Rosie-As-Promised

Rosie-As-Promised is based on RosieJS and is comptabile with the RosieJS API. Rosie is inspired by factory_girl.

Rosie-As-Promised is a fixtures replacement used to define objects (mostly for test data) that provides synchronous-until-they-are-not lifecycle hooks.

To use Rosie-As-Promised you first define a factory. The factory is defined in terms of attributes, sequences, options, and hooks. A factory can inherit from other factories. Once the factory is defined you use it to build objects.

Contents

• All Options Example

• Defining a Factory

  • New
  • Attribute
  • Attributes in bulk
  • Sequential Attribute
  • Build Options
  • Attribute Dependencies
  • Extending Factories

• Using a factory

All Options Example

const { faker } = require('@faker-js/faker')
const { Post, Comment, User, Like } = require('@models')

Factory
  .define('Base')
  .sequence('id')
  .onCreate(async (object) => {
    return await persistToDatastore(object)
  })
  .afterCreate(async (object) => {
    return await hydrateDataFromDatastore(object)
  })

Factory
  .define('Post', Post)
  .extend('Base')
  .attr('body', () => faker.lorem.paragraphs())
  .attr('author', () => Factory.build('User'))
  .option('commentCount', () => Math.floor(Math.random() * 5))
  .attr('comments', ['commentCount', 'id'], (count, postId) => Factory.buildList('Comment', count, { postId }))
  .option('likeCount', () => Math.floor(Math.random() * 15))
  .attr('likes', ['likeCount', 'id'], (count, postId) => Factory.buildList('List', count, { postId }))

Factory
  .define('Comment', Comment)
  .extend('Base')
  .attr('body', () => faker.lorem.paragraphs())
  .attr('author', () => Factory.build('User'))
  .attr('post', () => Factory.build('Post'))

Factory
  .define('Like', Like)
  .extend('Base')
  .attr('liker', () => Factory.build('User'))

Factory
  .define('User', User)
  .extend('Base')
  .attr('firstName', () => faker.person.firstName())
  .attr('lastName', () => faker.person.lastName())
  .attr('email', ['firstName', 'lastName'], (firstName, lastName) => faker.internet.exampleEmail({ firstName, lastName }))

Factory

New

Factories are defined by constructing a factory instance. Factories can also be registered view Factory.define which allows access to the factory instance through convience methods.

// anonymous
const gameFactory = new Factory() // factory
game.attributes() // {}

A Factory can be defined with a constructor

class Game {}

// anonymous
const gameFactory = new Factory(Game)
game.attributes() instanceOf Object // true
game.build() instanceOf Game // true

Attribute

const gameFactory = new Factory()
  .attr('isOver', false)
  .attr('createdAt', () => new Date())

game.attributes() // { isOver: false, createdAt: [date] }

Attributes in Bulk

const gameFactory = new Factory()
  .attrs({
    isOver: false,
    createdAt: () => new Date()
  })

game.attributes() // { isOver: false, createdAt: [date] }

Sequential Attributes

const gameFactory = new Factory()
  .sequence('id')
  .sequence('slug', (n) => `game-${id}`)

game.attributes() // { id: 1, slug: 'game-1' }

Build Options

You can specify options that are used to programmatically generate attributes. numberOfPlayers is defined as an option, not as an attribute. Therefore numberOfPlayers is not part of the output, it is only used to generate the players array.

const playerFactory = new Factory()
  .attr('position', () => {
    const positions = ['pitcher', 'catcher']
    const index = Math.floor(Math.random() * postitions.length)
    return positions[index]
  })

const gameFactory = new Factory()
  .option('numberOfPlayers', 2)
  .attr('players', ['numberOfPlayers'], (numberOfPlayers) => {
    const players = []
    for (let i = 0; i < numberOfPlayers; i++) {
      players.push(player.attributes())
    }
    return players
  })

game.attributes() // { players: [{ position: /* 'pitcher' or 'catcher' */ }, { position: /* 'pitcher' or 'catcher' */ }] }

Attribute Dependencies

In this updated example, id is defined as a sequence attribute, therefore it appears in the output, and can also be used in the generator function that creates the players array.

