CODEWITHSUNDEEP
unit-testingmockingnestjs
Mostafa
Mostafa

Reputation: 45

Mocking imported modules for a service

Suppose i want to write a unit test for a service which depends on services of another module.

Now here is my question. Is there any way to write my test so that i mock the module that MyService depends on such that i can use it in my unit test like this:

const moduleRef = await Test.createTestingModule({
    imports: [
        MockedModule,
    ],
    providers: [
        MyService,
    ],
});

Or i have to write a mock for each dependency service and use them like this:

const moduleRef = await Test.createTestingModule({
    providers: [
        MyService,
        {
            provider: DependencyService,
            useClass: DependencyServiceMock,
        }
    ],
});

Upvotes: 0

Views: 819

Answers (1)

Jay McDoniel
Jay McDoniel

Reputation: 70570

I suppose it would be possible to use a MockModule that provides and exports the same dependencies that the service would normally depend on. I haven't heard of someone trying that yet, but I don't see why it wouldn't work. So if you have

@Injectable()
export class MyService {
  constructor(private readonly depService: DependencyService) {}
...
}

Then in your mock module you would need

@Module({
  providers: [{
    provide: DependencyService,
    useClas: DependencyServiceMock,
  }],
  exports: [DependencyService],
})
export class MockedModule {}

And in your test you would need to do

beforeEach(async () => {
  const app = await Test.createTestModule({
    imports: [MockedModule],
    providers: [MySerivce],
  }).compile();
});
...

Upvotes: 1

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