def test_includes():
ll = LinkedList()
ll.insert('first')
assert ll.includes("second") is False
assert ll.includes("first") is True
ll.insert("another")
assert ll.includes("another") is True
def test_append_several():
ll = LinkedList()
ll.append(1)
ll.append(2)
ll.append(3)
assert ll.includes(3)
assert str(ll) == '{ 1 } -> { 2 } -> { 3 } -> NULL'
def test_not_includes():
list = LinkedList()
list.insert('rubber')
list.insert('baby')
list.insert('buggy')
list.insert('bumpers')
actual = list.includes('rad')
expected = False
assert actual == expected
def test_six():
ll1 = LinkedList()
ll1.insert("a").insert("b").insert("c").insert("d")
actual = ll1.includes("h")
expected = False
assert actual == expected
def test_five():
ll1 = LinkedList()
ll1.insert("a").insert("b").insert("c").insert("d")
actual = ll1.includes("c")
expected = True
assert actual == expected