A dog breed that is medium to large size, has longish fur, and comes in black and white?
border collies are like that, well medium i guess
Very specific my young padawan, but I can help you. A Collie would be a good dog but it is on the small side. A Dalmatian would good but it has short fur. Maybe a collie Dalmatian mix.SIBERIAN HUSKIES
English Springer Spaniel.
Old English sheepdog, some cocker spaniels, And border collies