1 files changed, 57 insertions, 0 deletions
diff --git a/js/src/tests/test262/built-ins/Array/prototype/copyWithin/coerced-values-start-change-start.js b/js/src/tests/test262/built-ins/Array/prototype/copyWithin/coerced-values-start-change-start.js
new file mode 100644
index 0000000000..0692e72247
--- /dev/null
+++ b/js/src/tests/test262/built-ins/Array/prototype/copyWithin/coerced-values-start-change-start.js
@@ -0,0 +1,57 @@
+// Copyright (C) 2019 Google. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-array.prototype.copywithin
+description: >
+  SECURITY: start argument is coerced to an integer value
+  and side effects change the length of the array so that
+  the start is out of bounds
+info: |
+  22.1.3.3 Array.prototype.copyWithin (target, start [ , end ] )
+
+  ...
+  8. Let relativeStart be ToInteger(start).
+  ...
+includes: [compareArray.js]
+---*/
+
+
+// make a long integer Array
+function longDenseArray(){
+    var a = [0];
+    for(var i = 0; i < 1024; i++){
+        a[i] = i;
+    }
+    return a;
+}
+
+function shorten(){
+    currArray.length = 20;
+    return 1000;
+}
+
+var array = [];
+array.length = 20;
+
+var currArray = longDenseArray();
+
+assert.compareArray(
+  currArray.copyWithin(0, {valueOf: shorten}), array,
+  'currArray.copyWithin(0, {valueOf: shorten}) returns array'
+);
+
+currArray = longDenseArray();
+Object.setPrototypeOf(currArray, longDenseArray());
+
+var array2 = longDenseArray();
+array2.length = 20;
+for(var i = 0; i < 24; i++){
+    array2[i] = Object.getPrototypeOf(currArray)[i+1000];
+}
+
+assert.compareArray(
+  currArray.copyWithin(0, {valueOf: shorten}), array2,
+  'currArray.copyWithin(0, {valueOf: shorten}) returns array2'
+);
+
+reportCompare(0, 0);