moment-timezone.js – Getting Error When Running in Jest Test

Question

I got an error using moment-timezone.js. It runs perfectly on a web page, but when I try to implement the test for it, the test result always returns an error like below.

This is the code I use on the web page:

import moment from 'moment-timezone';

class TimezoneCityItem extends React.Component {

  componentDidMount(){
    this.setState({
      time: moment.tz(this.props.timezone)
    })
  }

  render(){
    return (
      <div>{this.state.time.format('HH:mm')}</div>
    )
  }
}

This is timezoneListDummyData:

const timezoneList = [
  { name: 'los-angeles', title: 'Los Angeles', timezone: 'America/Los_Angeles' },
  { name: 'washington', title: 'Washington', timezone: 'America/New_York' },
  { name: 'london', title: 'London', timezone: 'Europe/London' },
  { name: 'dubai', title: 'Dubai', timezone: 'Asia/Dubai' },
  { name: 'hongkong', title: 'Hongkong', timezone: 'Asia/Hong_Kong' },
];

export default timezoneList;

this is code I use on my test file

import React from 'react';
import { shallow } from 'enzyme';
import TimezoneCityItem from '../TimezoneCity.item';
import timezoneList from '/lib/timezoneListDummyData'; // It just an array list of timezone

describe('<TimezoneCityItem />', () => {
   test('Should render TimezoneCityItem correctly', () => {
       const wrapper = shallow(<TimezoneCityItem {...timezoneList[0]} />);
       expect(wrapper).toMatchSnapshot();
   });
});

This is the version of the packages:

"moment": "~2.18.1",
"moment-timezone": "~0.5.13",

This is the error message:

Test suite failed to run
TypeError: Cannot read property 'split' of undefined

  at node_modules/moment-timezone/moment-timezone.js:36:34
  at Object.<anonymous>.moment (node_modules/moment-timezone/moment-timezone.js:14:20)
  at Object.<anonymous> (node_modules/moment-timezone/moment-timezone.js:18:2)
  at Object.<anonymous> (node_modules/moment-timezone/index.js:1:120)
  at Object.<anonymous> (imports/ui/components/mainLayout/TimezoneCity.item.jsx:3:49)
  at Object.<anonymous> (imports/ui/components/mainLayout/TimezoneCity.jsx:3:47)
  at Object.<anonymous> (imports/ui/components/mainLayout/MainLayout.jsx:6:47)
  at Object.<anonymous> (imports/ui/components/mainLayout/__tests__/MainLayout.test.js:3:19)
      at Generator.next (<anonymous>)
      at new Promise (<anonymous>)
      at Generator.next (<anonymous>)
      at <anonymous>

Answer 1

probably a little late for this, but for the benefit of others. The reason why we are getting this because moment-timezone expects a version number from the moment package.

As seen at moment-timezone.js

	var momentVersion = moment.version.split('.'),
		major = +momentVersion[0],
		minor = +momentVersion[1];

When you run jest, it tries to mock everything that you include, therefore moment is getting mocked. Since attributes are excluded, on only functions are mocked, you will either have to unmock moment and moment-timezone or include a fake version number to the mocked moment object.