diff --git a/library/core/tests/iter/adapters/chain.rs b/library/core/tests/iter/adapters/chain.rs
index df2596322de..b20105259aa 100644
--- a/library/core/tests/iter/adapters/chain.rs
+++ b/library/core/tests/iter/adapters/chain.rs
@@ -23,6 +23,7 @@ fn test_iterator_chain() {
     }
     assert_eq!(i, expected.len());
 }
+
 #[test]
 fn test_iterator_chain_advance_by() {
     fn test_chain(xs: &[i32], ys: &[i32]) {
@@ -55,6 +56,7 @@ fn test_iterator_chain_advance_by() {
     test_chain(&[0, 1, 2, 3, 4, 5], &[]);
     test_chain(&[0, 1, 2, 3, 4, 5], &[30, 40, 50, 60]);
 }
+
 #[test]
 fn test_iterator_chain_advance_back_by() {
     fn test_chain(xs: &[i32], ys: &[i32]) {
@@ -87,6 +89,7 @@ fn test_iterator_chain_advance_back_by() {
     test_chain(&[0, 1, 2, 3, 4, 5], &[]);
     test_chain(&[0, 1, 2, 3, 4, 5], &[30, 40, 50, 60]);
 }
+
 #[test]
 fn test_iterator_chain_nth() {
     let xs = [0, 1, 2, 3, 4, 5];
@@ -102,6 +105,7 @@ fn test_iterator_chain_nth() {
     assert_eq!(it.nth(5), Some(&5));
     assert_eq!(it.next(), None);
 }
+
 #[test]
 fn test_iterator_chain_nth_back() {
     let xs = [0, 1, 2, 3, 4, 5];
@@ -117,6 +121,7 @@ fn test_iterator_chain_nth_back() {
     assert_eq!(it.nth_back(5), Some(&0));
     assert_eq!(it.next(), None);
 }
+
 #[test]
 fn test_iterator_chain_last() {
     let xs = [0, 1, 2, 3, 4, 5];
@@ -127,6 +132,7 @@ fn test_iterator_chain_last() {
     assert_eq!(ys.iter().chain(&zs).last(), Some(&60));
     assert_eq!(zs.iter().chain(&zs).last(), None);
 }
+
 #[test]
 fn test_iterator_chain_count() {
     let xs = [0, 1, 2, 3, 4, 5];
@@ -135,6 +141,7 @@ fn test_iterator_chain_count() {
     assert_eq!(xs.iter().chain(&ys).count(), 10);
     assert_eq!(zs.iter().chain(&ys).count(), 4);
 }
+
 #[test]
 fn test_iterator_chain_find() {
     let xs = [0, 1, 2, 3, 4, 5];
@@ -147,6 +154,7 @@ fn test_iterator_chain_find() {
     assert_eq!(iter.find(|&&i| i == 100), None);
     assert_eq!(iter.next(), None);
 }
+
 #[test]
 fn test_iterator_chain_size_hint() {
     // this chains an iterator of length 0 with an iterator of length 1,
@@ -161,6 +169,7 @@ fn test_iterator_chain_size_hint() {
     assert_eq!(iter.next_back(), Some(()));
     assert_eq!(iter.size_hint(), (0, Some(0)));
 }
+
 #[test]
 fn test_iterator_chain_unfused() {
     // Chain shouldn't be fused in its second iterator, depending on direction
@@ -174,6 +183,7 @@ fn test_iterator_chain_unfused() {
     iter.next_back().unwrap();
     iter.next_back().unwrap_none();
 }
+
 #[test]
 fn test_chain_fold() {
     let xs = [1, 2, 3];
@@ -185,6 +195,7 @@ fn test_chain_fold() {
     iter.fold((), |(), &elt| result.push(elt));
     assert_eq!(&[2, 3, 1, 2, 0], &result[..]);
 }
+
 #[test]
 fn test_chain_try_folds() {
     let c = || (0..10).chain(10..20);
diff --git a/library/core/tests/iter/adapters/cloned.rs b/library/core/tests/iter/adapters/cloned.rs
index f1b3a4b7933..78babb7feab 100644
--- a/library/core/tests/iter/adapters/cloned.rs
+++ b/library/core/tests/iter/adapters/cloned.rs
@@ -16,6 +16,7 @@ fn test_cloned() {
     assert_eq!(it.len(), 0);
     assert_eq!(it.next_back(), None);
 }
+
 #[test]
 fn test_cloned_side_effects() {
     let mut count = 0;
@@ -32,6 +33,7 @@ fn test_cloned_side_effects() {
     }
     assert_eq!(count, 2);
 }
+
 #[test]
 fn test_cloned_try_folds() {
     let a = [1, 2, 3, 4, 5, 6, 7, 8, 9];
diff --git a/library/core/tests/iter/adapters/enumerate.rs b/library/core/tests/iter/adapters/enumerate.rs
index dfdf37dbedb..9a11a28f9b0 100644
--- a/library/core/tests/iter/adapters/enumerate.rs
+++ b/library/core/tests/iter/adapters/enumerate.rs
@@ -8,6 +8,7 @@ fn test_iterator_enumerate() {
         assert_eq!(i, x);
     }
 }
+
 #[test]
 fn test_iterator_enumerate_nth() {
     let xs = [0, 1, 2, 3, 4, 5];
@@ -29,6 +30,7 @@ fn test_iterator_enumerate_nth() {
     assert_eq!(i, x);
     assert_eq!(i, 3);
 }
+
 #[test]
 fn test_iterator_enumerate_nth_back() {
     let xs = [0, 1, 2, 3, 4, 5];
@@ -46,11 +48,13 @@ fn test_iterator_enumerate_nth_back() {
     assert_eq!(i, x);
     assert_eq!(i, 2);
 }
+
 #[test]
 fn test_iterator_enumerate_count() {
     let xs = [0, 1, 2, 3, 4, 5];
     assert_eq!(xs.iter().enumerate().count(), 6);
 }
+
 #[test]
 fn test_iterator_enumerate_fold() {
     let xs = [0, 1, 2, 3, 4, 5];
@@ -74,6 +78,7 @@ fn test_iterator_enumerate_fold() {
     });
     assert_eq!(i, 0);
 }
+
 #[test]
 fn test_enumerate_try_folds() {
     let f = &|acc, (i, x)| usize::checked_add(2 * acc, x / (i + 1) + i);
diff --git a/library/core/tests/iter/adapters/filter.rs b/library/core/tests/iter/adapters/filter.rs
index fd1519ce532..e39cb7e39c6 100644
--- a/library/core/tests/iter/adapters/filter.rs
+++ b/library/core/tests/iter/adapters/filter.rs
@@ -5,6 +5,7 @@ fn test_iterator_filter_count() {
     let xs = [0, 1, 2, 3, 4, 5, 6, 7, 8];
     assert_eq!(xs.iter().filter(|&&x| x % 2 == 0).count(), 5);
 }
+
 #[test]
 fn test_iterator_filter_fold() {
     let xs = [0, 1, 2, 3, 4, 5, 6, 7, 8];
@@ -23,6 +24,7 @@ fn test_iterator_filter_fold() {
     });
     assert_eq!(i, 0);
 }
+
 #[test]
 fn test_filter_try_folds() {
     fn p(&x: &i32) -> bool {
diff --git a/library/core/tests/iter/adapters/filter_map.rs b/library/core/tests/iter/adapters/filter_map.rs
index 807a35eb0b9..083ee85c950 100644
--- a/library/core/tests/iter/adapters/filter_map.rs
