Jest Mock React 组件仅在某些测试中答案

【问题标题】：Jest Mock React Component ONLY in some testsJest Mock React 组件仅在某些测试中
【发布时间】：2020-12-04 04:39:04
【问题描述】：

这个问题真好：Jest Mock module per test

它只是没有回答我关于如何仅在一个测试中模拟它并使用原始组件保留其余部分的问题。

如果我想为快照做一些模拟而不是为其他测试做一些模拟，那将是有意义的

这是我目前的尝试

import React from 'react'
import { render } from '@testing-library/react'

jest.mock('components/Photo', () =>
  jest.fn(() => jest.requireActual('components/Photo'))
)
import Photo from 'components/Photo'

import PhotoGrid from '.'

beforeEach(() => {
  Photo.mockReset()
})

test('default renders 9 photos if provided 9', () => {
  const photos = [...Array(9).keys()]
  const { getAllByTestId, debug } = render(<PhotoGrid photos={photos} />)

  debug()
  expect(getAllByTestId(PHOTO_COMP_TEST_ID)).toHaveLength(9)
})

test('renders with masonry grid style', () => {
  Photo.mockImplementation(() => <div />)
  const photos = [...Array(9).keys()]
  const { container, debug } = render(<PhotoGrid photos={photos} />)

  debug()

  expect(container).toMatchInlineSnapshot(`
    <div>
      ... 
    </div>
  `)
})

这是要测试的组件

import React from 'react'
import Masonry from 'react-masonry-css'
import './index.css'

import Photo from 'components/Photo'

function PhotoGrid({ photos, numberOfPhotos = 9 }) {
  const imgs = photos ? photos.slice(0, numberOfPhotos) : []

  const breakpointColumnsObj = {
    default: 4,
    1300: 3,
    900: 2,
    700: 1,
  }

  return (
    <Masonry
      breakpointCols={breakpointColumnsObj}
      className="my-masonry-grid"
      columnClassName="my-masonry-grid_column"
    >
      {imgs &&
        imgs.map(({ id, secret, server, farm }, index) => (
          <div key={index} className="masonry-item">
            <Photo id={id} secret={secret} server={server} farm={farm} />
          </div>
        ))}
    </Masonry>
  )
}

export default PhotoGrid

【问题讨论】：

这样有效吗？

标签： javascript reactjs unit-testing jestjs react-testing-library

【解决方案1】：

jest.mock(...) 你想在其中一个测试中模拟的组件。

使用 jest.requireActual(...) 实现默认行为。

使用 mockImplementation 实现自定义行为。

import React from 'react'
import { render } from '@testing-library/react'

jest.mock('components/Photo')
import Photo from 'components/Photo'

import PhotoGrid from '.'

// This maintains the original implementation for tests. 
// This step is important because if not done, it will
// result in empty render errors.
beforeEach(() => {
  Photo.mockImplementation(jest.requireActual('components/Photo'));
}) 
 

// This test will use original implementation of 'components/Photo'
test('default renders 9 photos if provided 9', () => {
  const photos = [...Array(9).keys()]
  const { getAllByTestId, debug } = render(<PhotoGrid photos={photos} />)

  debug()
  expect(getAllByTestId(PHOTO_COMP_TEST_ID)).toHaveLength(9)
})

// This test will use the mocked implementation of 'components/Photo'
test('renders with masonry grid style', () => {
  Photo.mockImplementation(() => <div />)
  const photos = [...Array(9).keys()]
  const { container, debug } = render(<PhotoGrid photos={photos} />)

  debug()

  expect(container).toMatchInlineSnapshot(`
    <div>
      ... 
    </div>
  `)
})

【讨论】：