// src/Hello.js
import React from 'react';

export default ({ show }) => (
  <div>
    {show ? <span>hello</span> : null}
  </div>
);

// tests/Hello.test.js
import { mount } from 'enzyme';
import React from 'react';
import Hello from '../src/Hello';

test('Hello', () => {
  const wrapper = mount(<Hello show />)

  expect(wrapper.find('span').length).toBe(1)

  wrapper.setProps({ show: false });
  expect(wrapper.find('span').length).toBe(0)

  wrapper.setProps({ show: true });
  wrapper.update(); // even though calling wrapper.update explicitly
  console.log(wrapper.debug()); // no span
  console.log(wrapper.html()); // has span
  expect(wrapper.find('span').length).toBe(1) // failed
});