babel-jest
Usage
If you are already using jest-cli, just add babel-jest and it will automatically compile JavaScript code using babel.
npm install --save-dev babel-jest
If you would like to write your own preprocessor, uninstall and delete babel-jest and set the config.transform option to your preprocessor.
Setup
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.
"transform": {
"^.+\\.jsx?$": "babel-jest"
},