useEffect() 的酶/Jest 测试

Question

我有一个看起来像这样的组件：

const PersonalGreeting = (): ReactElement => {
  const [date, setDate] = useState(new Date())
  useEffect(() => {
    const timer = setInterval(() => {
      setDate(new Date())
    }, 60000)

    return () => {
      clearInterval(timer)
    }
  }, [])

  return (
    <div>{date}></div>
  )
}

我遇到了一个错误，指出 Jest: "global" coverage threshold for functions (89%) not met: 88.73%，当我查看日志时，它特别指出 return () 中的 clearInterval(timer) 和 useEffect() 没有经过测试。这是一个屏幕截图：

老实说，我正在努力弄清楚他们想让我测试什么。这是我测试过的：

describe('PersonalGreeting', () => {
  const setTimeOfDay = jest.fn()
  // eslint-disable-next-line
  const useToggleMock: any = (initialState: string) => [
    initialState,
    setTimeOfDay
  ]

  beforeEach(() => {
    jest.spyOn(React, 'useState').mockImplementation(useToggleMock)
  })

  afterEach(() => {
    jest.clearAllTimers()
  })

  it('renders component as expected', () => {
    const wrapper = mount(
      <TestWrapper>
        <PersonalGreeting />
      </TestWrapper>
    )

    expect(wrapper.text().length > 0).toBe(true)
  })

  it('Checks time every minute', () => {
    jest.useFakeTimers()
    mount(
      <TestWrapper>
        <PersonalGreeting />
      </TestWrapper>
    )

    expect(setTimeOfDay).not.toBeCalled()

    // 1 minute
    jest.advanceTimersByTime(60000)
    expect(setTimeOfDay).toHaveBeenCalledTimes(1)
  })
})

Answer 1

您需要卸载组件，这将触发 useEffect()

中的返回函数

见docs

像这样

it('Should unmount component', () => {
  const wrapper = mount(
    <TestWrapper>
      <PersonalGreeting />
    </TestWrapper>
  )

  wrapper.unmount();
  // continue with your expect here

})