I try to write a UT for a service in Angular.

The Service will look like this

@Injectable()
export class TimeZoneStateService {
  constructor(
    @Optional()
    @Inject(GLOBAL_CONFIG)
    private config?: ViewConfig,
  ) {}
}

and the UT

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

import {
  GLOBAL_CONFIG,
  TimeZoneStateService,
} from '@sdo/givs-common-service';

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

  beforeEach(() => {
    TestBed.configureTestingModule({
      providers: [
        TimeZoneStateService,
        {
          provide: GLOBAL_CONFIG,
          useValue: {
            timeZoneResolver: () => 'America/Toronto',
          },
        },
      ],
    });
    service = TestBed.createComponent(TimeZoneStateService).componentInstance;
  });

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

the error message when I run the UT is

enter image description here

I try to pass the UT, and don’t know why the have such error