The Tor Browser / file revision

 /*

  * Any copyright is dedicated to the Public Domain.

  * http://creativecommons.org/licenses/publicdomain/

  */

 /* Create a prototype object with a setter property. */

 var protoSetterCount;

 var proto = ({ set x(v) { protoSetterCount++; } });

 /* Put a watchpoint on that setter. */

 var protoWatchCount;

 proto.watch('x', function() { protoWatchCount++; });

 /* Make an object with the above as its prototype. */

 function C() { }

 C.prototype = proto;

 var o = new C();

 /*

  * Set a watchpoint on the property in the inheriting object. We have

  * defined this to mean "duplicate the property, setter and all, in the

  * inheriting object." I don't think debugging observation mechanisms

  * should mutate the program being run, but that's what we've got.

  */

 var oWatchCount;

 o.watch('x', function() { oWatchCount++; });

 /*

  * Assign to the property. This should trip the watchpoint on the inheriting object and

  * the setter.

  */

 protoSetterCount = protoWatchCount = oWatchCount = 0;

 o.x = 1;

 assertEq(protoWatchCount, 0);

 assertEq(oWatchCount, 1);

 assertEq(protoSetterCount, 1);

 reportCompare(true, true);