Analysis and Quantification of Test Driven Development Approach
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Date
2002-09-06
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Abstract
Software industry is increasingly becoming more demanding on development schedules and resources. Often, software production deals with ever-changing requirements and with development cycles measured in weeks or months. To respond to these demands and still produce high quality software, over years, software practitioners have developed a number of strategies. One of the more recent one is Test Driven Development (TDD). This is an emerging object-oriented development practice that purports to aid in producing high quality software quickly. TDD has been popularized through the Extreme Programming (XP) methodology. TDD proponents profess that, for small to mid-size software, the technique leads to quicker development of higher quality code. Anecdotal evidence supports this. However, until now there has been little quantitative empirical support for this TDD claim.
The work presented in this thesis is concerned with a set of structured TDD experiments on very small programs with pair programmers. Programmers were both students and professionals. In each programmer category (students and professionals), one group used TDD and the other (control group) a waterfall-like software development approach. The experiments provide some interesting observations regarding TDD.
When TDD was used, both student and professional TDD developers appear to achieve higher code quality, as measured using functional black box testing. The TDD student pairs passed 16% more test cases while TDD professional pair passed 18% more test cases than the their corresponding control groups.
However, professional TDD developer pairs did spent about 16% more time on development. It was not established whether the increase in the quality was due to extra development time, or due to the TDD development process itself. On the other hand, the student experiments were time-limited. Both the TDD and the non-TDD student programmers had to complete the assignment in 75 minutes. Professional programmers took about 285 minutes on the average, to complete the same assignment. Consequently, the development cycle of the student-developed software was severely constrained and the resulting code was underdeveloped and of much poorer quality than the professional code. Still, it is interesting to note that the code developed using the TDD approach under these severe restrictions appears to be less faulty than the one developed using the more classical waterfall-like approach. It is conjectured that this may be due to the granularity of the TDD process, one to two test cases per feedback loop, which may encourage more frequent and tighter verification and validation episodes. These tighter cycles may result in a code that is better when compared to that developed by a coarser granularity waterfall-like model.
As part of the study, a survey was conducted of the participating programmers. The majority of the programmers thought that TDD was an effective approach, which improved their productivity.
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Keywords
testing, Extreme Programming, software methodologies, Software process, object oriented programming
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Degree
MS
Discipline
Computer Science
