Regression testing: Difference between revisions

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Sometimes re-emergence occurs because a fix gets lost through poor [[revision control]] practices (or simple [[human error]] in revision control). Often, a fix for a problem will be "[[software brittleness|fragile]]" in that it fixes the problem in the narrow case where it was first observed but not in more general cases which may arise over the lifetime of the software. Frequently, a fix for a problem in one area inadvertently causes a [[software bug]] in another area.

It may happen that when a feature is redesigned some of the same mistakes that were made in the original implementation of the feature also occur in the redesign. In most software development situations, it is considered [[Best Coding Practices|good coding practice]], when a bug is located and fixed, to record a test that exposes the bug and re-run that test regularly after subsequent changes to the program.<ref name="kolawa">{{cite book | last = Kolawa | first = Adam | author2 = Huizinga, Dorota | title = Automated Defect Prevention: Best Practices in Software Management | url = http://www.wiley.com/WileyCDA/WileyTitle/productCd-0470042125.html | year = 2007 | publisher = Wiley-IEEE Computer Society Press | page = 73 | isbn = 978-0-470-04212-0 | archive-date = 2012-04-25 | access-date = 2010-07-20 | archive-url = https://web.archive.org/web/20120425232401/http://www.wiley.com/WileyCDA/WileyTitle/productCd-0470042125.html | url-status = dead }}</ref>

Although this may be done through [[manual testing]] procedures using programming techniques, it is often done using [[automated testing]] tools.<ref>[http://safari.oreilly.com/0201794292/ch08lev1sec4 Automate Regression Tests When Feasible], Automated Testing: Selected Best Practices, Elfriede Dustin, Safari Books Online</ref> Such a [[test suite]] contains software tools that allow the testing environment to execute all the regression [[Test case (software)|test case]]s automatically; many projects have automated [[Continuous integration]] systems to re-run all regression tests at specified intervals and report any failures (which could imply a regression or an out-of-date test).<ref>{{cite web| url=http://www.drdobbs.com/tools/change-code-without-fear/206105233| title=Change Code Without Fear: Utilize a Regression Safety Net|last=daVeiga|first=Nada|work=[[Dr. Dobb's Journal]]| date=2008-02-06}}</ref>

Common strategies are to run such a system after every successful compile (for small projects), every night, or once a week. Those strategies can be automated by an external tool.

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{{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 broadlydone categorizedat asany level, from [[functionalunit testtesting|unit]]s orthrough to [[UnitSystem integration testing|unitsystem testsintegration]]. Functional tests exercise the complete program with various inputs. UnitThese tests exerciseare individualoften functions,automated [[subroutine]]s,due orto objectthe methods.need Bothfor functional testing toolsrepetition, and unit-testing tools tend tomay be automateddone andby aretest often third-party productstools 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.

==See also==

*[[Quality control]]

*[[Test-driven development]]

==References==