There is one other type of bias I believe to be in your report. There is no easy way to say "no". I don't have a test case for my "primary code" as you ask... And when I said "no" you asked me questions presuming I had... If I don't fill out these questions, does my initial "No" still count against your 66% testing rate... For instance, I stopped on page 3... I would say depending on your answer this whole survey could be so bunk as to be totally useless... And I agree, the real question is "where is the bias?"... While, I think I have identified it, I also think posting these results to the world would just solicit laughter by people more capable of conducting a survey. There is obviously something profoundly wrong here...

A more accurate representation would be to assume the code on CPAN is representative of people's production code... Now test the CPAN dists for tests... Here the bias is simple: the average CPAN programmer is more capable than the average programmer, by virtue of being a programmer AND knowing how to navigate CPAN... Which in my eyes has always been an issue. The learning curve to get something on CPAN, or give back your changes to CPAN is always more bureaucratic and difficult than making the simply making the change and keeping it to yourself. I would venture out and say no more than 20% of all Perl code under a build system (M:I, M:B, EU:MM) is under a test suite, and less than 20% of all Perl code is under a build system.