Right now, if you pass data to logEvent that doesn't match the schema, it will fail silently.
It would be nice if it returned false or an error.

The schema validation is asynchronous (on purpose) and it is done on the receiver end (not the sending end) but you can easily test validation on vagrant before events are "released in the wild".

Let us know if this makes sense, some docs: http://www.mediawiki.org/wiki/Extension:EventLogging/Guide#Installing_the_EventLogging_devserver