moment: Moment Doesn't work With Jest

after some more searching found the solution here https://github.com/aurelia/skeleton-navigation/issues/606#issuecomment-397051406

need to pass in "esModuleInterop": true under compilerOptions in tsconfig.json

Still having this problem with jest@28.1.0 and moment@2.29.2 I didn’t want to change any source or test files so my solution was to add the following mock to setupFilesAfterEnv file:

jest.mock('moment', () => ({
  default: jest.requireActual('moment')
}))

const moment = require("moment").default || require("moment") is what I came up with, but it only allows use to use moment as a function. // edit

import * as mom from "moment";
const moment = require("moment").default || require("moment");

Fixes angular / jest problem. But it’s still a hack.

This hack worked for me and Eslint is not complaining.

import moment = require("moment");

I’ve found 2 ways to use moment in Jest. ( for the note: I use Angular). I needed to test a component method that uses ‘moment()’. 1)

//    spec.ts file (my testing file)
import moment from 'moment'; 
// import exactly like this, not like   import * as moment from 'moment'.  Otherwise you'll get error "moment is not a function".

beforeEach(() => {
   // Pick any timestamp.  This fix works since moment() uses Date.now() under the hood.
    dateNowSpy = jest.spyOn(Date, 'now').mockImplementation(() => 1487076708000); 
}

afterEach(() => {
    dateNowSpy.mockRestore();
});

it('should call myMethod with moment()', () => {
        const selectSpy = spyOn(myComponent, 'myMethod');
        ... // trigger here the call to myMethod.
        expect(selectSpy).toHaveBeenCalledWith(moment()); // moment() will be called with our mocked date
});

The second option uses npm package MockDate https://www.npmjs.com/package/mockdate Briefly, it’s as follows (apply beforeEach/afterEach yourself)

import moment from 'moment';
import * as MockDate from 'MockDate';

MockDate.set(1434319925275);
expect(selectSpy).toHaveBeenCalledWith(moment());
MockDate.reset();

hmmm… it already seems to be part of the FAQ https://github.com/moment/moment/blob/develop/FAQ.md

I was facing this issue when i was using ts-jest for working with typescript and jest. I ended up using babel for typescript support with jest instead and I don’t face it anymore. Perhaps the ts-jest library may be doing something under the hood

FWIW, I updated my import to use moment-timezone and Jest is happy now:

import moment from 'moment-timezone';

Not sure what the regular moment package is having issues with.

It seems I only get this error when I set esModuleInterop to true… @KonradLinkowski - the hack helped though 😃

blem. But it’s still a hack.

Thank you sir, that helped.