Erik and/or Richard will please kindly preach here on the value of "testing" (where "testing" refers to "I tried and it worked").

You said it well, Jan

the best tester I ever had had a banner over his desk:

succesful testing does not prove the abscence of bugs, it only proves the abscence of known bugs

The thing is that something that is 'tested' rather than 'designed' may (is very likely to) have requirements that happen to be met in the context it is tested in. That is irrelevant, the moment the context changes.

Many have 'tested' that something 'works' and later found out that it 'worked only in the specific environment it was tested in I can not count the number of posts we have had here "I have this problem, it can not be my tested and working "design" (my quotes)". One very frequent is the one "I got a new PC an my thingy does not work with it" which many times end up with the absolute hogwash "it is proven that you do not need a MAX232(equivalent)". Then when after much 'wrestling" the poster finally install a 232 transciever, it suddenly works.

One recommnedation: you can test what you have with no comments, but there is no way in hades you can verify the design without them. Please note I do not call it 'code', without comments it does not deserve that name.

Erik