This would help you

describe('FilterPanelComponent', () => {
    let component: FilterBarComponent;
    let fixture: ComponentFixture<FilterBarComponent>;
    beforeEach(async(() => {
        TestBed.configureTestingModule({
            declarations: [
                FilterBarComponent
            ],
            imports: [],
            providers: [
                {
                    provide: SisenseService,
                    useClass: SisenseServiceStub
                },
                SisenseConfigService
            ]
        }).compileComponents();
    }));

    beforeEach(() => {
        fixture = TestBed.createComponent(FilterBarComponent);
        component = fixture.componentInstance;
        fixture.detectChanges();
    });

    it('should call getDataFromWidget() on init method',()=>{
        spyOn(component,'getDataFromWidget').and.callThrough();
        component.ngOnInit();
        expect(component.getDataFromWidget).toHaveBeenCalled()
    })

    it('getDataFromWidget should set selected member count',()=>{
        component.selectedMembersCount = 0;
        component.getDataFromWidget();
        expect(component.selectedMembersCount).toEqual(1);
        fixture.detectChanges();
        const htmlEle  = fixture.debugElement.nativeElement.querySelector('#some-count'); // For class try query(By.css('.some-count')).nativeElement;
        expect(htmlEle.innerHTML).toBe(1);        
    })
});

// this is the stub she is talking about
export class SisenseServiceStub{
    getWidgetData(){
        return of({
            queryResult : {
                value : {
                    data : 1
                }
            }
        })
    }
}

Few months back, I also saw some of my juniors struggling with unit tests. So, I wrote series of articles which can help you as well.

Give it a try and let me know if it helped. Here is how you play with stubs and spies