data-seeding-fixtures-builder

Data Seeding & Fixtures Builder

Generate realistic, deterministic seed data for development and testing.

Seed Data Strategy

// prisma/seed.ts
import { PrismaClient } from "@prisma/client";
import { faker } from "@faker-js/faker";

const prisma = new PrismaClient();

async function main() {
  console.log("🌱 Seeding database...");

  // Clear existing data
  await prisma.order.deleteMany();
  await prisma.user.deleteMany();

  // Seed users
  const users = await seedUsers(10);
  console.log(`✅ Created ${users.length} users`);

  // Seed orders
  const orders = await seedOrders(users, 50);
  console.log(`✅ Created ${orders.length} orders`);

  console.log("✅ Seeding complete!");
}

main()
  .catch((e) => {
    console.error(e);
    process.exit(1);
  })
  .finally(async () => {
    await prisma.$disconnect();
  });

Factory Functions

// factories/user.factory.ts
import { faker } from "@faker-js/faker";
import { PrismaClient, User } from "@prisma/client";

const prisma = new PrismaClient();

export interface UserFactoryOptions {
  email?: string;
  name?: string;
  role?: "USER" | "ADMIN";
}

export class UserFactory {
  static async create(options: UserFactoryOptions = {}): Promise<User> {
    return prisma.user.create({
      data: {
        email: options.email || faker.internet.email(),
        name: options.name || faker.person.fullName(),
        role: options.role || "USER",
        createdAt: faker.date.past(),
      },
    });
  }

  static async createMany(
    count: number,
    options: UserFactoryOptions = {}
  ): Promise<User[]> {
    return Promise.all(
      Array.from({ length: count }, () => this.create(options))
    );
  }

  static async createAdmin(): Promise<User> {
    return this.create({ role: "ADMIN" });
  }
}

// Usage:
// const user = await UserFactory.create();
// const admin = await UserFactory.createAdmin();
// const users = await UserFactory.createMany(10);

Realistic Fixtures

// fixtures/products.ts
import { Product } from "@prisma/client";

export const PRODUCT_FIXTURES: Omit<
  Product,
  "id" | "createdAt" | "updatedAt"
>[] = [
  {
    name: 'MacBook Pro 16"',
    description: "Powerful laptop for developers",
    price: 2499.99,
    stock: 50,
    category: "Electronics",
  },
  {
    name: "iPhone 15 Pro",
    description: "Latest flagship smartphone",
    price: 999.99,
    stock: 100,
    category: "Electronics",
  },
  {
    name: "AirPods Pro",
    description: "Wireless earbuds with noise cancellation",
    price: 249.99,
    stock: 200,
    category: "Electronics",
  },
];

// Seed products
async function seedProducts() {
  return Promise.all(
    PRODUCT_FIXTURES.map((product) => prisma.product.create({ data: product }))
  );
}