Exhaustive Unit Testing

Roy Smith roy at panix.com
Thu Nov 27 15:54:21 CET 2008

In article <492ea611$0$32680$9b4e6d93 at newsspool2.arcor-online.net>,
 Stefan Behnel <stefan_ml at behnel.de> wrote:

> Not to mention that you can sometimes look at awfully trivial code three
> times and only see the obvious bug in that code the fourth time you put an
> eye on it a good night's sleep later.

Or never see it.

Lately, I've been using Coverity (static code analysis tool) on a large C++ 
project.  I'm constantly amazed at the stuff it finds which is *so* obvious 
after it's pointed out, that I just never saw before.

> Expecting code paths in a nested if statement with nine conditions that are
> not worth testing due to obvious triviality, is pretty hubristic.

There's a well known theory in studies of the human brain which says people 
are capable of processing about 7 +/- 2 pieces of information at once.  
With much handwaving, that could be applied to testing by saying most 
people can think through 2 conditionals (4 paths), but it's pushing it when 
you get to 3 conditionals (8 paths), and once you get to 4 or more, it's 
probably hopeless to expect somebody to be able to fully understand all the 
possible code paths.

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