https://jsfiddle.net/3apqnhmw/

```jsx
class Foo extends React.Component {
  render() {
     return <div>Foo</div>
  }
}

class App extends React.Component {
  render() {
    return Foo
  }
}
```

When `App` returns `Foo` instead of `<Foo />` accidentally, Fiber does not catch this.
expect(this.wrapperRef.getTitle()).toBe('wrapper');
        expect(ReactDOM.findDOMNode(this.innerRef).className).toBe('inner');
        mounted = true;
      }
    }
    ReactTestUtils.renderIntoDocument(<Component />);
    expect(mounted).toBe(true);
  });
  it('should call refs at the correct time', () => {
    var log = [];
    class Inner extends React.Component {
      render() {
        log.push(`inner ${this.props.id} render`);
        return <div />;
      }
      componentDidMount() {
        log.push(`inner ${this.props.id} componentDidMount`);
      }
      componentDidUpdate() {
        log.push(`inner ${this.props.id} componentDidUpdate`);
      }
      componentWillUnmount() {
        log.push(`inner ${this.props.id} componentWillUnmount`);
      }
    }
    class Outer extends React.Component {