Ducer - Framework-Agnostic Data Factory

Motivation

Ducer is a framework-agnostic library that allows you to generate data for your application in a way that closely mimics real-world conditions. Whether you're inserting data directly into a database, calling a REST API, or interacting with GraphQL, Ducer provides full flexibility—you define the data providers.

Instead of manually seeding your database or mocking API responses, Ducer encourages you to generate test data in the same way your application does. This ensures consistency and makes it easier to test complex scenarios.

Key Features

✅ Generate data that accurately reflects real-world conditions.
✅ Support for complex, interdependent data structures.
✅ Easily customize data at different levels of nesting.
✅ Retrieve all generated data, including dependencies, if needed.

Usage

1. Simple scenarios

const iMake: Ducer = new Ducer();
iMake.addFactory(
  "user",
  async (userData: Partial<UserInput>): Promise<User> => {
    return {
      ...{
        id: 123,
        firstName: "John",
        lastName: "Doe",
        createdAt: new Date("2022-02-02"),
      },
      ...userData,
    };
  }
);
const { user } = await iMake.user();
expect(user).toMatchObject({
  id: expect.any(Number),
  firstName: expect.any(String),
  lastName: expect.any(String),
  createdAt: expect.any(Date),
});

2. Complex scenarios

In more complex scenarios, we may need to create factories based on other factories. For example, we need to create an article that should have an author.

const iMake: Ducer = new Ducer();
iMake.addFactory(
  "user",
  (userData: Partial<UserInput>): User => {
    // write to DB/call API whatever you need
    return {
      ...{
        id: 123,
        firstName: "John",
        lastName: "Doe",
        createdAt: new Date("2022-02-02"),
      },
      ...userData,
    };
  }
);
iMake.addFactory(
  "article",
  (
    article: Partial<ArticleInput>,
    { author }: { author: User } // author will be automatically created
  ) => {
    return {
      id: 456,
      title: "Generated title",
      author_id: author.id,
    };
  },
  // we declare dependencies, where author is dependency name
  // and "user" is referenced to existing factory
  { author: "user" }
);
const { article, author } = await iMake.article(
  { title: "My article" },
  { author: { firstName: "Tome" } }
);
expect(article).toEqual({
  id: 456,
  title: "Generated title",
  author_id: 123,
});
expect(author).toMatchObject({
  id: 123,
  firstName: "Tome",
  lastName: "Doe",
});

3. Integration with data providers

Ducer allows you to integrate with any data provider, such as databases or APIs.
Here’s an example using Drizzle ORM to write directly to a database:

import {
  user as userTable,
} from '@/database/schema/drizzle.js';

const iMake: Ducer = new Ducer();
iMake.addFactory(
  "user",
  async (userData: Partial<UserInput>): Promise<User> => {
    const defaultData: UserInput = {
      id: uuidv4(),
      firstName: "John",
      lastName: "Doe",
      createdAt: new Date("2022-02-02"),
    }
    
    const result = {
      ...defaultData,
      ...data,
    };
    await database.insert(userTable).values(defaultData);

    return result;
  }
);

Why Use Ducer?

• 🛠 Framework Agnostic: Works with any database, API, or service.
• 🔄 Reproducible Data: Ensures consistent test data across environments.
• 🔗 Supports Dependencies: Easily define complex object relationships.
• ⚡ Customizable: Define your own factories and extend them as needed.