ABSTRACT
Of the three levels of testing, the system level is closest to everyday experience. We test many things: a used car before we buy it, an online network service before we subscribe, and so on. A common pattern in these familiar forms is that we evaluate a product in terms of our expectations — not with respect to a specification or a standard. Consequently, the goal is not to find faults, but to demonstrate performance. Because of this, we tend to approach system testing from a functional standpoint instead of from a structural one. Because it is so intuitively familiar, system testing in practice tends to be less formal than it might be; and this is compounded by the reduced testing interval that usually remains before a delivery deadline.
