Add a test for the fix of issue 16589

Author: nham

src/libcoretest/lib.rs

@@ -29,4 +29,5 @@ mod ptr;
 mod raw;
 mod result;
 mod slice;
+mod str;
 mod tuple;

src/libcoretest/str.rs

@@ -0,0 +1,14 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#[test]
+fn strslice_issue_16589() {
+    assert!("bananas".contains("nana"));
+}