import * as React from 'react'
import {fireEvent} from '@testing-library/react'
import {renderHook} from '@testing-library/react-hooks'
import useLatest from './index'

describe('useLatest()', () => {
  it('should store the latest value', () => {
    const fnA = () => {}
    const fnB = () => {}
    const {result, rerender} = renderHook(({fn}) => useLatest(fn), {
      initialProps: {fn: fnA},
    })
    expect(result.current.current).toBe(fnA)
    rerender({fn: fnB})
    expect(result.current.current).toBe(fnB)
  })

  it('should work as expected in useEffect()', () => {
    const fnA = jest.fn()
    const fnB = jest.fn()
    const {rerender} = renderHook(
      ({fn}) => {
        const latest = useLatest(fn)
        React.useEffect(() => {
          window.addEventListener('click', () => latest.current())
        }, [latest])
      },
      {
        initialProps: {fn: fnA},
      }
    )

    fireEvent.click(window)
    expect(fnA).toBeCalledTimes(1)
    rerender({fn: fnB})
    fireEvent.click(window)
    expect(fnA).toBeCalledTimes(1)
    expect(fnB).toBeCalledTimes(1)
  })
})