Cost of fixing bugs

by RentTesters on June 22, 2011

the cost of fixing bugs detected during final system testing can be up to 200 times more than if it is found during in the requirements phase

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{ 3 comments }

agiletester September 20, 2008 at 4:52 am

There is the standard argument that the later a bug is fixed, the more expensive it is to fix. When you fix a bug not only affects the cost of fixing it, but also the way you fix it. As development work continues in the presence of a known bug, new dependencies on the code where the bug lives are likely to be added. Sometimes these dependencies will be on bug itself. Often, this happens without the developers realizing it. In general, as a piece of code acquires dependencies, it becomes riskier to change. I think this is even more true of bug-ridden code. So, the longer you wait before fixing the bug, the more risk is introduced in fixing it. When the risk of fixing a bug increases, the reaction of most developers is to stick with the potential fix that appears least risky (even if there is a ‘better’ alternative).

qaguru September 20, 2008 at 4:56 am

Average cost to fix a defect = (Number of people * number of days) * cost per person-day
____________________________________
(Number of fixed defects)
The number of defects you find isn’t enough information—it’s the number of defects you fix. Detecting defects is only the first step. Locating the failure, deciding how to fix it, developer testing (a.k.a. unit testing) the fix, system testing the fix, and looking for other defects this fix caused is why the fix value is what’s important. Let’s look at some examples. In these examples, I assume a person-day is $500.

sqamgr September 21, 2008 at 12:04 am

Are you trying to say that requirements review are very important, and that both dev and sqa have to spend considerable amount of time to try to find requirement gaps ? If so , I would like to hear an example on something that could be caught in the requirement phase that would cost 200 times as much to catch in Testing or Dev stage. Numbers would help…

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