+++ b/library/core/tests/iter/adapters/filter_map.rs
@@ -5,6 +5,7 @@ fn test_filter_map() {
     let it = (0..).step_by(1).take(10).filter_map(|x| if x % 2 == 0 { Some(x * x) } else { None });
     assert_eq!(it.collect::<Vec<usize>>(), [0 * 0, 2 * 2, 4 * 4, 6 * 6, 8 * 8]);
 }
+
 #[test]
 fn test_filter_map_fold() {
     let xs = [0, 1, 2, 3, 4, 5, 6, 7, 8];
diff --git a/library/core/tests/iter/adapters/flat_map.rs b/library/core/tests/iter/adapters/flat_map.rs
index fdd5d799e72..e21b82a7fe7 100644
--- a/library/core/tests/iter/adapters/flat_map.rs
+++ b/library/core/tests/iter/adapters/flat_map.rs
@@ -12,6 +12,7 @@ fn test_iterator_flat_map() {
     }
     assert_eq!(i, ys.len());
 }
+
 #[test]
 fn test_iterator_flat_map_fold() {
     let xs = [0, 3, 6];
@@ -34,6 +35,7 @@ fn test_iterator_flat_map_fold() {
     });
     assert_eq!(i, 0);
 }
+
 #[test]
 fn test_flat_map_try_folds() {
     let f = &|acc, x| i32::checked_add(acc * 2 / 3, x);
diff --git a/library/core/tests/iter/adapters/flatten.rs b/library/core/tests/iter/adapters/flatten.rs
index 5b74026c32c..084229bb092 100644
--- a/library/core/tests/iter/adapters/flatten.rs
+++ b/library/core/tests/iter/adapters/flatten.rs
@@ -13,6 +13,7 @@ fn test_iterator_flatten() {
     }
     assert_eq!(i, ys.len());
 }
+
 #[test]
 fn test_iterator_flatten_fold() {
     let xs = [0, 3, 6];
@@ -35,6 +36,7 @@ fn test_iterator_flatten_fold() {
     });
     assert_eq!(i, 0);
 }
+
 #[test]
 fn test_flatten_try_folds() {
     let f = &|acc, x| i32::checked_add(acc * 2 / 3, x);
@@ -52,6 +54,7 @@ fn test_flatten_try_folds() {
     assert_eq!(iter.try_rfold(0, i8::checked_add), None);
     assert_eq!(iter.next_back(), Some(35));
 }
+
 #[test]
 fn test_flatten_non_fused_outer() {
     let mut iter = NonFused::new(once(0..2)).flatten();
@@ -60,6 +63,7 @@ fn test_flatten_non_fused_outer() {
     assert_eq!(iter.next(), Some(0));
     assert_eq!(iter.next(), None);
 }
+
 #[test]
 fn test_flatten_non_fused_inner() {
     let mut iter = once(0..1).chain(once(1..3)).flat_map(NonFused::new);
diff --git a/library/core/tests/iter/adapters/fuse.rs b/library/core/tests/iter/adapters/fuse.rs
index 181cee719d9..5b9f8065fe1 100644
--- a/library/core/tests/iter/adapters/fuse.rs
+++ b/library/core/tests/iter/adapters/fuse.rs
@@ -11,6 +11,7 @@ fn test_fuse_nth() {
     assert_eq!(it.nth(2), None);
     assert_eq!(it.len(), 0);
 }
+
 #[test]
 fn test_fuse_last() {
     let xs = [0, 1, 2];
@@ -19,6 +20,7 @@ fn test_fuse_last() {
     assert_eq!(it.len(), 3);
     assert_eq!(it.last(), Some(&2));
 }
+
 #[test]
 fn test_fuse_count() {
     let xs = [0, 1, 2];
@@ -28,6 +30,7 @@ fn test_fuse_count() {
     assert_eq!(it.count(), 3);
     // Can't check len now because count consumes.
 }
+
 #[test]
 fn test_fuse_fold() {
     let xs = [0, 1, 2];
diff --git a/library/core/tests/iter/adapters/inspect.rs b/library/core/tests/iter/adapters/inspect.rs
index c411848e6f7..939e3a28a72 100644
--- a/library/core/tests/iter/adapters/inspect.rs
+++ b/library/core/tests/iter/adapters/inspect.rs
@@ -10,6 +10,7 @@ fn test_inspect() {
     assert_eq!(n, xs.len());
     assert_eq!(&xs[..], &ys[..]);
 }
+
 #[test]
 fn test_inspect_fold() {
     let xs = [1, 2, 3, 4];
diff --git a/library/core/tests/iter/adapters/intersperse.rs b/library/core/tests/iter/adapters/intersperse.rs
index 31af70171f1..4f65f1bdee3 100644
--- a/library/core/tests/iter/adapters/intersperse.rs
+++ b/library/core/tests/iter/adapters/intersperse.rs
@@ -17,6 +17,7 @@ fn test_intersperse() {
     let mut it = ys[..0].iter().map(|x| *x).intersperse(1);
     assert!(it.next() == None);
 }
+
 #[test]
 fn test_intersperse_size_hint() {
     let iter = std::iter::empty::<i32>().intersperse(0);
@@ -33,6 +34,7 @@ fn test_intersperse_size_hint() {
 
     assert_eq!([].iter().intersperse(&()).size_hint(), (0, Some(0)));
 }
+
 #[test]
 fn test_fold_specialization_intersperse() {
     let mut iter = (1..2).intersperse(0);
@@ -44,6 +46,7 @@ fn test_fold_specialization_intersperse() {
     let mut iter = (1..4).intersperse(0);
     iter.clone().for_each(|x| assert_eq!(Some(x), iter.next()));
 }
+
 #[test]
 fn test_try_fold_specialization_intersperse_ok() {
     let mut iter = (1..2).intersperse(0);
@@ -64,6 +67,7 @@ fn test_try_fold_specialization_intersperse_ok() {
         Some(())
     });
 }
+
 #[test]
 fn test_intersperse_with() {
     #[derive(PartialEq, Debug)]
@@ -84,6 +88,7 @@ fn test_intersperse_with() {
     let r = (0..3).intersperse_with(separator).collect::<Vec<_>>();
     assert_eq!(r, vec![0, 200, 1, 400, 2]);
 }
+
 #[test]
 fn test_intersperse_fold() {
     let v = (1..4).intersperse(9).fold(Vec::new(), |mut acc, x| {
@@ -112,6 +117,7 @@ fn test_intersperse_fold() {
     let v = NoneAtStart(0).intersperse(1000).fold(0, |a, b| a + b);
     assert_eq!(v, 0);
 }
+
 #[test]
 fn test_intersperse_collect_string() {
     let contents = vec![1, 2, 3];
diff --git a/library/core/tests/iter/adapters/map.rs b/library/core/tests/iter/adapters/map.rs
index 69866af472e..704acc12307 100644
--- a/library/core/tests/iter/adapters/map.rs
+++ b/library/core/tests/iter/adapters/map.rs
@@ -22,6 +22,7 @@ fn test_find_map() {
         if x % 2 == 0 { Some(x / 2) } else { None }
     }
 }
+
 #[test]
 fn test_map_try_folds() {
     let f = &|acc, x| i32::checked_add(2 * acc, x);
@@ -34,6 +35,7 @@ fn test_map_try_folds() {
