An Empirical Examination of Test-Driven Development

Despite a half century of advances, the software construction industry still shows signs of immaturity [1]. Professional software development organizations continue to struggle to produce reliable software in a predictable and repeatable manner. While a variety of development practices are advocated that might improve the situation, developers are often reluctant to adopt new, potentially better practices based on anecdotal evidence alone. Empirical evidence of a practice’s efficacy are rarely available or conclusive and adopting new practices is time-consuming, expensive, and risky. Test-driven development (TDD) is a new approach that offers the potential to significantly improve the state of software construction. TDD is a disciplined software development practice that focuses on software design by first writing automated unit-tests followed by production code in short, frequent iterations [3]. TDD focuses the developer’s attention on a software’s interface and behavior while growing the software architecture organically. This research applies empirical software engineering techniques to examine the ability of TDD to produce better software designs than more traditional Test-Last approaches produce in terms of reusability, extensibility, and maintainability. In addition, this research examines the pedagogical implications of the approach and results. If TDD proves to improve software quality at minimal cost, and if students can learn and benefit from TDD from early on, then this research can have a significant impact on the state of software construction. Software development organizations will recognize the benefits of TDD as both a design and testing approach, and they will be convinced to adopt TDD in appropriate situations. New textbooks and teaching materials can be written applying the test-driven learning approach developed in this research. As students learn to take a more disciplined approach to software development with TDD, they will carry this into professional software organizations and improve the overall state of software construction.