const playerFactory = new Factory()
  .sequence('id')
  .attr('position', ['id'], (id) => {
    const positions = ['pitcher', 'catcher']
    const index = id % 2
    return positions[index]
  })

const gameFactory = new Factory()
  .attr('players', () => {
    return [
      player.attributes(),
      player.attributes()
    ]
  })

gameFactory.attributes() // { players: [{ id: 1, position: 'pitcher' }, { id: 2, position: 'catcher' }] }

Attributes can depend on override data passed into attributes, build, and create.

const playerFactory = new Factory()
  .sequence('id')
  .attr('position', ['id'], (id) => {
    const positions = ['pitcher', 'catcher', '1st base', '2nd base', '3rd base', 'short stop']
    const index = 
    return positions[id % positions.length]
  })

const gameFactory = new Factory()
  .attr('players', ['players'], (players) => {
    return players.map(player => Factory.attributes(player))
  })

gameFactory.attributes({ players: [{ position: 'pitcher' }, { position: 'short stop' }] }) // { players: [{ id: 1, position: 'pitcher' }, { id: 2, position: 'short stop' }] }

Extending a Factory

Extend a factory to share configuration or to create specific factories

const playerFactory = new Factory()
  .sequence('id')
  .attr('isRetired', false)
  .attr('position', ['id'], (id) => {
    const positions = ['pitcher', 'catcher', '1st base', '2nd base', '3rd base', 'short stop']
    const index = 
    return positions[id % positions.length]
  })

  const retiredPlayerFactory = new Factory()
    .extend(player)
    .attr('isRetired', true)

playerFactory.attributes() // { id: 1, isRetired: false, position: 'catcher' }
retiredPlayerFactory.attributes() // { id: 1, isRetired: true, position: 'catcher' }

Using a Factory

class Player {}

const playerFactory = new Factory(Player)
  .sequence('id')
  .attr('isRetired', false)
  .attr('position', ['id'], (id) => {
    const positions = ['pitcher', 'catcher', '1st base', '2nd base', '3rd base', 'short stop']
    const index = 
    return positions[id % positions.length]
  })

Attributes

playerFactory.attributes()          // { id: 1, isRetired: false, position: 'catcher' }
playerFactory.attributes({ id: 4 }) // { id: 4, isRetired: false, position: '3rd base' }

Build

playerFactory.build()          // Player { id: 1, isRetired: false, position: 'catcher' }
playerFactory.build({ id: 4 }) // Player { id: 4, isRetired: false, position: '3rd base' }

Create

The onCreateHandler is registered in the factory definition. The .create method exists as an inflection point to allow for beforeCreate and afterCreate hooks to be registered.

playerFactory.onCreate((object, options) => {
  // perform sync or async work
  object.createLifeCycleWorkPerformedAt = new Date()
})

await playerFactory.create()                    // Player { id: 3, isRetired: false, position: '2nd base', createLifeCycleWorkPerformedAt: [date] }
await playerFactory.create({ isRetired: true }) // Player { id: 4, isRetired: true, position: '3rd base', createLifeCycleWorkPerformedAt: [date] }

Lifecycle Hooks

Multiple callbacks can be registered, and they will be executed in the order they are registered. The callbacks can manipulate the built object before it is returned to the callee.

If the callback doesn't return anything, rosie will return build object as final result. If the callback returns a value, rosie will use that as final result instead.

beforeBuild

chain method to register hooks to run before objects are built

const teamFactory = new Factory()
  .sequence('id')
  .sequence('name', (n) => `team-${n}`)

const playerFactory
  .sequence('teamId')
  .attr('team', ['teamId'], (teamId) => team.attributes({ id: teamId }))
  .beforeBuild((attributes, options) => {
    if (attributes?.team?.id) attributes.teamId = attributes.team.id
  })

const team = teamFactory.build({ id: 12 })
player.build({ team }) // Player { id: 1, isRetired: false, position: 'catcher', teamId: 12, team: { id: 12, name: 'team-12' } }

after

alias for afterBuild to maintain backwards compatibility

afterBuild

chain method to register hooks to run after objects are built

const playerFactory
  .sequence('teamId')

