[Haskell-cafe] Code coverage: mark certain function calls as covered

[amindfv at gmail.com]

> El 13 nov 2019, a las 05:04, Özgür Akgün <ozgurakgun at gmail.com> escribió:
> 
> This may sound like a bizarre request, but I feel I can't be the only one.
> 

I can give a +1 that this would be useful. Here's an annoying case I've run into that doesn't even require partial functions:

fiveDiv :: Int -> Either String Int
fiveDiv 0 = Left "Can't div by 0"
fiveDiv n = Right $ 5 `div` n

and the test cases are:

fiveDiv 8 === Right 0
and
isLeft (fiveDiv 0)

Now the string itself ("Can't div by 0") is marked as an uncovered expression. This trivial case could easily be covered but:

a) I've run into this frequently enough in more annoying cases, and

b) it feels more idiomatic to write a test that doesn't care about the contents of the string (and the test doesn't need to change if the string changes)

Tom