To test before or to test after - An experimental investigation of the impact of Test Driven Development

Test Driven Development (TDD) requires the developer to create the test suite before designing and writing the application program. Unlike traditional software development practices, in TDD test development precedes application development. Such a practice also redefines the role of the developer. Lately, TDD is growing in popularity as a part of Agile methodologies. There is a critical need for rigorous empirical research to understand the role and impact of TDD as a software development practice. The goal of this dissertation research is to fill this gap. A laboratory experiment was conducted to understand the influence of TDD on the outcomes of the software development process. Software quality, learning and task satisfaction were examined as outcome variables. In the experiment, groups that used the traditional method of software development were compared with those that used TDD. Individual programmers were also compared with paired programmers, when both used TDD. Individual programmers using TDD were found to produce a higher quality of software as compared to programmers using the traditional method of software development. Comprehension, as a part of the learning measure, was also found to be significantly higher in case of programmers using TDD as compared to those using the traditional method of software development. Programmers using TDD were also found to achieve higher task satisfaction as compared to those using the traditional method of software development. Another important finding of this study was that collaborating pairs outperformed second best programmers in nominal groups in terms of software quality, when both groups used TDD.