Jest ‘TypeError: is not a function’ in jest.mock

In my case, I had to mock a Node.js module. I’m using React and Redux in ES6, with Jest and Enzyme for unit tests.

In the file I’m using, and writing a test for, I’m importing the node modules as default:

import nodeModulePackage from 'nodeModulePackage';

So I needed to mock it as a default since I kept getting the error (0, _blah.default) is not a function..

My solution was to do:

jest.mock('nodeModulePackage', () => jest.fn(() => {}));

In my case, I just needed to override the function and make it return an empty object.

If you need to call a function on that node module, you’ll do the following:

jest.mock('nodeModulePackage', () => ({ doSomething: jest.fn(() => 'foo') }));