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.

expect(nodeValueSetter.mock.calls.length).toBe(1);
      ReactDOM.render(<div checked={false} />, container);
      expect(nodeValueSetter.mock.calls.length).toBe(2);
      ReactDOM.render(<div checked={true} />, container);
      expect(nodeValueSetter.mock.calls.length).toBe(3);
    });
    it('should ignore attribute whitelist for elements with the "is: attribute', () => {
      var container = document.createElement('div');
      ReactDOM.render(<button is="test" cowabunga="chevynova" />, container);
      expect(container.firstChild.hasAttribute('cowabunga')).toBe(true);
    });
    it('should not update when switching between null/undefined', () => {
      var container = document.createElement('div');
      var node = ReactDOM.render(<div />, container);
      var setter = jest.fn();
      node.setAttribute = setter;
      ReactDOM.render(<div dir={null} />, container);
      ReactDOM.render(<div dir={undefined} />, container);
      ReactDOM.render(<div />, container);
      expect(setter.mock.calls.length).toBe(0);
      ReactDOM.render(<div dir="ltr" />, container);
      expect(setter.mock.calls.length).toBe(1);
    });
    it('handles multiple child updates without interference', () => {
      
      
      
      var container = document.createElement('div');
      
      ReactDOM.render(