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.

ReactDOM.render(<div />, container);
      expect(stubStyle.display).toEqual('');
      expect(stubStyle.color).toEqual('');
    });
    it('should update styles when `style` changes from null to object', () => {
      var container = document.createElement('div');
      var styles = {color: 'red'};
      ReactDOM.render(<div style={styles} />, container);
      ReactDOM.render(<div />, container);
      ReactDOM.render(<div style={styles} />, container);
      var stubStyle = container.firstChild.style;
      expect(stubStyle.color).toEqual('red');
    });
    it('should not reset innerHTML for when children is null', () => {
      var container = document.createElement('div');
      ReactDOM.render(<div />, container);
      container.firstChild.innerHTML = 'bonjour';
      expect(container.firstChild.innerHTML).toEqual('bonjour');
      ReactDOM.render(<div />, container);
      expect(container.firstChild.innerHTML).toEqual('bonjour');
    });
    it('should reset innerHTML when switching from a direct text child to an empty child', () => {
      const transitionToValues = [null, undefined, false];
      transitionToValues.forEach(transitionToValue => {
        var container = document.createElement('div');
        ReactDOM.render(<div>bonjour</div>, container);
        expect(container.firstChild.innerHTML).toEqual('bonjour');
        ReactDOM.render(<div>{transitionToValue}</div>, container);
        expect(container.firstChild.innerHTML).toEqual('');
      });