create_node_mock_option.js

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

class MyComponent extends React.Component {
  constructor(props) {
    super(props);
    this.input = null;
  }
  componentDidMount() {
    this.input.focus();
  }
  render() {
    return <input type="text" ref={el => this.input = el} />
  }
}

let focused = false;
TestRenderer.create(
  <MyComponent />,
  {
    createNodeMock: (element) => {
      if (element.type === 'input') {
        // mock a focus function
        return {
          focus: () => {
            focused = true;
          }
        };
      }
      return null;
    }
  }
);
console.assert(focused === true);