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.

'&#x27;&quot;&lt;&gt;&amp;' +
          '</div>',
      );
    });
  });
  describe('unmountComponent', () => {
    
    if (!ReactDOMFeatureFlags.useFiber) {
      it('should clean up input value tracking', () => {
        var container = document.createElement('div');
        var node = ReactDOM.render(
          <input type="text" defaultValue="foo" />,
          container,
        );
        var tracker = inputValueTracking._getTrackerFromNode(node);
        spyOn(tracker, 'stopTracking');
        ReactDOM.unmountComponentAtNode(container);
        expect(tracker.stopTracking.calls.count()).toBe(1);
      });
      it('should clean up input textarea tracking', () => {
        var container = document.createElement('div');
        var node = ReactDOM.render(<textarea defaultValue="foo" />, container);
        var tracker = inputValueTracking._getTrackerFromNode(node);
        spyOn(tracker, 'stopTracking');
        ReactDOM.unmountComponentAtNode(container);
        expect(tracker.stopTracking.calls.count()).toBe(1);
      });
    }
    it('unmounts children before unsetting DOM node info', () => {
      class Inner extends React.Component {