is usually the first black box
test. The main goal is to find divergences between the
specification -- a precise description of the
program's behavior from the users point of view -- or design, and the
coded product. This is often done in the following way:
First, this specification is being analysed. For
each of the program's input field, the allowed inputs are written down.
It is useful to try to divide the possible inputs in so
called equivalence classes to reduce the
number of possible inputs which should be
tested.
Alternatively, a boundary value analysis can be done. The difference is that rather than
choosing any element in an equivalence class
as a representative , the focus is on
the edges of the appropriate equivalence class. Once more, the triangle
example helps to explain the usefullness of this test method. For all
input values to represent a triangle, two conditions have
to be fulfilled. First all integers have to be greater than zero, and
second, the sum of any two of them has to be greater than the third. A
likely error for the program is that is coded instead of
. Since the boundary value analysis explores situations on
and around the edges of the equivalence classes, it helps to find bugs
of this kind.