If you are already using
jest-cli, just add
yarn add --dev babel-jest babel-core
Note: If you are using babel version 7 you have to install
babel-jestwithyarn add --dev babel-jest 'babel-core@^7.0.0-0' @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