medium post 2

thing.1.spec.js

import React from 'react';
import PubSub from 'pubsub-js';

import { configure, shallow } from 'enzyme';
import Adapter from 'enzyme-adapter-react-16';
configure({ adapter: new Adapter() });

import Thing from './thing';

describe('thing', () => {
  let component;

  beforeEach(() => {
    spyOn(PubSub, 'publish');
  });

  describe('when the lifecycle events trigger', () => {
    it('will publish the correct message', () => {
      // we are ignoring componentWillMount() for now

      component = shallow(<Thing />);
      // rendering the component triggers componentDidMount()
      expect(PubSub.publish).toHaveBeenCalledWith('thing.did.mount');

      // updating the props triggers:
      // componentWillReceiveProps()
      // shouldComponentUpdate()
      // componentWillUpdate()
      component.setProps({});
      expect(PubSub.publish).toHaveBeenCalledWith('thing.will.receive.props');
      expect(PubSub.publish).toHaveBeenCalledWith('thing.should.update');
      expect(PubSub.publish).toHaveBeenCalledWith('thing.will.update');

      // when the component unmounts it triggers componentWillUnmount()
      component.unmount();
      expect(PubSub.publish).toHaveBeenCalledWith('thing.will.unmount');
    });
  });
});