Jest setup "SyntaxError: Unexpected token export"

Question

I'm implementing tests into an existing project that currently has no tests. My tests are failing to compile node_modules/ imports.

/Users/me/myproject/node_modules/lodash-es/lodash.js:10
export { default as add } from './add.js';
^^^^^^
SyntaxError: Unexpected token export
  
  at transformAndBuildScript (node_modules/jest-runtime/build/transform.js:320:12)
  at Object.<anonymous> (app/reducers/kind_reducer.js:2:43)
  at Object.<anonymous> (app/reducers/index.js:12:47)

The workaround I've found is to 'whitelist' node_modules in package.json jest config like this:

"jest": {
    "transformIgnorePatterns": [
      "!node_modules/"
    ]
  }

This seems like a hack because it takes over 1 minute to run a simple test that imports node_modules/lodash-es/lodash.js.

Answer 1

If none of the other solutions worked for you, you can try this in your jest

"moduleNameMapper": {
    "^lodash-es$": "lodash"
}

It will replace lodash-es with the commonjs version during testing runtime.

Answer 2

I had to add this into my .jestconfig:

"transformIgnorePatterns": [
  "<rootDir>/node_modules/(?!lodash-es)"
]