I have been tackling a unit test in Angular related to a singleton service. Specifically, I have a UserService that is declared as a singleton in the root module of the application. My goal is to create a unit test that verifies whether the instance of UserService remains consistent across the entire application. I have attempted the following approach, but it primarily focuses on checking the component and Testbed instance. Is there a way to write a single unit test that covers all the feature modules and ensures that we maintain the same instance? Any guidance would be greatly appreciated.
import { TestBed, ComponentFixture, inject } from '@angular/core/testing';
import { LoginComponent } from './login.component';
import { AuthService } from "./auth.service";
class MockAuthService extends AuthService {
isAuthenticated() {
return 'Mocked';
}
}
describe('Component: Login', () => {
let component: LoginComponent;
let fixture: ComponentFixture<LoginComponent>;
let testBedService: AuthService;
let componentService: AuthService;
beforeEach(() => {
// Refine the test module by declaring the test component
TestBed.configureTestingModule({
declarations: [LoginComponent],
providers: [AuthService]
});
// Configure the component with a different set of Providers
TestBed.overrideComponent(
LoginComponent,
{ set: { providers: [{ provide: AuthService, useClass: MockAuthService }] } }
);
// Create the component and the test fixture
fixture = TestBed.createComponent(LoginComponent);
// Get the test component from the fixture
component = fixture.componentInstance;
// AuthService provided to the TestBed
testBedService = TestBed.get(AuthService);
// AuthService provided by the Component (should return MockAuthService)
componentService = fixture.debugElement.injector.get(AuthService);
});
it('Service injected via inject(...) and TestBed.get(...) should be the same instance',
inject([AuthService], (injectService: AuthService) => {
expect(injectService).toBe(testBedService);
})
);
});