Add test for byteOffset coverage in %typedarray%.prototype.copywithin

test/built-ins/TypedArray/prototype/copyWithin/byteoffset.js

@@ -0,0 +1,33 @@
+// Copyright (C) 2021 Chengzhong Wu. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-%typedarray%.prototype.copywithin
+description: >
+  copyWithin should respect typedarray's byteOffset
+info: |
+  22.2.3.5%TypedArray%.prototype.copyWithin ( target, start [ , end ] )
+  ...
+  17. If count > 0, then
+    e. Let elementSize be the Element Size value specified in Table 72 for typedArrayName.
+    f. Let byteOffset be O.[[ByteOffset]].
+    g. Let toByteIndex be to × elementSize + byteOffset.
+    h. Let fromByteIndex be from × elementSize + byteOffset.
+  ...
+includes: [testTypedArray.js, compareArray.js]
+features: [TypedArray]
+---*/
+
+testWithTypedArrayConstructors(function(TA) {
+  var ta = new TA([0, 1, 2, 3]);
+  assert.compareArray(
+    new TA(ta.buffer, TA.BYTES_PER_ELEMENT).copyWithin(2, 0),
+    [1, 2, 1],
+    'copyWithin should respect typedarray\'s byteOffset'
+  );
+
+  assert.compareArray(
+    ta,
+    [0, 1, 2, 1],
+    'underlying arraybuffer should have been updated'
+  );
+});