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diff --git a/js/src/tests/non262/Array/length-truncate-with-indexed.js b/js/src/tests/non262/Array/length-truncate-with-indexed.js
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@@ -0,0 +1,101 @@
+/*
+ * Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/licenses/publicdomain/
+ * Contributor:
+ *   Jeff Walden <jwalden+code@mit.edu>
+ */
+
+//-----------------------------------------------------------------------------
+var BUGNUMBER = 858381;
+var summary =
+  "Array length setting/truncating with non-dense, indexed elements";
+
+print(BUGNUMBER + ": " + summary);
+
+/**************
+ * BEGIN TEST *
+ **************/
+
+function testTruncateDenseAndSparse()
+{
+  var arr;
+
+  // initialized length 16, capacity same
+  arr = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15];
+
+  // plus a sparse element
+  arr[987654321] = 987654321;
+
+  // lop off the sparse element and half the dense elements, shrink capacity
+  arr.length = 8;
+
+  assertEq(987654321 in arr, false);
+  assertEq(arr[987654321], undefined);
+  assertEq(arr.length, 8);
+}
+testTruncateDenseAndSparse();
+
+function testTruncateSparse()
+{
+  // initialized length 8, capacity same
+  var arr = [0, 1, 2, 3, 4, 5, 6, 7];
+
+  // plus a sparse element
+  arr[987654321] = 987654321;
+
+  // lop off the sparse element, leave initialized length/capacity unchanged
+  arr.length = 8;
+
+  assertEq(987654321 in arr, false);
+  assertEq(arr[987654321], undefined);
+  assertEq(arr.length, 8);
+}
+testTruncateSparse();
+
+function testTruncateDenseAndSparseShrinkCapacity()
+{
+  // initialized length 11, capacity...somewhat larger, likely 16
+  var arr = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
+
+  // plus a sparse element
+  arr[987654321] = 987654321;
+
+  // lop off the sparse element, reduce initialized length, reduce capacity
+  arr.length = 8;
+
+  assertEq(987654321 in arr, false);
+  assertEq(arr[987654321], undefined);
+  assertEq(arr.length, 8);
+}
+testTruncateDenseAndSparseShrinkCapacity();
+
+function testTruncateSparseShrinkCapacity()
+{
+  // initialized length 8, capacity same
+  var arr = [0, 1, 2, 3, 4, 5, 6, 7];
+
+  // capacity expands to accommodate, initialized length remains same (not equal
+  // to capacity or length)
+  arr[15] = 15;
+
+  // now no elements past initialized length
+  delete arr[15];
+
+  // ...except a sparse element
+  arr[987654321] = 987654321;
+
+  // trims sparse element, doesn't change initialized length, shrinks capacity
+  arr.length = 8;
+
+  assertEq(987654321 in arr, false);
+  assertEq(arr[987654321], undefined);
+  assertEq(arr.length, 8);
+}
+testTruncateSparseShrinkCapacity();
+
+/******************************************************************************/
+
+if (typeof reportCompare === "function")
+  reportCompare(true, true);
+
+print("Tests complete");