Tuesday, December 09, 2008
"TDD makes code development take longer."
Yes, it does. 15-30% longer.

"TDD *may* reduce bug counts..."
Real TDD WILL reduce bug counts. Expect about an order of magnitude. 60-90% comparably.

"I don't want to pay up front for testing or make the code take longer to be feature complete."
That is one choice - but it will be a costly one... Defects will not only be more frequent, but they will probably take longer to fix and be more complex as well.

From a financial perspective, (aside from the customer satisfaction) TDD just makes fiscal sense. I think we would need a compelling reason to give management and shareholders why we are NOT using it.

There is a new video posted on Channel 9 of an interview of one of the Microsoft researchers who contributed to a set of case studies published earlier this year. The case studies were done on 4 teams (3 Microsoft and 1 IBM), and they seem to agree with the statistics and team performance numbers I have been citing for years.

These numbers are motivators for me, and some of the primary reasons I practice TDD, support it, and try to spread the word.

Please take a look at the report and see for yourself if you agree...

TDD
Tuesday, December 09, 2008 12:17:56 PM (Pacific Standard Time, UTC-08:00)  #    Comments [2]  |  Trackback
Wednesday, December 10, 2008 6:37:01 PM (Pacific Standard Time, UTC-08:00)
Where did you get your numbers at the top of the post? Were those from the report or from somewhere else?
Wednesday, December 10, 2008 7:35:45 PM (Pacific Standard Time, UTC-08:00)
I have been using those numbers for years, not sure where they originally came from exactly - probably from someone's whitepaper back in 2004. My own experience agrees with the numbers, so I didn't have any reason to question them in general. The bug count on my first agile real TDD project was literally an order of magnitude lower than the lowest bug count seen in any project the organization produced prior. In other projects it has been a little higher, in the 60-90% range - but I have no real baseline for comparison to other non TDD projects other than anecdotal evidence from around the organizations.
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