def test_is_stable():
men_ranks, women_ranks = init_preferences()
matches = Matching(men_ranks, women_ranks)
assert (matches.is_stable() is False)
matches.match_pair('abe', 'ada')
matches.match_pair('ben', 'bea')
matches.match_pair('che', 'cee')
assert (matches.is_stable() is True)
matches = Matching(men_ranks, women_ranks)
matches.match_pair('abe', 'bea')
matches.match_pair('ben', 'ada')
matches.match_pair('che', 'cee')
assert (matches.is_stable() is False)
print("is_stable: OK!")
