What I expected happen: When I put the lead on the horse and walked up 1 block terrain the horse would follow me.
What actually: The horse got stuck at the edge of the block and was unable to jump up it.

Steps to reproduce:
1. Start a World in 1.9
2. Summon in an adult horse, or find some horses.
3. Attach a lead to the horse.
4. Walk up a 1 block steep hill.
5. watch the horse, he will not be able to go up it with you.