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.
render() {
            return <div ref="foo" />;
          }
        }
        const e = await render(<RefComponent />);
        expect(e.getAttribute('ref')).toBe(null);
      });
      itRenders('no children attribute', async render => {
        const e = await render(React.createElement('div', {}, 'foo'));
        expect(e.getAttribute('children')).toBe(null);
      });
      itRenders('no key attribute', async render => {
        const e = await render(<div key="foo" />);
        expect(e.getAttribute('key')).toBe(null);
      });
      itRenders('no dangerouslySetInnerHTML attribute', async render => {
        const e = await render(
          <div dangerouslySetInnerHTML={{__html: '<foo />'}} />,
        );
        expect(e.getAttribute('dangerouslySetInnerHTML')).toBe(null);
      });
    });
    describe('inline styles', function() {
      itRenders('simple styles', async render => {
        const e = await render(<div style={{color: 'red', width: '30px'}} />);
        expect(e.style.color).toBe('red');