无法运行 JEST 测试

Question

I'm facing an issue when I try to import something using require() function in jest test file.

script2.test.js

const fetch = require('node-fetch');

it('test function', () => {
  expect(4).toEqual(4);
});

Package.json

{
  "name": "jest-test",
  "version": "1.0.0",
  "description": "",
  "type": "module",
  "scripts": {
    "test": "jest --watchAll"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "@babel/cli": "^7.15.7",
    "@babel/core": "^7.15.8",
    "@babel/plugin-transform-async-to-generator": "^7.14.5",
    "@babel/preset-env": "^7.15.8",
    "jest": "^27.3.1"
  },
  "dependencies": {
    "node-fetch": "^3.0.0"
  },
  "jest": {
    "transform": {
      "^.+\\.(js|jsx)$": "babel-jest"
    }
  }
}

babel.config.cjs

module.exports = {presets: ['@babel/preset-env']}

I'm getting following errors when I run the test using npm test

FAIL  ./script2.test.js
  ● Test suite failed to run

    Jest encountered an unexpected token

    Jest failed to parse a file. This happens e.g. when your code or its dependencies use non-standard JavaScript syntax, or when Jest is not configured to support such syntax. 

    Out of the box Jest supports Babel, which will be used to transform your files into valid JS based on your Babel configuration.


    Details:
    
        C:\work\jest-udemy\node_modules\node-fetch\src\index.js:9
        import http from 'http';
        ^^^^^^
    
        SyntaxError: Cannot use import statement outside a module
    
        > 1 | const fetch = require('node-fetch');
        |                   ^

I'm new to JEST, any help is much appreciated. My Node version is 14.17.3 Thanks you.

Answer 1

It seems that one still needs to jump through the hoops to make jest work with ESM.

In package.json change your script to:

"test": "node --experimental-vm-modules node_modules/jest/bin/jest.js --watchAll"

And in script2.test.js use import :

import fetch from 'node-fetch';

PS This was tested with node 14.15.1