Editing Test-driven development (section)

{{Short description|Method of writing code}}
{{Software development process}}

'''Test-driven development''' ('''TDD''') is a way of writing [[source code|code]] that involves writing an [[test automation|automated]] [[unit testing|unit-level]] [[test case]] that fails, then writing just enough code to make the test pass, then [[refactoring]] both the test code and the production code, then repeating with another new test case.

Alternative approaches to writing automated tests is to write all of the production code before starting on the test code or to write all of the test code before starting on the production code. With TDD, both are written together, therefore shortening debugging time necessities.<ref>{{Cite journal |last1=Parsa |first1=Saeed |last2=Zakeri-Nasrabadi |first2=Morteza |last3=Turhan |first3=Burak |date=2025-01-01 |title=Testability-driven development: An improvement to the TDD efficiency |url=https://www.sciencedirect.com/science/article/pii/S0920548924000461 |journal=Computer Standards & Interfaces |volume=91 |pages=103877 |doi=10.1016/j.csi.2024.103877 |issn=0920-5489}}</ref>

TDD is related to the test-first programming concepts of [[extreme programming]], begun in 1999,<ref name="Cworld92">{{cite web |url=http://www.computerworld.com/softwaretopics/software/appdev/story/0,10801,66192,00.html |title=Extreme Programming |author=Lee Copeland |date=December 2001 |publisher=Computerworld |access-date=January 11, 2011 |archive-url=https://web.archive.org/web/20110605060209/http://www.computerworld.com/s/article/66192/Extreme_Programming?taxonomyId=063 |archive-date=June 5, 2011 |url-status=dead }}</ref> but more recently has created more general interest in its own right.<ref name=Newkirk>Newkirk, JW and Vorontsov, AA. ''Test-Driven Development in Microsoft .NET'', Microsoft Press, 2004.</ref>

Programmers also apply the concept to improving and [[software bug|debugging]] [[legacy code]] developed with older techniques.<ref name=Feathers>Feathers, M. Working Effectively with Legacy Code, Prentice Hall, 2004</ref>