def test_prepend():
l = BiList()
l.prepend(42)
l.prepend(43)
l.prepend(44)
l.prepend(45)
assert len(l) == 4
assert [el.value for el in l] == [45, 44, 43, 42]
def test_prepend_empty():
l = BiList()
l.prepend(42)
assert len(l) == 1
assert [el.value for el in l] == [42]