[Python-Dev] PEP 399: Pure Python/C Accelerator Module Compatibiilty Requirements

[Steven D'Aprano]

Brett Cannon wrote:
> In the grand python-dev tradition of "silence means acceptance", I consider
> this PEP finalized and implicitly accepted.

How long does that silence have to last?

I didn't notice a definition of what counts as "100% branch coverage". 
Apologies if I merely failed to notice it, but I think it should be 
explicitly defined.

Presumably it means that any time you have an explicit branch 
(if...elif...else, try...except...else, for...else, etc.) you need a 
test that goes down each branch. But it isn't clear to me whether it's 
sufficient to test each branch in isolation, or whether you need to test 
all combinations.

That is, if you have five branches, A or B, C or D, E or F, G or H, I or 
J, within a single code unit (function? something else?), is it 
sufficient to have at least one test that goes down each of A...J, or do 
you need to explicitly test each of:

A-C-E-G-I
A-C-E-G-J
A-C-E-H-I
A-C-E-H-J
A-C-F-G-I
...
B-D-F-H-J

(10 tests versus 32 tests).

If the latter, this could become impractical *very* fast. But if not, I 
don't see how we can claim 100% coverage when there are code paths which 
are never tested.

At the very least, I think you need to explicitly define what you mean 
by "100% branch coverage". Possibly this will assist in the disagreement 
between you and Antoine re "100% versus "comprehensive" coverage.



-- 
Steven