jest.mock does not mock generator methods in module

Created on 13 Apr 2018 · 3Comments · Source: facebook/jest

node: 8.9.4
os: macOS El Capitan (10.11.6)

When mocking a module that contains generator methods they are ignored and not properly mocked. I have created a slim example below.

module.js

function* generatorMethod() {
  yield 1;
  yield 2;
  yield 3;
}

module.exports.generatorMethod = generatorMethod;
module.exports.asyncMethod = async () => {
  return 1;
}
module.exports.syncMethod = () => {
  return 1;
}

module.test.js

jest.mock('./module');
const mod = require('./module');

describe('generator module method', () =>{
  test('does not get mocked', () => {
    expect(mod.syncMethod).toBeDefined();
    expect(mod.asyncMethod).toBeDefined();
    expect(mod.generatorMethod).toBeDefined();
  });
});

package.json

{
  "name": "test",
  "version": "1.0.0",
  "scripts": {
    "test": "jest"
  },
  "author": "",
  "license": "MIT",
  "description": "",
  "dependencies": {
    "jest": "^22.4.3"
  }
}

The test fails because the generatorMethod is not defined on the mocked module.

Help Wanted Needs Triage

Source