[Haskell-cafe] HSpec vs Doctest for TDD

Michael Orlitzky michael at orlitzky.com
Wed Jun 25 15:47:23 UTC 2014

On 06/25/2014 11:24 AM, Francesco Ariis wrote:
> On Wed, Jun 25, 2014 at 02:45:37PM +0200, Mateusz Kowalczyk wrote:
>> While I disagree with initial view that testing is useless, I certainly
>> disagree with this approach too. There are plenty proof-assistants using
>> type-checking to prove programs correct. That's not to say Haskell
>> itself is suited for such task. If you have a type system strong enough,
>> classical tests are no longer required because you can encode all the
>> properties you need in types proving at compile time that your program
>> is in fact correct.
> For non-believers, here is a blog post that opened my eyes on the matter [1].
> [1] http://lambda.jstolarek.com/2013/12/data-is-evidence/

None of that helps if you write the wrong program. Your program may
typecheck, but if you're expecting "42" as output and your program hums
the Star Trek theme instead, the fact that it correctly does the wrong
thing won't be much consolation.

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