spyOn not working on a dependency in Angular 7 unit tests

Question

I have a component that depends on SearchAttributeService. There is a method called searchAttributeValidation service that returns a Subject. I am subscribing to that subject like this:

  attributeSearchValidation(): void {
    this._searchAttributeService.searchAttributeValidation.subscribe((value: string) => {
      if (value === this._searchAttributeService.emptyAttributeSearchData) {
        this.searchAttributeIndicator = true;
      } else if (value === this._searchAttributeService.clearEmptyAttributeSearchDataValidation) {
        this.searchAttributeIndicator = false;
    });
  }

get searchAttributeValidation(): Subject<string> {
   return this.searchAttributeValidationSubject;
}

I am trying to test this method like this:

  searchAttributeService = TestBed.get(SearchAttributeService);
  let spy = spyOn(searchAttributeService, 'searchAttributeValidation').and.returnValue(of('EMPTY-DATA'));
  component.attributeSearchValidation();
  expect(spy).toHaveBeenCalled();
  expect(component.searchAttributeIndicator).toBeTruthy();

It does not call the searchAttributeValidation method at all during the test. I even provided the service TestBed.configureTestingModule({

The test fails with the message: Expected spy searchAttributeValidation to have been called.

Where am I going wrong?? Spent a whole day on it, but, couldn't figure out the issue?

Answer 1

spyOn is for methods but you are accessing a property, if it was a method you would be accessing it like

this._searchAttributeService.searchAttributeValidation().subscribe

with the call () paramaters.

If it is a getter property then use spyOnProperty or if it is an instance property then reassign it.

searchAttributeService.searchAttributeValidation = of('EMPTY-DATA');

and get rid of the expect to have been called.