Add Array#concat non-writable property tests

test/built-ins/Array/prototype/concat/create-species-with-non-writable-property-spreadable.js

@@ -0,0 +1,47 @@
+// Copyright (C) 2020 Alexey Shvayka. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-array.prototype.concat
+description: >
+  Non-writable properties are overwritten by CreateDataProperty.
+  (result object's "0" is non-writable, argument is spreadable)
+info: |
+  Array.prototype.concat ( ...arguments )
+
+  [...]
+  5. Repeat, while items is not empty
+    [...]
+    c. If spreadable is true, then
+      [...]
+      iv. Repeat, while k < len
+        [...]
+        3. If exists is true, then
+          [...]
+          b. Perform ? CreateDataPropertyOrThrow(A, ! ToString(n), subElement).
+    [...]
+features: [Symbol.species]
+includes: [propertyHelper.js]
+---*/
+
+var A = function(_length) {
+  Object.defineProperty(this, "0", {
+    value: 1,
+    writable: false,
+    enumerable: false,
+    configurable: true,
+  });
+};
+
+var arr = [];
+arr.constructor = {};
+arr.constructor[Symbol.species] = A;
+
+var res = arr.concat([2]);
+
+verifyProperty(res, "0", {
+  value: 2,
+  writable: true,
+  enumerable: true,
+  configurable: true,
+});

test/built-ins/Array/prototype/concat/create-species-with-non-writable-property.js

@@ -0,0 +1,47 @@
+// Copyright (C) 2020 Alexey Shvayka. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-array.prototype.concat
+description: >
+  Non-writable properties are overwritten by CreateDataProperty.
+  (result object's "0" is non-writable, argument is not spreadable)
+info: |
+  Array.prototype.concat ( ...arguments )
+
+  [...]
+  5. Repeat, while items is not empty
+    [...]
+    c. If spreadable is true, then
+      [...]
+      iv. Repeat, while k < len
+        [...]
+        3. If exists is true, then
+          [...]
+          b. Perform ? CreateDataPropertyOrThrow(A, ! ToString(n), subElement).
+    [...]
+features: [Symbol.species]
+includes: [propertyHelper.js]
+---*/
+
+var A = function(_length) {
+  Object.defineProperty(this, "0", {
+    value: 1,
+    writable: false,
+    enumerable: false,
+    configurable: true,
+  });
+};
+
+var arr = [];
+arr.constructor = {};
+arr.constructor[Symbol.species] = A;
+
+var res = arr.concat(2);
+
+verifyProperty(res, "0", {
+  value: 2,
+  writable: true,
+  enumerable: true,
+  configurable: true,
+});