def test_dll_add_head(): test_dll = DLL() test_dll.add_head(1) assert test_dll.head.data == 1 assert test_dll.tail.data == 1 test_dll.add_head(2) assert test_dll.head.data == 2 assert test_dll.tail.data == 1 test_dll.add_head(3) assert test_dll.head.data == 3 assert test_dll.tail.data == 1