Error: This method is only meant to be run on single node. 0 found instead

问题

I am testing a keybinding feature in a component. The component is rather simple, event listener for the keyup and fires up a redux action which will hide the component.

I have cleaned up my code here to only relevant information. I am able to make the test pass if I just use the store dispatch to make the action call but that of course will defeat the purpose of this test. I am using Enzyme to simulate the keyup event with the appropriate event data (keycode for esc) but I come across the error below.

MyComponent.js

import React, {Component, PropTypes} from 'react';
import styles from './LoginForm.scss';
import {hideComponent} from '../../actions';
import {connect} from 'react-redux';

class MyComponent extends Component {
  static propTypes = {
      // props
  };

  componentDidMount() {
    window.addEventListener('keyup', this.keybindingClose);
  }

  componentWillUnmount() {
    window.removeEventListener('keyup', this.keybindingClose);
  }

  keybindingClose = (e) => {
    if (e.keyCode === 27) {
      this.toggleView();
    }
  };

  toggleView = () => {
    this.props.dispatch(hideComponent());
  };

  render() {
    return (
      <div className={styles.container}>
        // render code
      </div>
    );
  }
}

export default connect(state => ({
  // code
}))(MyComponent);

MyComponent-test.js

import React from 'react';
import chai, {expect} from 'chai';
import chaiEnzyme from 'chai-enzyme';
import configureStore from 'redux-mock-store';
import {mount} from 'enzyme';
import {Provider} from 'react-redux';
import thunk from 'redux-thunk';
import {MyComponent} from '../../common/components';
import styles from '../../common/components/MyComponent/MyComponent.scss';

const mockStore = configureStore([thunk]);
let store;
chai.use(chaiEnzyme());

describe.only('<MyComponent/>', () => {
  beforeEach(() => {
    store = mockStore({});
  });

  afterEach(() => {
    store.clearActions();
  });

  it('when esc is pressed HIDE_COMPONENT action reducer is returned', () => {
    const props = {
      // required props for MyComponent
    };
    const expectedAction = {
      type: require('../../common/constants/action-types').HIDE_COMPONENT
    };
    const wrapper = mount(
      <Provider store={store} key="provider">
        <LoginForm {...props}/>
      </Provider>
      );
    // the dispatch function below will make the test pass but of course it is not testing the keybinding as I wish to do so
    // store.dispatch(require('../../common/actions').hideComponent());
    wrapper.find(styles.container).simulate('keyup', {keyCode: 27});
    expect(store.getActions()[0]).to.deep.equal(expectedAction);
  });
});

Error: This method is only meant to be run on single node. 0 found instead.

at ReactWrapper.single (/Users/[name]/repos/[repoName]/webpack/test.config.js:5454:18 <- webpack:///~/enzyme/build/ReactWrapper.js:1099:0)

at ReactWrapper.simulate (/Users/[name]/repos/[repoName]/webpack/test.config.js:4886:15 <- webpack:///~/enzyme/build/ReactWrapper.js:531:0)

at Context. (/Users/[name]/repos/[repoName]/webpack/test.config.js:162808:55 <- webpack:///src/test/components/MyComponent-test.js:39:40)

回答1:

That error happens when, as it says, you run it with any number of nodes other than 1.

Similar to jQuery, your find call will return some number of nodes (really it's a single wrapper that knows how many nodes your find selector has found). And you can't call simulate against 0 nodes! Or multiple.

The solution then is to figure out why your selector (the styles.container in wrapper.find(styles.container)) is returning 0 nodes, and make sure it returns exactly 1, and then simulate will work as you expect.

const container = wrapper.find(styles.container)
expect(container.length).to.equal(1)
container.simulate('keyup', {keyCode: 27});
expect(store.getActions()[0]).to.deep.equal(expectedAction);

Enzyme's debug method is really useful here. You could do console.log(container.debug()), or also console.log(container.html()) to make sure your component is rendering as expected during the test.

来源：https://stackoverflow.com/questions/37381916/error-this-method-is-only-meant-to-be-run-on-single-node-0-found-instead

标签

reactjs

mocha

redux

enzyme