"Well, actually, I think YOU should be the one to change, you know?" said Dan. "I think i've gotten enough changing for one day".
"What, why? I literally promised to pay you for therapy, like, 10 minutes ago!" Kat explained.
"Well, I changed my mind. Tasting your milk was actually an interesting experience. Sorry sis, this one is your problem." said Dan.
"Ugh, fine. I guess I'll just do it myself." answered Kat. "But you better help me milk my udder!"
"Here we go, full cow! God my udder is going to be so damn full..."
She casts a teleporting spell, sending them to a nearby farm. "Ok, now people don't get suspicious of why a random cow is here."
She read another spell from her book, and with a flick of her wand, Kat's form began to change.
Her body expands, making her torso significantly larger, more barrel shaped. her chest and hips expand, while her breasts shrink into her chest.
Then her face elongates to that of an actual dairy cow, while her teeth reshape into that more suitable for chewing grass and other plants.
Her tail grows and her udder expands. it starts to produce gallons of milk a second. Kat moans of the pressure building in her udder.
Dan could do nothing but stand there and watch his sister turn into a full dairy cow.
Kat's body continues to change, her hips adjusting, forcing her to go on all fours.
He vagina and ass move up her body and rest snuggly bellow her tail.
Her horns grow longer, and legs become more muscly to support the weight of a fully grown cow with an udder carrying more that 5 gallons of milk.
Then finally, her transformation is complete. Kat was now a full grown cow. Her magic test had been complete
"is it over?" Dan asked.
"I...I think it is" Said Kat. "I did it! I passed the test"
"Thanks Dan, for helping me go through the first stage of the test. I couldn't have done it without you"
"you're welcome," he responded. It was mid afternoon and they were still at that farm she teleported them to. "So, what now?" he asked.
"Well, you could help me with draining my udder." Kat said. "It's awfully full, and the pressure is getting to the point where I can't stand it!"
"What? Hell no! I already did it once, why do I have to do it a second time! Don't you have a magic spell in that book of yours to empty it for you?"
"Do you expect me to hold the wand in my mouth while chanting the words! Plus, if I say a word wrong, then there might be some huge consequence!"
"Then what do YOU want me to do? I couldn't drink all the milk from when you were an anthro, so what makes you think I could do any better?"
"You're my assistant, so do something! I'm just a cow!" She exclaimed
"Ok, fine. Jeez." He thought for a moment, then looked up and saw cows over in the distant fields. "I have an idea. You go over to those cows over there. Then, I'll go get a pail or something and milk you then? How does that sound"
Kat sighed. "It's worth a shot. But be quick! I don't want my udder to explode milk"
"Ok, I'll see you there"
"Good Luck."