     assert_eq!(iter.try_rfold(0, i8::checked_add), None);
     assert_eq!(iter.next_back(), Some(46));
 }
+
 #[test]
 fn test_filter_map_try_folds() {
     let mp = &|x| if 0 <= x && x < 10 { Some(x * 2) } else { None };
diff --git a/library/core/tests/iter/adapters/peekable.rs b/library/core/tests/iter/adapters/peekable.rs
index ee36ff41b03..390414d4aa2 100644
--- a/library/core/tests/iter/adapters/peekable.rs
+++ b/library/core/tests/iter/adapters/peekable.rs
@@ -59,6 +59,7 @@ fn test_iterator_peekable() {
     assert!(it.next_back().is_none());
     assert_eq!(it.len(), 0);
 }
+
 #[test]
 fn test_iterator_peekable_count() {
     let xs = [0, 1, 2, 3, 4, 5];
@@ -82,6 +83,7 @@ fn test_iterator_peekable_count() {
     let mut it = zs.iter().peekable();
     assert_eq!(it.peek(), None);
 }
+
 #[test]
 fn test_iterator_peekable_nth() {
     let xs = [0, 1, 2, 3, 4, 5];
@@ -95,6 +97,7 @@ fn test_iterator_peekable_nth() {
     assert_eq!(it.nth(2), Some(&5));
     assert_eq!(it.next(), None);
 }
+
 #[test]
 fn test_iterator_peekable_last() {
     let xs = [0, 1, 2, 3, 4, 5];
@@ -113,6 +116,7 @@ fn test_iterator_peekable_last() {
     assert_eq!(it.peek(), None);
     assert_eq!(it.last(), None);
 }
+
 #[test]
 fn test_iterator_peekable_fold() {
     let xs = [0, 1, 2, 3, 4, 5];
@@ -124,6 +128,7 @@ fn test_iterator_peekable_fold() {
     });
     assert_eq!(i, xs.len());
 }
+
 #[test]
 fn test_iterator_peekable_rfold() {
     let xs = [0, 1, 2, 3, 4, 5];
@@ -135,6 +140,7 @@ fn test_iterator_peekable_rfold() {
     });
     assert_eq!(i, xs.len());
 }
+
 #[test]
 fn test_iterator_peekable_next_if_eq() {
     // first, try on references
@@ -158,6 +164,7 @@ fn test_iterator_peekable_next_if_eq() {
     assert_eq!(it.next_if_eq("speed"), Some("speed".into()));
     assert_eq!(it.next_if_eq(""), None);
 }
+
 #[test]
 fn test_iterator_peekable_mut() {
     let mut it = vec![1, 2, 3].into_iter().peekable();
@@ -168,6 +175,7 @@ fn test_iterator_peekable_mut() {
     }
     assert_eq!(it.collect::<Vec<_>>(), vec![5, 2, 3]);
 }
+
 #[test]
 fn test_iterator_peekable_remember_peek_none_1() {
     // Check that the loop using .peek() terminates
@@ -185,6 +193,7 @@ fn test_iterator_peekable_remember_peek_none_1() {
     }
     assert_eq!(n, data.len());
 }
+
 #[test]
 fn test_iterator_peekable_remember_peek_none_2() {
     let data = [0];
@@ -193,6 +202,7 @@ fn test_iterator_peekable_remember_peek_none_2() {
     assert_eq!(iter.peek(), None);
     assert_eq!(iter.last(), None);
 }
+
 #[test]
 fn test_iterator_peekable_remember_peek_none_3() {
     let data = [0];
@@ -205,6 +215,7 @@ fn test_iterator_peekable_remember_peek_none_3() {
     assert_eq!(iter.peek(), None);
     assert_eq!(iter.nth(0), None);
 }
+
 #[test]
 fn test_peek_try_folds() {
     let f = &|acc, x| i32::checked_add(2 * acc, x);
@@ -251,6 +262,7 @@ fn test_peek_try_folds() {
     assert_eq!(iter.peek(), None);
     assert_eq!(iter.try_rfold((), |(), x| Err(x)), Ok(()));
 }
+
 #[test]
 fn test_peekable_non_fused() {
     let mut iter = NonFused::new(empty::<i32>()).peekable();
diff --git a/library/core/tests/iter/adapters/skip.rs b/library/core/tests/iter/adapters/skip.rs
index 76be892c337..cf60057a164 100644
--- a/library/core/tests/iter/adapters/skip.rs
+++ b/library/core/tests/iter/adapters/skip.rs
@@ -14,6 +14,7 @@ fn test_iterator_skip() {
     assert_eq!(i, ys.len());
     assert_eq!(it.len(), 0);
 }
+
 #[test]
 fn test_iterator_skip_doubleended() {
     let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
@@ -51,6 +52,7 @@ fn test_iterator_skip_doubleended() {
     let it = xs.iter().skip(5).rev();
     assert_eq!(it.last(), Some(&13));
 }
+
 #[test]
 fn test_iterator_skip_nth() {
     let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
@@ -66,6 +68,7 @@ fn test_iterator_skip_nth() {
     let mut it = xs.iter().skip(12);
     assert_eq!(it.nth(0), None);
 }
+
 #[test]
 fn test_iterator_skip_count() {
     let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
@@ -76,6 +79,7 @@ fn test_iterator_skip_count() {
     assert_eq!(xs.iter().skip(12).count(), 0);
     assert_eq!(xs.iter().skip(13).count(), 0);
 }
+
 #[test]
 fn test_iterator_skip_last() {
     let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
@@ -90,6 +94,7 @@ fn test_iterator_skip_last() {
     assert_eq!(it.next(), Some(&13));
     assert_eq!(it.last(), Some(&30));
 }
+
 #[test]
 fn test_iterator_skip_fold() {
     let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
@@ -127,6 +132,7 @@ fn test_iterator_skip_fold() {
     });
     assert_eq!(i, 1);
 }
+
 #[test]
 fn test_skip_try_folds() {
     let f = &|acc, x| i32::checked_add(2 * acc, x);
@@ -139,6 +145,7 @@ fn test_skip_try_folds() {
     assert_eq!(iter.try_rfold(0, i8::checked_add), None);
     assert_eq!(iter.next_back(), Some(24));
 }
+
 #[test]
 fn test_skip_nth_back() {
     let xs = [0, 1, 2, 3, 4, 5];
diff --git a/library/core/tests/iter/adapters/skip_while.rs b/library/core/tests/iter/adapters/skip_while.rs
index 73890d231ac..929d4f6e64f 100644
--- a/library/core/tests/iter/adapters/skip_while.rs
+++ b/library/core/tests/iter/adapters/skip_while.rs
@@ -12,6 +12,7 @@ fn test_iterator_skip_while() {
     }
     assert_eq!(i, ys.len());
 }
+
 #[test]
 fn test_iterator_skip_while_fold() {
     let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
