Testing Prolog code in Scryer

[panasenco]

I wanted to see how easy it would be to port SWI-Prolog unit testing to Scryer, but it depends on library(options) which depends on library(dicts) and it just unravels into a dependency hell.

Just wondering if there are other options or existing plans for a unit testing library inside Scryer?

[mthom]

I've wanted to port @pmoura's ISO Prolog tests to Scryer for a while:

https://github.com/LogtalkDotOrg/logtalk3/blob/master/tests/prolog/NOTES.md

They're notable in that they don't appear to depend on any unit testing library. At the barest level, a unit testing predicate should call its first argument, call the second to match the results over variables it shares with the first argument, and pretty-print success or failure to the terminal in an easy to read format. library(format) takes care of the pretty-printing, and the rest can be done in plain ISO Prolog.

[pmoura]

See #915, #916, #917, #918, and #919. Also #896 and #84.

[pmoura]

As of d9e42bf, I'm able to manually load Logtalk. I will be adding support to Scryer Prolog to key libraries and tools in the coming days.

[dcnorris]

Looking forward to the guidance that lgtunit will offer! Pending this, does Scryer have a means for testing non-exported predicates of a module? I note this SWI discussion of export and import directives, and grepping scryer-prolog/src/lib/ turns up nothing.

david@tarnhelm prolog % scryer-prolog
?- [tally].
   true.
?- import(tally:tally_pair/3). % try to get non-exported predicate
caught: error(existence_error(procedure,import/1),import/1)
?- 

[pmoura]

Currently, Scryer Prolog allows calling non-exported module predicates using explicit module qualification. For example:

$ scryer-prolog
?- use_module(library(lists)).
   true.
?- lists:length_addendum(A, B, C).
   A = [], B = C
;  ...

Thus, when using lgtunit, the test can be written by using explicit module qualification to call non-exported predicates. Continuing the example:

:- object(tests, extends(lgtunit)).

    test(lists_length_addendum_3, variant(A-B-C, []-X-X)) :-
         lists:length_addendum(A, B, C).

:- end_object.

The driver file (tester.lgt) for the tests would be:

:- use_module(library(lists)).

:- initialization((
    set_logtalk_flag(report, warnings),
    logtalk_load(lgtunit(loader)),
    logtalk_load(tests, [hook(lgtunit)]),
    tests::run
)).

Running the tests:

$ scryerlgt
...
?- {tester}.

Happy to provide more guidance on using lgtunit. But iy may be more appropriate to do it at https://github.com/LogtalkDotOrg/logtalk3/discussions if the questions are not Scryer Prolog specific.

[dcnorris]

TY; I should have tried explicit qualification 🤦‍♂️, since it makes perfect sense from the namespaces POV of languages I'm more familiar with, like R.