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.
return str && str.replace(/\(at .+?:\d+\)/g, '(at **)');
  }
  beforeEach(() => {
    jest.resetModules();
    React = require('react');
    ReactDOM = require('react-dom');
    ReactDOMFeatureFlags = require('ReactDOMFeatureFlags');
    ReactDOMServer = require('react-dom/server');
    ReactTestUtils = require('react-dom/test-utils');
    
    inputValueTracking = require('inputValueTracking');
  });
  describe('updateDOM', () => {
    it('should handle className', () => {
      var container = document.createElement('div');
      ReactDOM.render(<div style={{}} />, container);
      ReactDOM.render(<div className={'foo'} />, container);
      expect(container.firstChild.className).toEqual('foo');
      ReactDOM.render(<div className={'bar'} />, container);
      expect(container.firstChild.className).toEqual('bar');
      ReactDOM.render(<div className={null} />, container);
      expect(container.firstChild.className).toEqual('');
    });
    it('should gracefully handle various style value types', () => {
      var container = document.createElement('div');
      ReactDOM.render(<div style={{}} />, container);
      var stubStyle = container.firstChild.style;
      
      var setup = {display: 'block', left: '1px', top: 2, fontFamily: 'Arial'};
      ReactDOM.render(<div style={setup} />, container);