Mock Configuration

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Configure mock behavior with .final() and .impl()

Suites provides two methods for configuring mock behavior:

  • .mock().final() for immutable configurations
  • .mock().impl() for flexible implementations

Methods

.mock().final()

Creates an immutable mock configuration. Once set, the mock cannot be retrieved or modified. Use .final() for:

  • Fixed behavior that won’t change across tests
  • Configuration objects and primitives (non-class tokens)
  • Values that don’t need runtime control or verification

Signature

mock<D>(dependency: Type<D> | string | symbol)
  .final(implementation: DeepPartial<D>): TestBuilder

Parameters

ParameterTypeDescription
dependencyType<D> | string | symbolThe dependency to mock
implementationDeepPartial<D>Object with method implementations

Example

For class-based tokens (fixed behavior):

const { unit } = await TestBed.solitary(UserService)
  .mock(UserApi)
  .final({
    getRandom: async () => ({ id: 1, name: "John" }),
    getAll: async () => [{ id: 1, name: "John" }]
  })
  .compile();


// UserApi cannot be retrieved - behavior is fixed

For configuration objects and primitives:

const { unit } = await TestBed.solitary(PaymentService)
  .mock<DatabaseConfig>('DATABASE_CONFIG')
  .final({ host: 'localhost', port: 5432 })
  .mock<string>('API_KEY')
  .final('test-api-key-12345')
  .compile();


// Config values are injected but not retrievable

.mock().impl()

Creates a flexible mock configuration using the underlying mock library (Jest, Vitest, etc.). The stubFn callback corresponds to the installed doubles adapter: jest.fn() for Jest, vi.fn() for Vitest, or sinon.stub() for Sinon.

Signature

mock<D>(dependency: Type<D> | string | symbol)
  .impl(factory: (stubFn: () => MockFunction) => DeepPartial<D>): TestBuilder

Parameters

ParameterTypeDescription
dependencyType<D> | string | symbolThe dependency to mock
factory(stubFn) => DeepPartial<D>Factory function receiving the mock library’s stub function

Example

const { unit, unitRef } = await TestBed.solitary(UserService)
  .mock(UserApi)
  .impl(stubFn => ({
    getRandom: stubFn().mockResolvedValue({ id: 1, name: "John" }),
    getAll: stubFn().mockReturnValue([])
  }))
  .compile();


// UserApi can still be retrieved and modified
const userApi = unitRef.get(UserApi);
userApi.getRandom.mockResolvedValue({ id: 2, name: "Jane" });

Example

Multiple Mock Configurations

You can chain multiple mock configurations:

const { unit, unitRef } = await TestBed.solitary(OrderService)
  .mock(Database)
  .final({
    getOrder: async (id: string) => ({ id, items: [] })
  })
  .mock(EmailService)
  .impl(stubFn => ({
    send: stubFn().mockResolvedValue({ sent: true })
  }))
  .compile();


// Can retrieve EmailService and Logger, but not Database
const emailService = unitRef.get(EmailService);
const logger = unitRef.get(Logger);

See Also