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factory-bot is a factory library for Node.js. It works asynchronously and supports associations and the use of functions for generating attributes.



npm install factory-bot


Refer to the tutorial for a gentle introduction of building a simple user factory.

Here's the crash course:

const factory = require('factory-bot').factory;
const User    = require('../models/user');

factory.define('user', User, {
  username: 'Bob',
  score: 50,

factory.build('user').then(user => {
  console.log(user); // => User {username: 'Bob', score: 50}

Defining Models

Define models that have a constructor that takes an object with the attributes needed to instantiate an instance of the model.

For example:

class User {
    constructor(attrs = {}) {
    this.attrs = Object.assign({
      username: attrs.username || 'George',
      score: attrs.score || 27,
    }, attrs);

The factory methods will invoke this constructor during the construction of model objects.

Defining Factories

Define factories using the factory.define() method.

For example:

// Using objects as initializer
factory.define('product', Product, {
  // use sequences to generate values sequentially
  id: factory.sequence('Product.id', (n) => `product_${n}`),
  // use functions to compute some complex value
  launchDate: () => new Date(),
  // return a promise to populate data asynchronously
  asyncData: () => fetch('some/resource'),
factory.define('user', User, {
  // seq is an alias for sequence
  email: factory.seq('User.email', (n) => `user${n}@ymail.com`),

  // use the chance(http://chancejs.com/) library to generate
  // real-life like data.
  // For repeatable results, call factory.chance.seed(<value>) first.
  about: factory.chance('sentence'),

  // use assoc to associate with other models
  profileImage: factory.assoc('profile_image', '_id'),

  // or assocMany to associate multiple models
  addresses: factory.assocMany('address', 2, '_id'),

  // use assocAttrs to embed models that are not persisted
  creditCardNumber: factory.assocAttrs('credit_card', 'number', {type: 'masterCard'}),

  // use assocAttrs or assocAttrsMany to embed plain json objects
  twitterDetails: factory.assocAttrs('twitter_details'),
// Using functions as initializer
factory.define('account', Account, buildOptions => {
  let attrs = {
    confirmed: false,
    confirmedAt: null

  // use build options to modify the returned object
  if (buildOptions.confirmedUser) {
    attrs.confirmed = true;
    attrs.confirmedAt = new Date();
  return attrs;

// buildOptions can be passed while requesting an object
factory.build('account', {}, {confirmed: true});


Options can be provided when you define a factory:

factory.define('user', User, { foo: 'bar' }, options);

Alternatively you can set options for the factory that will get applied for all model-factories:


Currently the supported options are:

afterBuild: function(model, attrs, buildOptions)

Provides a function that is called after the model is built. The function should return the instance or a Promise for the instance.

afterCreate: function(model, attrs, buildOptions)

Provides a function that is called after a new model instance is saved. The function should return the instance or throw an error. For asynchronous functions, it should return a promise that resolves with the instance or rejects with the error.

factory.define('user', User, {foo: 'bar'}, {
  afterBuild: (model, attrs, buildOptions) => {
    return doSomethingAsync(model).then(() => {
      return model;
  afterCreate: (model, attrs, buildOptions) => {
    if ('something' === 'wrong') {
      throw new Error;
    return model;

Extending Factories

You can extend a factory using #extend:

factory.define('user', User, { username: 'Bob', expired: false });
factory.extend('user', 'expiredUser', { expired: true });
factory.build('expiredUser').then(user => {
  console.log(user); // => User { username: 'Bob', expired: true });

#extend(parent, name, initializer, options = {})

The #extend method takes the same options as #define except you can provide a different Model using options.model.

Using Factories


Generates and returns model attributes as an object hash instead of the model instance. This may be useful where you need a JSON representation of the model e.g. mocking an API response.

factory.attrs('post').then(postAttrs => {
  // postAttrs is a json representation of the Post model

factory.attrs('post', {title: 'Foo', content: 'Bar'}).then(postAttrs => {
  // builds post json object and overrides title and content

factory.attrs('post', {title: 'Foo'}, {hasComments: true}).then(postAttrs => {
  // builds post json object
  // overrides title
  // invokes the initializer function with buildOptions of {hasComments: true}

You can use Factory#attrsMany to generate a set of model attributes

factory.attrsMany('post', 5, [{title: 'foo1'}, {title: 'foo2'}]).then(postAttrsArray => {
  // postAttrsArray is an array of 5 post json objects


Builds a new model instance that is not persisted.

factory.build('post').then(post => {
  // post is a Post instance that is not persisted

The buildMany version builds an array of model instances.

factory.buildMany('post', 5).then(postsArray => {
  // postsArray is an array of 5 Post instances

Similar to Factory#attrs, you can pass attributes to override or buildOptions.

Factory#create(name, attrs, buildOptions)

Builds a new model instance that is persisted.

factory.create('post').then(post => {
  // post is a saved Post instance

Factory#createMany(name, num, attrs, buildOptions = {})

The createMany version creates an array of model instances.

factory.createMany('post', 5).then(postsArray => {
  // postsArray is an array of 5 Post saved instances

Similar to Factory#attrs and Factory#build, you can pass attrs to override and buildOptions. If you pass an array of attrs then each element of the array will be used as the attrs for a each model created.

Factory#createMany(name, attrs, buildOptions = {})

If you can pass an array of attrs then you can omit num and the length of the array will be used.


Destroys all of the created models. This is done using the adapter's destroy method. It might be useful to clear all created models before each test or testSuite.


Adapters provide support for different databases and ORMs. Adapters can be registered for specific models, or as the 'default adapter', which is used for any models for which an adapter has not been specified. See the adapter docs for usage, but typical usage is:

const FactoryBot = require('factory-bot');
const factory = FactoryBot.factory;
const adapter = new FactoryBot.MongooseAdapter();

// use the mongoose adapter as the default adapter

// Or use it only for one model-factory
factory.setAdapter(adapter, 'factory-name');


ObjectAdapter is a simple adapter that uses const model = new MyModel(), model.save() and model.destroy().

factory.setAdapter(new factory.ObjectAdapter());
class MyModel {
  save() {
    // save the model
  destroy() {
    // destroy the model
factory.define('model', MyModel);

Creating new Factories

You can create multiple factories which have different settings:

let anotherFactory = new factory.FactoryGirl();
anotherFactory.setAdapter(new MongooseAdapter()); // use the Mongoose adapter


This module is a fork or factory-girl, which indeed a fork of factory-lady.

This fork keeps the same API as the original module, but with bugfixes and some extra features.


This software is licensed under the MIT License.

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