@@ -31,6 +32,7 @@ fn test_iterator_skip_while_fold() {
     });
     assert_eq!(i, ys.len());
 }
+
 #[test]
 fn test_skip_while_try_fold() {
     let f = &|acc, x| i32::checked_add(2 * acc, x);
diff --git a/library/core/tests/iter/adapters/step.rs b/library/core/tests/iter/adapters/step.rs
index 195b4c85639..3d82a40cd29 100644
--- a/library/core/tests/iter/adapters/step.rs
+++ b/library/core/tests/iter/adapters/step.rs
@@ -23,6 +23,7 @@ fn test_steps_between() {
         None,
     );
 }
+
 #[test]
 fn test_step_forward() {
     assert_eq!(Step::forward_checked(55_u8, 200_usize), Some(255_u8));
@@ -59,6 +60,7 @@ fn test_step_forward() {
         None
     );
 }
+
 #[test]
 fn test_step_backward() {
     assert_eq!(Step::backward_checked(255_u8, 200_usize), Some(55_u8));
diff --git a/library/core/tests/iter/adapters/step_by.rs b/library/core/tests/iter/adapters/step_by.rs
index a1c2c64bb5d..6502c7fb795 100644
--- a/library/core/tests/iter/adapters/step_by.rs
+++ b/library/core/tests/iter/adapters/step_by.rs
@@ -29,6 +29,7 @@ fn test_iterator_step_by() {
     assert_eq!(it.next_back(), Some(0));
     assert_eq!(it.next_back(), None);
 }
+
 #[test]
 fn test_iterator_step_by_nth() {
     let mut it = (0..16).step_by(5);
@@ -46,6 +47,7 @@ fn test_iterator_step_by_nth() {
     assert_eq!(it.clone().nth(4), None);
     assert_eq!(it.clone().nth(42), None);
 }
+
 #[test]
 fn test_iterator_step_by_nth_overflow() {
     #[cfg(target_pointer_width = "8")]
@@ -91,6 +93,7 @@ fn test_iterator_step_by_nth_overflow() {
     (&mut it).step_by(1).nth(usize::MAX);
     assert_eq!(it.0, (usize::MAX as Bigger) * 1);
 }
+
 #[test]
 fn test_iterator_step_by_nth_try_fold() {
     let mut it = (0..).step_by(10);
@@ -107,6 +110,7 @@ fn test_iterator_step_by_nth_try_fold() {
     assert_eq!(it.next(), Some(100));
     assert_eq!(it.try_fold(0, i8::checked_add), Some(0));
 }
+
 #[test]
 fn test_iterator_step_by_nth_back() {
     let mut it = (0..16).step_by(5);
@@ -131,6 +135,7 @@ fn test_iterator_step_by_nth_back() {
     assert_eq!(it().nth_back(4), None);
     assert_eq!(it().nth_back(42), None);
 }
+
 #[test]
 fn test_iterator_step_by_nth_try_rfold() {
     let mut it = (0..100).step_by(10);
@@ -148,12 +153,14 @@ fn test_iterator_step_by_nth_try_rfold() {
     assert_eq!(it.next_back(), Some(100));
     assert_eq!(it.try_fold(0, i8::checked_add), Some(0));
 }
+
 #[test]
 #[should_panic]
 fn test_iterator_step_by_zero() {
     let mut it = (0..).step_by(0);
     it.next();
 }
+
 #[test]
 fn test_iterator_step_by_size_hint() {
     struct StubSizeHint(usize, Option<usize>);
@@ -232,6 +239,7 @@ fn test_iterator_step_by_size_hint() {
     assert!(TrustedLenCheck::test(a.iter()));
     assert!(!TrustedLenCheck::test(a.iter().step_by(1)));
 }
+
 #[test]
 fn test_step_by_skip() {
     assert_eq!((0..640).step_by(128).skip(1).collect::<Vec<_>>(), [128, 256, 384, 512]);
diff --git a/library/core/tests/iter/adapters/take.rs b/library/core/tests/iter/adapters/take.rs
index 6739855c8ad..89f9cb1e2ed 100644
--- a/library/core/tests/iter/adapters/take.rs
+++ b/library/core/tests/iter/adapters/take.rs
@@ -27,6 +27,7 @@ fn test_iterator_take() {
     assert_eq!(i, ys.len());
     assert_eq!(it.len(), 0);
 }
+
 #[test]
 fn test_iterator_take_nth() {
     let xs = [0, 1, 2, 4, 5];
@@ -50,6 +51,7 @@ fn test_iterator_take_nth() {
         i += 2;
     }
 }
+
 #[test]
 fn test_iterator_take_nth_back() {
     let xs = [0, 1, 2, 4, 5];
@@ -70,6 +72,7 @@ fn test_iterator_take_nth_back() {
     assert_eq!(it.nth_back(1), Some(&1));
     assert_eq!(it.nth_back(1), None);
 }
+
 #[test]
 fn test_iterator_take_short() {
     let xs = [0, 1, 2, 3];
@@ -96,6 +99,7 @@ fn test_iterator_take_short() {
     assert_eq!(i, xs.len());
     assert_eq!(it.len(), 0);
 }
+
 #[test]
 fn test_take_try_folds() {
     let f = &|acc, x| i32::checked_add(2 * acc, x);
diff --git a/library/core/tests/iter/adapters/take_while.rs b/library/core/tests/iter/adapters/take_while.rs
index 58856ac44bd..6f1ebab29b3 100644
--- a/library/core/tests/iter/adapters/take_while.rs
+++ b/library/core/tests/iter/adapters/take_while.rs
@@ -12,6 +12,7 @@ fn test_iterator_take_while() {
     }
     assert_eq!(i, ys.len());
 }
+
 #[test]
 fn test_take_while_folds() {
     let f = &|acc, x| i32::checked_add(2 * acc, x);
diff --git a/library/core/tests/iter/adapters/zip.rs b/library/core/tests/iter/adapters/zip.rs
index a8d524ccec9..a5bf19c43c9 100644
--- a/library/core/tests/iter/adapters/zip.rs
+++ b/library/core/tests/iter/adapters/zip.rs
@@ -17,6 +17,7 @@ fn test_zip_nth() {
     let mut it = ys.iter().zip(&xs);
     assert_eq!(it.nth(3), None);
 }
+
 #[test]
 fn test_zip_nth_side_effects() {
     let mut a = Vec::new();
@@ -38,6 +39,7 @@ fn test_zip_nth_side_effects() {
     assert_eq!(a, vec![1, 2, 3, 4, 5]);
     assert_eq!(b, vec![200, 300, 400, 500, 600]);
 }
+
 #[test]
 fn test_zip_next_back_side_effects() {
     let mut a = Vec::new();
@@ -63,6 +65,7 @@ fn test_zip_next_back_side_effects() {
     assert_eq!(a, vec![6, 5, 4, 3]);
     assert_eq!(b, vec![800, 700, 600, 500, 400]);
 }
+
 #[test]
 fn test_zip_nth_back_side_effects() {
     let mut a = Vec::new();
@@ -83,6 +86,7 @@ fn test_zip_nth_back_side_effects() {
     assert_eq!(a, vec![6, 5, 4, 3]);
     assert_eq!(b, vec![800, 700, 600, 500, 400]);
 }
+
 #[test]
