text: // See SERVER-9448
  // Test argument and receiver (aka 'this') objects and their children can be mutated
  // in Map, Reduce and Finalize functions
  
  var collection = db.mrMutableReceiver;
  collection.drop();
  collection.insert({a:1});
  
  var map = function() {
      // set property on receiver
      this.feed = {beef:1};
  
      // modify property on receiever
      this.a = {cake:1};
      emit(this._id, this.feed);
      emit(this._id, this.a);
  };
  
  var reduce = function(key, values) {
      // set property on receiver
      this.feed = {beat:1};
  
      // set property on key arg
      key.fed = {mochi:1};
  
      // push properties onto values array arg
      values.push(this.feed);
      values.push(key.fed);
  
      // modify each value in the (modified) array arg
      values.forEach(function(val) { val.mod = 1; });
      return {food:values};
  };
  
  var finalize = function(key, values) {
      // set property on receiver
      this.feed = {ice:1};
  
      // set property on key arg
      key.fed = {cream:1};
  
      // push properties onto values array arg
      printjson(values);
      values.food.push(this.feed);
      values.food.push(key.fed);
  
      // modify each value in the (modified) array arg
      values.food.forEach(function(val) { val.mod = 1; });
      return values;
  };
  
  var mr = collection.mapReduce(map, reduce, {finalize: finalize, out: {inline: 1}});
  printjson(mr);
  
  // verify mutated properties exist (order dictated by emit sequence and properties added)
  assert.eq(mr.results[0].value.food[0].beef, 1);
  assert.eq(mr.results[0].value.food[1].cake, 1);
  assert.eq(mr.results[0].value.food[2].beat, 1);
  assert.eq(mr.results[0].value.food[3].mochi, 1);
  assert.eq(mr.results[0].value.food[4].ice, 1);
  assert.eq(mr.results[0].value.food[5].cream, 1);
  mr.results[0].value.food.forEach(function(val) { assert.eq(val.mod, 1); });
  