1 files changed, 91 insertions, 0 deletions
diff --git a/library/core/tests/iter/traits/double_ended.rs b/library/core/tests/iter/traits/double_ended.rs
new file mode 100644
index 000000000..00ef4a6e6
--- /dev/null
+++ b/library/core/tests/iter/traits/double_ended.rs
@@ -0,0 +1,91 @@
+//! Note
+//! ----
+//! You're probably viewing this file because you're adding a test (or you might
+//! just be browsing, in that case, hey there!).
+//!
+//! If you've made a test that happens to use one of DoubleEnded's methods, but
+//! it tests another adapter or trait, you should *add it to the adapter or
+//! trait's test file*.
+//!
+//! Some examples would be `adapters::cloned::test_cloned_try_folds` or
+//! `adapters::flat_map::test_double_ended_flat_map`, which use `try_fold` and
+//! `next_back`, but test their own adapter.
+
+#[test]
+fn test_iterator_rev_nth_back() {
+    let v: &[_] = &[0, 1, 2, 3, 4];
+    for i in 0..v.len() {
+        assert_eq!(v.iter().rev().nth_back(i).unwrap(), &v[i]);
+    }
+    assert_eq!(v.iter().rev().nth_back(v.len()), None);
+}
+
+#[test]
+fn test_iterator_rev_nth() {
+    let v: &[_] = &[0, 1, 2, 3, 4];
+    for i in 0..v.len() {
+        assert_eq!(v.iter().rev().nth(i).unwrap(), &v[v.len() - 1 - i]);
+    }
+    assert_eq!(v.iter().rev().nth(v.len()), None);
+}
+
+#[test]
+fn test_rev() {
+    let xs = [2, 4, 6, 8, 10, 12, 14, 16];
+    let mut it = xs.iter();
+    it.next();
+    it.next();
+    assert!(it.rev().cloned().collect::<Vec<isize>>() == vec![16, 14, 12, 10, 8, 6]);
+}
+
+#[test]
+fn test_rev_try_folds() {
+    let f = &|acc, x| i32::checked_add(2 * acc, x);
+    assert_eq!((1..10).rev().try_fold(7, f), (1..10).try_rfold(7, f));
+    assert_eq!((1..10).rev().try_rfold(7, f), (1..10).try_fold(7, f));
+
+    let a = [10, 20, 30, 40, 100, 60, 70, 80, 90];
+    let mut iter = a.iter().rev();
+    assert_eq!(iter.try_fold(0_i8, |acc, &x| acc.checked_add(x)), None);
+    assert_eq!(iter.next(), Some(&70));
+    let mut iter = a.iter().rev();
+    assert_eq!(iter.try_rfold(0_i8, |acc, &x| acc.checked_add(x)), None);
+    assert_eq!(iter.next_back(), Some(&60));
+}
+
+#[test]
+fn test_rposition() {
+    fn f(xy: &(isize, char)) -> bool {
+        let (_x, y) = *xy;
+        y == 'b'
+    }
+    fn g(xy: &(isize, char)) -> bool {
+        let (_x, y) = *xy;
+        y == 'd'
+    }
+    let v = [(0, 'a'), (1, 'b'), (2, 'c'), (3, 'b')];
+
+    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() {
+    let u = (Box::new(0), Box::new(0));
+    let v: [(Box<_>, Box<_>); 4] = [u.clone(), u.clone(), u.clone(), u];
+    let mut i = 0;
+    v.iter().rposition(|_elt| {
+        if i == 2 {
+            panic!()
+        }
+        i += 1;
+        false
+    });
+}