Software Testing

Unlike physical systems, most of the defects in software are design errors. Read about the important purpose of software testing and differentiate between verification and validation and basic software testing terms. Compare and contrast the use of various testing strategies, including black-box, white-box, top-down, and bottom-up.

Test Techniques

Fault-based techniques

With different degrees of formalization, fault-based testing techniques devise test cases specifically aimed at revealing categories of likely or predefined faults.

Error guessing

In error guessing, test cases are specifically designed by software engineers trying to figure out the most plausible faults in a given program. A good source of information is the history of faults discovered in earlier projects, as well as the software engineer's expertise.

Mutation testing

A mutant is a slightly modified version of the program under test, differing from it by a small, syntactic change. Every test case exercises both the original and all generated mutants: if a test case is successful in identifying the difference between the program and a mutant, the latter is said to be "killed". Originally conceived as a technique to evaluate a test set, mutation testing is also a testing criterion in itself: either tests are randomly generated until enough mutants have been killed, or tests are specifically designed to kill surviving mutants. In the latter case, mutation testing can also be categorized as a code-based technique. The underlying assumption of mutation testing, the coupling effect, is that by looking for simple syntactic faults, more complex but real faults will be found. For the technique to be effective, a large number of mutants must be automatically derived in a systematic way.