def test_up_unsat():
# (x1|~x2|x3)&x2&(~x1|x3)&(x2|~x3) --> UNSAT
x1_var = Variable('x1')
x2_var = Variable('x2')
x3_var = Variable('x3')
x1 = Literal(x1_var, negated=False)
not_x1 = Literal(x1_var, negated=True)
x2 = Literal(x2_var, negated=False)
not_x2 = Literal(x2_var, negated=True)
x3 = Literal(x3_var, negated=False)
not_x3 = Literal(x3_var, negated=True)
clauses = [[x1, not_x2, x3], [x2], [not_x1, x3], [not_x2, not_x3]]
# literal_to_clauses = {x1: {0}, not_x1: {2}, not_x2: {0, 3}, x2: {1}, x3: {0, 2}, not_x3: {3}}
cnf = CnfFormula(clauses)
cnf = preprocess(cnf)
dpll = DPLL(cnf)
actual_cnf = dpll.unit_propagation()
assert actual_cnf is None
assert not dpll.get_full_assignment()[x3_var]
assert dpll.get_full_assignment()[x2_var]
def test_up_simple():
# (x1|~x2|x3)&x2&(~x1|x3) --> (x1|x3) & (~x1|x3)
x1_var = Variable('x1')
x2_var = Variable('x2')
x3_var = Variable('x3')
x1 = Literal(x1_var, negated=False)
not_x1 = Literal(x1_var, negated=True)
x2 = Literal(x2_var, negated=False)
not_x2 = Literal(x2_var, negated=True)
x3 = Literal(x3_var, negated=False)
clauses = [[x1, not_x2, x3], [x2], [not_x1, x3]]
cnf = CnfFormula(clauses)
cnf = preprocess(cnf)
dpll = DPLL(cnf)
actual_cnf = dpll.unit_propagation()
expected_cnf = [[x1, not_x2, x3], [not_x1, x3]]
assert dpll.get_full_assignment()[x2_var]
actual_cnf_real = [cl for cl in actual_cnf.clauses if cl != []]
assert actual_cnf_real == expected_cnf, dpll.get_full_assignment()