How can a meaningful unit test be written for this CLIPS rule ? The rule is declarative - it states the preconditions that must exist and is explicit about what the post-conditions are (the asserted facts). How can a unit test add value to this and not be merely a test that CLIPS itself actually works ?

gistfile1.scm

(defrule make-group
    (make-graphic ?sheet ?id)
    (dict-entry ?id Class "Group") 
    (not (dict-entry ?id isSubgraph ?))
    (dict-entry ?id Graphics ?array)
    (array ?array $?graphics)
    =>
    (assert (group ?id))
    (foreach ?graphic $?graphics
        (assert (make-graphic ?sheet ?graphic))
        (assert (graphic-parent ?id ?graphic))))