Add tests for %TypedArray%.prototype.sort stability

tc39/ecma262#1433

test/built-ins/TypedArray/stability.js

@@ -0,0 +1,44 @@
+// Copyright (C) 2019 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-%typedarray%.prototype.sort
+description: Stability of %TypedArray%.prototype.sort.
+info: |
+  https://github.com/tc39/ecma262/pull/1433
+includes: [testTypedArray.js, compareArray.js]
+features: [TypedArray]
+---*/
+
+// Treat 0..3, 4..7, etc. as equal.
+const compare = (a, b) => (a / 4 | 0) - (b / 4 | 0);
+
+testWithTypedArrayConstructors((TA) => {
+  // Create an array of the form `[0, 1, …, 126, 127]`.
+  const array = Array.from({ length: 128 }, (_, i) => i);
+
+  const typedArray1 = new TA(array);
+  assert(compareArray(
+    typedArray1.sort(compare),
+    array
+  ), 'pre-sorted');
+
+  // Reverse `array` in-place so it becomes `[127, 126, …, 1, 0]`.
+  array.reverse();
+
+  const typedArray2 = new TA(array);
+  assert(compareArray(
+    typedArray2.sort(compare),
+    [
+        3,   2,   1,   0,   7,   6,   5,   4,  11,  10,   9,   8,  15,
+       14,  13,  12,  19,  18,  17,  16,  23,  22,  21,  20,  27,  26,
+       25,  24,  31,  30,  29,  28,  35,  34,  33,  32,  39,  38,  37,
+       36,  43,  42,  41,  40 , 47,  46,  45,  44,  51,  50,  49,  48,
+       55,  54,  53,  52,  59,  58,  57,  56,  63,  62,  61,  60,  67,
+       66,  65,  64 , 71,  70,  69,  68,  75,  74,  73,  72,  79,  78,
+       77,  76,  83,  82,  81,  80,  87,  86,  85,  84,  91,  90,  89,
+       88,  95 , 94,  93,  92,  99,  98,  97,  96, 103, 102, 101, 100,
+      107, 106, 105, 104, 111, 110, 109, 108, 115, 114, 113, 112, 119,
+      118, 117, 116, 123, 122, 121, 120, 127, 126, 125, 124,
+    ]
+  ), 'unsorted');
+});