test/LetConst/seal.js

//-------------------------------------------------------------------------------------------------------
// Copyright (C) Microsoft. All rights reserved.
// Licensed under the MIT license. See LICENSE.txt file in the project root for full license information.
//-------------------------------------------------------------------------------------------------------

let x = "let x";

Object.preventExtensions(this);
Object.getOwnPropertyNames(this).forEach(function (p) {
    Object.defineProperty(this, p, { configurable: false });
});

if (Object.isSealed(this)) {
   WScript.Echo("PASS");
}