Add basic unit test for std::slice::Iter::as_slice.

src/libcollectionstest/slice.rs

@@ -645,6 +645,15 @@ fn test_iter_size_hints() {
     assert_eq!(xs.iter_mut().size_hint(), (5, Some(5)));
 }
 
+#[test]
+fn test_iter_as_slice() {
+    let xs = [1, 2, 5, 10, 11];
+    let mut iter = xs.iter();
+    assert_eq!(iter.as_slice(), &[1, 2, 5, 10, 11]);
+    iter.next();
+    assert_eq!(iter.as_slice(), &[2, 5, 10, 11]);
+}
+
 #[test]
 fn test_iter_as_ref() {
     let xs = [1, 2, 5, 10, 11];