测试异步嵌套组件

Question

假设我有以下包装组件：

'use strict'

import React, {PropTypes, PureComponent} from 'react'
import {update} from '../../actions/actions'
import LoadFromServerButton from '../LoadFromServerButton'
import {connect} from 'react-redux'

export class FooDisplay extends PureComponent {
  render () {
    return (
      <p>
        <span className='foo'>
          {this.props.foo}
        </span>
        <LoadFromServerButton updateFunc={this.props.update} />
      </p>
    )
  }
}

export const mapStateToProps = (state) => {
  return {foo: state.foo.foo}
}

FooDisplay.propTypes = {
  foo: PropTypes.string
}

export const mapDispatchToProps = (dispatch) => {
  return {
    update: (foo) => dispatch(update(foo))
  }
}

export default connect(mapStateToProps, mapDispatchToProps)(FooDisplay)

以及以下内部组件：

'use strict'

import React, {PropTypes, PureComponent} from 'react'
import {get} from '../../actions/actions'
import ActiveButton from '../ActiveButton'
import {connect} from 'react-redux'

export class LoadFromServerButton extends PureComponent {
  doUpdate () {
    return this.props.get().then(this.props.updateFunc)
  }

  render () {
    return (
      <ActiveButton action={this.doUpdate.bind(this)} actionArguments={[this.props.foo]} text='fetch serverside address' />
    )
  }
}

export const mapStateToProps = (state) => {
  return {foo: state.foo.foo}
}

export const mapDispatchToProps = (dispatch) => {
  return {
    get: () => dispatch(get())
  }
}

LoadAddressFromServerButton.propTypes = {
  updateFunc: PropTypes.func.isRequired
}

export default connect(mapStateToProps, mapDispatchToProps)(LoadFromServerButton)

ActiveButton 是一个非常薄的按钮包装器，带有 onclick 和参数解构。

现在假设我的 get 操作如下所示：

export const get = () => dispatch => http('/dummy_route')
      .spread((response, body) => dispatch(actOnThing(update, body)))

现在如果我这样写一个测试：

/* global window, test, expect, beforeAll, afterAll, describe */

'use strict'

import React from 'react'
import FooDisplay from './index'
import {mount} from 'enzyme'
import {Provider} from 'react-redux'
import configureStore from '../../store/configureStore'
import nock, {uriString} from '../../config/nock'
import _ from 'lodash'


const env = _.cloneDeep(process.env)
describe('the component behaves correctly when integrating with store and reducers/http', () => {
  beforeAll(() => {
    nock.disableNetConnect()
    process.env.API_URL = uriString
  })

  afterAll(() => {
    process.env = _.cloneDeep(env)
    nock.enableNetConnect()
    nock.cleanAll()
  })

  test('when deep rendering, the load event populates the input correctly', () => {
    const store = configureStore({
      address: {
        address: 'foo'
      }
    })
    const display = mount(<Provider store={store}><FooDisplay /></Provider>,
        {attachTo: document.getElementById('root')})
    expect(display.find('p').find('.address').text()).toEqual('foo')
    const button = display.find('LoadFromServerButton')
    expect(button.text()).toEqual('fetch serverside address')
    nock.get('/dummy_address').reply(200, {address: 'new address'})
    button.simulate('click')
  })
})

这会导致：

Unhandled rejection Error: Error: connect ECONNREFUSED 127.0.0.1:8080

经过一番思考，这是由于测试没有返回承诺，因为按钮单击导致承诺在引擎盖下触发，因此，afterAll 立即运行，清理 nock，并且一个真正的http连接通过网络。

如何测试这种情况？我似乎没有一个简单的方法来返回正确的承诺......如何测试这些更新导致的 DOM 更新？

Answer 1

为了只模拟导入模块的一种方法，请使用 .requireActual(...)

jest.mock('../your_module', () => ({
    ...(jest.requireActual('../your_module')),
    YourMethodName: () => { return { type: 'MOCKED_ACTION'}; }
}));

Answer 2

正如您所提到的，问题是您没有承诺从测试中返回。因此，要让 get 返回一个已知的承诺，您可以直接模拟 get 而无需使用 nock：

import {get} from '../../actions/actions'
jest.mock('../../actions/actions', () => ({get: jest.fn}))

这会将动作模块替换为对象{get: jestSpy}

然后你可以在你的测试中创建一个promise并让get返回这个并且从你的测试中返回这个promise：

it('', ()=>{
  const p = new Promise.resolve('success')
  get.mockImplementation(() => p)//let get return the resolved promise
  //test you suff
  return p
})