`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.

dispatchConfig,
      ReactDOMComponentTree.getInstanceFromNode(node),
      fakeNativeEvent,
      node
    );
    
    
    event.persist();
    Object.assign(event, eventData);
    if (dispatchConfig.phasedRegistrationNames) {
      EventPropagators.accumulateTwoPhaseDispatches(event);
    } else {
      EventPropagators.accumulateDirectDispatches(event);
    }
    ReactUpdates.batchedUpdates(function() {
      EventPluginHub.enqueueEvents(event);
      EventPluginHub.processEventQueue(true);
    });
  };
}
function buildSimulators() {
  ReactTestUtils.Simulate = {};
  var eventType;
  for (eventType in EventPluginRegistry.eventNameDispatchConfigs) {
    /**
     * @param {!Element|ReactDOMComponent} domComponentOrNode
     * @param {?object} eventData Fake event data to use in SyntheticEvent.
     */
    ReactTestUtils.Simulate[eventType] = makeSimulator(eventType);
  }