How to mock specific function in object using Jest?

Question

I\'m testing a React/Reflux application using Jest. I have the following function in a store:

onLoad: function() {
  c         


        

Answer 1

I have found jest mock instance function It's here

eg:

import expect from 'expect';

jest.mock('../libs/utils/Master');
import Master from '../libs/utils/Master';

Master.mockImplementation(() => {
  return {
    returnOne: jest.fn().mockReturnValueOnce(1)
  }
})
describe('test Master', function() {
  it('test search', function() {
    let master = new Master();
    expect(master.returnOne()).toEqual(1);
  });
});

Answer 2

Almost there, all you need to do is

const onLoad = jest.fn().mockImplementation(function () {
    var p1 = new Post();//Add your stuff here
    this.posts = [p1];
    console.log("mocked function");
  });
PostStore.onLoad = onLoad.bind(PostStore); //PostStore is your object.