Impl Extend for BytesMut

tests/test_bytes.rs

@@ -290,6 +290,13 @@ fn inline_storage() {
     assert_eq!(*bytes, zero[0..inline_cap()]);
 }
 
+#[test]
+fn extend() {
+    let mut bytes = BytesMut::with_capacity(0);
+    bytes.extend(LONG);
+    assert_eq!(*bytes, LONG[..]);
+}
+
 #[test]
 fn stress() {
     // Tests promoting a buffer from a vec -> shared in a concurrent situation