Jasmine angular unit testing BehaviorSubject

Question

i have some service like this

calendar-domain.service.ts

@Injectable()
export class CalendarDomainService {
  private _calendarWeek = new BehaviorSubject<CalendarWeekTo | null>(null);
  get calendarWeek$(): Observable<CalendarWeekTo | null> {
    return this._calendarWeek.asObservable();
  }

  setCalendarWeek(calendarWeek: CalendarWeekTo): void {
    this._calendarWeek.next(calendarWeek);
  }
}

And unit test like this

calendar-domain.service.spec.ts

import { CUSTOM_ELEMENTS_SCHEMA, NO_ERRORS_SCHEMA } from '@angular/core';
import { TestBed } from '@angular/core/testing';

import { CalendarDomainService } from './calendar-domain.service';

describe('CalendarDomainService', () => {
    let service: CalendarDomainService;

    beforeEach(() => {
        TestBed.configureTestingModule({
            providers: [CalendarDomainService],
            schemas: [CUSTOM_ELEMENTS_SCHEMA, NO_ERRORS_SCHEMA]
        });
        service = TestBed.inject(CalendarDomainService);
    });

    it('should be created', () => {
        expect(service).toBeTruthy();
    });
});

As you may see i didn't test those two function, because honest I don't know how even to start testing, any info about how to start, thanks

Answer 1

You can use the done Callback on the test itself and subscribe normally to the subject.

it('Should emit next value of the week', (done)=>{
   service.setCalendarWeek(<yourvaluehere>);
   service.calendarWeek$.subscribe(v=> {
     expect(v).toBe(<yourvaluehere>)
     done();
   });
});