componentDidMount() {
        this.test = 'test';
      }
      render() {
        return <div />;
      }
    }
    class Foo extends React.Component {
      render() {
        fooInstance = this;
        return <Bar ref="bar" />;
      }
    }
    ReactNoop.render(<Foo />);
    ReactNoop.flush();
    expect(fooInstance.refs.bar.test).toEqual('test');
  });
});