 fn test_zip_next_back_side_effects_exhausted() {
     let mut a = Vec::new();
@@ -107,6 +111,7 @@ fn test_zip_next_back_side_effects_exhausted() {
     assert_eq!(a, vec![1, 2, 3, 4, 6, 5]);
     assert_eq!(b, vec![200, 300, 400]);
 }
+
 #[test]
 fn test_zip_cloned_sideffectful() {
     let xs = [CountClone::new(), CountClone::new(), CountClone::new(), CountClone::new()];
@@ -125,6 +130,7 @@ fn test_zip_cloned_sideffectful() {
     assert_eq!(&xs, &[1, 1][..]);
     assert_eq!(&ys, &[1, 1, 0, 0][..]);
 }
+
 #[test]
 fn test_zip_map_sideffectful() {
     let mut xs = [0; 6];
@@ -143,6 +149,7 @@ fn test_zip_map_sideffectful() {
     assert_eq!(&xs, &[1, 1, 1, 1]);
     assert_eq!(&ys, &[1, 1, 1, 1, 0, 0]);
 }
+
 #[test]
 fn test_zip_map_rev_sideffectful() {
     let mut xs = [0; 6];
@@ -166,6 +173,7 @@ fn test_zip_map_rev_sideffectful() {
     assert_eq!(&xs, &[1, 1, 1, 1, 1, 1]);
     assert_eq!(&ys, &[1, 1, 1, 1]);
 }
+
 #[test]
 fn test_zip_nested_sideffectful() {
     let mut xs = [0; 6];
@@ -178,6 +186,7 @@ fn test_zip_nested_sideffectful() {
     }
     assert_eq!(&xs, &[1, 1, 1, 1, 1, 0]);
 }
+
 #[test]
 fn test_zip_nth_back_side_effects_exhausted() {
     let mut a = Vec::new();
@@ -202,6 +211,7 @@ fn test_zip_nth_back_side_effects_exhausted() {
     assert_eq!(a, vec![1, 2, 3, 4, 6, 5]);
     assert_eq!(b, vec![200, 300, 400]);
 }
+
 #[test]
 fn test_zip_trusted_random_access_composition() {
     let a = [0, 1, 2, 3, 4];
diff --git a/library/core/tests/iter/mod.rs b/library/core/tests/iter/mod.rs
index 6216d0a3288..ac51ec797ac 100644
--- a/library/core/tests/iter/mod.rs
+++ b/library/core/tests/iter/mod.rs
@@ -6,6 +6,9 @@ mod traits;
 use core::cell::Cell;
 use core::convert::TryFrom;
 use core::iter::*;
+
+pub fn is_trusted_len<I: TrustedLen>(_: I) {}
+
 #[test]
 fn test_multi_iter() {
     let xs = [1, 2, 3, 4];
@@ -13,6 +16,7 @@ fn test_multi_iter() {
     assert!(xs.iter().eq(ys.iter().rev()));
     assert!(xs.iter().lt(xs.iter().skip(2)));
 }
+
 #[test]
 fn test_counter_from_iter() {
     let it = (0..).step_by(5).take(10);
@@ -20,7 +24,6 @@ fn test_counter_from_iter() {
     assert_eq!(xs, [0, 5, 10, 15, 20, 25, 30, 35, 40, 45]);
 }
 
-pub fn is_trusted_len<I: TrustedLen>(_: I) {}
 #[test]
 fn test_functor_laws() {
     // identity:
@@ -41,6 +44,7 @@ fn test_functor_laws() {
     }
     assert_eq!((0..10).map(f).map(g).sum::<usize>(), (0..10).map(h).sum());
 }
+
 #[test]
 fn test_monad_laws_left_identity() {
     fn f(x: usize) -> impl Iterator<Item = usize> {
@@ -48,10 +52,12 @@ fn test_monad_laws_left_identity() {
     }
     assert_eq!(once(42).flat_map(f.clone()).sum::<usize>(), f(42).sum());
 }
+
 #[test]
 fn test_monad_laws_right_identity() {
     assert_eq!((0..10).flat_map(|x| once(x)).sum::<usize>(), (0..10).sum());
 }
+
 #[test]
 fn test_monad_laws_associativity() {
     fn f(x: usize) -> impl Iterator<Item = usize> {
@@ -77,6 +83,7 @@ pub fn extend_for_unit() {
     }
     assert_eq!(x, 5);
 }
+
 #[test]
 fn test_try_fold_specialization_intersperse_err() {
     let orig_iter = ["a", "b"].iter().copied().intersperse("-");
diff --git a/library/core/tests/iter/range.rs b/library/core/tests/iter/range.rs
index 2ba787325ad..68cc34d5ddb 100644
--- a/library/core/tests/iter/range.rs
+++ b/library/core/tests/iter/range.rs
@@ -23,6 +23,7 @@ fn test_range() {
         (isize::MAX as usize + 2, Some(isize::MAX as usize + 2))
     );
 }
+
 #[test]
 fn test_char_range() {
     use std::char;
@@ -37,6 +38,7 @@ fn test_char_range() {
     assert_eq!(('\u{D7FF}'..'\u{E000}').count(), 1);
     assert_eq!(('\u{D7FF}'..'\u{E000}').size_hint(), (1, Some(1)));
 }
+
 #[test]
 fn test_range_exhaustion() {
     let mut r = 10..10;
@@ -65,6 +67,7 @@ fn test_range_exhaustion() {
     assert_eq!(r.next_back(), None);
     assert_eq!(r, 100..10);
 }
+
 #[test]
 fn test_range_inclusive_exhaustion() {
     let mut r = 10..=10;
@@ -124,6 +127,7 @@ fn test_range_inclusive_exhaustion() {
     assert_eq!(r.next_back(), None);
     assert_eq!(r, 100..=10);
 }
+
 #[test]
 fn test_range_nth() {
     assert_eq!((10..15).nth(0), Some(10));
@@ -139,6 +143,7 @@ fn test_range_nth() {
     assert_eq!(r.nth(10), None);
     assert_eq!(r, 20..20);
 }
+
 #[test]
 fn test_range_nth_back() {
     assert_eq!((10..15).nth_back(0), Some(14));
@@ -155,6 +160,7 @@ fn test_range_nth_back() {
     assert_eq!(r.nth_back(10), None);
     assert_eq!(r, 10..10);
 }
+
 #[test]
 fn test_range_from_nth() {
     assert_eq!((10..).nth(0), Some(10));
@@ -171,6 +177,7 @@ fn test_range_from_nth() {
 
     assert_eq!((0..).size_hint(), (usize::MAX, None));
 }
+
 #[test]
 fn test_range_from_take() {
     let mut it = (0..).take(3);
@@ -183,11 +190,13 @@ fn test_range_from_take() {
     assert_eq!((0..).take(0).size_hint(), (0, Some(0)));
     assert_eq!((0..).take(usize::MAX).size_hint(), (usize::MAX, Some(usize::MAX)));
 }
+
 #[test]
 fn test_range_from_take_collect() {
     let v: Vec<_> = (0..).take(3).collect();
     assert_eq!(v, vec![0, 1, 2]);
 }
+
 #[test]
 fn test_range_inclusive_nth() {
     assert_eq!((10..=15).nth(0), Some(10));
@@ -210,6 +219,7 @@ fn test_range_inclusive_nth() {
     assert_eq!(r, exhausted_via_next);
     assert_eq!(ExactSizeIterator::is_empty(&r), true);
 }
+
 #[test]
 fn test_range_inclusive_nth_back() {
     assert_eq!((10..=15).nth_back(0), Some(15));
