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 update styles if updated to null multiple times', () => {
      var styles = null;
      var container = document.createElement('div');
      ReactDOM.render(<div style={styles} />, container);
      styles = {display: 'block'};
      var stubStyle = container.firstChild.style;
      ReactDOM.render(<div style={styles} />, container);
      expect(stubStyle.display).toEqual('block');
      ReactDOM.render(<div style={null} />, container);
      expect(stubStyle.display).toEqual('');
      ReactDOM.render(<div style={styles} />, container);
      expect(stubStyle.display).toEqual('block');
      ReactDOM.render(<div style={null} />, container);
      expect(stubStyle.display).toEqual('');
    });
    it('should allow named slot projection on both web components and regular DOM elements', () => {
      var container = document.createElement('div');
      ReactDOM.render(
        <my-component>
          <my-second-component slot="first" />
          <button slot="second">Hello</button>
        </my-component>,
        container,
      );
      var lightDOM = container.firstChild.childNodes;
      expect(lightDOM[0].getAttribute('slot')).toBe('first');
      expect(lightDOM[1].getAttribute('slot')).toBe('second');
    });
    it('should skip reserved props on web components', () => {