extending list1_ = 0x6290000041e0 list1->slab_ = 0x629000009198 str1 = 0x629000004180 str2 = 0x629000004168 .. ints -- before pop(0) ints[0] = 4 ints[1] = 5 ints[2] = 6 -- after mutation ints[0] = 42 ints[1] = 43 ints[2] = 6 list_repeat length = 3 list_repeat length = 3 item 0 1 item 1 1 . forward iteration over list x = 1 x = 2 x = 3 backward iteration over list x = 3 x = 2 x = 1 init.size() = 2 .-- before pop(0) ints[0] = 5 ints[1] = 6 ints[2] = 7 ints[3] = 8 pop() pop(0) .. List ints ...... Total: 12 tests (695 ticks, 0.001 sec), 131 assertions Pass: 12, fail: 0, skip: 0.