Stress test

Im having a girl but I see a lot of ladies talking about stress test because their babies are super active and what not... do you determine a stress test based of their heart beat or their activity.? Her heart rate is roughly 137-142. My babygirl has been super like I mean super active ... like it almost feels like she’s up for 3/4 hours straight just wiggling and swimming in there and then at nights time she hardly moves and is able to let me sleep through the entire night( other than going to pee) I know it’s a good thing for them to move but was just cirious to know how others determine this stress test 🤔