I am not new to coding. I have been coding (seriously) for over 15 years now. I have always had some testing for my code. However, over the last few months I have been learning test driven design/development (TDD) using Ruby on Rails. So far, I'm not seeing the benefit.
I see some benefit to writing tests for some things, but very few. And while I like the idea of writing the test first, I find I spend substantially more time trying to debug my tests to get them to say what I really mean than I do debugging actual code. This is probably because the test code is often substantially more complicated than the code it tests. I hope this is just inexperience with the available tools (RSpec in this case).
I must say though, at this point, the level of frustration mixed with the disappointing lack of performance is beyond unacceptable. So far, the only value I'm seeing from TDD is a growing library of RSpec files that serve as templates for other projects/files. Which is not much more useful, maybe less useful, than the actual project code files.
In reading the available literature, I notice that TDD seems to be a massive time sink up front, but pays off in the end. I'm just wondering, are there any real world examples? Does this massive frustration ever pay off in the real world?
I really hope I did not miss this question somewhere else on here. I searched, but all the questions/answers are several years old at this point. It was a rare occasion when I found a developer who would say anything bad about TDD, which is why I have spent as much time on this as I have. However, I noticed that nobody seems to point to specific real-world examples. I did read one answer that said the guy debugging the code in 2011 would thank you for have a complete unit testing suite (I think that comment was made in 2008).
So, I'm just wondering, after all these years, do we finally have any examples showing the payoff is real? Has anybody actually inherited or gone back to code that was designed/developed with TDD and has a complete set of unit tests and actually felt a payoff? Or did you find that you were spending so much time trying to figure out what the test was testing (and why it was important) that you just tossed out the whole mess and dug into the code?
Best Answer
This paper demonstrates that TDD adds 15-35% development time in return for a 40-90% reduction in defect density on otherwise like-for-like projects.
The article refers full paper (pdf) - Nachiappan Nagappan, E. Michael Maximilien, Thirumalesh Bhat, and Laurie Williams. “Realizing quality improvement through test driven development: results and experiences of four industrial teams“. ESE 2008.
Full paper also briefly summarizes the relevant empirical studies on TDD and their high level results (section 3 Related Works), including George and Williams 2003, Müller and Hagner (2002), Erdogmus et al. (2005) , Müller and Tichy (2001), Janzen and Seiedian (2006).