Angular 2 testing components with observables - unit-testing

Question

I am testing a angular component and the code is
ngOnInit(): void {
this.getNar();
}
getNar(): void {
let self = this;
this.dashboardService.getNar().subscribe(
res => self.narIds = res.narIds,
error => self.error = error,
function () {
self.narIds.forEach(element => {
// Some Code
});
}
);
}
The Service provider for this i.e Dashboard Service is
getNar(): Observable<any> {
return this.http.get(Config.Api.GetNar + '1/nar').map((res: Response) => res.json());
}
And my Test cases are:
let res = '"narIds":[{"id":1,"narId":"104034-1","narName":"SDLC Platform"},{"id":2,"narId":"64829-1","narName":"EMS-EMS"}]';
describe('Application Health Component', () => {
beforeEach( async(() => {
TestBed.configureTestingModule({
providers: [MockBackend, DashboardService],
imports: [ChartsModule, SlimScrollModule, HttpModule],
declarations: [CompletedFilterPipe, ApplicationHealthComponent]
})
.compileComponents()
.then(createComponent);
}));
it('should call the getNar when ngOnInit is called', async(() => {
spyOn(dashboardService, 'getNar').and.returnValue(Observable.of(res));
comp.ngOnInit();
expect(dashboardService.getNar).toHaveBeenCalled();
}));
});
function createComponent() {
fixture = TestBed.createComponent(ApplicationHealthComponent);
comp = fixture.componentInstance;
dashboardService = fixture.debugElement.injector.get(DashboardService);
};
The problem I am getting is the test case gives an error that forEach is undefined.

Answer 1

The error message is not that forEach function is not defined, it's that your object "self.narIds" is undefined. Fairly sure this is due to the way you declared your onComplete function in Observable.subscribe
related to this Rx Subscribe OnComplete fires but cannot use the data
change your
function () {
self.narIds.forEach(element => {
// Some Code
});
code to
() => {
self.narIds.forEach(element => {
// Some Code
});