Add Object.keys test

test/built-ins/Object/keys/order-after-define-property.js

@@ -0,0 +1,48 @@
+// Copyright (C) 2020 Alexey Shvayka. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-object.keys
+description: >
+  Property names are returned in ascending chronological order of creation
+  that is unaffected by [[DefineOwnProperty]].
+info: |
+  Object.keys ( O )
+
+  [...]
+  2. Let nameList be ? EnumerableOwnPropertyNames(obj, key).
+  3. Return CreateArrayFromList(nameList).
+
+  EnumerableOwnPropertyNames ( O, kind )
+
+  [...]
+  2. Let ownKeys be ? O.[[OwnPropertyKeys]]().
+  [...]
+
+  OrdinaryOwnPropertyKeys ( O )
+
+  [...]
+  3. For each own property key P of O that is a String but is not an array index,
+  in ascending chronological order of property creation, do
+    a. Add P as the last element of keys.
+  [...]
+  5. Return keys.
+features: [Proxy]
+includes: [compareArray.js]
+---*/
+
+var obj = {};
+Object.defineProperty(obj, "a", {
+  get: function() {},
+  set: function(_value) {},
+  enumerable: true,
+  configurable: true,
+});
+obj.b = 2;
+Object.defineProperty(obj, "a", {value: 1});
+assert.compareArray(Object.keys(obj), ["a", "b"]);
+
+var fn = () => {};
+fn.a = 1;
+Object.defineProperty(fn, "length", {enumerable: true});
+assert.compareArray(Object.keys(fn), ["length", "a"]);