def test_str():
    list = LinkedList()
    list.insert(3)
    list.insert(5)
    list.insert(7)
    list.insert(9)
    assert list.__str__() == "{ 9 } -> { 7 } -> { 5 } -> { 3 } -> NULL"
def test_zio_2nd_longer():
    list1 = LinkedList()
    list2 = LinkedList()
    list1.append(1)
    list2.append(4)
    list2.append(5)
    list1.zipLists(list2)
    assert list1.__str__() == "{ 1 } -> { 4 } -> { 5 } -> NULL"
def test_zip_2nd_empty():
    list1 = LinkedList()
    list2 = LinkedList()
    list1.append(1)
    list1.append(2)
    list1.append(3)
    list1.zipLists(list2)
    assert list1.__str__() == "{ 1 } -> { 2 } -> { 3 } -> NULL"
def test_zio_same_length():
    list1 = LinkedList()
    list2 = LinkedList()
    list1.append(1)
    list1.append(2)
    list1.append(3)
    list2.append(4)
    list2.append(5)
    list2.append(6)
    list1.zipLists(list2)
    assert list1.__str__(
    ) == "{ 1 } -> { 4 } -> { 2 } -> { 5 } -> { 3 } -> { 6 } -> NULL"
def test_zip_empty():
    list1 = LinkedList()
    list2 = LinkedList()
    list1.zipLists(list2)
    assert list1.__str__() == "NULL"