The Impact of Test Driven Development on the Evolution of a Reusable Framework of Components – An Industrial Case Study

Test driven development (TDD) is a software engineering technique to promote fast feedback, task-oriented development, improved quality assurance and more comprehensible low-level software design. Benefits have been shown for non-reusable software development in terms of improved quality (e.g. lower defect density). We have carried out an empirical study of a framework of reusable components, to see whether these benefits can be shown for reusable components. The framework is used in building new applications and provides services to these applications during runtime. The three first versions of this framework were developed using traditional test-last development, while for the two latest versions TDD was used. Our results show benefits in terms of reduced mean defect density (35.86%), when using TDD, over two releases. Mean change density was 76.19% lower for TDD than for test-last development. Finally, the change distribution for the TDD approach was 33.3% perfective, 5.6% adaptive and 61.1% preventive.