[Python-ideas] where statement in Pyret

[Tarek Ziadé]

Le 11/10/13 11:00 AM, Markus Unterwaditzer a écrit :
> While it is a nice idea, i don't think this feature deserves its own
> syntax. Besides doctests, another way of achieving this in Python
> might be:
>
> def sum(l):
> # implementation of sum
>
> def test_sum():
> assert sum([]) == 0
> assert sum([1, 2, 3]) == 6
>
> which IMO is nice enough.
yes, that's what we all already do: tests in test_xxx functions. And the
adopted convention
is to have the tests in dedicated tests modules, which defeats the
benefit of having
real isolated unit tests just by the function code.

And even if we place the test function just besides the tested function,
Python will not
make any distinction : they are both just functions.

Having the ability to distinguish tests and regular code at the language
level
has benefits like the ability to ignore tests when you run the app in
production etc.

Cheers
Tarek
>
> -- Markus
>
> "Tarek Ziadé" <tarek at ziade.org> wrote:
>
>     Hey
>
>     I've read about Pyret on hackernews: http://www.pyret.org/
>
>     and found the 'where' statement very compeling. Functions can end
>     with a where that contains small unit
>     tests.
>
>     From the documentation example:
>
>     fun sum(l):
>       cases(List) l:
>         | empty => 0
>         | link(first, rest) => first + sum(rest)
>       end
>     where:
>       sum([]) is 0
>       sum([1, 2, 3]) is 6
>     end
>
>      
>     It's quite similar to the doctests ideas I guess - but not
>     intended to be documentation like them.
>
>     I ended up disliking docttests because of this doc+test duality by
>     the way: it often ends up as a
>     not so good documentation and not so good tests.
>
>     Anyways, having a dedicated keyword to append after a function
>     some tests as part of the language
>     has benefits imho:
>
>     - the scope is reduced to the function - so it helps making 'real'
>     isolated unit tests.
>     - we do have the unittest conventions, but here it make tests a
>     first class citizen in the language.
>
>     Cheers
>     Tarek
>
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