Why does it take so much time to create unit tests?
Unit tests are an important part of any application. However, the development of robust unit tests takes time. One of the things that takes a lot of that time is mocking all the dependencies. Angular CLI doesn't help you a lot, because it only generates the initial .spec file with default TestBed configuration. So how can you speed up unit test development in Angular?
Mock the dependencies with NG-Mocks library
NG-Mocks is a testing library that helps to mock all the dependencies. It has plenty of helper functions. I would like to show you two of them that might help you the most.
Speedup TestBed module configuration with MockProvider function
Each component or service might depend on other components and services. Here's an example of a service that depends on HttpClient, Router and OAuthService:
@Injectable({
providedIn: 'root',
})
export class AuthService {
constructor(
private http: HttpClient,
private router: Router,
private oauthService: OAuthService,
) {
this.configureSSO();
}
/**
* OAuthService needs to be configured in order to use its Single Sign-On feature
*/
private configureSSO() {
this.oauthService.configure(authConfig);
this.oauthService.tokenValidationHandler = new JwksValidationHandler();
this.oauthService.loadDiscoveryDocumentAndTryLogin();
}
loginWithSSO(): void {
// ...
}
logoutWithSSO(): void {
// ...
}
loginUserAndRedirect(): Observable<boolean> {
return this.http.post('http://localhost:4200/', 'some payload').pipe(
switchMap(() => {
this.router.navigate(['/dashboard']);
return of(true);
}),
);
}
}
Let's implement the test config for that service. The default approach would be to use the TestBed.configureTestingModule() function to configure all the dependencies. What needs to be passed into that function:
-
HttpClientTestingModule, which configures HttpClientTestingBackend used by HttpClient. - Mock of
OAuthService.
describe('AuthService', () => {
let service: AuthService;
let router: Router;
let httpMock: HttpTestingController;
let oAuthService: OAuthService;
beforeEach(() => {
TestBed.configureTestingModule({
imports: [HttpClientTestingModule],
providers: [
{
provide: OAuthService,
useValue: {
configure: () => {},
loadDiscoveryDocumentAndTryLogin: () => {},
tokenValidationHandler: new JwksValidationHandler(),
},
},
],
});
router = TestBed.inject(Router);
httpMock = TestBed.inject(HttpTestingController);
oAuthService = TestBed.inject(OAuthService);
service = TestBed.inject(AuthService);
});
});
At least two tests need to be added. Both of them would contain spyOn functions to detect when a specific method gets called on an instance of a specific class:
describe('AuthService', () => {
let service: AuthService;
let router: Router;
let httpMock: HttpTestingController;
let oAuthService: OAuthService;
beforeEach(() => {...});
it('should configure SSO on initialization ', () => {
// Arrange
const configureSpy = spyOn(oAuthService, 'configure');
const tokenValidationHandlerSpy = spyOnProperty(oAuthService, 'tokenValidationHandler', 'set');
const loadDiscoveryDocumentAndTryLoginSpy = spyOn(oAuthService, 'loadDiscoveryDocumentAndTryLogin');
const httpClientSpy: HttpClient = jasmine.createSpyObj(['post']);
// Act
new AuthService(httpClientSpy, router, oAuthService);
// Assert
expect(configureSpy).toHaveBeenCalledWith(authConfig);
expect(tokenValidationHandlerSpy).toEqual(new JwksValidationHandler());
expect(loadDiscoveryDocumentAndTryLoginSpy).toHaveBeenCalled();
});
it('should send a POST request to the server and navigate to "/dashboard" on success', () => {
// Arrange
const navigateSpy = spyOn(router, 'navigate');
// Act
service.loginUserAndRedirect().subscribe();
// Assert
const req = httpMock.expectOne('http://localhost:4200/');
expect(req.request.method).toBe('POST');
req.flush({}); // Simulate a successful response
expect(navigateSpy).toHaveBeenCalledWith(['/dashboard']);
});
});
Now let's replace the mock of OAuthService in TestBed with NG-Mocks MockProvider helper function:
beforeEach(() => {
TestBed.configureTestingModule({
imports: [HttpClientTestingModule],
providers: [MockProvider(OAuthService)],
});
//...
});
MockProvider(OAuthService) creates empty dummies as methods of OAuthService which is totally ok for implemented tests.
Spy all methods of services using ngMocks.autoSpy
ngMocks.autoSpy is an awesome feature if you want to get rid of all spied methods in your tests. In order to use it in the specific test, it needs to be added on top of the .spec file:
ngMocks.autoSpy('jasmine');
describe('AuthService', () => {
//...
})
After that tests need to be updated:
ngMocks.autoSpy('jasmine');
describe('AuthService', () => {
let service: AuthService;
let router: Router;
let httpMock: HttpTestingController;
let oAuthService: OAuthService;
beforeEach(() => {
TestBed.configureTestingModule({
imports: [HttpClientTestingModule],
providers: [MockProvider(OAuthService), MockProvider(Router)],
});
router = TestBed.inject(Router);
httpMock = TestBed.inject(HttpTestingController);
oAuthService = TestBed.inject(OAuthService);
service = TestBed.inject(AuthService);
});
it('should configure SSO on initialization ', () => {
// Assert
expect(oAuthService.configure).toHaveBeenCalledWith(authConfig);
expect(oAuthService.tokenValidationHandler).toEqual(new JwksValidationHandler());
expect(oAuthService.loadDiscoveryDocumentAndTryLogin).toHaveBeenCalled();
});
it('should send a POST request to the server and navigate to "/dashboard" on success', () => {
// Act
service.loginUserAndRedirect().subscribe();
// Assert
const req = httpMock.expectOne('http://localhost:4200/');
expect(req.request.method).toBe('POST');
req.flush({}); // Simulate a successful response
expect(router.navigate).toHaveBeenCalledWith(['/dashboard']);
});
});
As you can see, now it's a bit less code in the tests.
Make tests more maintainable
One more exciting thing from NG-Mocks is a proposal on how to make tests more maintainable. The idea is to write tests without scoped variables. Basically, specific arrangements need to be applied to specific tests so that each test is self-sufficient and does not rely on scoped variables:
ngMocks.autoSpy('jasmine');
describe('AuthService', () => {
let service: AuthService;
beforeEach(() => {
TestBed.configureTestingModule({
imports: [HttpClientTestingModule],
providers: [MockProvider(OAuthService), MockProvider(Router)],
});
service = TestBed.inject(AuthService);
});
it('should configure SSO on initialization ', () => {
// Arrange
const oAuthService = TestBed.inject(OAuthService);
// Assert
expect(oAuthService.configure).toHaveBeenCalledWith(authConfig);
expect(oAuthService.tokenValidationHandler).toEqual(new JwksValidationHandler());
expect(oAuthService.loadDiscoveryDocumentAndTryLogin).toHaveBeenCalled();
});
it('should send a POST request to the server and navigate to "/dashboard" on success', () => {
// Arrange
const httpMock = TestBed.inject(HttpTestingController);
const router = TestBed.inject(Router);
// Act
service.loginUserAndRedirect().subscribe();
// Assert
const req = httpMock.expectOne('http://localhost:4200/');
expect(req.request.method).toBe('POST');
req.flush({}); // Simulate a successful response
expect(router.navigate).toHaveBeenCalledWith(['/dashboard']);
});
});
As you can see now arrangements are applied to specific tests. That should make them more maintainable as we add other tests into that .spec file.
Conclusion
I hope NG-Mocks will help you with unit test development and improve your overall developer experience as you create Angular applications. Happy coding!
Top comments (0)