faker

# setup-faker.sh — Install Faker.js.
npm install --save-dev @faker-js/faker

// generate-data.ts — Basic Faker.js usage for common data types.
// Generates names, emails, addresses, and more.
import { faker } from '@faker-js/faker';

const user = {
  id: faker.string.uuid(),
  firstName: faker.person.firstName(),
  lastName: faker.person.lastName(),
  email: faker.internet.email(),
  avatar: faker.image.avatar(),
  phone: faker.phone.number(),
  address: {
    street: faker.location.streetAddress(),
    city: faker.location.city(),
    state: faker.location.state(),
    zip: faker.location.zipCode(),
    country: faker.location.country(),
  },
  company: faker.company.name(),
  jobTitle: faker.person.jobTitle(),
  bio: faker.lorem.paragraph(),
  createdAt: faker.date.past(),
};

console.log(user);

// generate-users.ts — Generate an array of fake users with consistent shape.
// Useful for seeding databases or populating test fixtures.
import { faker } from '@faker-js/faker';

interface User {
  id: string;
  name: string;
  email: string;
  role: 'admin' | 'user' | 'moderator';
  isActive: boolean;
  createdAt: Date;
}

function createRandomUser(): User {
  return {
    id: faker.string.uuid(),
    name: faker.person.fullName(),
    email: faker.internet.email().toLowerCase(),
    role: faker.helpers.arrayElement(['admin', 'user', 'moderator']),
    isActive: faker.datatype.boolean({ probability: 0.8 }),
    createdAt: faker.date.between({ from: '2023-01-01', to: new Date() }),
  };
}

const users = faker.helpers.multiple(createRandomUser, { count: 100 });
console.log(`Generated ${users.length} users`);

// seeded-data.ts — Use seeds for reproducible fake data across test runs.
// Same seed always produces the same data.
import { faker } from '@faker-js/faker';

faker.seed(42);

const user1 = faker.person.fullName();
const email1 = faker.internet.email();

// Reset seed for a different but equally reproducible set
faker.seed(123);
const user2 = faker.person.fullName();

// localized-data.ts — Generate fake data in different languages and locales.
// Each locale produces culturally appropriate names, addresses, etc.
import { faker, fakerDE, fakerFR, fakerJA } from '@faker-js/faker';

const germanUser = {
  name: fakerDE.person.fullName(),
  address: fakerDE.location.streetAddress(),
  phone: fakerDE.phone.number(),
};

const frenchUser = {
  name: fakerFR.person.fullName(),
  city: fakerFR.location.city(),
};

const japaneseUser = {
  name: fakerJA.person.fullName(),
  city: fakerJA.location.city(),
};

// seeds/seed-database.ts — Database seeder using Faker for realistic test data.
// Creates users, products, and orders with proper relationships.
import { faker } from '@faker-js/faker';
import { db } from '../src/db';

async function seed() {
  faker.seed(42);

  const userIds: string[] = [];
  for (let i = 0; i < 50; i++) {
    const [user] = await db('users').insert({
      name: faker.person.fullName(),
      email: faker.internet.email().toLowerCase(),
      avatar_url: faker.image.avatar(),
      created_at: faker.date.past({ years: 2 }),
    }).returning('id');
    userIds.push(user.id);
  }

  const productIds: string[] = [];
  for (let i = 0; i < 200; i++) {
    const [product] = await db('products').insert({
      name: faker.commerce.productName(),
      description: faker.commerce.productDescription(),
      price: parseFloat(faker.commerce.price({ min: 5, max: 500 })),
      category: faker.commerce.department(),
      image_url: faker.image.urlPicsumPhotos(),
      in_stock: faker.datatype.boolean({ probability: 0.85 }),
    }).returning('id');
    productIds.push(product.id);
  }

  for (let i = 0; i < 500; i++) {
    const userId = faker.helpers.arrayElement(userIds);
    const itemCount = faker.number.int({ min: 1, max: 5 });

    const [order] = await db('orders').insert({
      user_id: userId,
      status: faker.helpers.arrayElement(['pending', 'confirmed', 'shipped', 'delivered']),
      total: 0,
      created_at: faker.date.recent({ days: 90 }),
    }).returning('id');

    let total = 0;
    for (let j = 0; j < itemCount; j++) {
      const productId = faker.helpers.arrayElement(productIds);
      const quantity = faker.number.int({ min: 1, max: 3 });
      const price = parseFloat(faker.commerce.price({ min: 5, max: 100 }));
      total += price * quantity;

      await db('order_items').insert({
        order_id: order.id,
        product_id: productId,
        quantity,
        price,
      });
    }

    await db('orders').where({ id: order.id }).update({ total });
  }

  console.log('Seeded: 50 users, 200 products, 500 orders');
}

seed().then(() => process.exit(0));

// tests/user-service.test.ts — Using Faker inside unit tests for random but realistic data.
// Each test gets unique data; seed for reproducibility when debugging.
import { faker } from '@faker-js/faker';
import { UserService } from '../src/services/userService';

describe('UserService', () => {
  const service = new UserService();

  it('should validate email format', () => {
    const validEmail = faker.internet.email();
    expect(service.isValidEmail(validEmail)).toBe(true);

    const invalidEmail = faker.person.firstName();
    expect(service.isValidEmail(invalidEmail)).toBe(false);
  });

  it('should create user with all fields', async () => {
    const input = {
      name: faker.person.fullName(),
      email: faker.internet.email(),
      age: faker.number.int({ min: 18, max: 99 }),
    };

    const user = await service.create(input);
    expect(user.name).toBe(input.name);
    expect(user.email).toBe(input.email);
    expect(user.id).toBeDefined();
  });
});

// helpers/fake-helpers.ts — Custom Faker helpers for domain-specific data.
// Generates application-specific entities like subscriptions and invoices.
import { faker } from '@faker-js/faker';

export function fakeSubscription() {
  const plans = ['free', 'pro', 'enterprise'] as const;
  const plan = faker.helpers.arrayElement(plans);

  return {
    id: faker.string.uuid(),
    plan,
    price: plan === 'free' ? 0 : plan === 'pro' ? 19.99 : 99.99,
    startDate: faker.date.past(),
    renewalDate: faker.date.future(),
    isActive: faker.datatype.boolean({ probability: 0.9 }),
  };
}

export function fakeInvoice() {
  return {
    id: `INV-${faker.string.alphanumeric(8).toUpperCase()}`,
    amount: parseFloat(faker.finance.amount({ min: 10, max: 5000 })),
    currency: faker.finance.currencyCode(),
    status: faker.helpers.arrayElement(['draft', 'sent', 'paid', 'overdue']),
    dueDate: faker.date.soon({ days: 30 }),
    lineItems: faker.helpers.multiple(
      () => ({
        description: faker.commerce.productName(),
        quantity: faker.number.int({ min: 1, max: 10 }),
        unitPrice: parseFloat(faker.commerce.price()),
      }),
      { count: { min: 1, max: 5 } }
    ),
  };
}