The Tor Browser / file revision

 // This was the actual bug

 assertRaises(StopIteration, function() {

     Iterator.prototype.next();

     Iterator.prototype.next();

 });

 // The error should have triggered here, but was masked by a latent bug

 assertRaises(StopIteration, function() {

     Iterator.prototype.next();

 });

 // Found by fuzzing

 assertRaises(StopIteration, function() {

     (new Iterator({})).__proto__.next();

 });

 function assertRaises(exc, callback) {

     var caught = false;

     try {

         callback();

     } catch (e) {

         assertEq(e instanceof StopIteration, true);

         caught = true;

     }

     assertEq(caught, true);

 }