const teamFactory = new Factory()
  .sequence('id')
  .sequence('name', (n) => `team-${n}`)
  .attrs('players', ['id'], (teamId) => {
    const count = Math.floor(Math.random() * 4) + 1 // up to 4
    const players = []
    for (let i=0; i<count; i++){
      players.push(playerFactory.build(( teamId ))
    }
    return players
  })
  .afterbuild((object, options) => {
    object.playerCount = object.players.length
  })

teamFactory.build() // { id: 1, name: 'team-1', players: [ { teamId: 1, /* ... */}, { teamId: 1, /* ... */}, { teamId: 1, /* ... */} ], playerCount: 3 }

beforeCreate

chain method to register hooks to run before the create hook is called

async function isSlugUnique (slug) {
  // check data store for uniqueness
}

const teamFactory = new Factory()
  .sequence('id')
  .sequence('name', 'blue jays')
  .sequence('slug', ['name'], (name) => name.slice(0, 4))
  .beforeCreate(async (object, options) => {
    let i = 0
    let strSlug = object.slug

    while (await isSlugUnique(strSlug) === false) {
      strSlug = object.slug + `-${i++}`
    }

    object.slug = strSlug
  })

await teamFactory.create({ name: 'blue hornets'}) // { ..., slug: 'blue', ... }
await teamFactory.create({ name: 'blue birds' })  // { ..., slug: 'blue-0', ... }

onCreate

builder method to register the "create" functionality for the factory

const dbRecordFactory = new Factory()
  .onCreate(async (object, options) => {
    object = await persistToDataStore(object)
  })

const teamFactory = new Factory()
  .extend(dbRecordFactory)
  .sequence('name', 'blue jays')

await teamFactory.create({ name: 'blue hornets'}) // { id: 1, name: 'blue hornets', createdAt: [date], updatedAt: [date], _version: 1 }

afterCreate

factory builder chain method to register hooks to run after the onCreateHandler is called

const gameFactory = new Factory()
  .extend(dbRecordFactory)
  .attr('matchDate', () => new Date())
  .attr('homeTeamId', () => Factory.create('team').then(r => r.id)
  .attr('awayTeamId', () => Factory.create('team').then(r => r.id)
  .afterCreate((object, options) => {
    object = await hydrateRelationships(object)
  })

await gameFactory.create() // Game { id: 1, ..., homeTeam: Team { players: [ Player {}, Player {} ] }, awayTeam: Team { players: [ Player {}, Player {} ] } }

Convenience Methods

class Game {}

Factory.define

Factory.define('Game', Game)
// is equivalent to
Factory.factories['Game'] = new Factory(Game)

Factory.attributes

Factory.attributes('Game', attributes, options)
// is equivalent to
Factory.factories['Game'].attributes(attributes, options)

Factory.build

Factory.build('Game', attributes, options)
// is equivalent to
Factory.factories['Game'].build(attributes, options)

Factory.buildList

Factory.buildList('Game', number, attributes, options)
// is equivalent to
Factory.factories['Game'].buildList(number, attributes, options)

Factory.create

Factory.create('Game', attributes, options)
// is equivalent to
Factory.factories['Game'].create(attributes, options)

Factory.createList

Factory.createList('Game', number, attributes, options)
// is equivalent to
Factory.factories['Game'].createList(number, attributes, options)

Usage in Node.js

To use Rosie in node, you'll need to import it first:

import { Factory } from 'rosie';
// or with `require`
const Factory = require('rosie').Factory

require('./factories') // folder with factory defintions

module.exports { Factory }

You might also choose to use unregistered factories, as it fits better with node's module pattern:

// factories/game.js
import { Factory } from 'rosie';

export default new Factory().sequence('id').attr('is_over', false);
// etc

To use the unregistered Game factory defined above:

import Game from './factories/game';

const game = Game.build({ is_over: true });

A tool like babel is currently required to use this syntax.

You can also extend an existing unregistered factory:

// factories/scored-game.js
import { Factory } from 'rosie';
import Game from './game';

export default new Factory().extend(Game).attrs({
  score: 10,
});

Rosie API

As stated above the rosie factory signatures can be broken into factory definition and object creation.

