使用 mount() 的酶测试无法使用 React 模态对话框的内容 [英] Content of React modal dialogs is not available to Enzyme tests using mount()

问题描述

我有一个带有模态对话框的 React 组件(使用 reactstrap 构建，但其他人报告了 react-bootstrap 和其他类型的模态组件存在类似问题).Enzyme 在模态框内找不到任何组件，即使它们在实际应用程序中渲染得很好.最小的例子:

I have a React component with a modal dialog (built using reactstrap, but others have reported similar problems with react-bootstrap and other types of modal components). Enzyme cannot find any of the components inside the modal, even though they render fine in the actual app. Minimal example:

import React from 'react'
import { Modal } from 'reactstrap'

export default class MyModal extends React.Component {

    render() {
        return (
            <div className="outside"> Some elements outside of the dialog </div>
            <Modal isOpen={this.props.modalOpen}>
                <div className="inside"> Content of dialog </div>
            </Modal>
         );
    } 
}

我想像这样测试内容(在本例中使用 jest)

I would like to test the contents (in this case using jest) like this

import React from 'react'
import MyModal  from './MyModal'
import { mount } from 'enzyme'

it('renders correctly', () => {
    const wrapper = mount( <MyModal modalOpen/> );

    expect(wrapper).toMatchSnapshot();

    // Passes
    expect(wrapper.find('.outside')).toHaveLength(1);

    // Fails, 0 length
    expect(wrapper.find('.inside')).toHaveLength(1);
});

测试正确找到了 Modal 之外的内容，但没有找到里面的任何内容.查看快照显示，确实，<Modal> 内的任何内容都没有被渲染.但是，如果我将 mount 替换为 shallow，它确实有效.问题是我需要 mount 来测试像 componentDidMount 这样的生命周期方法.

The test finds the contents outside of the Modal correctly, but does not find anything inside. Looking at the snapshot shows that, indeed, nothing inside the <Modal> is rendered. However it does work if I replace mount with shallow. The problem with that is I need mount to test lifecycle methods like componentDidMount.

mount 为什么不渲染模态框的内容?我认为重点在于它渲染了整个子元素树.

Why doesn't mount render the contents of the modal? I thought the whole point was that it rendered the entire tree of child elements.

推荐答案

这在 React 16 + Enzyme 3 中不再是问题，因为 React 16 支持门户组件.

This is no longer a problem in React 16 + Enzyme 3, because React 16 supports portal components.

在 React 15 和之前的版本中，问题在于模式对话框(在大多数实现中)是一个 门户 组件.这意味着它会创建直接附加到文档根目录的 DOM 元素，而不是作为父 React 组件的子元素.

In React 15 and before, the problem is that a modal dialog is (in most implementations) a portal component. This means it creates DOM elements that are attached directly to the document root, rather than being children of the parent React component.

的 find 方法mount 创建的 ReactWrapper 从顶层组件创建的元素开始遍历 DOM，所以找不到 modal 的内容.但是 Enzyme 的 shallow 并没有附加到 DOM，而是构建了自己的包含模态内容的组件树.

The find method of the ReactWrapper created by mount looks through the DOM starting with the element created by the top level component, so it can't find the contents of the modal. But Enzyme's shallow doesn't attach to a DOM, and instead builds its own component tree which contains the modal contents.

要测试一个门户组件，您首先需要找到已附加到文档正文的 DOM 元素.然后你可以围绕它们创建一个新的 ReactWrapper 以便所有常用的 Enzyme 函数都可以工作:

To test a portal component, you first need to find the DOM elements that have been attached to the document body. Then you can create a new ReactWrapper around them so that all the usual Enzyme functions work:

import React from 'react'
import MyModal  from './MyModal'
import { mount, ReactWrapper } from 'enzyme'

it('renders correctly', () => {
    const wrapper = mount( <MyModal modalOpen/> );

    expect(wrapper).toMatchSnapshot();

    // Passes
    expect(wrapper.find('.outside')).toHaveLength(1);

    // Construct new wrapper rooted at modal content
    inside_els = document.getElementsByClassName("inside")[0]
    inside_wrapper = new ReactWrapper(inside_els, true)

    // Passes
    expect(inside_wrapper.find('.inside')).toHaveLength(1);
});

目前，这是 Enzyme 中的一个open bug.

Currently, this is an open bug in Enzyme.

更新:在测试完成后，Enzyme 似乎也会将模式附加到 DOM，因此您可能会在以后的测试中打开多个对话框.如果这是一个问题，您可以像这样在每次测试后清除 DOM:

Update: It seems that Enzyme also leaves the modal attached to the DOM after the test finishes, so you may end up with multiple dialogs open in a later test. If this is a problem, you can clear the DOM after each test like this:

afterEach(() => {
  var node = global.document.body;
  while (node.firstChild) {
    node.removeChild(node.firstChild);
  }
}); 

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