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 // Define a test object

 var test = {x:1,y:2};

 // Put the object into dictionary mode by deleting 

 // a property that was not the last one added.

 delete test.x;

 // Define a an accessor property with a setter that 

 // itself calls Object.defineProperty

 Object.defineProperty(test, "foo", {

     get: function() { return 1; },

     set: function(v) { 

         Object.defineProperty(this, "foo", { value: v });

         // Prints the correct object descriptor

         assertEq(this.foo, 33);

     },

     configurable: true

 });

 // Add another property, so generateOwnShape does not replace the foo property.

 test.other = 0;

 // This line prints 1, as expected

 assertEq(test.foo, 1);

 // Now set the property.  This calls the setter method above.

 // And the setter method prints the expected value and property descriptor.

 test.foo = 33;

 // Finally read the newly set value.

 assertEq(test.foo, 33);

 // Check that enumeration order is correct.

 var arr = [];

 for (var x in test) arr.push(x);

 assertEq("" + arr, "y,other");