A Hunter can train his/her pet to have increased resistances to Arcane, Fire, Frost, Nature, or Shadow damage. The resistance boosts received from this training stacks with the pet's inherited resistances, which is approximately 40% of the Hunter's resistances.
Each school of magic damage resistance is trained separately.
A Warlock's pet gains 0.4 resistance for every 1 point of resistance it's master has.
See the Partial Resists table for further information.