def test_empty():
""" test 2 empty lists passed in"""
L1 = LinkedList()
L2 = LinkedList()
actual = zip_lists(L1, L2)
expected = 'cannot zip two empty lists'
assert actual == expected
def long_list():
lists = LinkedList()
lists.insert('i')
lists.insert('g')
lists.insert('e')
lists.insert('c')
lists.insert('a')
return lists
def list_two():
lists = LinkedList()
lists.insert('h')
lists.insert('f')
lists.insert('d')
lists.insert('b')
return lists
def list_one():
lists = LinkedList()
lists.insert('g')
lists.insert('e')
lists.insert('c')
lists.insert('a')
return lists
def test_first_empty():
""" test list 1 is empty """
L1 = LinkedList()
L2 = LinkedList()
L2.insert(4)
L2.insert(5)
L2.insert(6)
actual = str(zip_lists(L1, L2))
expected = 'cannot zip into empty list'
assert actual == expected
def test_second_empty():
""" test list 2 is empty """
L1 = LinkedList()
L2 = LinkedList()
L1.insert(1)
L1.insert(2)
L1.insert(3)
actual = str(zip_lists(L1, L2))
expected = 'list 2 empty; list 1 unchanged'
assert actual == expected
def test_happy():
""" test 2 lists of equal length """
L1 = LinkedList()
L2 = LinkedList()
L1.insert(1)
L2.insert(1)
L1.insert(2)
L2.insert(2)
L1.insert(3)
L2.insert(3)
actual = str(zip_lists(L1, L2))
expected = '{ 3 } -> { 3 } -> { 2 } -> { 2 } -> { 1 } -> { 1 } -> NULL'
assert actual == expected