10.2 Black-Box Testing

There are two basic approaches to testing: black-box and white-box. In black-box testing the structure of the program is not considered. Test cases are decided solely on the basis of the requirements or specifications of the program or module, and the internals of the module or the program are not considered for selection of test cases. In this section, we will present some techniques for generating test cases for black-box testing. White-box testing is discussed in the next section.

In black-box testing, the tester only knows the inputs that can be given to the system and what output the system should give. In other words, the basis for deciding test cases in functional testing is the requirements or specifications of the system or module. This form of testing is also called functional or behavioral testing.

The most obvious functional testing procedure is exhaustive testing, which as we have stated, is impractical. One criterion for generating test cases is to generate them randomly. This strategy has little chance of resulting in a set of test cases that is close to optimal (i.e., that detects the maximum errors with minimum test cases). Hence, we need some other criterion or rule for selecting test cases. There are no formal rules for designing test cases for functional testing. In fact, there are no precise criteria for selecting test cases. However, there are a number of techniques or heuristics that can be used to select test cases that have been...