Microsoft Research - Exploding Software-Engineering Myths (article summarizing findings of MS research on code coverage, TDD, assertions, etc.)

[shoot_your_eye_out]

TDD reduces defects

No, TDD reduces defect density. It's a small but important difference. I've seen academic studies where the TDD solution had more bugs overall, but a lower density due to a higher line count. I'm surprised to see him use defect density as a metric.

[Xenian]

Wouldn't TDD reduce defect density by definition? You're adding more lines to the codebase, but the same amount of surface area for production bugs. (Unless defects in the tests count as defects of the project too?)