Angular 4：如何测试订阅中的事件

Question

I have a component and in the constructor, I subscribe to an event.

I send an event via an event service

import {Injectable} from '@angular/core';
import {Observable} from "rxjs/Observable";
import {Subject} from "rxjs/Subject";

@Injectable ()
export class EventService {
  private sendSource    = new Subject<string> ();

  sendMessage (message: string) {
    this.sendSource.next (message);
  }
 getMessage (): Observable<any> {
   return this.sendSource.asObservable ();
 }
}

The component contructor:

constructor (private eventService: EventService) {
    this.subscription = this.eventService.getMessage()
      .subscribe (message => {
        this.menu = message;
      });
}

The .spec file:

it ('should receive event', async (() => {
    eventService = new EventService ();
    eventService.sendMessage ('test');

    fixture.detectChanges ();
    fixture.whenStable ().then (() => {
      expect (component.menu).toBeEqual('test');
    });
}));

My Problem: The this.menu property do not change when I send an event.

Can somebody explain my error in reasoning? Thanks in advance.

Answer 1

You're instantiating the service in the test, but where / how do you inject it in the component ? I suspect you use a different instance.

If you've added the service as a provider in the TestBed configuration you can get an instance of it using the injector:

const eventService = fixture.debugElement.injector.get(EventService);

And then you can call the sendMessage method and you should get something in the component.