A sample spec using a beforeEach block

preferences.service.spec.ts

describe('PreferencesService', () => {
  describe('.getPreference', () => {
    let service: PreferencesService;
    let testValue: Observable<string>;
    let result: Observable<string>;
    let getItemSpy: jasmine.Spy;
    
    beforeEach(() => {
      testValue = scheduled(['test value'], asapScheduler);
      getItemSpy = jasmine.createSpy('getItem').and.returnValue(testValue);
      service = new PreferencesService({ getItem: getItemSpy } as LocalStorage);
      result = service.getPreference('test key');
    });

    it('should call getItem from LocalStorage', () => {
      expect(getItemSpy).toHaveBeenCalled();
    });

    it('should return the value from LocalStorage', () => {
      expect(result).toBe(testValue);
    });
  });
});