笑话模拟反应上下文

问题描述

我需要一些帮助，以了解如何使用React Context测试应用程序.

I need some help understanding how one can test an application using React Context.

这是我的示例设置.

context.js

import React from 'react'

export const AppContext = React.createContext()

App.js

import React from 'react'

import MyComponent from './MyComponent'
import {AppContext} from './context'

const App extends React.Component {

  state = {
    items: []
  }

  handleItemAdd = newItem => {
    const {items} = this.state
    items.push(newItem)
    this.setState(items)
  }

  render() {
    return (
      <AppContext.Provider value={{
        addItem: this.handleItemAdd
      }}>
        <MyComponent />
      </AppContext.Provider>
    )
  }
}

export default App

MyComponent.js

import React from 'react'

import {AppContext} from './context'

const MyComponent extends React.Component {
  render() {
    return (
      <AppContext.Consumer>
        {addItem =>
          <button onClick={() => addItem('new item')}>
            Click me
          </button>
        }
      </AppContext.Consumer>
    )
  }
}

export default MyComponent

这是一个简化的示例.想象在App和MyComponent之间有更多的层，因此使用React Context.

This is a simplified example. Imagine that there are more layers between App and MyComponent, hence the use of React Context.

这是我的MyComponent测试文件.

MyComponent.test.js

import React from 'react'
import {render, fireEvent} from 'react-testing-library'

test('component handles button click', () => {
  const {getByText} = render(
    <MyComponent />
  )
  const button = getByText('Click me')
  fireEvent.click(button)
  expect...?
}

问题是，AppContext.Consumer是MyComponent的实现的一部分，因此在此测试中，我无法直接访问它.如何模拟AppContext.Consumer，以便实际上可以验证单击按钮会触发函数调用?

The thing is, AppContext.Consumer is part of the implementation of MyComponent, so in this test I don't have direct access to it. How do I mock AppContext.Consumer so I am actually able to verify that clicking a button fires a function call?

我知道理论上可以通过在App中渲染MyComponent来进行测试，但是我只想为MyComponent编写单元测试.

I know that in theory I can test this by rendering MyComponent in my App, but I want to write a unit test for MyComponent only.

推荐答案

您只需使用组件呈现上下文即可.

You just render the context with your component.

const addItem = jest.fn()
render(
  <AppContext.Provider value={{ addItem }}>
    <MyComponent />
  </ApppContext.Provider>
)

请参见使用react-testing-library模拟上下文

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