IME horses love consistency and predictability. So it is not surprising that they will learn to anticipate parts of a test if you ride it too often.
Fellow boarder was excited about going to her first schooling show. She rode the test quite often trying to perfect things. Then her horse started some of the transitions before she aided and slightly before the markers! Trainer pointed out the error of her ways and advised her to practice mostly indifferent parts of the arena and out of order most of the time.
My horse is convinced that he can figure out what we are doing and beat me to it! Sometimes it helps - like anticipating trot lengthening on the diagonal and using that to get some nice collection. But if we practice simple changes on the center line more than a couple times he will try to go on auto-pilot and changes through the trot or going across to counter canter become a challenge. He keeps me aware of changing things up and making sure he waits for me!