I assume the test will be that they will hook the mask over your mouth and nose so they can measure oxygen output (results come through on the computer screen), while you are running. They will also attach that ECG or at least a heart rate monitor to your chest so they can correlate your heart rate during the run on the treadmill.
In this case, it would definitely be beneficial. But then again, finding out how much stress you can take during running would be of benefit to anyone with a health condition such as yours.
Koffee