Testing form input elements with enzyme

TestInput.test.jsx

import React from 'react'; // 16.2.0
import {mount} from 'enzyme'; // 3.2.0

it('does something', () => {
  class TestInput extends React.Component {
    constructor(props) {
      super(props);
      this.state = {
        inputValue: 'before',
      };
    }

    render() {
      return <input value={this.state.inputValue} onChange={event => this.setState({inputValue: event.target.value})} />
    }
  }

  const wrapper = mount(<TestInput />);
  const input = wrapper.find('input');
  input.simulate('change', {target: {value: 'after'}});

  expect(wrapper.state('inputValue')).toBe('after');
  expect(input.instance().value).toBe('after');
});