Add module namespace object test.

Author: woess

graal-js/src/com.oracle.truffle.js.test/js/module/module_namespace_object.mjs

@@ -0,0 +1,31 @@
+/*
+ * Copyright (c) 2022, 2022, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * Licensed under the Universal Permissive License v 1.0 as shown at http://oss.oracle.com/licenses/upl.
+ */
+
+load('../assert.js');
+
+import * as ns from './module_namespace_object.mjs';
+
+assertThrows(() => ns.answer, ReferenceError);
+
+assertThrows(() => Object.seal(ns), ReferenceError);
+assertThrows(() => Object.freeze(ns), ReferenceError);
+assertThrows(() => Object.isSealed(ns), ReferenceError);
+assertThrows(() => Object.isFrozen(ns), ReferenceError);
+
+export const answer = 42;
+
+assertSame(42, ns.answer);
+
+Object.seal(ns);
+assertThrows(() => Object.freeze(ns), TypeError);
+assertTrue(Object.isSealed(ns));
+assertFalse(Object.isFrozen(ns));
+
+let o = Object.create(ns);
+assertTrue('answer' in o);
+assertSame(42, o.answer);
+assertSame('Module', o[Symbol.toStringTag]);