Failing tests because of the daylight saving time change-CodePudding

I have tests where Im using getByText function in react-testing-library. Im looking for element in DOM that has value "10-10-2020 12:00". But after daylight saving time change, all my tests have failed because due to the change, the display text has changed to "10-10-2020 13:00" (one hour forwards) and now Im not able to get those elements. I will have to update my tests, but they will obviously fail once again when the time is changed in winter.

It happens because e.g. new Date('2020-01-01T00:00:00.000Z') returns 01 01 2020 01:00:00 instead of 01 01 2020 00:00:00 because of the timezones.

Is there any workaround or fix to make my tests resistant to daylight saving time change and timezones?

CodePudding user response：

Setting the hardcoded date and time for jest should help:

jest.useFakeTimers('modern')

beforeEach(() => {
  const hardcodedDate = new Date('2022-03-20T12:00:00Z')
  jest.setSystemTime(hardcodedDate.getTime())
})

It means in your tests you will always have the same system time, which will help with daylight saving time change (or any time change)

UPD: to see the date in the tests before the daylight saving you should change the hardcoded day before it started (for example in the UK it's 27 March)