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.

});
    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,
      );
      expect(container.textContent).toEqual('bonjour');
    });
    it('should not incur unnecessary DOM mutations for attributes', () => {
      var container = document.createElement('div');
      ReactDOM.render(<div id="" />, container);
      var node = container.firstChild;
      var nodeSetAttribute = node.setAttribute;
      node.setAttribute = jest.fn();
      node.setAttribute.mockImplementation(nodeSetAttribute);
      var nodeRemoveAttribute = node.removeAttribute;
      node.removeAttribute = jest.fn();