old_contents: import React from 'react';
  import ReactDOM from 'react-dom';
  import Lifecycle from './Lifecycle.js';
  
  
  it('renders without crashing', () => {
    const div = document.createElement('div');
    ReactDOM.render(<Lifecycle><div>hello</div></Lifecycle>, div);
  });
  
  
  it('calls componentWillMount', () => {
    const div = document.createElement('div');
    const props = {
      componentWillMount: jest.fn()
    };
    ReactDOM.render(<Lifecycle {...props}><div>hello</div></Lifecycle>, div);
    expect(props.componentWillMount).toHaveBeenCalled();
  });
  
new_contents: import React from 'react';
  import ReactDOM from 'react-dom';
  import Lifecycle from './Lifecycle.js';
  
  
  it('renders without crashing', () => {
    const div = document.createElement('div');
    ReactDOM.render(<Lifecycle><div>hello</div></Lifecycle>, div);
  });
  
  
  it('calls componentWillMount', () => {
    const div = document.createElement('div');
    const props = {
      componentWillMount: jest.fn()
    };
    ReactDOM.render(<Lifecycle {...props}><div>hello</div></Lifecycle>, div);
    expect(props.componentWillMount).toHaveBeenCalled();
  });
  
  it('calls componentWillUnmount', () => {
    const div = document.createElement('div');
    const props = {
      componentWillUnmount: jest.fn()
    };
    ReactDOM.render(<Lifecycle {...props}><div>hello</div></Lifecycle>, div);
    expect(props.componentWillUnmount).not.toHaveBeenCalled();
    ReactDOM.render(<b>goodbye</b>, div);
    expect(props.componentWillUnmount).toHaveBeenCalled();
  });
  
subject: Add another Lifecycle test case