Structured Testing - McCabe and Associates

One essential ingredient in any testing methodology is to limit the program logic during
development so that the program can be understood, and the amount of testing required to verify
the logic is not overwhelming. A developer who, ignorant of the implications of complexity,
expects to verify a module such as that of Figure 3-9 with a handful of tests is heading for
disaster. The size of the module in Figure 3-9 is only 30 lines of source code. The size of several
of the previous graphs exceeded 60 lines, for example the 282-line module in Figure 3-1.
In practice, large programs often have low complexity and small programs often have high
complexity. Therefore, the common practice of attempting to limit complexity by controlling
only how many lines a module will occupy is entirely inadequate. Limiting complexity
directly is a better alternative.
22
Figure 3-9. Control flow graph with complexity 28.