['I have a math test tomorrow and it is the biggest one of the semester.', 'wow. I hope you have studied hard so you will do well.', "I've been studying all night. It's going to be a real doozy. I am quite nervous!"]
Well as long as you have studied hard you should do well. Just relax knowing you have prepared yourself.
I have a math test tomorrow. My stomach won't stop churning.