How do I stub new Date() using sinon?

Question

I want to verify that various date fields were updated properly but I don't want to mess around with predicting when new Date() was called. How do I stub out the Date constructor?

import sinon = require('sinon');
import should = require('should');

describe('tests', () => {
  var sandbox;
  var now = new Date();

  beforeEach(() => {
    sandbox = sinon.sandbox.create();
  });

  afterEach(() => {
    sandbox.restore();
  });

  var now = new Date();

  it('sets create_date', done => {
    sandbox.stub(Date).returns(now); // does not work

    Widget.create((err, widget) => {
      should.not.exist(err);
      should.exist(widget);
      widget.create_date.should.eql(now);

      done();
    });
  });
});

In case it is relevant, these tests are running in a node app and we use TypeScript.

score 97 · Accepted Answer · edited Aug 22 '18 at 19:10

97

I suspect you want the useFakeTimers function:

var now = new Date();
var clock = sinon.useFakeTimers(now.getTime());
//assertions
clock.restore();

This is plain JS. A working TypeScript/JavaScript example:

var now = new Date();

beforeEach(() => {
    sandbox = sinon.sandbox.create();
    clock = sinon.useFakeTimers(now.getTime());
});

afterEach(() => {
    sandbox.restore();
    clock.restore();
});

edited Aug 22 '18 at 19:10

Josh Kelley

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answered Jul 23 '15 at 15:06

Alex Booker

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Awesome, that looks like it does what I needed. Once I get a finally working version I'll edit it into your answer and accept it. – MrHen Jul 23 '15 at 15:34
1

As of sinon v5, the `sinon` object is a sandbox which keeps track of the `sinon.useFakeTimers`, which can be invoked with `sinon.restore()`, allowing the `sandbox` and `clock` variables in the above to be dropped: https://sinonjs.org/guides/migrating-to-5.0.html#sinon-is-now-a-default-sandbox – pzrq Sep 20 '19 at 00:42
1

only a minor observation here: when you use a sandbox (as you should), you don't need to `clock.restore()`, as the sandbox handles it – Gerardo Lima Mar 24 '20 at 18:22

score 21 · Answer 2 · edited May 23 '22 at 08:08

21

I found this question when i was looking to solution how to mock Date constructor ONLY. I wanted to use same date on every test but to avoid mocking setTimeout. Sinon is using [lolex][1] internally Mine solution is to provide object as parameter to sinon:

let clock;

before(() => {
    clock = sinon.useFakeTimers({
        now: new Date(2019, 1, 1, 0, 0),
        shouldAdvanceTime: true,
        toFake: ["Date"],
    });
})

after(() => {
    clock.restore();
})

Other possible parameters you can find in [lolex][1] API [1]: https://github.com/sinonjs/lolex#api-reference

edited May 23 '22 at 08:08

Jarno

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answered Jan 07 '19 at 08:11

Anatoli Klamer

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2

This answer is incredible and shows knowledge about the sinon/lolex API. it should be marked as correct, as it also solves the need of having a lot of `clock.tick()`s around the test. – yuriploc May 06 '20 at 20:21

realplay · Answer 3 · 2019-02-22T19:45:19.000

18

sinon.useFakeTimers() was breaking some of my tests for some reason, I had to stub Date.now()

sinon.stub(Date, 'now').returns(now);

In that case in the code instead of const now = new Date(); you can do

const now = new Date(Date.now());

Or consider option of using moment library for date related stuff. Stubbing moment is easy.

edited Feb 22 '19 at 19:45

answered Feb 13 '19 at 19:43

realplay

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This worked for me except that `Date.now()` returns a timestamp, so I think the `now` method should be stubbed with the timestamp returned by `Date.now()` instead of creating a new Date with `new Date()`. Basically the second line should be: `const now = Date.now();` – adamgy May 06 '21 at 16:50

How do I stub new Date() using sinon?

3 Answers3