Vela - NestJS for the Edge

The TestingModuleBuilder provides override methods to replace providers and framework components with test doubles. All overrides must be applied before calling .compile().

Overriding Providers

Replace a provider by token using .overrideProvider():

const module = await Test.createTestingModule({
  controllers: [SpiritsController],
  providers: [SpiritsService],
})
  .overrideProvider(SpiritsService)
  .useValue({ findAll: () => ['mock-spirit'] })
  .compile();

useValue

Supply a mock object directly:

.overrideProvider(SpiritsService)
.useValue({ findAll: () => ['mock-spirit'] })

useClass

Replace with an alternative class:

.overrideProvider(SpiritsService)
.useClass(MockSpiritsService)

useFactory

Use a factory function with optional injected dependencies:

.overrideProvider(SpiritsService)
.useFactory({
  factory: (config) => new MockSpiritsService(config),
  inject: [ConfigService],
})

Overriding Guards

Replace a guard to bypass authorization in tests:

.overrideGuard(AuthGuard)
.useValue({ canActivate: () => true })

Overriding Interceptors

Replace an interceptor to skip transformation or logging logic:

.overrideInterceptor(LoggingInterceptor)
.useValue({ intercept: (ctx, next) => next.handle() })

Overriding Filters

Replace an exception filter with a no-op:

.overrideFilter(HttpExceptionFilter)
.useValue({ catch: () => {} })

Overriding Pipes

Replace a pipe to skip validation or transformation:

.overridePipe(ValidationPipe)
.useValue({ transform: (value) => value })

Full Example

import { Test } from '@velajs/testing';
import { SpiritsController } from './spirits.controller';
import { SpiritsService } from './spirits.service';
import { AuthGuard } from './auth.guard';

describe('SpiritsController', () => {
  let module;

  beforeAll(async () => {
    module = await Test.createTestingModule({
      controllers: [SpiritsController],
      providers: [SpiritsService],
    })
      .overrideProvider(SpiritsService)
      .useValue({ findAll: () => ['Calcifer', 'Ember'] })
      .overrideGuard(AuthGuard)
      .useValue({ canActivate: () => true })
      .compile();
  });

  afterAll(async () => {
    await module.close();
  });

  it('should return mocked spirits', () => {
    const service = module.get(SpiritsService);
    expect(service.findAll()).toEqual(['Calcifer', 'Ember']);
  });
});

Overrides