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

Code-based techniques

Control-flow-based criteria

Control-flow-based coverage criteria is aimed at covering all the statements or blocks of statements in a program, or specified combinations of them. Several coverage criteria have been proposed, like condition/decision coverage. The strongest of the control-flow-based criteria is path testing, which aims to execute all entry-to-exit control flow paths in the flowgraph. Since path testing is generally not feasible because of loops, other less stringent criteria tend to be used in practice, such as statement testing, branch testing, and condition/decision testing. The adequacy of such tests is measured in percentages; for example, when all branches have been executed at least once by the tests, 100% branch coverage is said to have been achieved.

Data flow-based criteria

In data-flow-based testing, the control flowgraph is annotated with information about how the program variables are defined, used, and killed (undefined). The strongest criterion, all definition-use paths, requires that, for each variable, every control flow path segment from a definition of that variable to a use of that definition is executed. In order to reduce the number of paths required, weaker strategies such as all-definitions and all-uses are employed.

Reference models for code-based testing

Although not a technique in itself, the control structure of a program is graphically represented using a flowgraph in code-based testing techniques. A flowgraph is a directed graph the nodes and arcs of which correspond to program elements. For instance, nodes may represent statements or uninterrupted sequences of statements, and arcs the transfer of control between nodes.