If you want to have the contracts enforced in the test submodule, all you have
to do is add (require (submod “..”)) to the submodule.
You don’t need to use define/contract, and you don’t need to use module*
instead of module+.
You can just use
#lang racket
(provide
(contract-out
; convert a fahrenheit temperature to a celsius
[fahrenheit->celsius (-> (and/c number? (>=/c -459.67)) number?)]))
(define (fahrenheit->celsius f)
(/ (* 5 (- f 32)) 9))
(module+ test
(require rackunit (submod "..")) ; the (submod "..") makes it enforce the
contracts
(check-equal? (fahrenheit->celsius -40) -40)
(check-equal? (fahrenheit->celsius 32) 0)
(check-equal? (fahrenheit->celsius 212) 100)
;; this checks that it raises a contract-error
(check-exn exn:fail:contract?
(λ () (fahrenheit->celsius -500))))
On May 22, 2015, at 7:58 AM, Atticus <attic...@posteo.org> wrote:
>> Yes, there is :
>> http://docs.racket-lang.org/style/Units_of_Code.html?q=define%2Fcontract#%28part._.Contracts%29
>
> Thank you for the link. The "How to Program Racket" Guide will be really
> helpful.
>
> But I must admit I'm a little confused. Looking at the *fahrenheit* example
> in the
> Guide:
>
> ;;;;
> #lang racket
>
> (provide
> (contract-out
> ; convert a fahrenheit temperature to a celsius
> [fahrenheit->celsius (-> number? number?)]))
>
> (define (fahrenheit->celsius f)
> (/ (* 5 (- f 32)) 9))
>
> (module+ test
> (require rackunit)
> (check-equal? (fahrenheit->celsius -40) -40)
> (check-equal? (fahrenheit->celsius 32) 0)
> (check-equal? (fahrenheit->celsius 212) 100))
> ;;;;
>
> This example implies that the contracts are enforced in the test
> submodule (contrary to Matthews example) but modifing the example shows
> that this is not the case:
>
> ;;;;
> (provide
> (contract-out
> ; convert a fahrenheit temperature to a celsius
> [fahrenheit->celsius (-> integer? integer?)]))
>
> (define (fahrenheit->celsius f)
> (/ (* 5 (- f 32)) 9))
>
> (module+ test
> (require rackunit)
> (check-equal? (fahrenheit->celsius -40) -40)
> (check-equal? (fahrenheit->celsius 32) 0)
> (check-equal? (fahrenheit->celsius 212.1) 100.05555555555556))
> ;;;;
>
> This is not very clear and confusing. If I would read the guide and I
> didn't know about Matthews example I would assume that the test in the
> modified example fails.
>
> My conclusion is:
> When using contracts with submodules use define/contract instead of
> (provide (contract-out ...))
>
>
>> black-box tests are always embedded in documentation so that
>> if the documentation does not show errors, then the system is reasonably
>> correct (for bugs that already found).
>> source code can keep elegant, and leave all the dirty things to scribble.
>
> This is a really nice idea. Thanks for sharing.
>
>
> WarGrey Gyoudmon Ju <juzhenli...@gmail.com> writes:
>
>> On Fri, May 22, 2015 at 5:41 PM, Atticus <attic...@posteo.org> wrote:
>>
>>>
>>> Imho it would be nice if there was a small hint in the documentation
>>> about that case, perhaps there is and I didn't see it?
>>
>>
>> Yes, there is :
>> http://docs.racket-lang.org/style/Units_of_Code.html?q=define%2Fcontract#%28part._.Contracts%29
>>
>>
>> In practice, I design tests in a system level abstraction.
>>
>> black-box tests are always embedded in documentation so that
>> if the documentation does not show errors, then the system is reasonably
>> correct (for bugs that already found).
>> source code can keep elegant, and leave all the dirty things to scribble.
>>
>> I almost do not write white-box tests since Racket and Typed Racket itself
>> has already formal enough,
>> moreover these tests or verifications can also be moved to documentation if
>> needed.
>
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