Can I test setInterval with Jasmine?

Question

I have this statement in my code, and I was wondering how I could test the setInterval using Jasmine.

const x = setInterval(() => {
    const countdown = getElementById('countdownWrapper');
    const systemTime = ...
    const now = new Date().getTime();
    const endTime = systemTime - now;

    countdown.querySelector('.countdown-time').innerHTML = time();

    if (endTime < 0) {
        clearInterval(x);
        countdown.classList.remove('countdown-time--show');
    }
}, 1000);

systemTime is fed from an epoch value in a DATA-CONTENT attribute in the HTML.

Any help would be greatly appreciated

Possible duplicate of [How jasmine clock works?](https://stackoverflow.com/questions/28889562/how-jasmine-clock-works) — mooga, Jun 15 '18 at 22:50

score 6 · Accepted Answer · edited Sep 04 '19 at 22:04

6

beforeEach(function() {
  timerCallback = jasmine.createSpyObj("setInterval");
  jasmine.clock().install();
});

afterEach(function() {
  jasmine.clock().uninstall();
});

it("causes a timeout to be called", function() {
  setTimeout(function() {
    timerCallback();
  }, 1000);

  expect(setInterval).not.toHaveBeenCalled();

  jasmine.clock().tick(1001);

  expect(setInterval).toHaveBeenCalled();
});

edited Sep 04 '19 at 22:04

Benny Code

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answered Jun 15 '18 at 22:49

mooga

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Where would I call the code I am testing, as I have tried it in the beforeEach before the SpyOn, I have also created `let timerCallback` before the beforeEach, but I am still getting `createSpyObj requires a non-empty array or object of method names to create spies for thrown. Error: : Expected a spy, but got undefined.` This sounds like the function isn't firing – Takuhii Jun 16 '18 at 06:50
Fantastic, thanks for the help, but at which point do I call my script to test? I've placed it in the beforeEach, but I am getting this error `createSpyObj requires a non-empty array or object of method names to create spies for thrown Error: : Expected a spy, but got Function. Usage: expect().toHaveBeenCalled()` – Takuhii Jun 16 '18 at 17:20
I am using Headless Chrome to run the unit tests, would that make a difference? – Takuhii Jun 17 '18 at 08:36

score 0 · Answer 2 · answered Jan 25 '22 at 23:30

0

Correction to Benny's answer:

timerCallback = jasmine.createSpyObj("test", {setInterval: 0});
AND
expect(timerCallback.setInterval).not.toHaveBeenCalled();

Also, this DOESN'T test setInterval, that's been mocked here. This tests setTimeout!

answered Jan 25 '22 at 23:30

Robert Duff

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Can I test setInterval with Jasmine?

2 Answers2