The Typemock Insider Blog has linked to a case study performed by the research department over at Microsoft; Evaluating the Efficacy of Test-Driven Development: Industrial Caste Studies. Not surprisingly, the results “indicate that while the development of both the systems utilizing TDD took extra time upfront the resulting quality was higher than teams that adopted a non-TDD approach by an order of at least two times.”:
Project A - Outcome Measures:
| Metric Description | Value |
| Actual defects/KLOC (using TDD) | X |
| Defects/KLOC of comparable team in org
but not using TDD | 2.6X |
| Increase in time taken to code the feature because of TDD (%) [Management estimates] | 25-35% |
Project B - Outcome Measures:
| Metric Description | Value |
| Actual defects/KLOC (using TDD) | Y |
| Defects/KLOC of comparable team in org
but not using TDD | 4.2Y |
| Increase in time taken to code the feature because of TDD (%) [Management estimates] | 15% |
I think its also worth noting that Project A was was a C/C++ project on the Windows networking team, whereas Project B was a C++/C# project on a web services application in the MSN division.
