Jasmine: How to unit test my date filters that uses moment.js?

Question

I want to write unit tests for my date filters created using moment.js.

E.g.

app.filter('timeFormat', function () {
    return function (date) {
        return moment(date).format("LT");
    };
});

What's the best way to test the above filter?

Does the following test look good? Or do I have to mock the moment functions? If so, how can we achieve that?

describe('Filter: timeFormat', function () {

    'use strict';

    var $filter;

    beforeEach(module('someApp'));

    beforeEach(inject(function (_$filter_) {
        $filter = _$filter_;
    }));

    it('should return time in localized time format', function () {
        var filterTime = $filter('timeFormat');

        var date = new Date();
        var expectedTime = "5:46 AM";

        date.setHours(5);
        date.setMinutes(46);

        expect(filterTime(date)).toEqual(expectedTime);

        expectedTime = "2:34 PM";
        date.setHours(14);
        date.setMinutes(34);

        expect(filterTime(date)).toEqual(expectedTime);

        expectedTime = "12:59 PM";
        date.setHours(12);
        date.setMinutes(59);

        expect(filterTime(date)).toEqual(expectedTime);

        expectedTime = "11:59 PM";
        date.setHours(23);
        date.setMinutes(59);

        expect(filterTime(date)).toEqual(expectedTime);
    });
});

Your tests look fine to me. The only thing i don't like is that you have multiple asserts in one test. — Maria Ines Parnisari, Dec 08 '15 at 00:51

score 9 · Answer 1 · edited May 23 '17 at 11:54

There is a common rule saying that you should not mock what you do not own. If you mock momentjs functions, you can run into issues in the future.

Imagine that in some future release momentjs would change what LT format means (doubtful, but you can see the problem). After upgrade to the new version, your tests would detect this regression if you used momentjs implementation in your unit tests. On the contrary, if you would mock it and record something like return "5:46 AM" if moment is called with "LT", then your tests would be green although production code would not work due to the momentjs upgrade.

However, if your question is about something different and this was only a minimal example, you can (but you should not) mock moment with callFake:

spyOn(window, 'moment').and.callFake(function (date) {
  return {
    format: function (format) { /* your format implementation */ }
  };
});

I like your point about why external libraries should not be mocked. — Manoj Shrestha, Dec 08 '15 at 16:54

score 0 · Answer 2 · answered Feb 10 '16 at 23:26

0

you can try as below:

var expectedTime = '5:46 AM';
var momentTime = moment(expectedTime);
date.setHours(5);
date.setMinutes(46);
expect(filterTime(date)).toEqual(momentTime._i);

where _i is for time in momentTime object.

answered Feb 10 '16 at 23:26

Nish

137
1
10

Jasmine: How to unit test my date filters that uses moment.js?

2 Answers2