public void Publish_Message_Correctly()
{
_publisher.Subscribe(_handler);
Assert.AreEqual(0, _handler.Counter);
_publisher.Publish(new TestMessage(5));
// Without calling Deliver, messages shouldn't be delivered.
Assert.AreEqual(0, _handler.Counter);
_publisher.Deliver(_messageHistory);
Assert.AreEqual(5, _handler.Counter);
}