The Art of Software Testing, Second Edition

5.2. Incremental Testing

In performing the process of module testing, there are two key considerations: the design of an effective set of test cases, which was discussed in the previous section, and the manner in which the modules are combined to form a working program. The second consideration is important because it has implications for the form in which module test cases are written, the types of test tools that might be used, the order in which modules are coded and tested, the cost of generating test cases, and the cost of debugging (locating and repairing detected errors). In short, then, it is a consideration of substantial importance. In this section, two approaches, incremental and nonincremental testing, are discussed. In the next section, two incremental approaches, top-down and bottom-up development or testing, are explored.

The question pondered here is the following: Should you test a program by testing each module independently and then combining the modules to form the program, or should you combine the next module to be tested with the set of previously tested modules before it is tested? The first approach is called nonincremental or "big-bang" testing or integration; the second approach is known as incremental testing or integration.

The program in Figure 5.7 is used as an example. The rectangles represent the six modules (subroutines or procedures) in the program. The lines connecting the modules represent the control hierarchy of the program; that is, module ...