Getting `TypeError: jest.fn is not a function`

Question

I'm trying to create the following unit test using Jest.

jest.dontMock("pointsAwardingActions.js");
describe("points awarding actions", () => {
  describe("award points", () => {
    it("should dispatch begin ajax action", () => {
      var pointsAwardingActions = require("pointsAwardingActions.js");
      const mockedDispatch = jest.fn();
    });
  });
});

But I'm getting the following error after running npm test .

TypeError: jest.fn is not a function

This is some section of my package.json :

{
  "scripts": {
    "test": "jest"
  },
  "author": "alayor",
  "license": "ISC",
  "jest": {
    "scriptPreprocessor": "<rootDir>/node_modules/babel-jest",
    "testFileExtensions": ["spec.js"],
    "moduleFileExtensions": ["js"],
    "collectCoverage": "true"
  },
  "dependencies": {
    "babel-cli": "6.8.0",
    "babel-core": "6.8.0",
    "babel-jest": "^6.0.1",
    "babel-loader": "6.2.4",
    "babel-plugin-react-display-name": "2.0.0",
    "babel-polyfill": "6.8.0",
    "babel-preset-es2015": "6.6.0",
    "babel-preset-react": "6.5.0",
    "babel-preset-react-hmre": "1.1.1",
    "expect": "1.19.0",
    "express": "4.13.4",
    "jest": "^0.1.40",
    "jest-cli": "^0.8.1",
    ...
  }
}

What could be the reason I'm getting that error?

Answer 1

The jest object is automatically in scope within every test file, so there's no need to import it explicitly. If you do want to import the jest object directly, you want to import the jest-mock module, not the jest-cli module, via:

// Not necessary inside a Jest test file
import jest from 'jest-mock';

const mock = jest.fn();

Answer 2

It is a bit weird that documentation isn't mentioning that jest is not require('jest'); but require('jest-mock') , the following code should work on v22:

const jest = require('jest-mock');
const spy = jest.fn();

Answer 3

You're using a very old version of Jest that don't support jest.fn . Jest has significantly improved since then and I highly recommend you to update to the latest version.

Also they don't do auto mocking now.

Answer 4

It's already included in your Jest package, so please make sure that you type correct like this: ( "mockReturnValue" ).

It will clear your error.