@mockmaster/data

Data factories and fake data generation for mock-master

Part of the mock-master monorepo.

Installation

npm install @mockmaster/data

Features

• Factory System - Define reusable data factories with sequences
• Faker.js Integration - Generate realistic fake data
• Type Safe - Full TypeScript support with type inference
• Functional API - Pure functions, immutable data

Usage

Define a Factory

import { defineFactory, build, fake } from '@mockmaster/data'

const userFactory = defineFactory('user', {
  id: (ctx) => ctx.sequence('user'),
  name: () => fake.person.fullName(),
  email: () => fake.internet.email(),
  role: () => fake.helpers.arrayElement(['admin', 'user', 'guest']),
})

Build Data

// Generate with defaults
const user1 = build(userFactory)
// { id: 1, name: 'John Doe', email: '[email protected]', role: 'user' }

const user2 = build(userFactory)
// { id: 2, name: 'Jane Smith', email: '[email protected]', role: 'admin' }

// Override specific fields
const admin = build(userFactory, { overrides: { role: 'admin' } })
// { id: 3, name: 'Bob Johnson', email: '[email protected]', role: 'admin' }

Build Multiple

import { buildList } from '@mockmaster/data'

const users = buildList(userFactory, 10)
// Array of 10 users with sequential IDs

Reset Sequences

import { resetSequences } from '@mockmaster/data'

// Reset all sequences (useful in test setup)
resetSequences()

const user = build(userFactory)
// { id: 1, ... } - starts from 1 again

API

defineFactory<T>(name: string, definition: FactoryDefinition<T>): Factory<T>

Defines a reusable factory for generating test data.

build<T>(factory: Factory<T>, options?: BuildOptions<T>): T

Builds a single instance from a factory.

buildList<T>(factory: Factory<T>, count: number, options?: BuildOptions<T>): T[]

Builds multiple instances from a factory.

resetSequences(): void

Resets all sequence counters to 1.

fake

Re-exported Faker.js instance for generating realistic data:

• fake.person.fullName()
• fake.internet.email()
• fake.datatype.number()
• fake.helpers.arrayElement(array)
• And many more!

Examples

Complex Factory

const postFactory = defineFactory('post', {
  id: (ctx) => ctx.sequence('post'),
  title: () => fake.lorem.sentence(),
  body: () => fake.lorem.paragraphs(3),
  authorId: () => fake.datatype.number({ min: 1, max: 100 }),
  tags: () => fake.helpers.arrayElements(['typescript', 'testing', 'mocking'], 2),
  createdAt: () => fake.date.past(),
})

Use in Tests

import { describe, it, beforeEach } from 'vitest'
import { resetSequences } from '@mockmaster/data'

describe('User API', () => {
  beforeEach(() => {
    resetSequences() // Reset for deterministic tests
  })

  it('should create user', () => {
    const user = build(userFactory, { overrides: { role: 'admin' } })
    // Test with generated user...
  })
})

Links

• Main Documentation
• Faker.js Documentation
• npm Organization

License

MIT