Realizing quality improvement through test driven development: results and experiences of four industrial teams


Test-driven development (TDD) is a software development practice that has been used sporadically for decades. With this practice, a software engineer cycles minute-by-minute between writing failing unit tests and writing implementation code to pass those tests. Test-driven development has recently re-emerged as a critical enabling practice of agile software development methodologies. However, little empirical evidence supports or refutes the utility of this practice in an industrial context. Case studies were conducted with three development teams at Microsoft and one at IBM that have adopted TDD. The results of the case studies indicate that the pre-release defect density of the four products decreased between 40% and 90% relative to similar projects that did not use the TDD practice. Subjectively, the teams experienced a 15–35% increase in initial development time after adopting TDD.

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At IBM we would like to thank the Raleigh and Guadalajara development teams; in particular, Julio Sanchez of Guadalajara and Dale Heeks from the FVT team. At Microsoft we would like to thank the Windows, MSN, and DevDiv teams that participated in this study without whom this work would not have been possible and the agile development community at Microsoft for valuable feedback on earlier work. This work done by Dr. Williams was supported by the National Science Foundation under CAREER Grant Nos. 0346903.

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Correspondence to Nachiappan Nagappan.

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Editor: Pankaj Jalote

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Nagappan, N., Maximilien, E.M., Bhat, T. et al. Realizing quality improvement through test driven development: results and experiences of four industrial teams. Empir Software Eng 13, 289–302 (2008).

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  • Test driven development
  • Empirical study
  • Defects/faults
  • Development time