Let me begin by saying I'm not a huge fan of rewarding with food (in the classroom or at home) but once in a while, a little treat can make the day a little more sweet.
I've done these little testing encouragers for a while, and I've found some wonderful ideas online, but last year was the first year I made all of my own.
My students have 6 individual tests (2 math, 2 reading, 2 writing) so I made up 6 little printables for them with the matching candies. I was able to get all these candies from the Dollar Store, and 2 bags of each were more than enough for my class. Before the students came into the classroom each day, I had their testing booklets out, a new sharpened pencil and eraser on their desk, and one of the little treats set out. I also like to display an encouraging quote over the whiteboard during the test, as well.

And if you're looking for a little fun to celebrate testing being over (yay!), or even to calm the nerves before testing, I've made a great little drama circle all about "testing day" (or week ... ugh). You can take a peek at it HERE.