def test_add_start(self):
     List.add_start(List, '3')
     self.assertEqual(List.to_string(List), '[3, 4]')
     print(List.to_string(List))
 def test_get_length(self):
     self.assertEqual(List.get_length(List), 2)
     print(List.to_string(List))
 def test_add_end(self):
     List.add_end(List, '4')
     self.assertEqual(List.to_string(List), '[4]')
     print(List.to_string(List))