Spy on the result of an Observable Subscription with Jasmine

I am Jasmine unit testing an angular component, which uses Observables. My component has this lifecycle hook that I am testing:

ngOnInit() {
this.dataService.getCellOEE(this.cell).subscribe(value => this.updateChart(value));
}


I have a test that ensures that getCellOEE has been called, but now I want to check that updateChart is called when the observable resolves with a new value. This is what I have so far:

let fakeCellService = {
getCellOEE: function (value): Observable<Array<IOee>> {
return Observable.of([{ time: moment(), val: 67 }, { time: moment(), val: 78 }]);
}
};

describe('Oee24Component', () => {
let component: Oee24Component;
let service: CellService;
let injector: Injector;
let fixture: ComponentFixture<Oee24Component>;

beforeEach(async(() => {
TestBed.configureTestingModule({
declarations: [Oee24Component],
providers: [{ provide: CellService, useValue: fakeCellService }]
})
.compileComponents();
}));

beforeEach(() => {
fixture = TestBed.createComponent(Oee24Component);
component = fixture.componentInstance;
injector = getTestBed();
service = injector.get(CellService)
fixture.detectChanges();
spyOn(service, 'getCellOEE').and.returnValue({ subscribe: () => { } });
spyOn(component, 'updateChart');
});

it('should get cell oee on init', () => {
component.ngOnInit();
expect(service.getCellOEE).toHaveBeenCalled();
});

it('should update chart on new data', () => {
component.ngOnInit();
expect(component.updateChart).toHaveBeenCalled();
});
});


However, I get the error:

chrome 56.0.2924 (Windows 10 0.0.0) Oee24Component should update chart on new data FAILED

Expected spy updateChart to have been called.
​

Presumably this is a timing issue because the observable hasn't necessarily resolved when the test checks? If that is the case, how do I set this up correctly?

Update:


Here is my component:

@Component({
selector: 'app-oee24',
templateUrl: './oee24.component.html',
styleUrls: ['./oee24.component.css']
})
export class Oee24Component implements OnInit {
public barChartData: any[] = [{ data: [], label: 'OEE' }];

constructor(public dataService: CellService) { }

ngOnInit() {
this.dataService.getCellOEE(this.cell).subscribe(value => this.updateChart(value));
}

updateChart(data: Array<IOee>) {
this.barChartData[0].data = data.map(val => val.val);
}
}

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