We used to throw if event listener is not a function in Stack:

```js
ReactDOM.render(
  <h1 onClick={{}}>Hello World!</h1>,
  document.getElementById('container')
);
```

<img width="565" alt="screen shot 2017-08-08 at 3 41 08 pm" src="https://user-images.githubusercontent.com/810438/29077502-2646412e-7c50-11e7-8c99-3b7f6c0a2589.png">

Fiber silently ignores this.

I think we should throw. This would let us add support for objects (e.g. for passive listener configuration) if we want to in a minor rather than a major.
);
      expectDev(console.error.calls.argsFor(1)[0]).toBe(
        'Warning: Invalid DOM property `autofocus`. Did you mean `autoFocus`?\n    in input',
      );
    });
    it('should suggest property name if available (ssr)', () => {
      spyOn(console, 'error');
      ReactDOMServer.renderToString(
        React.createElement('label', {for: 'test'}),
      );
      ReactDOMServer.renderToString(
        React.createElement('input', {type: 'text', autofocus: true}),
      );
      expectDev(console.error.calls.count()).toBe(2);
      expectDev(console.error.calls.argsFor(0)[0]).toBe(
        'Warning: Invalid DOM property `for`. Did you mean `htmlFor`?\n    in label',
      );
      expectDev(console.error.calls.argsFor(1)[0]).toBe(
        'Warning: Invalid DOM property `autofocus`. Did you mean `autoFocus`?\n    in input',
      );
    });
  });
  describe('whitespace', () => {
    it('renders innerHTML and preserves whitespace', () => {
      const container = document.createElement('div');
      const html = '\n  \t  <span>  \n  testContent  \t  </span>  \n  \t';
      const elem = <div dangerouslySetInnerHTML={{__html: html}} />;
      ReactDOM.render(elem, container);
      expect(container.firstChild.innerHTML).toBe(html);
    });