[Python-Dev] Tests for internal functionality

[Ivan Pozdeev]

In https://github.com/python/cpython/pull/6541 , I was requested to add tests for an internal C function.

As I wrote in https://github.com/python/cpython/pull/6541#issuecomment-445514807 , it's not clear from the codebase

1) where tests for internal (as opposed to public) functionality should be located
     * I only ran across very few tests for private functionality and they were located alongside the public tests. See e.g. 
https://github.com/python/cpython/pull/12140 -- site._getuserbase is a private function.

2) what spec one should test against since there's no official docs for internal functionality

That time, they let it slide, but of course this is not something to make a habit of. It still bothers me that I left unfinished business there.
Any thoughts?

-- 
Regards,
Ivan