The point of the event is to allow external code (like the test suite) to attach additional handlers to the client when it's created. However, we have a problem in that WithHandler doesn't attach handlers to a client, it creates a new client. So we need to be able to get the client back from the event handlers if they've added any handlers. That's why it's getting the client object back out from the eventargs: the client object may have changed.

There's a reasonable argument to be made to verify that the client coming back from the event handler's isn't null.