Does Test-Driven Development Really Improve Software Design Quality?

Support for test-driven development [TDD] is growing in many development contexts beyond its common association with extreme programming. By focusing on how TDD influences design characteristics, we hope to raise awareness of TDD as a design approach and assist others in decisions on whether and how to adopt TDD. Our results indicate that test-first programmers are more likely to write software in more and smaller units that are less complex and more highly tested. We weren´t able to confirm claims that TDD improves cohesion while lowering coupling, but we anticipate ways to clarify the questions these design characteristics raised. In particular, we´re working to eliminate the confounding factor of accessor usage in the cohesion metrics.