def test_U(self):
l = DLlist()
l.push_front('A')
l.push_front('B')
l.push_front('C')
l.push_front('D')
self.assertTrue(len(l) == 4 and
l[-1] == 'A' and
l[-2] == 'B' and
l[-3] == 'C' and
l[-4] == 'D')
def test_T(self):
l = DLlist()
l.push_front('A')
l.push_front('B')
l.push_front('C')
l.push_front('D')
self.assertTrue(len(l) == 4 and
l[0] == 'D' and
l[1] == 'C' and
l[2] == 'B' and
l[3] == 'A')