Angular 12 unit test, spy a function inside subscribe - unit-testing

Question

I'm subscribing to a behavior subject in onInit and based on the result I'm calling a function. My code is like
subscription = new Subscription();
constructor(private myService: MyService) {}
ngOnInit() {
this.subscription = this.myService.event.subscribe(response => {
if(response){
this.myFunction();
}
});
}
myFunction() {}
and I'm test this by trying like below
describe('AppComponent', () => {
let event = new BehaviorSubject(false);
beforeEach(async () => {
await TestBed.configureTestingModule({
declarations: [
AppComponent
], imports: [
], providers: [{
provide: MyService, useValue: {
event: event
}
}]
}).compileComponents();
});
it('should create', () => {
expect(component).toBeTruthy();
});
it('should call myFunction', (done) => {
const myService = fixture.debugElement.injector.get(MyService);
myService.event.next(true);
component.ngOnInit();
const spy = spyOn(component, 'myFunction');
myService.event.subscribe((event: boolean) => {
expect(spy).toHaveBeenCalled();
done();
})
});
});
and I'm getting my spy is not called. Please help me to fix my code. Thanks a lot.

Answer 1

You're spying too late it seems.
Try the following:
// !! Spy first
const spy = spyOn(component, 'myFunction');
// !! Then call ngOnInit
component.ngOnInit();
Edit
Try with fakeAsync and tick.
it('should call myFunction, fakeAsync(() => {
const myService = fixture.debugElement.injector.get(MyService);
myService.event.next(true);
const spy = spyOn(component, 'myFunction');
component.ngOnInit();
tick();
expect(spy).toHaveBeenCalled();
}));
The fakeAsync/tick should hopefully wait until the subscribe is done before moving on to the expect.