def test_complex_merge():
bag1 = LetterBag("xxyyzzz")
bag2 = LetterBag("xyyyzzzz")
bag1.merge(bag2)
assert bag1.as_string() == "xxyyyzzzz"
def test_simple_merge():
bag_abbc = LetterBag("abbc")
bag_abccd = LetterBag("abccd")
bag_abbc.merge(bag_abccd)
assert bag_abbc.as_string() == "abbccd"