factory for building JavaScript objects, mostly useful for setting up test data.

Getting Started

If you're using Node, you'll want to install using npm:

npm install steam-factory --save-dev

You will need to instanciate the factory before using it.

var Factory = require("steam-factory");

If you're not using npm, be sure to load Steam Factory into your enviroment.

Once Required, assuming you have a directory structure of spec/factories or test/factories, all you'll need load your factories definitions

var Factory = require('steam-factory');
Factory.sequence("userId", function(n) {
  return n;
Factory.define("user", function() {
  name: "John Doe",
  userId: Factory.generate("userId");

Each factory has a name and a set of attributes, functions and other factories that will define the state of the returned object

Factory.define("user", [new User(), {
    name: "John Doe",
    admin: false
Factory.define("admin", ["user", {
    admin: true

It is highly recommended that you have one factory for each entity that provides the simplest set of attributes necessary to create an instance of that entity. I.e: If you're creating model objects, that means that you should only provide attributes that are required through validations and that do not have defaults. Other factories can be created through inheritance to cover common scenarios for each class.

Attempting to define multiple factories with the same name will raise an error.

Factories can be defined anywhere

SteamFactory supports several different build strategies: build, create, and attributesFor.

// Returns a User instance that's not saved 
user ="user")
// Returns a hash of attributes that can be used to build a User instance 
attrs = SteamFactory.attributesFor("user")
// Passing a function to any of the methods above will yield the return object"user", function(user){

it's possible to override the defined attributes by passing an object, or an array of objects, functions and factories:

// Build a User instance and override the firstName property 
user ="user", {firstName: "John"})
// => "John" 
describe("User//fullName", function() {
  var user ="user", [new User(), {
      firstName: "John",
      lastName: "Doe"
  it("fullName", function() {
      expect(user.fullName).to.equal("John Doe");

Most factory attributes can be added using static values that are evaluated when the factory is defined, but some attributes (such as associations and other attributes that must be dynamically generated) will need values assigned each time an instance is generated. These "lazy" attributes can be added by passing a block instead of a parameter:

User.generateActivationCode = function(){ /* Activation code*/ };
Factory.define("activeUser", ["user", function() {
  activationCode: Factory.generates(User.generateActivationCode),
sequence("randomString", LoremIpsum.generateLine);
sequence("randomParagraph", LoremIpsum.generateParagraph);
Factory.define("post", {
  title: Factory.generate("randomString")
  body:  Factory.generate("randomParagraph")

Aliases allow you to use named associations more easily.

  firstName: "John",
  lastName:  "Doe",
Factory.alias("user", ["author", "commenter"]);
  title: "How to read a book effectively",
  body:  "There are five steps involved."
Factory("comment", {
  body: "Great article!"

Attributes can be based on the values of other attributes using the evaluator that is yielded to lazy attribute blocks:

Factory("user", {
  firstName "Joe"
  lastName  "Blow"
  email:  Factory.generates(function(){ return user.firstName + "" });

It's possible to set up associations within factories.

Factory.define("post", {
  author:"user", {firstName: "Alice"})

Generating data for a has_many relationship is a bit more involved, depending on the amount of flexibility desired, but here's a surefire example of generating associated data.

// post factory with a `belongs_to` association for the user 
Factory.define("post", {title: "Through the Looking Glass"});
Factory.define("user", {name "John Doe"});
Factory.define("userWithPost", ["user", function(user){
    // userWithPost will create post data after the user has been created 
    // the functions yields one value the user instance itself 
    posts: ["post", {author: user}),"post", {author: user}),"post", {author: user}),"post", {author: user}),"post", {author: user})

This allows us to do:

SteamFactory.create("user").posts.length;         // 0 
SteamFactory.Create("userWithPost").posts.length; // 5 

You can easily create multiple factories for the same class without repeating common attributes by nesting factories:

Factory.define("post", {title: "Through the Looking Glass"});
Factory.define("approvedPost", ["post", {approved: true}]);
approvedPost = SteamFactory.create("approvedPost");
ApprovedPost.title;    // => "A title" 
approvedPost.approved; // => true 

As mentioned above, it's good practice to define a basic factory for each class with only the attributes required to create it. Then, create more specific factories that extend from this basic one. Factory definitions are still code, so keep them DRY.

Unique values in a specific format (for example, e-mail addresses) can be generated using sequences. Sequences are defined by calling sequence in a definition block, and values in a sequence are generated by calling SteamFactory.generate:

// Defines a new sequence
SteamFactory.define("email", function(n){ return "person" + n + ""});
// => ""
// => ""

Sequences can be used for attributes:

Factory.define("user", {
  email: Factory.generate("email")

You can also override the initial value:

SteamFactory.define("email", function(n){ return "person" + n + ""}, 100);
// => "" 

Composition allow you to group attributes together and then apply them to any factory.

Factory.alias("user", "author");
Factory.define("published", {published: true});
Factory.define("unpublished", {published: true});
Factory.define("weekLongPublishing", {
    startAt:  Factory.generate("aWeekAgo"),
    endAt:    Factory.generate("now")
Factory.define("weekLongPublishing", {
    startAt:  Factory.generate("aMonthAgo"),
    endAt:    Factory.generate("now")
Factory.define("story", {
  title "My awesome story",
// Define factories by reusing other factories 
Factory.define("weekLongPublishedStory",    ["published", "weekLongPublishing"]);
Factory.define("monthLongPublishedStory",  ["published", "monthLongPublishedStory"]);
Factory.define("weekLongUnpublishedStory",  ["unpublished", "weekLongPublishing"]);
Factory.define("monthLongUnpublishedStory", ["unpublished", "monthLongPublishedStory"]);

Composition that define the same attributes won't raise AttributeDefinitionErrors;