Same as https://github.com/facebook/react/issues/10103, but for the server renderer. You can look at implementation in https://github.com/facebook/react/pull/11168 and do something very similar in `ReactPartialRenderer.js`.
render() {
          return (
            <span>
              {'hello'} {'world'}
            </span>
          );
        }
      }
      const response = ReactDOMServer.renderToStaticMarkup(<TestComponent />);
      expect(response).toBe('<span>hello world</span>');
    });
    it('should not use comments for empty nodes', () => {
      class TestComponent extends React.Component {
        render() {
          return null;
        }
      }
      const response = ReactDOMServer.renderToStaticMarkup(<TestComponent />);
      expect(response).toBe('');
    });
    it('should only execute certain lifecycle methods', () => {
      function runTest() {
        const lifecycle = [];
        class TestComponent extends React.Component {