Angina can occur during exercise when your heart muscle becomes short of fuel. Exercise testing is a convenient way of measuring the heart's response to exercise. It is also sometimes used in the assessment of high blood pressure and some heart rhythm disturbances. It is simply an ECG recording made whilst you walk on a treadmill. It may sound frightening but a treadmill is simply a machine with a band, like an escalator. The band continuously rotates during the test. 
Every few minutes, usually three, the band moves faster and becomes a little steeper. The response of your heat gives a lot of information. We look at changes in your heart rate, blood pressure and also changes in the ECG recording. The test takes up to 45 minutes including time for preparation and cool down.
I hope that this article has been useful, if you have any questions or comments please do use the Contact me section.