test-renderer-api.js

import React from 'react';
import TestRenderer from 'react-test-renderer';

const Child = props => <div>{props.children}</div>;
const Counter = props => <div>{props.count}</div>;

class App extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      count: 0
    };
  }
  render() {
    return (
      <section>
        <div>bar</div>
        <Child><p>Hello</p></Child>
        <div>bar</div>
        <button onClick={() => this.setState({count: this.state.count + 1})}>
          ++
        </button>
        <Counter count={this.state.count} />
      </section>
    );
  }
}

const root = TestRenderer.create(<App />).root;

// find a component by Type
console.assert(root.find(node => node.type === Child).props.children.type === 'p');
// find a component by Props
console.assert(root.findByProps({children: 'Hello'}).type === 'p');

// find all components by Type
console.assert(root.findAllByType('div').length === 4);

// initial state
const instance = root.instance;
console.assert(root.findByType(Counter).props.count === 0);
console.assert(instance.state.count === 0);

// click the button
const button = root.findByType('button').props.onClick();
console.assert(root.findByType(Counter).props.count === 1);
console.assert(instance.state.count === 1);

// setState directly
instance.setState({count: instance.state.count + 1});
console.assert(root.findByType(Counter).props.count === 2);
console.assert(instance.state.count === 2);