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Types

TypeScript type definitions used throughout Suites.

Core Types​

Mocked<T>​

A deeply nested mock type. All methods become mock functions, nested objects are mocked recursively.

interface UserService {
  repository: {
    find(id: string): User;
    save(user: User): void;
  };
  validate(user: User): boolean;
}

const service: Mocked<UserService> = unitRef.get(UserService);

// All methods mocked, including nested
service.validate.mockReturnValue(true);
service.repository.find.mockResolvedValue(testUser);
service.repository.save.mockReturnValue(undefined);

How Mocked<T> Works: Module Augmentation​

The Mocked<T> type is always imported from @suites/unit, never from adapter packages. Suites uses TypeScript's module augmentation to automatically provide the correct library-specific types.

Single Import Point​

// ✅ Always import from @suites/unit
import { Mocked } from '@suites/unit';

// ❌ Never import from adapter packages
// import { Mocked } from '@suites/doubles.jest';  // Wrong!

Automatic Type Resolution​

When an adapter package (like @suites/doubles.jest) is installed, it automatically augments the @suites/unit module with library-specific types:

// @suites/doubles.jest/unit.d.ts (internal - you never see this)
declare module '@suites/unit' {
  export type Mocked<T> = jest.Mocked<T>;  // Overrides base type
}

This means the same Mocked<T> import resolves to different concrete types based on which adapter is installed.

Zero Configuration

This works automatically when you install an adapter package. No manual configuration needed - TypeScript resolves the correct types based on your installed dependencies.

Why This Architecture Matters​

Because Suites is framework agnostic. The same test code works across Jest, Vitest, and Sinon without changes. Only the installed adapter package determines which library-specific types and methods are available.

Maintains Dependency Inversion: The @suites/unit package never depends on adapter packages. Instead, adapters augment the base package - following proper dependency inversion principle.

// This exact code works with any adapter installed
describe('UserService', () => {
  let service: UserService;
  let database: Mocked<Database>;

  beforeAll(async () => {
    const { unit, unitRef } = await TestBed.solitary(UserService).compile();
    service = unit;

    // Return Mocked type corresponding to installed adapter
    database = unitRef.get(Database); 
  });
});

See Also​