`SyntheticEvent.type` is undefined when received by the handler. Or the nativeEvent type for that matter.

Needs to be added in here somewhere: https://github.com/facebook/react/blob/3a4e1dbb5b2957875cab6af11a5e5934e125a0d8/src/test/ReactTestUtils.js#L496

I realize that it's not sustainable to have to set _all_ the possible fields for a simulated event, but the type at least makes sense for verification that you're getting the right _sort_ of event.

Object.assign(fakeNativeEvent, nativeEventData);
    if (ReactTestUtils.isDOMComponent(domComponentOrNode)) {
      ReactTestUtils.simulateNativeEventOnDOMComponent(
        eventType,
        domComponentOrNode,
        fakeNativeEvent
      );
    } else if (domComponentOrNode.tagName) {
      
      ReactTestUtils.simulateNativeEventOnNode(
        eventType,
        domComponentOrNode,
        fakeNativeEvent
      );
    }
  };
}
Object.keys(topLevelTypes).forEach(function(eventType) {
  
  var convenienceName = eventType.indexOf('top') === 0 ?
    eventType.charAt(3).toLowerCase() + eventType.substr(4) : eventType;
  /**
   * @param {!Element|ReactDOMComponent} domComponentOrNode
   * @param {?Event} nativeEventData Fake native event to use in SyntheticEvent.
   */
  ReactTestUtils.SimulateNative[convenienceName] =
    makeNativeSimulator(eventType);
});
module.exports = ReactTestUtils;