Newsgroups: comp.software-eng
Path: utzoo!utgpu!cunews!bnrgate!bigsur!bcars305!ppblais
From: ppblais@bcars305.bnr.ca (Pierre P. Blais)
Subject: Re: Code inspections
Message-ID: <1991Jan31.151559.16415@bigsur.uucp>
Sender: news@bigsur.uucp
Reply-To: ppblais@bcars305.bnr.ca (Pierre P. Blais)
Organization: Bell-Northern Research, Ottawa, Canada
References: <14964@megatest.UUCP> <156342@felix.UUCP>
Date: Thu, 31 Jan 91 15:15:59 GMT

I have had some experience with code inspections which I would
like to relate to you.

From my experience, I think that code inspections should be started
after a certain amount of (sanity) testing is done. This prevents
wasting the inspector's time in uncovering (obvious) defects. This
is the same argument as using the compiler to find syntax errors
instead of having a human spend time reading the code looking for
them.

Now, how do you decide when enough testing has been done and code
inspection should start?  From empirical data, one can determine
how many defects are detected per person-hour of testing and code
inspection.  When less defects are detected in one hour of testing
than there would be during an inspection, it is time to start in-
specting.

Code inspections have the advantage that they spread the knowledge
about the software to people other than the author.  Selection of
inspectors should done on that basis. In addition, code comments
are reviewed for usability; there is no way to test for that by
running the code.

The main drawback to inspections is the drain on human resources.
If a code inspection team consists of four people including the
author, the author usually ends up "owing" three people.  In this
case, developers usually spend three times more time inspecting
other people's code than theirs.

Also, some projects may be so large that a pace of 150 lines of
code per hour makes it impossible to inspect all code within a
reasonable period of time (taking into account no more than one
three hour inspection session per day to combat fatigue and bore-
dom).

All in all, when used judiciously, at the right time, and when they
are planned properly, code inspections are well worth their time.

--
Pierre P. Blais                                  Bell-Northern Research
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