*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('should warn for unknown string event handlers', () => {
      spyOn(console, 'error');
      var container = document.createElement('div');
      ReactDOM.render(<div onUnknown="alert(&quot;hack&quot;)" />, container);
      expect(container.firstChild.hasAttribute('onUnknown')).toBe(false);
      expect(container.firstChild.onUnknown).toBe(undefined);
      ReactDOM.render(<div onunknown="alert(&quot;hack&quot;)" />, container);
      expect(container.firstChild.hasAttribute('onunknown')).toBe(false);
      expect(container.firstChild.onunknown).toBe(undefined);
      ReactDOM.render(<div on-unknown="alert(&quot;hack&quot;)" />, container);
      expect(container.firstChild.hasAttribute('on-unknown')).toBe(false);
      expect(container.firstChild['on-unknown']).toBe(undefined);
      expectDev(console.error.calls.count(0)).toBe(3);
      expectDev(normalizeCodeLocInfo(console.error.calls.argsFor(0)[0])).toBe(
        'Warning: Unknown event handler property `onUnknown`. It will be ignored.\n    in div (at **)',
      );
      expectDev(normalizeCodeLocInfo(console.error.calls.argsFor(1)[0])).toBe(
        'Warning: Unknown event handler property `onunknown`. It will be ignored.\n    in div (at **)',
      );
      expectDev(normalizeCodeLocInfo(console.error.calls.argsFor(2)[0])).toBe(
        'Warning: Unknown event handler property `on-unknown`. It will be ignored.\n    in div (at **)',
      );
    });
    it('should warn for unknown function event handlers', () => {
      spyOn(console, 'error');
      var container = document.createElement('div');
      ReactDOM.render(<div onUnknown={function() {}} />, container);
      expect(container.firstChild.hasAttribute('onUnknown')).toBe(false);
      expect(container.firstChild.onUnknown).toBe(undefined);