factory.js

var util = require("util");
var Factory = require("rosie").Factory;

Factory.define('child')
    .sequence('id')

Factory.define('parent')
    .sequence('id')
    .attr('children', function () {
        return [
            Factory.attributes('child', {parent_id: this.id()}),
            Factory.attributes('child', {parent_id: this.id()}),
            Factory.attributes('child', {parent_id: this.id()}),
        ];
    })

console.log(util.inspect(Factory.build('parent', {id: 42})));

{ id: 42,
  children: 
   [ { parent_id: 1, id: 1 },
     { parent_id: 2, id: 2 },
     { parent_id: 3, id: 3 } ] }