from review: more robust test

This also checks the contents and not only the capacity in case IntoIter's clone implementation is changed to add capacity at the end. Extra capacity at the beginning would be needed to make InPlaceIterable work.

Co-authored-by: Giacomo Stevanato <giaco.stevanato@gmail.com>

library/alloc/tests/vec.rs

@@ -1100,12 +1100,12 @@ fn test_from_iter_specialization_panic_during_drop_leaks() {
 #[test]
 fn test_collect_after_iterator_clone() {
     let v = vec![0; 5];
-    let mut i = v.into_iter().peekable();
+    let mut i = v.into_iter().map(|i| i + 1).peekable();
     i.peek();
     let v = i.clone().collect::<Vec<_>>();
+    assert_eq!(v, [1, 1, 1, 1, 1]);
     assert!(v.len() <= v.capacity());
 }
-
 #[test]
 fn test_cow_from() {
     let borrowed: &[_] = &["borrowed", "(slice)"];