Editing Regression testing (section)

==Background==
As software is updated or changed, or reused on a modified target, emergence of new faults and/or re-emergence of old faults is quite common.

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 }}</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]]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to re-run all regression tests at specified intervals and report any failures (which could imply a regression or an out-of-date test).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.

Regression testing is an integral part of the [[extreme programming]] software development method. In this method, design documents are replaced by extensive, repeatable, and automated testing of the entire software package throughout each stage of the [[software development process]]. Regression testing is done after functional testing has concluded, to verify that the other functionalities are working.

In the corporate world, regression testing has traditionally been performed by a [[software quality assurance]] team after the development team has completed work. However, defects found at this stage are the most costly to fix. This problem is being addressed by the rise of [[unit testing]]. Although developers have always written test cases as part of the development cycle, these test cases have generally been either [[functional testing|functional tests]] or [[unit testing|unit tests]] that verify only intended outcomes. Developer testing compels a developer to focus on unit testing and to include both positive and negative test cases.<ref>{{cite web|url=http://www.sys-con.com/read/47359.htm|title=Developer Testing Is 'In': An interview with Alberto Savoia and Kent Beck|last=Dudney|first=Bill|date=2004-12-08|access-date=2007-11-29}}</ref>