R. David Murray <[email protected]> added the comment:
I haven't reviewed your tests, but a couple quick comments: we generally prefer
duck typing to the use of isintance or ABCs, but sometimes the latter is better
(it's a judgement call). I haven't done a deep dive in the code you modified,
but from the looks of the code quoted in your patch I'd say that doing
'iter(v)' inside the try/except would be the way to find out if one can loop
over the object, which appears to be the only aspect of sequenceness the code
cares about.
As for coverage, you are right that it is quite possible to get caught up in
the statistics. That said, if you *don't* have domain knowledge, giving us a
set of tests to look at and evaluate is better than not having such a set of
tests. Pointing out any tests that you aren't sure about the validity of is
helpful in any case.
The overall goal of the test suite is to test the *API* of the library
functions. This is so that alternate implementations can use it as a
validation test suite (Sometimes we have CPython specific tests, in which case
we mark them as such). So testing internal implementation details is not as
helpful as testing behavior. If you find you have to use a "white box" test
(one that pokes at the internals as opposed to making an appropriate call to
the API), then the code you can't otherwise test becomes suspect and an
appropriate subject for another issue ("what is this code for? I can't get it
to trigger.")
Finally, your point about comprehensive tests at least showing up behavior
changes is valid. If you write tests that you aren't sure are "correct
behavior", put in an XXX comment to that effect. If you just have no idea, you
can mark a whole block of tests as "this improves coverage, I have no idea if
the behavior is valid or not", and we'll either sort it out when we review or
commit the tests or just leave the comment in.
Thanks for working on this.
----------
nosy: +r.david.murray
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