*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.
it('removes a property when it becomes invalid', function() {
      spyOn(console, 'error');
      var container = document.createElement('div');
      ReactDOM.render(<div whatever={0} />, container);
      ReactDOM.render(<div whatever={() => {}} />, container);
      var el = container.firstChild;
      expect(el.hasAttribute('whatever')).toBe(false);
      expectDev(console.error.calls.argsFor(0)[0]).toContain(
        'Warning: Invalid value for prop `whatever` on <div> tag.',
      );
    });
    it('warns on bad casing of known HTML attributes', function() {
      spyOn(console, 'error');
      var el = ReactTestUtils.renderIntoDocument(<div SiZe="30" />);
      expect(el.getAttribute('size')).toBe('30');
      expectDev(console.error.calls.argsFor(0)[0]).toContain(
        'Warning: Invalid DOM property `SiZe`. Did you mean `size`?',
      );
    });
  });
  describe('Object stringification', function() {
    it('allows objects on known properties', function() {
      var el = ReactTestUtils.renderIntoDocument(<div acceptCharset={{}} />);
      expect(el.getAttribute('accept-charset')).toBe('[object Object]');
    });
    it('should pass objects as attributes if they define toString', () => {
      var obj = {
        toString() {
          return 'hello';
        },