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Comment by vrde | Hacker News Reader

Please be specific.

In my experience, even if you are building a quick'n'dirty prototype, you'll always need to fire up a terminal or run the GUI to interact/play with the prototype you are building, to see if it "works".

In this case you may apply a --this is my very own definition-- "lightweight TDD approach" just to automate all the procedures that you normally do to test your prototype. Moreover, since you are writing a test for something that does not exist, it may help you defining better what you want from your experimental code, because you are using your prototype before it even exists :)

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TDD takes longer. Studies conducted at Microsoft and HP (or possibly IBM), found that development time with TDD was 10-30% longer. That's probably minimum, and in high degree determined by the TDD experience level of the team members.

The massive upside is that there is much less defects in the end product (think it was 50-80% in the study, but can't recall exactly).

Depending on the project, the extra time needed, might or might not be worth it.

Take a somewhat complex web app, that is used for a marketing campaign. It has a life time of only 2 months. In this case it does not make sense to use TDD, as the lower defect rate and "future-proofing" qualities, might very well not be worth an increased budget.

The reference:

http://research.microsoft.com/en-us/news/features/nagappan-1...

Yes. My experience with TDD is that it did save time, but not necessarily in initial development. The long-term effect of fewer defects combined with the capability for a higher release velocity is a net savings.

As a counter example, I'm working with a company that uses TDD for their current development, but employees work on a platform with little test coverage. As a consequence of lacking unit tests, they're only able to release a few versions each year because their manual testing burden is so high (estimated by one manager as about half of the cost of a release). They've found that TDD for their new features doesn't escalate the QA cost as significantly as not doing it. Bottom line: it's a little more time up front, but they've found it to be a long-term gain.

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