11     assert_eq!("3", chain.next().unwrap().to_string());  in test_iter()
12     assert_eq!("2", chain.next().unwrap().to_string());  in test_iter()
13     assert_eq!("1", chain.next().unwrap().to_string());  in test_iter()
14     assert_eq!("0", chain.next().unwrap().to_string());  in test_iter()
23     assert_eq!("0", chain.next().unwrap().to_string());  in test_rev()
24     assert_eq!("1", chain.next().unwrap().to_string());  in test_rev()
25     assert_eq!("2", chain.next().unwrap().to_string());  in test_rev()
26     assert_eq!("3", chain.next().unwrap().to_string());  in test_rev()
37     assert_eq!("3", chain.next().unwrap().to_string());  in test_len()
40     assert_eq!("0", chain.next_back().unwrap().to_string());  in test_len()
43     assert_eq!("2", chain.next().unwrap().to_string());  in test_len()
46     assert_eq!("1", chain.next_back().unwrap().to_string());  in test_len()
63     assert_eq!("3", chain.next().unwrap().to_string());  in test_clone()
64     assert_eq!("2", chain.next().unwrap().to_string());  in test_clone()
65     assert_eq!("1", chain.next().unwrap().to_string());  in test_clone()
66     assert_eq!("0", chain.next().unwrap().to_string());  in test_clone()