Well, it isn't as much as I'm waiting for the most opportune moment and more like Johnatan wants more information.
You just gave an all too good opportunity during the toilet scene and the dog acted out of its own volition.
The dog is nowhere a match for a Servant so wasting off just to test you has no meaning.
Still, I want to give you a fair warning.
Don't meet this particular dog for the third time.
It has certain consequences.