Babel jest plugin

If you are already using jest-cli, add babel-jest and it will automatically compile JavaScript code using Babel.

yarn add --dev babel-jest @babel/core

If you would like to write your own preprocessor, uninstall and delete babel-jest and set the config.transform option to your preprocessor.

Note: this step is only required if you are using babel-jest with additional code preprocessors.

To explicitly define babel-jest as a transformer for your JavaScript code, map .js files to the babel-jest module. Typescript files are also supported.

By default, it loads your existing Babel configuration (if any)

"transform": {
  "\\.[jt]sx?$": "babel-jest"
},

You can also pass further babel options

"transform": {
  "\\.[jt]sx?$": ["babel-jest", { "extends": "./babel.config.js", "plugins": ["babel-plugin-transform-import-meta"] }]
},

By default, babel-jest includes babel-preset-jest. In addition to the babel options, we introduce a new option, excludeJestPreset, which allows you to disable this behavior. Note that this will break jest.mock hoisting.

"transform": {
  "\\.[jt]sx?$": ["babel-jest", { "excludeJestPreset": true }],
}