The cause-effect graphing helps to systematically select efficient tests. It gives a useful side effect, as it allows you to detect the incompleteness and ambiguity in the original specifications.
- A functional diagram is a formal language into which a natural language specification is translated. A diagram can be associated with a digital logic circuit (combinatorial logical network), but to describe it, a simpler notation (recording form) is used rather than the conventional form of recording adopted in electronics. To understand the cause-effect graphing, it is not necessary to know electronics, but it is desirable to understand Boolean logic (specifically, logical operators and, or not). With this technique tests are developed in several stages.
- The specification is divided into “working” areas. This is due to the fact that the functional diagrams become too cumbersome when applying the technique to large specifications. For example, when a time-sharing system is being tested, the work area can be a specification of a separate command. When testing the compiler as a working area, each individual programming language operator can be considered.
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- The specification defines the causes and effects. The reason is a separate input condition or equivalence class of input conditions. The corollary is the output condition or the transformation of the system (the residual effect that the input condition exerts on the state of the program or system). For example, if the program message causes the main file to be updated, then the change in it is the transformation of the system; a confirmation message would be an output condition. Causes and effects are determined by successive reading (word by word) of the specification. At the same time, words or phrases that describe causes and effects are highlighted. Each reason and effect is assigned a separate number.
- The semantic content of the specification is analyzed, which is transformed into a Boolean graph that connects causes and effects. This is the functional diagram.
- The diagram is supplied with notes specifying constraints and describing combinations of causes and (or) effects that are impossible due to syntactic or external constraints.
- By methodically tracing the states of the diagram’s conditions, it is transformed into a decision table with bounded inputs. Each column of the decision table corresponds to the test.
- The decision table columns are converted to tests.
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