Additionally factories can be defined and accessed via the Factory singleton, or they can be created and maintained by the callee.

Factory declaration functions

Once you have an instance returned from a Factory.define or a new Factory() call, you do the actual of work of defining the objects. This is done using the methods below (note these are typically chained together as in the examples above):

Factory.define

• Factory.define(factory_name) - Defines a factory by name. Return an instance of a Factory that you call .attr, .option, .sequence, and .after on the result to define the properties of this factory.
• Factory.define(factory_name, constructor) - Optionally pass a constuctor function, and the objects produced by .build will be passed through the constructor function.

instance.attr:

Use this to define attributes of your objects

• instance.attr(attribute_name, default_value) - attribute_name is required and is a string, default_value is the value to use by default for the attribute
• instance.attr(attribute_name, generator_function) - generator_function is called to generate the value of the attribute
• instance.attr(attribute_name, dependencies, generator_function) - dependencies is an array of strings, each string is the name of an attribute or option that is required by the generator_function to generate the value of the attribute. This list of dependencies will match the parameters that are passed to the generator_function

instance.attrs:

Use this as a convenience function instead of calling instance.attr multiple times

• instance.attrs({attribute_1: value_1, attribute_2: value_2, ...}) - attribute_i is a string, value_i is either an object or generator function.

See instance.attr above for details. Note: there is no way to specify dependencies using this method, so if you need that, you should use instance.attr instead.

instance.option:

Use this to define options. Options do not appear in the generated object, but they can be used in a generator_function that is used to configure an attribute or sequence that appears in the generated object. See the Programmatic Generation Of Attributes section for examples.

• instance.option(option_name, default_value) - option_name is required and is a string, default_value is the value to use by default for the option
• instance.option(option_name, generator_function) - generator_function is called to generate the value of the option
• instance.option(option_name, dependencies, generator_function) - dependencies is an array of strings, each string is the name of an option that is required by the generator_function to generate the value of the option. This list of dependencies will match the parameters that are passed to the generator_function

instance.sequence:

Use this to define an auto incrementing sequence field in your object

• instance.sequence(sequence_name) - define a sequence called sequence_name, set the start value to 1
• instance.sequence(sequence_name, generator_function) - generator_function is called to generate the value of the sequence. When the generator_function is called the pre-incremented sequence number will be passed as the first parameter, followed by any dependencies that have been specified.
• instance.sequence(sequence_name, dependencies, generator_function) - dependencies is an array of strings, each string is the name of an attribute or option that is required by the generator_function to generate the value of the option. The value of each specified dependency will be passed as parameters 2..N to the generator_function, noting again that the pre-incremented sequence number is passed as the first parameter.

instance.after:

• instance.after(callback) - register a callback function that will be called at the end of the object build process. The callback is invoked with two params: (build_object, object_options). See the Post Build Callback section for examples.

Object building functions

build

Returns an object that is generated by the named factory. attributes and options are optional parameters. The factory_name is required when calling against the rosie Factory singleton.

• Factory.build(factory_name, attributes, options) - when build is called against the rosie Factory singleton, the first param is the name of the factory to use to build the object. The second is an object containing attribute override key value pairs, and the third is a object containing option key value pairs
• instance.build(attributes, options) - when build is called on a factory instance only the attributes and options objects are necessary

buildList

Identical to .build except it returns an array of built objects. size is required, attributes and options are optional

• Factory.buildList(factory_name, size, attributes, options) - when buildList is called against the rosie Factory singleton, the first param is the name of the factory to use to build the object. The attributes and options behave the same as the call to .build.
• instance.buildList(size, attributes, options) - when buildList is called on a factory instance only the size, attributes and options objects are necessary (strictly speaking only the size is necessary)

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Install the test dependencies (yarn install - requires NodeJS and yarn)
4. Make your changes and make sure the tests pass (yarn test)
5. Commit your changes (git commit -am 'Added some feature')
6. Push to the branch (git push origin my-new-feature)
7. Create new Pull Request

Credits

Thanks to Daniel Morrison for the name and Jon Hoyt for inspiration and brainstorming the idea.