@@ -233,6 +243,7 @@ fn test_range_inclusive_nth_back() {
     assert_eq!(r, exhausted_via_next_back);
     assert_eq!(ExactSizeIterator::is_empty(&r), true);
 }
+
 #[test]
 fn test_range_len() {
     assert_eq!((0..10_u8).len(), 10);
@@ -241,6 +252,7 @@ fn test_range_len() {
     assert_eq!((11..10_u8).len(), 0);
     assert_eq!((100..10_u8).len(), 0);
 }
+
 #[test]
 fn test_range_inclusive_len() {
     assert_eq!((0..=10_u8).len(), 11);
@@ -249,6 +261,7 @@ fn test_range_inclusive_len() {
     assert_eq!((11..=10_u8).len(), 0);
     assert_eq!((100..=10_u8).len(), 0);
 }
+
 #[test]
 fn test_range_step() {
     #![allow(deprecated)]
@@ -271,6 +284,7 @@ fn test_range_step() {
     assert_eq!((i16::MIN..i16::MAX).step_by(i16::MAX as usize).size_hint(), (3, Some(3)));
     assert_eq!((isize::MIN..isize::MAX).step_by(1).size_hint(), (usize::MAX, Some(usize::MAX)));
 }
+
 #[test]
 fn test_range_inclusive_step() {
     assert_eq!((0..=50).step_by(10).collect::<Vec<_>>(), [0, 10, 20, 30, 40, 50]);
@@ -278,6 +292,7 @@ fn test_range_inclusive_step() {
     assert_eq!((200..=255u8).step_by(10).collect::<Vec<_>>(), [200, 210, 220, 230, 240, 250]);
     assert_eq!((250..=255u8).step_by(1).collect::<Vec<_>>(), [250, 251, 252, 253, 254, 255]);
 }
+
 #[test]
 fn test_range_last_max() {
     assert_eq!((0..20).last(), Some(19));
@@ -288,6 +303,7 @@ fn test_range_last_max() {
     assert_eq!((-20..0).max(), Some(-1));
     assert_eq!((5..5).max(), None);
 }
+
 #[test]
 fn test_range_inclusive_last_max() {
     assert_eq!((0..=20).last(), Some(20));
@@ -304,12 +320,14 @@ fn test_range_inclusive_last_max() {
     r.next();
     assert_eq!(r.max(), None);
 }
+
 #[test]
 fn test_range_min() {
     assert_eq!((0..20).min(), Some(0));
     assert_eq!((-20..0).min(), Some(-20));
     assert_eq!((5..5).min(), None);
 }
+
 #[test]
 fn test_range_inclusive_min() {
     assert_eq!((0..=20).min(), Some(0));
@@ -319,6 +337,7 @@ fn test_range_inclusive_min() {
     r.next();
     assert_eq!(r.min(), None);
 }
+
 #[test]
 fn test_range_inclusive_folds() {
     assert_eq!((1..=10).sum::<i32>(), 55);
@@ -356,6 +375,7 @@ fn test_range_inclusive_folds() {
     assert_eq!(it.try_rfold(0, |a, b| Some(a + b)), Some(0));
     assert!(it.is_empty());
 }
+
 #[test]
 fn test_range_size_hint() {
     assert_eq!((0..0usize).size_hint(), (0, Some(0)));
@@ -379,6 +399,7 @@ fn test_range_size_hint() {
     assert_eq!((imin..imax).size_hint(), (usize::MAX, Some(usize::MAX)));
     assert_eq!((imin..imax + 1).size_hint(), (usize::MAX, None));
 }
+
 #[test]
 fn test_range_inclusive_size_hint() {
     assert_eq!((1..=0usize).size_hint(), (0, Some(0)));
diff --git a/library/core/tests/iter/sources.rs b/library/core/tests/iter/sources.rs
index 38152e3711f..d0114ade6e4 100644
--- a/library/core/tests/iter/sources.rs
+++ b/library/core/tests/iter/sources.rs
@@ -9,6 +9,7 @@ fn test_repeat() {
     assert_eq!(it.next(), Some(42));
     assert_eq!(repeat(42).size_hint(), (usize::MAX, None));
 }
+
 #[test]
 fn test_repeat_take() {
     let mut it = repeat(42).take(3);
@@ -21,11 +22,13 @@ fn test_repeat_take() {
     assert_eq!(repeat(42).take(0).size_hint(), (0, Some(0)));
     assert_eq!(repeat(42).take(usize::MAX).size_hint(), (usize::MAX, Some(usize::MAX)));
 }
+
 #[test]
 fn test_repeat_take_collect() {
     let v: Vec<_> = repeat(42).take(3).collect();
     assert_eq!(v, vec![42, 42, 42]);
 }
+
 #[test]
 fn test_repeat_with() {
     #[derive(PartialEq, Debug)]
@@ -36,6 +39,7 @@ fn test_repeat_with() {
     assert_eq!(it.next(), Some(NotClone(42)));
     assert_eq!(repeat_with(|| NotClone(42)).size_hint(), (usize::MAX, None));
 }
+
 #[test]
 fn test_repeat_with_take() {
     let mut it = repeat_with(|| 42).take(3);
@@ -48,6 +52,7 @@ fn test_repeat_with_take() {
     assert_eq!(repeat_with(|| 42).take(0).size_hint(), (0, Some(0)));
     assert_eq!(repeat_with(|| 42).take(usize::MAX).size_hint(), (usize::MAX, Some(usize::MAX)));
 }
+
 #[test]
 fn test_repeat_with_take_collect() {
     let mut curr = 1;
@@ -60,6 +65,7 @@ fn test_repeat_with_take_collect() {
     .collect();
     assert_eq!(v, vec![1, 2, 4, 8, 16]);
 }
+
 #[test]
 fn test_successors() {
     let mut powers_of_10 = successors(Some(1_u16), |n| n.checked_mul(10));
@@ -70,12 +76,14 @@ fn test_successors() {
     assert_eq!(empty.next(), None);
     assert_eq!(empty.next(), None);
 }
+
 #[test]
 fn test_once() {
     let mut it = once(42);
     assert_eq!(it.next(), Some(42));
     assert_eq!(it.next(), None);
 }
+
 #[test]
 fn test_once_with() {
     let count = Cell::new(0);
@@ -92,6 +100,7 @@ fn test_once_with() {
     assert_eq!(it.next(), None);
     assert_eq!(count.get(), 1);
 }
+
 #[test]
 fn test_empty() {
     let mut it = empty::<i32>();
diff --git a/library/core/tests/iter/traits/accum.rs b/library/core/tests/iter/traits/accum.rs
index 9d7425449f7..f3eeb31fe58 100644
--- a/library/core/tests/iter/traits/accum.rs
+++ b/library/core/tests/iter/traits/accum.rs
@@ -7,6 +7,7 @@ fn test_iterator_sum() {
     assert_eq!(v.iter().cloned().sum::<i32>(), 55);
     assert_eq!(v[..0].iter().cloned().sum::<i32>(), 0);
 }
+
 #[test]
 fn test_iterator_sum_result() {
     let v: &[Result<i32, ()>] = &[Ok(1), Ok(2), Ok(3), Ok(4)];
@@ -31,6 +32,7 @@ fn test_iterator_sum_result() {
     let v: &[Result<i32, ()>] = &[Ok(1), Err(()), Ok(3), Ok(4)];
