Shift-left testing: Difference between revisions

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{{Short description|Type of software testing}}

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'''Shift-left testing'''<ref>{{cite web|url=https://web.archive.org/web/20150905082941/https://insights.sei.cmu.edu/sei_blog/2015/03/four-types-of-shift-left-testing.html |title=Four Types of Shift Left Testing |author=Donald Firesmith | date=23 March 2015 |archive-url=https://web.archive.org/web/20150905082941/https://insights.sei.cmu.edu/sei_blog/2015/03/four-types-of-shift-left-testing.html |access-date=27 March 2015|archive-date=2015-09-05 }}</ref> is an approach to [[software testing]] and [[system testing]] in which testing is performed earlier in the [[software development life cycle|lifecycle]] (i.e. moved left on the project timeline). It is the first half of the maxim "Testtest early and often.".<ref>{{cite web |url=https://msdn.microsoft.com/en-us/library/vstudio/ee330950%28v=vs.110%29.aspx |title=Test Early and Often |author=Microsoft | date=2012 |access-date=27 March 2015 |archive-date=2 April 2015 |archive-url=https://web.archive.org/web/20150402174955/https://msdn.microsoft.com/en-us/library/vstudio/ee330950(v=vs.110).aspx |url-status=live }}</ref> It was coined by Larry Smith in 2001.<ref>{{Cite journal|last=Smith|first=Larry|date=September 2001|title=Shift-Left Testing|url=https://www.drdobbs.com/shift-left-testing/184404768|journal=Dr. Dobb's Journal|volume=26|number=9|pages=56, 62|access-date=2020-06-04|archive-date=2020-06-21|archive-url=https://web.archive.org/web/20200621040103/https://www.drdobbs.com/shift-left-testing/184404768|url-status=live}}</ref><ref>{{Cite web|url=http://collaboration.cmc.ec.gc.ca/science/rpn/biblio/ddj/Website/articles/DDJ/2001/0109/0109e/0109e.htm|archive-url=https://web.archive.org/web/20140810171940/http://collaboration.cmc.ec.gc.ca/science/rpn/biblio/ddj/Website/articles/DDJ/2001/0109/0109e/0109e.htm|url-status=dead|archive-date=2014-08-10|title=Sep01: Shift-Left Testing|date=2014-08-10|access-date=2019-09-06}}</ref>

== Harm duebecause toof late testing ==

Shift-left testing is important because it helpsaims to prevent the following types of harm duecaused toby late testing:

* Testers may be less involved in initial planning, often resulting in insufficientInsufficient resources being allocated to testing.

* DefectsUndiscovered defects in requirements, architecture, and design, remainalong undiscovered whilewith significant effort is wasted while implementing them.

* Difficulty [[Debuggingdebugging]] (including identifying, localizing, fixing, and regression testing defects) becomes harder as more software is produced and integrated.

* Reduced [[code coverage]] during testing{{Citation needed|date=October 2017}} as a result of [[Encapsulation (object-oriented programming)|Encapsulationencapsulation]] impedesimpeding [[white-box testing]], reducing [[code coverage]] during testing.{{Citation needed|date=October 2017}}

* A “bow wave” of [[technical debt]] that can cause a project to fail.

* There is less time to fix defects found by testing, thereby increasing the likelihood that they will be postponed until later increments or versions of the system. This creates a “bow wave” of [[technical debt]] that can sink projects if it grows too large.

== Types of shift-left testing ==

There are four basic ways to shift testing earlier in the life-cycle (that is, leftward on the classic [[V-model]]). These can be referred to as traditional shift-left testing,<ref>{{cite web |url=http://www.velocitypartners.net/blog/2014/01/28/agile-testing-the-agile-test-automation-pyramid/ |title=Agile Testing - The Agile Test Automation Pyramid |author=Velocity Partners | date=28 January 2014 |access-date=27 March 2015 |archive-date=2 April 2015 |archive-url=https://web.archive.org/web/20150402164204/http://www.velocitypartners.net/blog/2014/01/28/agile-testing-the-agile-test-automation-pyramid/ |url-status=live }}</ref> incremental shift-left testing, Agile/DevOps shift-left testing,<ref>{{cite web |url=http://www.slideshare.net/Urbancode/shift-left |title=Shift Left: Approaches and Practices |author=Paul Bahrs | date=6 November 2014 |access-date=27 March 2015 |archive-date=6 April 2015 |archive-url=https://web.archive.org/web/20150406145122/http://www.slideshare.net/Urbancode/shift-left |url-status=live }}</ref><ref>{{cite web |url=https://www.ibm.com/developerworks/community/blogs/invisiblethread/entry/enabling_devops_success_with_shift_left_continuous_testing?lang=en |title=Enabling DevOps Success with Shift Left Continuous Testing |author=Dibbe Edwards |website=[[IBM]] |date=18 September 2014 |access-date=27 March 2015 |archive-date=2 April 2015 |archive-url=https://web.archive.org/web/20150402110506/https://www.ibm.com/developerworks/community/blogs/invisiblethread/entry/enabling_devops_success_with_shift_left_continuous_testing?lang=en |url-status=live }}</ref> and model-based shift-left testing.<ref>{{cite web |url=http://blog.sei.cmu.edu/post.cfm/using-v-models-testing-315 |title=Using V Models for Testing |author=Donald Firesmith | date=11 November 2013 |access-date=27 March 2015 |archive-date=2 April 2015 |archive-url=https://web.archive.org/web/20150402110448/http://blog.sei.cmu.edu/post.cfm/using-v-models-testing-315 |url-status=live }}</ref>

=== Traditional shift-left testing ===

As illustrated in the following figure, traditional shift-left moves the emphasis of testing lower down (and therefore slightly to the left) on the right hand side of the classic V model. Instead of emphasizing acceptance and system level testing (e.g., [[GUI testing]] with record and playback tools<ref>{{cite web |url=https://msdn.microsoft.com/en-us/library/dd286714.aspx |title=Record and Playback Manual Tests |author=Microsoft | date= 2013 |access-date=27 March 2015 |archive-date=2 April 2015 |archive-url=https://web.archive.org/web/20150402113241/https://msdn.microsoft.com/en-us/library/dd286714.aspx |url-status=live }}</ref>), traditional shift-left concentrates on [[unit testing]] and [[integration testing]] (e.g., using [[API testing]] and modern test tools). The transition to traditional shift-left testing has largely been completed.{{By whom|date=April 2016}}

<gallery>

Traditional-Shift-Left.jpg|Traditional shift-left testing

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=== Model-based shift-left testing ===

The previous forms all concentrated on testing earlier in the development cycle. However, they all test ''after'' software exists and seek to uncover only implementation defects.{{cn|date=January 2021}}

Model-based testing moves testing to the left side of the Vs, by testing requirements, architecture, and design models. This shift begins testing almost immediately, instead of waiting a long time (traditional testing), medium time (incremental testing), or short time (Agile/DevOps) for software to become available to the right side of the Vs. This trend is just beginning.

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== References ==

{{reflist}}

== External links ==

* [https://devopedia.org/shift-left "Shift Left" Devopedia]

{{Software testing}}

[[Category:Software testing]]