hooks/packages/interval/client.test.ts at develop · simmo/hooks · GitHub

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import { renderHook } from '@testing-library/react-hooks'
import useInterval from '.'

describe('useInterval', () => {
  const callback = jest.fn().mockName('mock callback')

  afterEach(() => {
    callback.mockClear()
  })

  test('executes callback after delay', () => {
    renderHook(({ interval }) => useInterval(callback, interval), {
      initialProps: { interval: 500 },
    })

    expect(callback).not.toBeCalled()

    jest.advanceTimersByTime(1000)

    expect(callback).toBeCalled()
    expect(callback).toHaveBeenCalledTimes(2)
  })

  test('pauses interval if no delay', () => {
    const { rerender } = renderHook(
      ({ interval }) => useInterval(callback, interval),
      {
        initialProps: { interval: 500 },
      }
    )

    jest.advanceTimersByTime(500)
    expect(callback).toHaveBeenCalledTimes(1)

    rerender({ interval: null })

    jest.advanceTimersByTime(500)
    expect(callback).toHaveBeenCalledTimes(1)

    rerender({ interval: 500 })

    jest.advanceTimersByTime(500)
    expect(callback).toHaveBeenCalledTimes(2)
  })
})