the speed of Babel's tests suite) and has complete support for the Node.js ESM implementation. However, it doesn't provide support for most of Jest's advanced features.
The lists below are not comprehensive: feel free to start a discussion regarding any other missing Jest feature!
expect
, test
, it
, describe
, beforeAll
, afterAll
, beforeEach
, afterEach
jest.fn
, jest.spyOn
, jest.clearAllMocks
, jest.resetAllMocks
jest.useFakeTimers
, jest.useRealTimers
, jest.setSystemTime
, jest.advanceTimersByTime
--testNamePattern
/-t
, --maxWorkers
, --runInBand
setupFiles
, setupFilesAfterEnv
, snapshotSerializers
, maxWorkers
, snapshotFormat
, snapshotResolver
import
/require
mocks. You can use a custom mocking library such as esmock
or proxyquire
.ts-node/esm
.--frozen-intrinsics
to prevent such modifications.import.meta.jest
. You can use the jest
global instead.process.chdir
. This runner uses Node.js workers, that don't support process.chdir()
. It provides a simple polyfill so that process.chdir()
calls still affect the process.cwd()
result, but they won't affect all the other Node.js API (such as fs.*
or path.resolve
).babel-plugin-istanbul
(Jest's default coverage provider). However, you have to manually run that plugin:
babel.config.json
file to your project with these contents:
{
"plugins": ["babel-plugin-istanbul"]
}
and you can run Babel in Jest using a Node.js ESM loader such as babel-register-esm
.After installing jest
and jest-light-runner
, add it to your Jest config.
In package.json
:
{
"jest": {
"runner": "jest-light-runner"
}
}
or in jest.config.js
:
module.exports = {
runner: "jest-light-runner",
};
You can specify custom ESM loaders using Node.js's --loader
option. Jest's CLI doesn't allow providing Node.js-specific options, but you can do it by using the NODE_OPTIONS
environment variable:
NODE_OPTIONS="--loader ts-node/esm" jest
Or, if you are using cross-env
to be able to provide environment variables on multiple OSes:
cross-env NODE_OPTIONS="--loader ts-node/esm" jest
Don't run Node.js directly:
node --loader ts-node/esm ./node_modules/.bin/jest
This will result in ERR_UNKNOWN_FILE_EXTENSION
, due to the loader argument not being passed to the sub-processes. This is a known limitation, and ts-node documentation recommends using NODE_OPTIONS.
If you are running transpiled code and you want to load their source maps to map errors to the original code, you can install the source-map-support
package and add the following to your Jest configuration:
setupFiles: ["source-map-support/register"];
This project follows semver, and it's currently in the 0.x
release line.
It is used to run tests in the babel/babel
and prettier/prettier
repositories, but there are no internal tests for the runner itself. I would gladly accept a pull requests adding a test infrastructure!
If you use this package and it has helped with your tests, please consider sponsoring me on GitHub! You can also donate to Jest on their OpenCollective page.