     assert_eq!(v.iter().cloned().sum::<S>(), S(Err(())));
 }
+
 #[test]
 fn test_iterator_sum_option() {
     let v: &[Option<i32>] = &[Some(1), Some(2), Some(3), Some(4)];
@@ -38,6 +40,7 @@ fn test_iterator_sum_option() {
     let v: &[Option<i32>] = &[Some(1), None, Some(3), Some(4)];
     assert_eq!(v.iter().cloned().sum::<Option<i32>>(), None);
 }
+
 #[test]
 fn test_iterator_product() {
     let v: &[i32] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
@@ -45,6 +48,7 @@ fn test_iterator_product() {
     assert_eq!(v[1..5].iter().cloned().product::<i32>(), 24);
     assert_eq!(v[..0].iter().cloned().product::<i32>(), 1);
 }
+
 #[test]
 fn test_iterator_product_result() {
     let v: &[Result<i32, ()>] = &[Ok(1), Ok(2), Ok(3), Ok(4)];
@@ -52,6 +56,7 @@ fn test_iterator_product_result() {
     let v: &[Result<i32, ()>] = &[Ok(1), Err(()), Ok(3), Ok(4)];
     assert_eq!(v.iter().cloned().product::<Result<i32, _>>(), Err(()));
 }
+
 #[test]
 fn test_iterator_product_option() {
     let v: &[Option<i32>] = &[Some(1), Some(2), Some(3), Some(4)];
diff --git a/library/core/tests/iter/traits/double_ended.rs b/library/core/tests/iter/traits/double_ended.rs
index 24059f8a3e4..24523883516 100644
--- a/library/core/tests/iter/traits/double_ended.rs
+++ b/library/core/tests/iter/traits/double_ended.rs
@@ -6,6 +6,7 @@ fn test_iterator_rev_nth_back() {
     }
     assert_eq!(v.iter().rev().nth_back(v.len()), None);
 }
+
 #[test]
 fn test_iterator_rev_nth() {
     let v: &[_] = &[0, 1, 2, 3, 4];
@@ -14,6 +15,7 @@ fn test_iterator_rev_nth() {
     }
     assert_eq!(v.iter().rev().nth(v.len()), None);
 }
+
 #[test]
 fn test_iterator_len() {
     let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
@@ -21,6 +23,7 @@ fn test_iterator_len() {
     assert_eq!(v[..10].iter().count(), 10);
     assert_eq!(v[..0].iter().count(), 0);
 }
+
 #[test]
 fn test_rev() {
     let xs = [2, 4, 6, 8, 10, 12, 14, 16];
@@ -29,6 +32,7 @@ fn test_rev() {
     it.next();
     assert!(it.rev().cloned().collect::<Vec<isize>>() == vec![16, 14, 12, 10, 8, 6]);
 }
+
 #[test]
 fn test_double_ended_map() {
     let xs = [1, 2, 3, 4, 5, 6];
@@ -41,6 +45,7 @@ fn test_double_ended_map() {
     assert_eq!(it.next_back(), Some(-4));
     assert_eq!(it.next(), None);
 }
+
 #[test]
 fn test_double_ended_enumerate() {
     let xs = [1, 2, 3, 4, 5, 6];
@@ -53,6 +58,7 @@ fn test_double_ended_enumerate() {
     assert_eq!(it.next_back(), Some((2, 3)));
     assert_eq!(it.next(), None);
 }
+
 #[test]
 fn test_double_ended_zip() {
     let xs = [1, 2, 3, 4, 5, 6];
@@ -66,6 +72,7 @@ fn test_double_ended_zip() {
     assert_eq!(it.next_back(), Some((3, 3)));
     assert_eq!(it.next(), None);
 }
+
 #[test]
 fn test_double_ended_filter() {
     let xs = [1, 2, 3, 4, 5, 6];
@@ -75,6 +82,7 @@ fn test_double_ended_filter() {
     assert_eq!(it.next().unwrap(), &2);
     assert_eq!(it.next_back(), None);
 }
+
 #[test]
 fn test_double_ended_filter_map() {
     let xs = [1, 2, 3, 4, 5, 6];
@@ -84,6 +92,7 @@ fn test_double_ended_filter_map() {
     assert_eq!(it.next().unwrap(), 4);
     assert_eq!(it.next_back(), None);
 }
+
 #[test]
 fn test_double_ended_chain() {
     let xs = [1, 2, 3, 4, 5];
@@ -127,6 +136,7 @@ fn test_double_ended_chain() {
     assert_eq!(CrazyIterator::new().chain(0..10).rev().last(), Some(0));
     assert!((0..10).chain(CrazyIterator::new()).rev().any(|i| i == 0));
 }
+
 #[test]
 fn test_double_ended_flat_map() {
     let u = [0, 1];
@@ -143,6 +153,7 @@ fn test_double_ended_flat_map() {
     assert_eq!(it.next(), None);
     assert_eq!(it.next_back(), None);
 }
+
 #[test]
 fn test_double_ended_flatten() {
     let u = [0, 1];
@@ -159,6 +170,7 @@ fn test_double_ended_flatten() {
     assert_eq!(it.next(), None);
     assert_eq!(it.next_back(), None);
 }
+
 #[test]
 fn test_double_ended_range() {
     assert_eq!((11..14).rev().collect::<Vec<_>>(), [13, 12, 11]);
@@ -171,6 +183,7 @@ fn test_double_ended_range() {
         panic!("unreachable");
     }
 }
+
 #[test]
 fn test_rev_try_folds() {
     let f = &|acc, x| i32::checked_add(2 * acc, x);
diff --git a/library/core/tests/iter/traits/iterator.rs b/library/core/tests/iter/traits/iterator.rs
index a2b418fbf80..d3799b55e40 100644
--- a/library/core/tests/iter/traits/iterator.rs
+++ b/library/core/tests/iter/traits/iterator.rs
@@ -68,6 +68,7 @@ fn test_lt() {
     assert!(c.iter().gt(b.iter()) == (c[0] > b[0]));
     assert!(c.iter().ge(b.iter()) == (c[0] >= b[0]));
 }
+
 #[test]
 fn test_cmp_by() {
     use core::cmp::Ordering;
@@ -83,6 +84,7 @@ fn test_cmp_by() {
     assert_eq!(xs().cmp_by(ys().rev(), f), Ordering::Less);
     assert_eq!(xs().cmp_by(ys().take(2), f), Ordering::Greater);
 }
+
 #[test]
 fn test_partial_cmp_by() {
     use core::cmp::Ordering;
@@ -105,6 +107,7 @@ fn test_partial_cmp_by() {
     assert_eq!(xs().partial_cmp_by(ys(), f), None);
     assert_eq!(ys().partial_cmp_by(xs(), f), Some(Ordering::Greater));
 }
+
 #[test]
 fn test_eq_by() {
     let f = |x: i32, y: i32| x * x == y;
@@ -120,6 +123,7 @@ fn test_eq_by() {
     assert!(!xs().eq_by(ys().take(3), f));
     assert!(xs().take(3).eq_by(ys().take(3), f));
 }
+
 #[test]
 fn test_iterator_nth() {
     let v: &[_] = &[0, 1, 2, 3, 4];
@@ -128,6 +132,7 @@ fn test_iterator_nth() {
     }
     assert_eq!(v.iter().nth(v.len()), None);
 }
+
 #[test]
 fn test_iterator_nth_back() {
