如何为angular2 +

Question

配置服务和工厂service.ts文件

import { Injectable, Injector } from '@angular/core';
import { AppConfig } from './app.config';
import { environment } from '../../environments/environment';
import { LOCATION_INITIALIZED } from '@angular/common';
import { HttpClient } from '@angular/common/http';


@Injectable()
export class ConfigService {
  public config: AppConfig;
  public constructor() {}
}

export function configFactory(http: HttpClient, injector: Injector, configSrv: ConfigService) {
  const configFileName = environment.configFilePath;
     return () => new Promise<any>((resolve: any) => {
       const locationInitialized = injector.get(LOCATION_INITIALIZED, Promise.resolve(null));
       locationInitialized.then(() => {
         http.get(configFileName).subscribe(res => {
         configSrv.config = <AppConfig>res;
           resolve(null);
         }, error => {
           console.error('INITIALIZATION:', error);
           resolve(null);
         });
       });
     });
 }

---

环境文件

export const environment = {
  production: false,
  configFilePath: 'config/app.config.json',
};

app.config.json

{    
    "apiBaseUrl": "http://localhost:9999/api/"
}

在写测试用例时遇到错误为 错误TypeError：无法读取未定义的属性' apiBaseUrl '

如何为上述代码编写茉莉花单元测试用例？

代码单元测试代码

import { TestBed, inject, fakeAsync } from '@angular/core/testing';
import { ConfigService, configFactory } from './config.service';

import { Injector, APP_INITIALIZER } from '@angular/core';
import { MockBackend, MockConnection } from '@angular/http/testing';
import { BaseRequestOptions, ConnectionBackend, Http, HttpModule, Response, ResponseOptions, RequestOptions } from '@angular/http';
import { HttpClient } from '@angular/common/http';
//import { environment } from '../../environments/environment';

describe('ConfigService', () => {
  beforeEach(() => {
    TestBed.configureTestingModule({
      providers: [ConfigService]
    });
  });

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

如何使用模拟编写针对配置工厂功能的单元测试？