This is just bike shedding - you can completely ignore me, since this is just an opinion. 
Since it's not passed in the constructor, and nothing else is setting it in the setup, then I think it makes sense that testing it's a `WeakLocks` object after `CassScalingGroupCollection` is set up is enough?  And nothing prevents something else from coming along afterward to set it again.

But this is fine as is.  :)  Please don't block on this comment.