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.
ReactDOM.render(<div />, container);
      expect(container.firstChild.innerHTML).toEqual('bonjour');
    });
    it('should reset innerHTML when switching from a direct text child to an empty child', () => {
      const transitionToValues = [null, undefined, false];
      transitionToValues.forEach(transitionToValue => {
        var container = document.createElement('div');
        ReactDOM.render(<div>bonjour</div>, container);
        expect(container.firstChild.innerHTML).toEqual('bonjour');
        ReactDOM.render(<div>{transitionToValue}</div>, container);
        expect(container.firstChild.innerHTML).toEqual('');
      });
    });
    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,