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I would like to mock the Date constructor so that whenever I call new Date(), it always return specific time.
I found Sinon.js provide useFakeTimers to mock time. But the following code doesn't work for me.
sinon.useFakeTimers(new Date(2011,9,1)); //expect : 'Sat Oct 01 2011 00:00:00' , //result : 'Thu Oct 27 2011 10:59:44‘ var d = new Date(); 
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You can use date-faker to mock what new Date() or Date. now() returns.
To mock a constructor like new Date() with Jest and JavaScript, we can use the setSystemTime method. beforeAll(() => { jest. useFakeTimers("modern"); jest. setSystemTime(new Date(2022, 3, 1)); }); afterAll(() => { jest.
import { advanceBy, advanceTo } from 'jest-date-mock'; test('usage', () => { advanceTo(new Date(2018, 5, 27, 0, 0, 0)); // reset to date time. const now = Date. now(); advanceBy(3000); // advance time 3 seconds expect(+new Date() - now).
sinon.useFakeTimers accepts a timestamp (integer) as parameter, not a Date object.
Try with
clock = sinon.useFakeTimers(new Date(2011,9,1).getTime()); new Date(); //=> return the fake Date 'Sat Oct 01 2011 00:00:00' clock.restore(); new Date(); //=> will return the real time again (now) If you use anything like setTimeout, make sure you read the docs because the useFakeTimers will disrupt the expected behavior of that code.
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