asp-selftest 0.0.11

A tool for running in-source unittests for Anwer Set Programming (ASP)

asp-selftest

In-source test runner for Answer Set Programming (ASP) with Clingo.

It provides:

* `asp-tests`: a standalone (Python) tool to run tests in a logic program.
* `bin/runasptests.sh`: Bash script to find all .lp files and run their tests.

Both tools stop at first failure.

GOAL

Enable first class unit testing in ASP using native ASP code and as much known concepts and as few magic as possible.

IDEA

1. Use #program's to identify units and their dependencies. Here we have a unit called unitA with a unit test for it called testunitA.

   #program unit_A.
   
   #program test_unit_A(unit_A).
   

   The implicit program base (see Clingo Guide) must be referenced explicitly if needed.

2. Extend the notion of #program by allowing the use of functions instead of only constants. This allows #program units with constants being tested. Here is a unit step that is tested with constant a being substituted with 2:

   #program step(a).
   
   #program test_step(step(2)).
   

   Note that using this feature makes the program incompatible with Clingo. The test runner has an option to transform a extended program back to compatible Clingo without running the tests.

3. Within a test program, use assert with @all to ensure universal truths that must be in every model. We use @all to communicate to the runtime that this particular assert must be checked for presence in every model. Its argument is just a name for identification.

    #program step(n).
    fact(n).
   
    #program test_step(step(3)).
    assert(@all("step fact"))  :-  fact(3).
   

   Note that "step fact" is just a way of distinquishing the assert. It can be an atom, a string, a number or anything else. Pay attention to the uniqueness in case of variables in the body. Take note of point 5 below.

4. To enable testing constraints and to guard tests for empty model sets, we use @models to check for the expected number of models. In the example above, we would add:

    assert(@models(1)).
   

5. Care must be taken if variables in the body lead to expansion and conjunctions. See duplicate_assert.lp. The system gives a warning for:

    assert(@all(id_uniq))  :-  def_id(Id, _, _),  { def_id(Id, _, _) } = 1.
   

   Instead you have to write:

    assert(@all(id_uniq(Id)))  :-  def_id(Id, _, _),  { def_id(Id, _, _) } = 1.
   

TESTING

Tests are run using the testrunner:

$ python asp-tests example.lp
teststep,  2 asserts,  10 models.  OK

To use the program without the tests: Not Yet Implemented. But you can use the base program anywhere of course, since all #programs are ignored by default.