1 files changed, 42 insertions, 0 deletions
diff --git a/library/core/tests/iter/adapters/flatten.rs b/library/core/tests/iter/adapters/flatten.rs
index f8ab8c9d4..690fd0c21 100644
--- a/library/core/tests/iter/adapters/flatten.rs
+++ b/library/core/tests/iter/adapters/flatten.rs
@@ -168,3 +168,45 @@ fn test_trusted_len_flatten() {
     assert_trusted_len(&iter);
     assert_eq!(iter.size_hint(), (20, Some(20)));
 }
+
+#[test]
+fn test_flatten_count() {
+    let mut it = once(0..10).chain(once(10..30)).chain(once(30..40)).flatten();
+
+    assert_eq!(it.clone().count(), 40);
+    it.advance_by(5).unwrap();
+    assert_eq!(it.clone().count(), 35);
+    it.advance_back_by(5).unwrap();
+    assert_eq!(it.clone().count(), 30);
+    it.advance_by(10).unwrap();
+    assert_eq!(it.clone().count(), 20);
+    it.advance_back_by(8).unwrap();
+    assert_eq!(it.clone().count(), 12);
+    it.advance_by(4).unwrap();
+    assert_eq!(it.clone().count(), 8);
+    it.advance_back_by(5).unwrap();
+    assert_eq!(it.clone().count(), 3);
+    it.advance_by(3).unwrap();
+    assert_eq!(it.clone().count(), 0);
+}
+
+#[test]
+fn test_flatten_last() {
+    let mut it = once(0..10).chain(once(10..30)).chain(once(30..40)).flatten();
+
+    assert_eq!(it.clone().last(), Some(39));
+    it.advance_by(5).unwrap(); // 5..40
+    assert_eq!(it.clone().last(), Some(39));
+    it.advance_back_by(5).unwrap(); // 5..35
+    assert_eq!(it.clone().last(), Some(34));
+    it.advance_by(10).unwrap(); // 15..35
+    assert_eq!(it.clone().last(), Some(34));
+    it.advance_back_by(8).unwrap(); // 15..27
+    assert_eq!(it.clone().last(), Some(26));
+    it.advance_by(4).unwrap(); // 19..27
+    assert_eq!(it.clone().last(), Some(26));
+    it.advance_back_by(5).unwrap(); // 19..22
+    assert_eq!(it.clone().last(), Some(21));
+    it.advance_by(3).unwrap(); // 22..22
+    assert_eq!(it.clone().last(), None);
+}