diff --git a/test/mjsunit/harmony/proxies-json.js b/test/mjsunit/harmony/proxies-json.js
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+++ b/test/mjsunit/harmony/proxies-json.js
@@ -0,0 +1,178 @@
+// Copyright 2012 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Flags: --harmony-proxies
+
+function testStringify(expected, object) {
+  // Test fast case that bails out to slow case.
+  assertEquals(expected, JSON.stringify(object));
+  // Test slow case.
+  assertEquals(expected, JSON.stringify(object, undefined, 0));
+}
+
+// Test serializing a proxy, function proxy and objects that contain them.
+var handler1 = {
+  get: function(target, name) {
+    return name.toUpperCase();
+  },
+  enumerate: function(target) {
+    return ['a', 'b', 'c'];
+  },
+  getOwnPropertyDescriptor: function(target, name) {
+    return { enumerable: true };
+  }
+}
+
+var proxy1 = Proxy.create(handler1);
+testStringify('{"a":"A","b":"B","c":"C"}', proxy1);
+
+var proxy_fun = Proxy.createFunction(handler1, function() { return 1; });
+testStringify(undefined, proxy_fun);
+testStringify('[1,null]', [1, proxy_fun]);
+
+var parent1a = { b: proxy1 };
+testStringify('{"b":{"a":"A","b":"B","c":"C"}}', parent1a);
+
+var parent1b = { a: 123, b: proxy1, c: true };
+testStringify('{"a":123,"b":{"a":"A","b":"B","c":"C"},"c":true}', parent1b);
+
+var parent1c = [123, proxy1, true];
+testStringify('[123,{"a":"A","b":"B","c":"C"},true]', parent1c);
+
+// Proxy with side effect.
+var handler2 = {
+  get: function(target, name) {
+    delete parent2.c;
+    return name.toUpperCase();
+  },
+  enumerate: function(target) {
+    return ['a', 'b', 'c'];
+  },
+  getOwnPropertyDescriptor: function(target, name) {
+    return { enumerable: true };
+  }
+}
+
+var proxy2 = Proxy.create(handler2);
+var parent2 = { a: "delete", b: proxy2, c: "remove" };
+var expected2 = '{"a":"delete","b":{"a":"A","b":"B","c":"C"}}';
+assertEquals(expected2, JSON.stringify(parent2));
+parent2.c = "remove";  // Revert side effect.
+assertEquals(expected2, JSON.stringify(parent2, undefined, 0));
+
+// Proxy with a get function that uses the first argument.
+var handler3 = {
+  get: function(target, name) {
+    if (name == 'valueOf') return function() { return "proxy" };
+    return name + "(" + target + ")";
+  },
+  enumerate: function(target) {
+    return ['a', 'b', 'c'];
+  },
+  getOwnPropertyDescriptor: function(target, name) {
+    return { enumerable: true };
+  }
+}
+
+var proxy3 = Proxy.create(handler3);
+var parent3 = { x: 123, y: proxy3 }
+testStringify('{"x":123,"y":{"a":"a(proxy)","b":"b(proxy)","c":"c(proxy)"}}',
+              parent3);
+
+// Empty proxy.
+var handler4 = {
+  get: function(target, name) {
+    return 0;
+  },
+  enumerate: function(target) {
+    return [];
+  },
+  getOwnPropertyDescriptor: function(target, name) {
+    return { enumerable: false };
+  }
+}
+
+var proxy4 = Proxy.create(handler4);
+testStringify('{}', proxy4);
+testStringify('{"a":{}}', { a: proxy4 });
+
+// Proxy that provides a toJSON function that uses this.
+var handler5 = {
+  get: function(target, name) {
+    if (name == 'z') return 97000;
+    return function(key) { return key.charCodeAt(0) + this.z; };
+  },
+  enumerate: function(target) {
+    return ['toJSON', 'z'];
+  },
+  getOwnPropertyDescriptor: function(target, name) {
+    return { enumerable: true };
+  }
+}
+
+var proxy5 = Proxy.create(handler5);
+testStringify('{"a":97097}', { a: proxy5 });
+
+// Proxy that provides a toJSON function that returns undefined.
+var handler6 = {
+  get: function(target, name) {
+    return function(key) { return undefined; };
+  },
+  enumerate: function(target) {
+    return ['toJSON'];
+  },
+  getOwnPropertyDescriptor: function(target, name) {
+    return { enumerable: true };
+  }
+}
+
+var proxy6 = Proxy.create(handler6);
+testStringify('[1,null,true]', [1, proxy6, true]);
+testStringify('{"a":1,"c":true}', {a: 1, b: proxy6, c: true});
+
+// Object containing a proxy that changes the parent's properties.
+var handler7 = {
+  get: function(target, name) {
+    delete parent7.a;
+    delete parent7.c;
+    parent7.e = "5";
+    return name.toUpperCase();
+  },
+  enumerate: function(target) {
+    return ['a', 'b', 'c'];
+  },
+  getOwnPropertyDescriptor: function(target, name) {
+    return { enumerable: true };
+  }
+}
+
+var proxy7 = Proxy.create(handler7);
+var parent7 = { a: "1", b: proxy7, c: "3", d: "4" };
+assertEquals('{"a":"1","b":{"a":"A","b":"B","c":"C"},"d":"4"}',
+             JSON.stringify(parent7));
+assertEquals('{"b":{"a":"A","b":"B","c":"C"},"d":"4","e":"5"}',
+             JSON.stringify(parent7));