Testing React portals with enzyme

So I'm having a hard time writing tests for a modal component using React fiber's portal. Because my modal mounts to a domNode on the root of the <body /> but because that domNode doesn't exist, the test fails.

Some code to give, context:

index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
    <meta name="theme-color" content="#000000">
    <link rel="manifest" href="%PUBLIC_URL%/manifest.json">
    <link rel="shortcut icon" href="%PUBLIC_URL%/favicon.ico">
    <title>React App</title>
  </head>
  <body>
    <noscript>
      You need to enable JavaScript to run this app.
    </noscript>
    <div id="modal-root"></div>
    <div id="root"></div>
  </body>
</html>

App.js

import React, { Component } from 'react';
import logo from './logo.svg';
import './App.css';
import { Modal, ModalHeader } from './Modal';

class App extends Component {
  constructor(props) {
    super(props);
    this.state = { show: false };
    this.toggleModal = this.toggleModal.bind(this);
  }

  toggleModal(show) {
    this.setState({ show: show !== undefined ? show : !this.state.show });
  }

  render() {
    return (
      <div className="App">
        <header className="App-header">
          <img src={logo} className="App-logo" alt="logo" />
          <h1 className="App-title">Welcome to React</h1>
        </header>
        <p className="App-intro">
          To get started, edit <code>src/App.js</code> and save to reload.
        </p>
        <button onClick={() => this.toggleModal()}>show modal</button>
        <Modal toggle={this.toggleModal} show={this.state.show}>
          <ModalHeader>
            <span>I'm a header</span>
            <button onClick={() => this.toggleModal(false)}>
              <span aria-hidden="true">&times;</span>
            </button>
          </ModalHeader>
          <p>Modal Body!!!</p>
        </Modal>
      </div>
    );
  }
}

export default App;

Modal.js

import React, { Fragment } from 'react';
import ReactDOM from 'react-dom';
import PropTypes from 'prop-types';
// the next components are styled components, they are just for adding style no logic at all
import {
  ModalBackdrop,
  ModalContent,
  ModalDialog,
  ModalWrap,
} from './components';

class Modal extends React.Component {
  constructor(props) {
    super(props);
    this.el = document.createElement('div');
    this.modalRoot = document.getElementById('modal-root');
    this.outerClick = this.outerClick.bind(this);
  }

  componentDidMount() {
    this.modalRoot.appendChild(this.el);
    this.modalRoot.parentNode.style.overflow = '';
  }

  componentWillUpdate(nextProps) {
    if (this.props.show !== nextProps.show) {
      this.modalRoot.parentNode.style.overflow = nextProps.show ? 'hidden' : '';
    }
  }

  componentWillUnmount() {
    this.props.toggle(false);
    this.modalRoot.removeChild(this.el);
  }

  outerClick(event) {
    event.preventDefault();
    if (
      event.target === event.currentTarget ||
      event.target.nodeName.toLowerCase() === 'a'
    ) {
      this.props.toggle(false);
    }
  }

  render() {
    const ModalMarkup = (
      <Fragment>
        <ModalBackdrop show={this.props.show} />
        <ModalWrap show={this.props.show} onClick={this.outerClick}>
          <ModalDialog show={this.props.show}>
            <ModalContent>{this.props.children}</ModalContent>
          </ModalDialog>
        </ModalWrap>
      </Fragment>
    );
    return ReactDOM.createPortal(ModalMarkup, this.el);
  }
}

Modal.defaultProps = {
  show: false,
  toggle: () => {},
};

Modal.propTypes = {
  children: PropTypes.node.isRequired,
  show: PropTypes.bool,
  toggle: PropTypes.func,
};

export default Modal;

And last but not least the test: Modal.test.js

import React from 'react';
import Modal from './Modal.component';
import {
  ModalBackdrop,
  ModalContent,
  ModalDialog,
  ModalWrap,
} from './components';

describe('Modal component', () => {
  const Child = () => <div>Yolo</div>;

  it('should render all the styled components and the children', () => {
    const component = mount(
      <Modal>
        <Child />
      </Modal>
    );
    expect(component.find(ModalBackdrop).exists()).toBeTruthy();
    expect(component.find(ModalWrap).exists()).toBeTruthy();
    expect(component.find(ModalWrap).contains(ModalDialog)).toBeTruthy();
    expect(component.find(ModalDialog).contains(ModalContent)).toBeTruthy();
    expect(component.find(ModalContent).contains(Child)).toBeTruthy();
  });
});

