1 files changed, 39 insertions, 0 deletions
diff --git a/js/src/tests/test262/built-ins/Atomics/add/expected-return-value.js b/js/src/tests/test262/built-ins/Atomics/add/expected-return-value.js
new file mode 100644
index 0000000000..3498caa9a7
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+++ b/js/src/tests/test262/built-ins/Atomics/add/expected-return-value.js
@@ -0,0 +1,39 @@
+// |reftest| skip-if(!this.hasOwnProperty('Atomics')||!this.hasOwnProperty('SharedArrayBuffer')||(this.hasOwnProperty('getBuildConfiguration')&&getBuildConfiguration('arm64-simulator'))) -- Atomics,SharedArrayBuffer is not enabled unconditionally, ARM64 Simulator cannot emulate atomics
+// Copyright (C) 2018 Rick Waldron.  All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-atomics.add
+description: >
+  Atomics.add returns the value that existed at the
+  index prior to the operation.
+info: |
+  Atomics.add( typedArray, index, value )
+
+  1. Return ? AtomicReadModifyWrite(typedArray, index, value, add).
+
+  AtomicReadModifyWrite( typedArray, index, value, op )
+
+  ...
+  9. Return GetModifySetValueInBuffer(buffer, indexedPosition,
+                                      elementType, v, op).
+
+
+  GetModifySetValueInBuffer( arrayBuffer,
+    byteIndex, type, value, op [ , isLittleEndian ] )
+
+  ...
+  16. Return RawBytesToNumber(type, rawBytesRead, isLittleEndian).
+
+features: [Atomics, SharedArrayBuffer, TypedArray]
+---*/
+
+const i32a = new Int32Array(
+  new SharedArrayBuffer(Int32Array.BYTES_PER_ELEMENT * 4)
+);
+const newValue = 0b00000001000000001000000010000001;
+
+assert.sameValue(Atomics.add(i32a, 0, newValue), 0, 'Atomics.add(i32a, 0, newValue) returns 0');
+assert.sameValue(i32a[0], newValue, 'The value of i32a[0] equals the value of `newValue` (0b00000001000000001000000010000001)');
+
+reportCompare(0, 0);