Is there hard evidence of the ROI of unit testing?

Question

Unit testing sounds great to me, but I\'m not sure I should spend any time really learning it unless I can convince others that is has significant value. I have to convince

Answer 1

More about TDD than strictly unit testing, here is a link to the Realizing quality improvement through test driven development: results and experiences of four industrial teams paper, by Nagappan, E. Michael Maximilien, Thirumalesh Bhat, and Laurie Williams. paper published by Microsoft Empirical Software Engineering and Measurement (ESM) group and already mentionned here.

The team found was that the TDD teams produced code that is between 60% and 90% percent better (in terms of defect density) than non-TDD teams. However TDD teams took between 15% and 35% longer to complete their projects.