OverrideBy

Kind: Interface

Source: packages/testing/interfaces/override-by.interface.ts

Part of: Testing

OverrideBy defines the strategies available when overriding a provider, guard, interceptor, pipe, or filter in a testing module. Each strategy returns a TestingModuleBuilder, allowing overrides to be chained before compiling the module.

Properties

Diagram

mermaid
graph LR
  A[TestingModuleBuilder<br/>overrideProvider / overrideGuard] --> B[OverrideBy]
  B --> C[useValue]
  B --> D[useFactory]
  B --> E[useClass]
  C --> F[TestingModuleBuilder]
  D --> F
  E --> F
  F --> G[compile()]

Usage

ts
import { Test } from '@nestjs/testing';
import { UsersService } from './users.service';
import { UsersController } from './users.controller';

const usersServiceMock = {
  findAll: jest.fn().mockResolvedValue([{ id: 1, name: 'Ada' }]),
};

const moduleRef = await Test.createTestingModule({
  controllers: [UsersController],
  providers: [UsersService],
})
  .overrideProvider(UsersService)
  .useValue(usersServiceMock)
  .compile();

// Alternative override strategies:
// .overrideProvider(UsersService).useClass(MockUsersService)
// .overrideProvider(UsersService).useFactory({
//   factory: () => usersServiceMock,
//   inject: [],
// })

AI Coding Instructions

• Use useValue for simple mocks, stubs, and fixed test doubles that do not require dependency injection.
• Use useClass when the replacement should be instantiated as a provider and may have its own dependencies.
• Use useFactory for dynamically created overrides; provide required dependencies through OverrideByFactoryOptions.
• Always call an override method such as overrideProvider() before calling useValue, useFactory, or useClass.
• Preserve the returned TestingModuleBuilder to support chaining additional overrides before calling compile().