fix: modern jest timers

[thymikee]

Summary

Fixes #391

Test plan

Added regression tests.

[mdjastrzebski]

LGTM

[pke]

I wanted to report, that modern fake timers still (again?) don't work in @testing-library/[email protected]
When enabled all tests run into timeouts.

test("renders greeting depending on time", () => {
  jest.useFakeTimers("modern")
  jest.setSystemTime(new Date("2020-11-19T09:00:00.000+01:00"))
  const { getByText } = render(<Greeting/>)
  expect(getByText("Good day)).toBeTruthy()
})

Uncommenting the first 2 lines in the test make it work (but now always pass due to its dependency on current time).

[thymikee]

@pke we're aware of the issue and tracking it here: #506 Feel free to help reviewing and testing the ongoing work: #568 :)