An External Replication on the Effects of Test-driven Development [pdf]
This study, like most software development studies I've seen, is seriously flawed. It doesn't justify the sensational title here on HN.* The sample size was tiny. (20 students)* The participants were selected by convenience. (They were students in the researcher's class.)* The majority of participants had no professional experience. (Six students had prior professional experience. Only three had more than two years' experience.)* The programming problems were trivial. (The Bowling Kata and an 'equivalent complexity' Mars Rover API problem.)Maybe, maybe you could use this to draw conclusions about how TDD affects novices working on simple algorithmic problems. Given the tiny sample size and sampling by convenience, I'm not sure you can even draw that much of a conclusion.But it won't tell you anything about whether or not TDD impacts development time or code quality in real-world development.