It seems problematic to allow arbitary non-lowercase attribute on HTML nodes. Because the server has no ability to keep them case sensitive (HTML isn't). So they will end up different on the client.

We should probably warn if the attribute is not a known one *and* is not lowercase.
);
      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');
    });
    it('should transition from innerHTML to children in nested el', () => {
      var container = document.createElement('div');
      ReactDOM.render(
        <div><div dangerouslySetInnerHTML={{__html: 'bonjour'}} /></div>,
        container,
      );
      expect(container.textContent).toEqual('bonjour');
      ReactDOM.render(<div><div><span>adieu</span></div></div>, container);
      expect(container.textContent).toEqual('adieu');
    });
    it('should transition from children to innerHTML in nested el', () => {
      var container = document.createElement('div');
      ReactDOM.render(<div><div><span>adieu</span></div></div>, container);
      expect(container.textContent).toEqual('adieu');
      ReactDOM.render(
        <div><div dangerouslySetInnerHTML={{__html: 'bonjour'}} /></div>,
        container,