A codesandbox so you can see it in action

So after a lot of fighting, experiment and hope. I managed to get the test working, the secret, which is kind obvious after I finally remember that is a possibility, is to modify jsdom and add our domNode, we just can't forget to unmount the component after each test.

Modal.test.js

import React from 'react';
import { mount } from 'enzyme';
import Modal from './Modal.component';
import {
  ModalBackdrop,
  ModalContent,
  ModalDialog,
  ModalWrap,
} from './components';

describe('Modal component', () => {
  const Child = () => <div>Yolo</div>;
  let component;

  // add a div with #modal-root id to the global body
  const modalRoot = global.document.createElement('div');
  modalRoot.setAttribute('id', 'modal-root');
  const body = global.document.querySelector('body');
  body.appendChild(modalRoot);

  afterEach(() => {
    component.unmount();
  });

  it('should render all the styled components and the children', () => {
    component = mount(
      <Modal>
        <Child />
      </Modal>,
    );
    expect(component.find(ModalBackdrop).exists()).toBeTruthy();
    expect(component.find(ModalWrap).exists()).toBeTruthy();
    expect(component.find(ModalWrap).contains(ModalDialog)).toBeTruthy();
    expect(component.find(ModalDialog).contains(ModalContent)).toBeTruthy();
    expect(component.find(ModalContent).contains(Child)).toBeTruthy();
  });

  it('should trigger toggle when clicked', () => {
    const toggle = jest.fn();
    component = mount(
      <Modal toggle={toggle}>
        <Child />
      </Modal>,
    );

    component.find(ModalWrap).simulate('click');
    expect(toggle.mock.calls).toHaveLength(1);
    expect(toggle.mock.calls[0][0]).toBeFalsy();
  });

  it('should mount modal on the div with id modal-root', () => {
    const modalRoot = global.document.querySelector('#modal-root');
    expect(modalRoot.hasChildNodes()).toBeFalsy();

    component = mount(
      <Modal>
        <Child />
      </Modal>,
    );

    expect(modalRoot.hasChildNodes()).toBeTruthy();
  });

  it('should clear the div with id modal-root on unmount', () => {
    const modalRoot = global.document.querySelector('#modal-root');

    component = mount(
      <Modal>
        <Child />
      </Modal>,
    );

    expect(modalRoot.hasChildNodes()).toBeTruthy();
    component.unmount();
    expect(modalRoot.hasChildNodes()).toBeFalsy();
  });

  it('should set overflow hidden on the boddy element', () => {
    const body = global.document.querySelector('body');
    expect(body.style.overflow).toBeFalsy();

    component = mount(
      <Modal>
        <Child />
      </Modal>,
    );

    component.setProps({ show: true });

    expect(body.style.overflow).toEqual('hidden');

    component.setProps({ show: false });
    expect(body.style.overflow).toBeFalsy();
  });
});

One big small thing, is that enzyme doesn't have full support for react 16 yet, github issue. And theoretically all tests should pass, but they were still failing the solution was to change the wrapper on the modal, instead of using <Fragment /> we need to use the old plain <div />

Modal.js render method:

render() {
    const ModalMarkup = (
      <div>
        <ModalBackdrop show={this.props.show} />
        <ModalWrap show={this.props.show} onClick={this.outerClick}>
          <ModalDialog show={this.props.show}>
            <ModalContent>{this.props.children}</ModalContent>
          </ModalDialog>
        </ModalWrap>
      </div>
    );
    return ReactDOM.createPortal(ModalMarkup, this.el);
  }

You can find a repo with all the code here

来源：https://stackoverflow.com/questions/48094581/testing-react-portals-with-enzyme

标签

reactjs

jestjs

enzyme

jsdom