2.2.3 Testing non-deterministic predicates

Non-deterministic predicates succeed zero or more times. Their results are tested either using findall/3 or setof/3 followed by a value-check or using the all or set options. The following are equivalent tests:

test(member) :-
        findall(X, member(X, [a,b,c]), Xs),
        Xs == [a,b,c].

test(member, all(X == [a,b,c])) :-
        member(X, [a,b,c]).