def test_implies(a: nnf.NNF, b: nnf.NNF):
if a.implies(b):
event("Implication")
for model in a.models():
assert b.condition(model).valid()
else:
event("No implication")
assert any(not b.condition(model).valid() for model in a.models())
def test_simplify_preserves_meaning(sentence: nnf.NNF, merge_nodes):
simple = sentence.simplify(merge_nodes)
assert sentence.equivalent(simple)
for model in sentence.models():
assert simple.satisfied_by(model)
for model in simple.models():
assert sentence.condition(model).simplify(merge_nodes) == nnf.true
def test_random_equivalent(a: nnf.NNF, b: nnf.NNF):
if a.vars() != b.vars():
if a.equivalent(b):
event("Equivalent, different vars")
assert b.equivalent(a)
for model in a.models():
assert b.condition(model).valid()
for model in b.models():
assert a.condition(model).valid()
else:
event("Not equivalent, different vars")
assert (any(not b.condition(model).valid() for model in a.models())
or any(not a.condition(model).valid()
for model in b.models()))
else:
if a.equivalent(b):
event("Equivalent, same vars")
assert b.equivalent(a)
assert model_set(a.models()) == model_set(b.models())
else:
event("Not equivalent, same vars")
assert model_set(a.models()) != model_set(b.models())
def test_forget(sentence: nnf.NNF):
# Assumption to reduce the time in testing
assume(sentence.size() <= 15)
# Test that forgetting a backbone variable doesn't change the theory
T = sentence & Var('added_var')
assert sentence.equivalent(T.forget({'added_var'}))
# Test the tseitin projection
assert sentence.equivalent(sentence.to_CNF().forget_aux())
# Test that models of a projected theory are consistent with the original
names = list(sentence.vars())[:2]
T = sentence.forget(names)
assert not any([v in T.vars() for v in names])
for m in T.models():
assert sentence.condition(m).satisfiable()
