test-data-factory-builder

Test Data Factory Builder

Create composable factories for consistent test data.

Factory Pattern

// factories/UserFactory.ts
import { faker } from "@faker-js/faker";

export class UserFactory {
  private data: Partial<User> = {};

  static create(overrides?: Partial<User>): User {
    return new UserFactory().with(overrides).build();
  }

  with(overrides: Partial<User>): this {
    this.data = { ...this.data, ...overrides };
    return this;
  }

  withEmail(email: string): this {
    this.data.email = email;
    return this;
  }

  withRole(role: UserRole): this {
    this.data.role = role;
    return this;
  }

  asAdmin(): this {
    this.data.role = "ADMIN";
    return this;
  }

  build(): User {
    return {
      id: this.data.id || faker.string.uuid(),
      email: this.data.email || faker.internet.email(),
      name: this.data.name || faker.person.fullName(),
      role: this.data.role || "USER",
      createdAt: this.data.createdAt || faker.date.past(),
      ...this.data,
    };
  }
}

// Usage
const user = UserFactory.create();
const admin = UserFactory.create().asAdmin().build();
const specific = UserFactory.create({ email: "[email protected]" });

Builder Pattern

// builders/OrderBuilder.ts
export class OrderBuilder {
  private user?: User;
  private items: OrderItem[] = [];
  private status: OrderStatus = "PENDING";

  forUser(user: User): this {
    this.user = user;
    return this;
  }

  withItem(product: Product, quantity: number = 1): this {
    this.items.push({
      id: faker.string.uuid(),
      productId: product.id,
      quantity,
      price: product.price,
    });
    return this;
  }

  withStatus(status: OrderStatus): this {
    this.status = status;
    return this;
  }

  asPaid(): this {
    this.status = "PAID";
    return this;
  }

  async build(): Promise<Order> {
    if (!this.user) {
      throw new Error("User is required");
    }

    const total = this.items.reduce(
      (sum, item) => sum + item.price * item.quantity,
      0
    );

    return {
      id: faker.string.uuid(),
      userId: this.user.id,
      items: this.items,
      total,
      status: this.status,
      createdAt: new Date(),
    };
  }
}

// Usage
const order = await new OrderBuilder()
  .forUser(user)
  .withItem(laptop, 2)
  .withItem(phone, 1)
  .asPaid()
  .build();