Tips for setting up various mock services for testing an Angular 2 component

I am working with two Mock services:

@Injectable()
class UserRegistrationServiceMock {
    registerBasicDetails(details: UserRegistrationDetails) {
        let response: UserRegistrationResponse = new UserRegistrationResponse();
        response.success = false;
        response.userMessage = 'Test Message';                
        return Observable.of(response);
    }

    registerAdvancedDetails() {        
    }
}

@Injectable()
class UserRegistrationServiceSuccessMock {
    registerBasicDetails(details: UserRegistrationDetails) {
        let response: UserRegistrationResponse = new UserRegistrationResponse();
        response.success = true;
        response.userMessage = 'Test Message';
        return Observable.of(response);
    }

    registerAdvancedDetails() {
    }
}

When setting up my Jasmine test, I include the service definitions in the "beforeEachProviders" and "beforeEach" methods:

beforeEachProviders(() => [        
 provide(UserRegistrationService, { useClass: UserRegistrationServiceMock })
]);

beforeEach(inject([UserRegistrationService], (_userRegistration))

Then, in my test, I use the user registration service to initialize the component:

it('should create an instance', () => {
        let component: BasicRegistrationComponent =
            new BasicRegistrationComponent(null, formBuilder, promptWindow, userInfo, translator, userRegistration);
        expect(component).toBeTruthy();
    });

My question now is how can I provide the second mock implementation of the service for my component?

Answer №1

To provide the second mock class, follow the same steps as you did for the first one.

Make sure to include it in the beforeEachProviders() and beforeEach blocks:

beforeEachProviders(() => [        
  provide(UserRegistrationService, { useClass: UserRegistrationServiceMock }),
  provide(UserRegistrationServiceSuccess, { useClass: UserRegistrationServiceSuccessMock })
]);

beforeEach(inject([UserRegistrationService, UserRegistrationServiceSuccess], (_userRegistration, _userSuccess))

A helpful tip is to only inject the dependencies you need for each specific test, rather than injecting everything into every test (unless there's only one test in the file). Keep the beforeEachProviders setup, but in your component test, try this approach instead of using beforeEach:

it("should create an instance", inject([UserRegistrationService, UserRegistrationServiceSuccess], (_userRegistration : UserRegistrationServiceMock, _userSuccess : UserRegistrationServiceSuccessMock) => {
        let component: BasicRegistrationComponent =
        new BasicRegistrationComponent(null, formBuilder, promptWindow, userInfo, translator, userRegistration);
        expect(component).toBeTruthy();
}));

If you're using mock services, make sure to refer to them as shown above, for example:

_userRegistration : UserRegistrationServiceMock
. Essentially, the inject statement indicates that when the test is expecting UserRegistrationService, it will receive UserRegistrationServiceMock but will be referred to as _userRegistration. Feel free to reach out if you need further clarification :)

Answer №2

An effective method I have discovered for achieving this is to utilize nested describe statements in the following manner:

describe('SomeComponent', () => {

   describe("General Registration Process", () => {
       beforeEachProviders(() => [        
           provide(UserRegistrationService, { useClass: UserRegistrationServiceMock })
       ]);

       beforeEach(inject([UserRegistrationService], (_userRegistration))

       it('should instantiate properly', () => {
          let component: BasicRegistrationComponent =
             new BasicRegistrationComponent(null, formBuilder, promptWindow, userInfo, translator, userRegistration);
           expect(component).toBeTruthy();
       });
    });

    describe("Registration Validation", () => {
        beforeEachProviders(() => [        
            provide(UserRegistrationService, { useClass: UserRegistrationServiceSuccessMock })
        ]);

        beforeEach(inject([UserRegistrationService], (_userRegistration))

        it('should create an instance', () => {
           let component: BasicRegistrationComponent =
              new BasicRegistrationComponent(null, formBuilder, promptWindow, userInfo, translator, userRegistration);
            expect(component).toBeTruthy();
        });
    });
});

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