A stress test or a non stress test? Because they are different a non stress test is just a monitor that they put on you to measure the babies movements. A stress test actually induced contractions and is used to see how baby reacts, like if there is movement or if there is a drop in heart rate.
Don't be worried I had one every week during my last trimester with my first baby. It is a precaution and they should tell you when to worry.