I've learnt to never trust a dog...
A dog around his owner is completely different then a dog by himself with you the stranger that he's never met before.
I'm in no way bad mouthing dog's in any way shape or form because I love dogs... but in my line of work I have to confront dogs every day and i've been bit a time or two by very large dogs along with little ankle biters.
They can be unpredictable at times, just gotta watch what your doing and stay smart.