Аргумент типа 'Observable <LoginRequest>' не может быть назначен параметру типа 'LoginRequest'

Я пытаюсь выполнить модульное тестирование, используя Karma/Jasmine, я получаю ошибку

Аргумент типа "Observable" не присваивается параметру типа "LoginRequest". Свойство 'userid' отсутствует в типе 'Observable'

Я получаю ошибку во время компиляции в login.service.spec.ts, где я service.login(loginRequest); ,

login.service.spec.ts

import { ComponentFixture, TestBed, inject } from '@angular/core/testing';
import { ApiConnectorService } from '../api-handlers/api-connector.service';
import { LoginService } from './login.service';
import { HttpClient, HttpHandler } from '@angular/common/http'; 
import { Observable } from 'rxjs';
import { of } from 'rxjs/observable/of';
import { LoginResponse, LoginRequest } from './login.contract';


class ApiConnectorServiceStub {
  constructor() { }
  post(address: string, payload: LoginRequest): Observable<LoginResponse> {
    let str:LoginResponse = {token:'success'};
    return  of(str);
  }
}
describe('LoginService', () => {
  let service: LoginService;
  let fixture: ComponentFixture<LoginService>;

  beforeEach(() => {
    TestBed.configureTestingModule({
           providers: [LoginService, ApiConnectorService, HttpClient, HttpHandler,
          {provide: ApiConnectorService, useClass: ApiConnectorServiceStub}]
    });
  });

  it('should be created', inject([LoginService], (service: LoginService) => {
    expect(service).toBeTruthy();
  }));

  it('should call post on apiConnectorService with right parameters when login is called',
                                          inject([LoginService], (service: LoginService) => {
    const apiConnectorStub = TestBed.get(ApiConnectorService);
    const str:LoginResponse = {token:'success'};
    const spy = spyOn(apiConnectorStub, 'post').and.returnValue(of(str));
    const lRequest: LoginRequest={userid:'[email protected]',password:'hsjshsj',newpassword:'hsjshsj'};
    const loginRequest = of(lRequest);
    service.login(loginRequest);

    expect(spy).toHaveBeenCalledWith('/api/login', loginRequest);
  })); 

});

login.service.ts

import { Injectable } from '@angular/core';
import { ApiConnectorService } from '../api-handlers/api-connector.service';
import { LoginRequest, LoginResponse } from './login.contract';
import { Observable } from 'rxjs/Observable';
import { map } from 'rxjs/operators';
import * as marked from 'marked';

@Injectable()
export class LoginService {

  constructor(private apiConnector: ApiConnectorService) { }
  login(payload: LoginRequest): Observable<LoginResponse> {
    console.log('Login payload ', payload);
    return this.apiConnector.post('/api/login', payload)
      .pipe(
        map((data: LoginResponse) => data)
      )
  }

}

login.contract.ts

export interface LoginRequest {
    env?: string;
    userid: string;
    password: string;
    newpassword: string;
}

export interface LoginResponse {
    token: string;
}

API-connector.service.ts

import { Injectable } from '@angular/core';
import { HttpClient, HttpParams } from '@angular/common/http';
import { ErrorObservable } from 'rxjs/observable/ErrorObservable';
import { Observable } from 'rxjs/Observable';
import {environment} from '../../../environments/environment';
import { catchError } from 'rxjs/operators/catchError';


@Injectable()
export class ApiConnectorService {

  constructor(private http: HttpClient) { }

 private  getQueryString(params): string {
    const queryString = Object.keys(params).map(key => key + '=' + params[key]).join('&');
    console.log('QUERY STRING', queryString);
    return ('?' + queryString);
  }

  private formatErrors(error: any) {
    return new ErrorObservable(error.error);
  }
  post(path: string, body: Object): Observable<any> {
    // console.log('API SERVICE BODY', body)
    return this.http.post(
      '${environment.base_url}${path}',
      body
    ).pipe(catchError(this.formatErrors));
  }
}