I kind of feel compelled to test private functions as I am following more and more one of our latest QA recommendation in our project:
No more than 10 in cyclomatic complexity per function.
Now the side effect of the enforcing of this policy is that many of my very large public functions get divided in many more focused, better named private function.
The public function still there (of course) but is essentially reduced to called all those private 'sub-functions'
That is actually cool, because the callstack is now much easier to read (instead of a bug within a large function, I have a bug in a sub-sub-function with the name of the previous functions in the callstack to help me to understand 'how I got there')
However, it now seem easier to unit-test directly those private functions, and leave the testing of the large public function to some kind of 'integration' test where a scenario needs to be addressed.
Just my 2 cents.
