As the other poster pointed out, this paper is measuring nothing, or at least it is not written in a way to let us know. I find it unremarkable that a sudden f

As the other poster pointed out, this paper is measuring nothing, or at least it is not written in a way to let us know. I find it unremarkable that a sudden focus on quality and testing reduced the bug rate. It does not follow that TDD is the cause, nor that TDD is the best of multiple options. Its a well known effect in experimental design - measurement alters what you measure. Get depressed people to watch and talk about a dog video. I can predict that they will be less depressed. Not so much because dog videos are great at reducing depression, but because all of a sudden so much experimental interest is being directed at them. It would be almost churlish to not feel better, if you know what I mean. So, we don't design experiments that way - if your hypothesis is that dog videos cure depression, you need to do exactly the same protocol, but with cat videos, or I don't know, truck videos, or whatever, so both groups get the same attention, both are trying to reduce their depression and so on (I'm assuming unblinded here because obviously the TDD paper was unblinded, obviously we have better methods for the depression study than my suggestion here). Kudos for bring empiricism into the discussion, but I do find the paper lacking. I wrote above that I don't use TDD yet achieve low defect rates and good design. I think it is because, no matter how you do it, if you focus on those things you will more likely achieve them than if you don't. I hypothesize (don't be mad!) that TDD works for some simply because it brings the issue of quality to the forefront of their mind. Whereas, I'm already always thinking "is this line of code going to kill somebody"; I've tried TDD, and it always seemed like it added little to actively inhibited me. Your mileage will vary.