mock window object in Jest fails

I am trying to mock the window. So I have a __mocks__ with window.js which is just that

const window = { mycs: { APP: {} } }; export default window;

And then my setup file looks like

import 'babel-polyfill'; import _ from 'lodash'; import jest from 'jest'; jest.mock('window');

I am getting Cannot read property default of undefined Any idea?