class MockAuthService {
  currentUser = of(fromSeeds.userAuth);
}
describe('AuthEffects', () => {
  ...
  let authService: AuthService;

beforeEach(async () => {
   TestBed.configureTestingModule({
   ......,
  { provide: AuthService,  useClass: MockAuthService },
  ...
  })
})

 describe('listen$', () => {
    beforeEach(async () => {
       TestBed.overrideProvider(authService.currentUser, {
         useValue: of({ ...fromSeeds.userAuth, emailVerified: false })
       });
    });
    it('should', () => {
     // test here
    })
  });