1 files changed, 75 insertions, 0 deletions
diff --git a/js/src/tests/non262/PrivateName/modify-non-extensible.js b/js/src/tests/non262/PrivateName/modify-non-extensible.js
new file mode 100644
index 0000000000..7e9af31895
--- /dev/null
+++ b/js/src/tests/non262/PrivateName/modify-non-extensible.js
@@ -0,0 +1,75 @@
+// |reftest| 
+
+// Returns the argument in the constructor to allow stamping private fields into
+// arbitrary objects.
+class OverrideBase {
+  constructor(o) {
+    return o;
+  }
+};
+
+class A extends OverrideBase {
+  #a = 1;
+  g() {
+    return this.#a
+  }
+
+  static gs(o) {
+    return o.#a;
+  }
+  static inca(obj) {
+    obj.#a++;
+  }
+}
+
+var obj = {};
+Object.seal(obj);
+new A(obj);  // Add #a to obj, but not g.
+assertEq('g' in obj, false);
+assertEq(A.gs(obj), 1);
+A.inca(obj);
+assertEq(A.gs(obj), 2);
+
+// Ensure that the object remains non-extensible
+obj.h = 'hi'
+assertEq('h' in obj, false);
+
+
+Object.freeze(obj);
+A.inca(obj);  // Despite being frozen, private names are modifiable.
+assertEq(A.gs(obj), 3);
+assertEq(Object.isFrozen(obj), true);
+
+var proxy = new Proxy({}, {});
+assertEq(Object.isFrozen(proxy), false);
+
+new A(proxy);
+assertEq(A.gs(proxy), 1);
+
+// Note: this doesn't exercise the non-native object
+// path in TestIntegrityLevel like you might expect.
+//
+// For that see below.
+Object.freeze(proxy);
+assertEq(Object.isFrozen(proxy), true);
+
+A.inca(proxy);
+assertEq(A.gs(proxy), 2)
+
+var target = { a: 10 };
+Object.freeze(target);
+new A(target);
+assertEq(Object.isFrozen(target), true)
+
+var getOwnKeys = [];
+var proxy = new Proxy(target, {
+  getOwnPropertyDescriptor: function (target, key) {
+    getOwnKeys.push(key);
+    return Reflect.getOwnPropertyDescriptor(target, key);
+  },
+});
+
+Object.isFrozen(proxy);
+assertEq(getOwnKeys.length, 1);
+
+if (typeof reportCompare === 'function') reportCompare(0, 0);