
7.7 Domains and Testability

In order to perform domain testing and to make a program testable for a particular domain there is a need to ensure that values of input domains are to be supplied with care. This requires following steps so as to ensure testability using appropriate input domains.

7.7.1 Linearizing transformations

Nonlinear domains are not appropriate to test a program segments. So any nonlinear domain shall be converted into linear domains. This can be done by applying linearizing transformations. General nonlinear domains are polynomials and logarithmic in nature.

Polynomials linearizing transformation: Polynomials linearizing transformation involves replacement of polynomials terms like x, x2, x3 etc. by using replacement by new variable; y1 = x, y2 = x2, y3= x3 etc. Such transformations convert problems that are difficult to solve into the problems that can be solved.

Logarithmic Transforms: Products such as (a*b*c) can be linearized by substituting p = log(a), q = log(b), r = log(c) .

There can be other transformations which convert nonlinear functions into linearizable forms by using appropriate approximating polynomials.

7.7.2 Coordinate Transformations

In nice boundaries that have parallel input domain values, domain value of a particular boundary differs with domain value of another boundary just by a constant. During testing we have to pick up one representative input value of a particular boundary and arrive at other input values corresponding to other boundaries by performing appropriate transformations.

If the domains are ugly, then there will be nonparallel boundary sets. Testing nonparallel boundary sets is practically not possible since for a given set of domain input value there will not be any associated achievable predicate path. Under such situations suitable coordinate transformations shall be used to convert unparallel domains into orthogonal boundaries. Following this, independent testing by using different boundary sets can be done on each orthogonal boundary.






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