*feature*

>Warning: A component is `contentEditable` and contains `children` managed by React. It is now your responsibility to guarantee that none of those nodes are unexpectedly modified or duplicated. This is probably not intentional.

It would help heaps if I would know _which_ component is causing this.
render() {
          return <input>moo</input>;
        }
      }
      var container = document.createElement('div');
      expect(function() {
        ReactDOM.render(<X />, container);
      }).toThrowError(
        'input is a void element tag and must neither have `children` ' +
          'nor use `dangerouslySetInnerHTML`.\n\nThis DOM node was rendered by `X`.',
      );
    });
    it('should support custom elements which extend native elements', () => {
      var container = document.createElement('div');
      spyOn(document, 'createElement').and.callThrough();
      ReactDOM.render(<div is="custom-div" />, container);
      expect(document.createElement).toHaveBeenCalledWith('div', {
        is: 'custom-div',
      });