[Python-Dev] PEP 399: Pure Python/C Accelerator Module Compatibiilty Requirements (original) (raw)

Terry Reedy tjreedy at udel.edu
Sun Apr 17 08:32:57 CEST 2011

On 4/17/2011 1:32 AM, R. David Murray wrote:

As Brett said, people do come to depend on the details of the implementation. But IMO the PEP should be clarified to say that the tests we are talking about should be tests of the published API. That is, blackbox tests, not whitebox tests.

I think 100% branch coverage is barking up the wrong tree. Better to say comprehensive api coverage. Bugs on the tracker generally come from not having that. (I am not saying 'all' to allow for bugs that happen from weird interactions or corner cases in spite of what could reasonably be called comprehensive._

I don't think the PEP is asking this either (or if it is I agree it shouldn't be). The way to get full branch coverage (and yes Exarkun is right, this is about individual branches; see coverage.py --branch) is to provide test cases that exercise the published API such that those branches are taken. If you can't do that, then what is that branch of the Python code for? If you can do that, how is the test case testing an implementation detail? It is testing the behavior of the API.

Right.

-- Terry Jan Reedy

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