I might have a heart condition and am having a stress test done. What will they do in the test?

Depends on type. They stress test will attempt to define areas of the heart at risk for myocardial infarction (heart attack). How it is done depends on the type. A treadmill only test will have you walk on a treadmill and measure the ECG response. A nuclear adds myocardial perfusion imaging and a scan to add additional sensitivity and specificity. A pharmacologic uses a drug to dilate arteries so you don't walk.
Depends on test. It all depends on which type of stress test was ordered. Some require you to walk on a treadmill where as others will give you medications. Some may use an ecg, ultrasound or obtain nuclear imaging.