Jul 18, 2012

Functionality Testing

Functional testing is typically the base-line technique for designing test cases, for a number of reasons. Functional test case design should begin as part of the requirements specification process, and continue through each level of design and interface specification; it is the only test design technique
with such wide and early applicability. Moreover, functional testing is effective in finding some classes of fault that typically elude so-called “whitebox” or “glass-box” techniques of structural or fault-based testing. Functional testing techniques can be applied to any description of application behavior, from an informal partial description to a formal specification and at any level of granularity, from module to system testing. Finally, functional test cases are typically less expensive to design and execute than white-box tests.

Testing is aimed at verification and validation — that is, at finding any discrepancies
between what a software/application does and what it is intended to do —
one must obviously refer to requirements as expressed by users and specified by software engineers. A functional specification, i.e., a description of the expected behavior of the software, is the primary source of information for test case specification.

Functional testing, also known as black-box or specification-based testing, denotes techniques that derive test cases from functional specifications.Usually functional testing techniques produce test case specifications that identify classes of test cases and be instantiated to produce individual test

Functional testing can be applied at any level of granularity where some form of specification
is available, from overall system testing to individual units, although the level of
granularity and the type of software influence the choice of the specification styles and
notations, and consequently the functional testing techniques that can be used.

The core of functional test case design is partitioning the possible behaviors of the software into a finite number of classes that can reasonably expected to consistently be correct or incorrect. In practice, the test case designer often must also complete the job of formalizing the specification far
enough to serve as the basis for identifying classes of behaviors. An important side effect of test design is highlighting weaknesses and incompleteness of program specifications.Deriving functional test cases is an analytical process which decomposes
Specifications into test cases.

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