如何使用Jest,Enzyme for React-Native模拟单元测试中的事件

Question

我正在试图弄清楚如何在React-Native应用程序中使用Jest测试"onPress"事件,这样我就可以确保调用正确的函数.

我浏览了文档和Google,但在React-Native中找不到它的解决方案.

这是我发现应该适用于React-Native的enzyme:

const mockFunc = jest.fn();
const component = mount(<MyComponent onPress={mockFunc} />);
component.simulate('press');
expect(mockFunc).toHaveBeenCalled();

但这不起作用.似乎mount不起作用,我得到这个输出:

ReferenceError:未定义文档

我尝试使用shallow但是TouchableOpacity当我查看函数的输出时没有得到渲染...而你已经猜到了,它也不起作用.不知道该怎么办.

有没有人找到一种方法来测试React-Native上的事件？

谢谢

Answer 1

酶不支持React-Native,因为它的呈现方式不同而且不使用DOM.这就是你收到错误的原因ReferenceError: document is not defined.您可以查看此问题以获取更多信息.React团队目前正在努力公开一种.find()方法react-test-renderer来模拟对组件的操作.然后它应该适用于React/React-native而不需要DOM环境.

你可以做一个黑客(这就是我们在公司里所做的),它正在渲染一个扩展TouchableOpacity并映射onClick到调用的自定义组件onPress.像这样的东西:

const mockPressable = (name) => {
  const RealComponent = require.requireActual(name);

  class Component extends RealComponent {

    render() {
      return React.createElement(
        RealComponent.displayName || RealComponent.name,
        { ...this.props, onClick: this.props.onPress },
        this.props.children
      );
    }

  }

  return Component;
};


jest.mock('TouchableOpacity', () => mockPressable('TouchableOpacity'));

在你的测试代码中,你打电话component.simulate('click').

这是一个黑客,我不确定这样做的后果是什么,但它对我们的用例有效.

Answer 2

我能够像你在React Native中的问题中所描述的那样运行测试.这是我的配置:

的package.json

"scripts": {
  ...
  "test": "node_modules/jest/bin/jest.js",
}

"devDependencies": {
  ...
  "enzyme": "^3.1.0",
  "enzyme-adapter-react-16": "^1.0.1",
  "enzyme-to-json": "^3.1.2",
  "jest": "^21.2.1",
  "jest-enzyme": "^4.0.0",
  "jest-expo": "~21.0.0",
}

"jest": {
  "preset": "jest-expo",
  "setupFiles": [
    "./test/jestSetup.js"
  ],
  "snapshotSerializers": [
    "./node_modules/enzyme-to-json/serializer"
  ]
}

测试/ jestSetup.js

import { configure, shallow, render, mount } from 'enzyme'
import Adapter from 'enzyme-adapter-react-16'

configure( { adapter: new Adapter() } )

// enzyme
global.shallow = shallow
global.render = render
global.mount = mount

示例组件:

import React from 'react'
import { Button } from 'react-native'

const CancelButton = ( props ) =>
  <Button
    { ...props }
    onPress={ () => { props.navigation.goBack() } }
    title="Cancel"
  />

export { CancelButton }

示例测试

import React from 'react'
import { CancelButton } from '../CancelButton'

test( 'onPress', () => {
  const goBackFunc = jest.fn()

  const navigation = {
    goBack: goBackFunc,
  }

  const component = shallow(
    <CancelButton
      navigation={ navigation }
    />
  )

  component.simulate( 'press' )
  expect( goBackFunc ).toHaveBeenCalled()
} )

.babelrc

{
  "presets": ["babel-preset-expo"],
  "env": {
    "development": {
      "plugins": ["transform-react-jsx-source"]
    }
  }
}

Answer 3

您应该shallow改用，然后调用.dive()

const mockFunc = jest.fn();
const component = shallow(<MyComponent onPress={mockFunc} />);    
component.dive().simulate('press');
expect(mockFunc).toHaveBeenCalled();