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.

});
    it('should empty element when removing innerHTML', () => {
      var container = document.createElement('div');
      ReactDOM.render(
        <div dangerouslySetInnerHTML={{__html: ':)'}} />,
        container,
      );
      expect(container.firstChild.innerHTML).toEqual(':)');
      ReactDOM.render(<div />, container);
      expect(container.firstChild.innerHTML).toEqual('');
    });
    it('should transition from string content to innerHTML', () => {
      var container = document.createElement('div');
      ReactDOM.render(<div>hello</div>, container);
      expect(container.firstChild.innerHTML).toEqual('hello');
      ReactDOM.render(
        <div dangerouslySetInnerHTML={{__html: 'goodbye'}} />,
        container,
      );
      expect(container.firstChild.innerHTML).toEqual('goodbye');
    });
    it('should transition from innerHTML to string content', () => {
      var container = document.createElement('div');
      ReactDOM.render(
        <div dangerouslySetInnerHTML={{__html: 'bonjour'}} />,
        container,
      );
      expect(container.firstChild.innerHTML).toEqual('bonjour');
      ReactDOM.render(<div>adieu</div>, container);
      expect(container.firstChild.innerHTML).toEqual('adieu');