@code-snap/mock

A lightweight TypeScript utility for creating mock objects with deep merging capabilities. This package allows you to define default objects and override them with partials to simulate different scenarios easily.

Installation

npm install @code-snap/mock

or with Yarn:

yarn add @code-snap/mock

Usage

Creating a Mock Object

The createMock function generates a mock object from a default structure. You can override parts of it using partials.

import { createMock, MockUsecases } from '@code-snap/mock';

type Person = {
  age: number;
  address: {
    city: string;
    street: string;
  };
};

const PersonMock = createMock<Person>({
  age: 1,
  address: {
    city: 'ExampleCity',
    street: 'Teststreet',
  },
});

console.log(PersonMock.create());
// Output: { age: 1, address: { city: 'ExampleCity', street: 'Teststreet' } }

Defining Use Cases

Use cases allow you to define reusable scenarios as partial objects that can override the default structure.

const Usecases = {
  NO_ADDRESS: { address: undefined },
  ADULT: { age: 21 },
} satisfies MockUsecases<Person>;

console.log(PersonMock.create(Usecases.ADULT));
// Output: { age: 21, address: { city: 'ExampleCity', street: 'Teststreet' } }

Faker.js Support

@code-snap/mock supports @faker-js/faker, allowing you to generate realistic test data with ease.

import { createMock } from '@code-snap/mock';
import { faker } from '@faker-js/faker';

type User = {
  name: string;
  email: string;
};

const UserMock = createMock<User>({
  name: faker.name.fullName(),
  email: faker.internet.email(),
});

console.log(UserMock.create());

API Reference

createMock<T>(defaultObj: T): Mock<T>

Creates a mock object from a given default object.

• Parameters:
  • defaultObj: T – The base object to use as a template.
• Returns:
  • A Mock<T> object with a create method for generating mock instances.

Mock<T>.create(overrides?: DeepPartial<T>): T

Creates a mock object with optional overrides.

• Parameters:
  • overrides?: DeepPartial<T> – A deep partial structure to override parts of the mock.
• Returns:
  • A new instance of the mock object with the applied overrides.

MockUsecases<T>

A type that defines a collection of use cases, where each key represents a scenario and the value is a DeepPartial<T> override. This acts as a helper type to ensure type saftey.

Why Use @code-snap/mock?

• 🔹 Simple API – Define mock objects and override them with ease.
• 🔹 Type-safe – Ensures type safety with TypeScript.
• 🔹 Deep merging – Merges nested properties correctly.
• 🔹 Reusable scenarios – Define and reuse mock configurations with MockUsecases<T>.
• 🔹 Faker.js support – Easily integrate with @faker-js/faker for dynamic test data.

License

This package is licensed under the MIT License.