无法解析 Class: (?) 的所有参数，尽管它已提供

Question

我目前正在为使用ngxs进行状态管理的服务编写一些测试用例。我似乎无法弄清楚下面的代码有什么问题：

// auth.service.ts
@Injectable({
    providedIn: 'root'
})
export class AuthService {
    @Select(SessionState) session$;
    constructor(private http: HttpClient, private store: Store) {
    }
}



// session.state.ts
export interface SessionStateModel {
    user: User | null;
    token: string | null;
    state: 'authenticated' | 'guest' | 'invalid.credentials' | 'error' | 'pending';
    response?: HttpErrorResponse | string | any;
}

export const defaultSessionState: SessionStateModel = {
    user: null,
    token: null,
    state: 'guest',
    response: null
};

@State<SessionStateModel>({
    name: 'session',
    defaults: defaultSessionState
})
export class SessionState {
    constructor(private auth: AuthService) {
    }
}


// session.state.spec.ts
describe('should handle login, logout and errors properly', () => {
    let store: Store;
    let backend: HttpTestingController;

    beforeEach(() => {
        TestBed.configureTestingModule({
            imports: [
                HttpClientTestingModule,
                NgxsModule.forRoot([SessionState])
            ],
            providers: [
                AuthService
            ]
        });

        backend = TestBed.get(HttpTestingController);
        store = TestBed.get(Store);
    });

    afterEach(() => {
        // After every test, assert that there are no more pending requests.
        backend.verify();
    });

    it('should handle successful login', () => {
        // oversimplified...
        expect(true).toBe(true);
    });
});

当我用 运行它时ng test，karma 返回以下异常： Error: Can't resolve all parameters for SessionState: (?).

这没有任何意义，我，因为我已经providing对什么是必要的SessionState（这是AuthService）的TestBed.configureTestingModule。我似乎无法弄清楚我在这里错过了什么？

Answer 1

可能您缺少@Injectable()服务SessionState。这也可能引发错误。

@Injectable()
export class SessionState {
    constructor(private auth: AuthService) {
    }
}