Editing Regression testing (section)

==Uses==
Regression testing can be used not only for testing the ''[[correctness (computer science)|correctness]]'' of a program but often also for tracking the quality of its output.<ref>{{cite web |url=http://www.wrox.com/WileyCDA/Section/id-291252.html |title=Regression Testing, Programmer to Programmer |last=Kolawa |first=Adam |author-link=Adam Kolawa |work=Wrox }}</ref> For instance, in the design of a [[compiler]], regression testing could track the code size and the time it takes to compile and execute the test suite cases.

{{Quotation |text=Also as a consequence of the introduction of new bugs, program maintenance requires far more system testing per statement written than any other programming. Theoretically, after each fix, one must run the entire batch of test cases previously run against the system to ensure that it has not been damaged in an obscure way. In practice, such ''regression testing'' must indeed approximate this theoretical idea, and it is very costly.|author=[[Fred Brooks]]|title=''[[The Mythical Man Month]]''|source=p. 122}}

Regression tests can be broadly categorized as [[functional test]]s or [[Unit testing|unit tests]]. Functional tests exercise the complete program with various inputs. Unit tests exercise individual functions, [[subroutine]]s, or object methods. Both functional testing tools and unit-testing tools tend to be automated and are often third-party products that are not part of the compiler suite. A functional test may be a scripted series of program inputs, possibly even involving an automated mechanism for controlling mouse movements and clicks. A unit test may be a set of separate functions within the code itself or a driver layer that links to the code without altering the code being tested.