This usually means that the user mixed up our lowercase/uppercase naming convention; see https://github.com/facebook/react/pull/3429#issuecomment-85166440.

We could add a message like

> Warning: The tag <commentBox> is unrecognized in this browser. If you meant to render a React component, start its name with an uppercase letter.

We'd check this only once per tag and only in development mode.

return (str + '').replace(/([.?*+\^$\[\]\\(){}|-])/g, '\\$1');
    }
    function genMarkup(props) {
      return ReactDOMServer.renderToString(<div {...props} />);
    }
    function toHaveInnerhtml(actual, expected) {
      var re = '^' + quoteRegexp(expected) + '$';
      return new RegExp(re).test(actual);
    }
    it('should handle dangerouslySetInnerHTML', () => {
      var innerHTML = {__html: 'testContent'};
      expect(
        toHaveInnerhtml(
          genMarkup({dangerouslySetInnerHTML: innerHTML}),
          'testContent',
        ),
      );
    });
  });