Mocking Observable of SpyObject in Jasmine

Question

My component subscribes to an observable of a service like that:

  ngOnInit(): void {
    this.sub.add(
      this.notesService.notes$.subscribe(notes => {
        this.notes = notes.map(note => {
          let profilePicture = generateProfilePicture(note.creator)
            return {
              ...note,
              color: profilePicture.color,
              initials: profilePicture.initials
            }
        })
      })
    );
  } 

In my unit test I created a spyobject for the NoteService. How can I stub the note$ observable?

providers: [
        ConfirmationService,
        {
          provide: HttpClient,
          useValue: jasmine.createSpyObj("HttpClient", ["get", "post", "put", "delete"])
        },
        {
          provide: NotesService,
          useValue: jasmine.createSpyObj("NotesService",
            ["addNote", "getNotesByRefId", "editNote", "deleteNote"])
        }
      ]

Answer 1

Typings apart (use as any when needed) :

const trigger = new Subject<any>();
let trigger$: Observable<any>;

beforeEach(() => {
  trigger$ = trigger.asObservable().pipe(first());
  component.notesService.notes$ = trigger$;
})

it('Should XXX', () => {
  trigger$.subscribe(() => {
    expect(...);
  });

  component.ngOnOnInit();

  trigger.next('Value that the observable should emit');
})