When using `waitFor` the `jest.setSystemTime` is reset to actual system time

[coreyjv]

• @testing-library/dom version: @testing-library/dom@7.31.2
• Testing Framework and version: jest@26.6.0
• DOM Environment: jsdom@16.4.0

What you did:

Attempting to use fake timers and assert those dates and times after using waitFor

What happened:

The system time was reset to the current time after waitFor.

Reproduction:

import { render, screen, waitFor } from '@testing-library/react';

beforeEach(() => {
  jest.useFakeTimers('modern');
  jest.setSystemTime(new Date("2023-02-18"));
})

afterEach(() => {
  jest.runOnlyPendingTimers()
  jest.useRealTimers()
})

test('test the fake timer', async () => {
  render((<p>text</p>));

  await waitFor(() => screen.getByText('text'))

  expect(new Date().getFullYear()).toEqual(2023)
});

Problem description:

Test results:

  ● test the fake timer

    expect(received).toEqual(expected) // deep equality

    Expected: 2023
    Received: 2021

      16 |   await waitFor(() => screen.getByText('text'))
      17 |
    > 18 |   expect(new Date().getFullYear()).toEqual(2023)
         |                                    ^
      19 | });
      20 |

When using waitFor it appears that the system time that was set using Jest's fake timers was reset to the current time. If you remove the waitFor the test passes as expected.

[eps1lon]

This was fixed in #966 (released in 8.x)

[coreyjv]

Thank you!