     let v: &[_] = &[0, 1, 2, 3, 4];
@@ -136,6 +141,7 @@ fn test_iterator_nth_back() {
     }
     assert_eq!(v.iter().nth_back(v.len()), None);
 }
+
 #[test]
 fn test_iterator_advance_by() {
     let v: &[_] = &[0, 1, 2, 3, 4];
@@ -150,6 +156,7 @@ fn test_iterator_advance_by() {
     assert_eq!(v.iter().advance_by(v.len()), Ok(()));
     assert_eq!(v.iter().advance_by(100), Err(v.len()));
 }
+
 #[test]
 fn test_iterator_advance_back_by() {
     let v: &[_] = &[0, 1, 2, 3, 4];
@@ -164,6 +171,7 @@ fn test_iterator_advance_back_by() {
     assert_eq!(v.iter().advance_back_by(v.len()), Ok(()));
     assert_eq!(v.iter().advance_back_by(100), Err(v.len()));
 }
+
 #[test]
 fn test_iterator_rev_advance_back_by() {
     let v: &[_] = &[0, 1, 2, 3, 4];
@@ -178,12 +186,14 @@ fn test_iterator_rev_advance_back_by() {
     assert_eq!(v.iter().rev().advance_back_by(v.len()), Ok(()));
     assert_eq!(v.iter().rev().advance_back_by(100), Err(v.len()));
 }
+
 #[test]
 fn test_iterator_last() {
     let v: &[_] = &[0, 1, 2, 3, 4];
     assert_eq!(v.iter().last().unwrap(), &4);
     assert_eq!(v[..1].iter().last().unwrap(), &0);
 }
+
 #[test]
 fn test_iterator_max() {
     let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
@@ -192,6 +202,7 @@ fn test_iterator_max() {
     assert_eq!(v[..0].iter().cloned().max(), None);
     assert_eq!(v.iter().cloned().map(Mod3).max().map(|x| x.0), Some(8));
 }
+
 #[test]
 fn test_iterator_min() {
     let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
@@ -200,6 +211,7 @@ fn test_iterator_min() {
     assert_eq!(v[..0].iter().cloned().min(), None);
     assert_eq!(v.iter().cloned().map(Mod3).min().map(|x| x.0), Some(0));
 }
+
 #[test]
 fn test_iterator_size_hint() {
     let c = (0..).step_by(1);
@@ -239,6 +251,7 @@ fn test_iterator_size_hint() {
     assert_eq!(vi.clone().map(|&i| i + 1).size_hint(), (10, Some(10)));
     assert_eq!(vi.filter_map(|_| Some(0)).size_hint(), (0, Some(10)));
 }
+
 #[test]
 fn test_all() {
     let v: Box<[isize]> = Box::new([1, 2, 3, 4, 5]);
@@ -247,6 +260,7 @@ fn test_all() {
     assert!(!v.iter().all(|&x| x > 100));
     assert!(v[..0].iter().all(|_| panic!()));
 }
+
 #[test]
 fn test_any() {
     let v: Box<[isize]> = Box::new([1, 2, 3, 4, 5]);
@@ -255,6 +269,7 @@ fn test_any() {
     assert!(!v.iter().any(|&x| x > 100));
     assert!(!v[..0].iter().any(|_| panic!()));
 }
+
 #[test]
 fn test_find() {
     let v: &[isize] = &[1, 3, 9, 27, 103, 14, 11];
@@ -262,6 +277,7 @@ fn test_find() {
     assert_eq!(*v.iter().find(|&&x| x % 3 == 0).unwrap(), 3);
     assert!(v.iter().find(|&&x| x % 12 == 0).is_none());
 }
+
 #[test]
 fn test_try_find() {
     let xs: &[isize] = &[];
@@ -287,6 +303,7 @@ fn test_try_find() {
         Ok(false)
     }
 }
+
 #[test]
 fn test_try_find_api_usability() -> Result<(), Box<dyn std::error::Error>> {
     let a = ["1", "2"];
@@ -300,6 +317,7 @@ fn test_try_find_api_usability() -> Result<(), Box<dyn std::error::Error>> {
 
     Ok(())
 }
+
 #[test]
 fn test_position() {
     let v = &[1, 3, 9, 27, 103, 14, 11];
@@ -307,6 +325,7 @@ fn test_position() {
     assert_eq!(v.iter().position(|x| *x % 3 == 0).unwrap(), 1);
     assert!(v.iter().position(|x| *x % 12 == 0).is_none());
 }
+
 #[test]
 fn test_count() {
     let xs = &[1, 2, 2, 1, 5, 9, 0, 2];
@@ -314,26 +333,31 @@ fn test_count() {
     assert_eq!(xs.iter().filter(|x| **x == 5).count(), 1);
     assert_eq!(xs.iter().filter(|x| **x == 95).count(), 0);
 }
+
 #[test]
 fn test_max_by_key() {
     let xs: &[isize] = &[-3, 0, 1, 5, -10];
     assert_eq!(*xs.iter().max_by_key(|x| x.abs()).unwrap(), -10);
 }
+
 #[test]
 fn test_max_by() {
     let xs: &[isize] = &[-3, 0, 1, 5, -10];
     assert_eq!(*xs.iter().max_by(|x, y| x.abs().cmp(&y.abs())).unwrap(), -10);
 }
+
 #[test]
 fn test_min_by_key() {
     let xs: &[isize] = &[-3, 0, 1, 5, -10];
     assert_eq!(*xs.iter().min_by_key(|x| x.abs()).unwrap(), 0);
 }
+
 #[test]
 fn test_min_by() {
     let xs: &[isize] = &[-3, 0, 1, 5, -10];
     assert_eq!(*xs.iter().min_by(|x, y| x.abs().cmp(&y.abs())).unwrap(), 0);
 }
+
 #[test]
 fn test_by_ref() {
     let mut xs = 0..10;
@@ -342,6 +366,7 @@ fn test_by_ref() {
     assert_eq!(partial_sum, 10);
     assert_eq!(xs.next(), Some(5));
 }
+
 #[test]
 fn test_is_sorted() {
     assert!([1, 2, 2, 9].iter().is_sorted());
@@ -354,6 +379,7 @@ fn test_is_sorted() {
     assert!(!["c", "bb", "aaa"].iter().is_sorted());
     assert!(["c", "bb", "aaa"].iter().is_sorted_by_key(|s| s.len()));
 }
+
 #[test]
 fn test_partition() {
     fn check(xs: &mut [i32], ref p: impl Fn(&i32) -> bool, expected: usize) {
@@ -389,6 +415,7 @@ fn test_partition() {
     check(xs, |&x| x < 3, 3); // small
     check(xs, |&x| x > 6, 3); // large
 }
+
 #[test]
 fn test_iterator_rev_advance_by() {
     let v: &[_] = &[0, 1, 2, 3, 4];
diff --git a/library/core/tests/iter/traits/mod.rs b/library/core/tests/iter/traits/mod.rs
index edacebc4b51..a31b622addf 100644
--- a/library/core/tests/iter/traits/mod.rs
+++ b/library/core/tests/iter/traits/mod.rs
@@ -19,11 +19,13 @@ fn test_rposition() {
     assert_eq!(v.iter().rposition(f), Some(3));
     assert!(v.iter().rposition(g).is_none());
 }
+
 #[test]
 fn test_rev_rposition() {
     let v = [0, 0, 1, 1];
     assert_eq!(v.iter().rev().rposition(|&x| x == 1), Some(1));
 }
+
 #[test]
 #[should_panic]
 fn test_rposition_panic() {