"Where is the data supporting this claim? I don't believe it is true."
This is one central premise of TDD and is not proven or disproven yet. What we can say is that previous software methodologies were lacking, and cannot prove or disprove their superiority over TDD with regards to this statement. If you distill all debates about TDD down to their essence, it revolves around this premise.
I am fine with someone being skeptical of this claim, but I would prefer if they offered A) a measure we can use to test this hypothesis and B) a contrasting methodology that performs better with regards to the measurements provided in A. The single biggest outstanding problem in software engineering is finding a metric by which we can judge software quality objectively. Because it is such an elusive goal other less precise proxies for software quality have been proposed to stand in for the more complex metric. TDD hangs it's shingle on "testability". Even though this has obvious defects, I've seen no evidence for any other objective measure as a more precise indicator of software quality and quite a few advantages to "testability". Namely, it is measurable.
"Why do you think so many of us feel that it is an ideology? Are we seeing ghosts and imagining the whole thing?"
No, I'm sure that you have encountered well meaning but flawed practitioners of TDD. Your skepticism of their process doesn't bother me. What bothers me is your (and DHH's) painting of all TDD folks as cultists. I don't believe this stuff because Uncle Bob told me to believe it. I believe it because my experience shows that rigorous use of TDD practices trend toward better software than a lack of rigor outside of an objective measure for software quality.
If you have an alternate rigorous approach that you believe trends (or better yet is provably) better in software quality, by all means outline it. I know that TDD is flawed and am happy to find its successor.
Let me ask you this, prior to the rise of TDD, how prevalent do you think automated testing was? If it was very prevalent why is it only after the rise of TDD that automated testing became a central part of any build workflow and the entire concept of Continuous Integration/Deployment developed?
In my experience, automated testing prior to the rise of TDD was not wide spread. But maybe I was seeing ghosts and imagining that.
Neither of us ever said all TDD folks are cultist. We are both tired of being told that we are absolutely doing it wrong if we don't practice TDD. For an example of people telling us this please see this talk by bob Martin and jump to the 58 minute mark. http://m.youtube.com/watch?v=WpkDN78P884
Bob is not an obscure figure by any stretch of the imagination. You have admitted to having no real data to back up the claim that writing tests first leads to better code, yet we have bob here telling us we are absolutely wrong if we don't follow his religion.
This is one central premise of TDD and is not proven or disproven yet. What we can say is that previous software methodologies were lacking, and cannot prove or disprove their superiority over TDD with regards to this statement. If you distill all debates about TDD down to their essence, it revolves around this premise.
I am fine with someone being skeptical of this claim, but I would prefer if they offered A) a measure we can use to test this hypothesis and B) a contrasting methodology that performs better with regards to the measurements provided in A. The single biggest outstanding problem in software engineering is finding a metric by which we can judge software quality objectively. Because it is such an elusive goal other less precise proxies for software quality have been proposed to stand in for the more complex metric. TDD hangs it's shingle on "testability". Even though this has obvious defects, I've seen no evidence for any other objective measure as a more precise indicator of software quality and quite a few advantages to "testability". Namely, it is measurable.
"Why do you think so many of us feel that it is an ideology? Are we seeing ghosts and imagining the whole thing?"
No, I'm sure that you have encountered well meaning but flawed practitioners of TDD. Your skepticism of their process doesn't bother me. What bothers me is your (and DHH's) painting of all TDD folks as cultists. I don't believe this stuff because Uncle Bob told me to believe it. I believe it because my experience shows that rigorous use of TDD practices trend toward better software than a lack of rigor outside of an objective measure for software quality.
If you have an alternate rigorous approach that you believe trends (or better yet is provably) better in software quality, by all means outline it. I know that TDD is flawed and am happy to find its successor.
Let me ask you this, prior to the rise of TDD, how prevalent do you think automated testing was? If it was very prevalent why is it only after the rise of TDD that automated testing became a central part of any build workflow and the entire concept of Continuous Integration/Deployment developed?
In my experience, automated testing prior to the rise of TDD was not wide spread. But maybe I was seeing ghosts and imagining that.