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.
return str && str.replace(/\(at .+?:\d+\)/g, '(at **)');
  }
  beforeEach(() => {
    jest.resetModules();
    React = require('react');
    ReactDOM = require('react-dom');
    ReactDOMFeatureFlags = require('ReactDOMFeatureFlags');
    ReactDOMServer = require('react-dom/server');
    ReactTestUtils = require('react-dom/test-utils');
    
    inputValueTracking = require('inputValueTracking');
  });
  describe('updateDOM', () => {
    it('should handle className', () => {
      var container = document.createElement('div');
      ReactDOM.render(<div style={{}} />, container);
      ReactDOM.render(<div className={'foo'} />, container);
      expect(container.firstChild.className).toEqual('foo');