Angular测试如何防止ngOnInit调用直接测试方法

我有一个组件.在其中,ngOnInit函数调用组件的另一个函数来检索用户List.我想制作两个系列的小提琴：

>首先测试ngOnInit是否被正确触发并填充用户列表
>第二次我想测试我的刷新函数,它也调用getUserList()

当我调用fixture.detectChanges()时,使用ngOnInit触发器的第一个测试正常工作.

问题

我的问题是在测试刷新功能时：一旦我调用fixture.detectChanges(),就会触发ngOnInit,然后我无法知道结果的来源以及我的refresh()函数是否会被正确测试.

在我对refresh()方法的第二系列测试之前,有没有办法“删除”或“阻止”ngOnInit()所以它没有在fixture.detectChanges()上调用？

我试着看看overrideComponent,但它似乎不允许删除ngOnInit().

或者除了在我的情况下使用fixture.detectChanges之外,有没有办法检测更改？

码

这是组件,存根服务和我的spec文件的代码.

零件

import { Component,OnInit,ViewContainerRef } from '@angular/core';

import { UserManagementService } from '../../shared/services/global.api';
import { UserListItemComponent } from './user-list-item.component';

@Component({
  selector: 'app-user-list',templateUrl: './user-list.component.html'
})
export class UserListComponent implements OnInit {
  public userList = [];

  constructor(
    private _userManagementService: UserManagementService,) { }

  ngOnInit() {
    this.getUserList();
  }

  onRefreshUserList() {
    this.getUserList();
  }

  getUserList(notifyWhenComplete = false) {
    this._userManagementService.getListUsers().subscribe(
      result => {
        this.userList = result.objects;
      },error => {
        console.error(error);        
      },() => {
        if (notifyWhenComplete) {
          console.info('Notification');
        }
      }
    );
  }
}

组件规范文件

import { NO_ERRORS_SCHEMA } from '@angular/core';
import {
  async,fakeAsync,ComponentFixture,TestBed,tick,inject
} from '@angular/core/testing';

import { Observable } from 'rxjs/Observable';

// Components
import { UserListComponent } from './user-list.component';

// Services
import { UserManagementService } from '../../shared/services/global.api';
import { UserManagementServiceStub } from '../../testing/services/global.api.stub';

let comp:    UserListComponent;
let fixture: ComponentFixture<UserListComponent>;
let service: UserManagementService;

describe('UserListComponent',() => {
  beforeEach(async(() => {
    TestBed.configureTestingModule({
      declarations: [UserListComponent],imports: [],providers: [
        {
          provide: UserManagementService,useClass: UserManagementServiceStub
        }
      ],schemas: [ NO_ERRORS_SCHEMA ]
    })
    .compileComponents();
  }));

  tests();
});

function tests() {
  beforeEach(() => {
    fixture = TestBed.createComponent(UserListComponent);
    comp = fixture.componentInstance;

    service = TestBed.get(UserManagementService);
  });

  it(`should be initialized`,() => {
    expect(fixture).toBeDefined();
    expect(comp).toBeDefined();
  });

  it(`should NOT have any user in list before ngOnInit`,() => {
    expect(comp.userList.length).toBe(0,'user list is empty before init');
  });

  it(`should get the user List after ngOnInit`,async(() => {
    fixture.detectChanges(); // This triggers the ngOnInit and thus the getUserList() method

    // Works perfectly. ngOnInit was triggered and my list is OK
    expect(comp.userList.length).toBe(3,'user list exists after init');
  }));

  it(`should get the user List via refresh function`,fakeAsync(() => {
    comp.onRefreshUserList(); // Can be commented,the test will pass because of ngOnInit trigger
    tick();

    // This triggers the ngOnInit which ALSO call getUserList()
    // so my result can come from getUserList() method called from both source: onRefreshUserList() AND through ngOnInit().
    fixture.detectChanges(); 

    // If I comment the first line,the expectation is met because ngOnInit was triggered!    
    expect(comp.userList.length).toBe(3,'user list after function call');
  }));
}

存根服务(如果需要)

import { Observable } from 'rxjs/Observable';

export class UserManagementServiceStub {
  getListUsers() {
    return Observable.from([      
      {
        count: 3,objects: 
        [
          {
            id: "7f5a6610-f59b-4cd7-b649-1ea3cf72347f",name: "user 1",group: "any"
          },{
            id: "d6f54c29-810e-43d8-8083-0712d1c412a3",name: "user 2",{
            id: "2874f506-009a-4af8-8ca5-f6e6ba1824cb",name: "user 3",group: "any"
          }
        ]
      }
    ]);
  }
}

我的考验

我尝试了一些“解决方法”,但我发现它有点……冗长,也许是矫枉过正！

例如：

it(`should get the user List via refresh function`,fakeAsync(() => {
    expect(comp.userList.length).toBe(0,'user list must be empty');

    // Here ngOnInit is called,so I override the result from onInit
    fixture.detectChanges();
    expect(comp.userList.length).toBe(3,'ngOnInit');

    comp.userList = [];
    fixture.detectChanges();
    expect(comp.userList.length).toBe(0,'ngOnInit');

    // Then call the refresh function
    comp.onRefreshUserList(true);
    tick();
    fixture.detectChanges();

    expect(comp.userList.length).toBe(3,'user list after function call');
}));