Added test for issue 703 (rust-lang#879)

Author: zhassan-aws

tests/kani/Vectors/push_u8.rs

@@ -0,0 +1,14 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+// Check that Kani doesn't get stuck on a program involving a Vector of u8
+// https://github.com/model-checking/kani/issues/703
+
+fn main() {
+    let mut v: Vec<u8> = Vec::new();
+    v.push(5);
+    v.push(255);
+    assert_eq!(v.len(), 2);
+    assert_eq!(v[0], 5);
+    assert_eq!(v[1], 255);
+}