Testing nested function in jasmine

Question

I want make a testing in my project and the function I want test is a nested function, there function in function

the function like this:

  ngOnInit() {
    this.getMenu()
  }

this is my test spec:

    describe('NavigationComponent', () => {
        let component: NavigationComponent;
        let fixture: ComponentFixture<NavigationComponent>;

        beforeEach(async(() => {
          TestBed.configureTestingModule({
            imports: [

            ],
            providers: [
              { provide: AuthenticationService, useClass: MockAuthenticationService }
            ]
          })
          .compileComponents();
        }));

        beforeEach(() => {
          fixture = TestBed.createComponent(NavigationComponent);
          //navComponent = TestBed.createComponent(NavigationComponent);
          component = fixture.componentInstance;
          fixture.detectChanges();
        });

  it('getMenu should called', ()=>{
        spyOn(component, 'getMenu');                  
        fixture.detectChanges();                      
        expect(component.getMenu).toHaveBeenCalled();
    })

It's work when I test ngOnInit, but I don't know how to test "getMenu"

thanks for the help

Amit Chigadani · Accepted Answer · 2018-11-16 04:25:04Z

3

You can check if the method getMenu() was called or not when ngOnInit() ran.

What you have to do is spy on that method and then verify.

spyOn(compInstance, 'getMenu');                  //spy on getMenu
fixture.detectChanges();                         //calls ngOnInit() and updates dom
expect(compInstance.getMenu).toHaveBeenCalled(); //verify getMenu() invokation

If you want to test the logic of getMenu(), then you can directly call it from your test spec and then verify its output.

let res = compInstance.getMenu();
expect(res).toBe('pizza');

edited Nov 16, 2018 at 4:25

answered Nov 16, 2018 at 4:19

Amit Chigadani

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5 Comments

pahlevi Over a year ago

I try it and I get this message <spyOn> : could not find an object to spy upon for getMenu() Usage: spyOn(<object>, <methodName>)

Amit Chigadani Over a year ago

Can you please show your test spec? Better add that to your question.

pahlevi Over a year ago

I add my test spec

Amit Chigadani Over a year ago

Comment out fixture.detectChanges() inside before each and check. Because when first detectChanges happens ngOnInit() gets called. So before spying, getMenu() will be called. To avoid this, you have to spy on any method before it is being called.

pahlevi Over a year ago

after I comment I still get that message: <spyOn> : could not find an object to spy upon for getMenu() Usage: spyOn(<object>, <methodName>)

Ankit Choudhary · Accepted Answer · 2020-12-24 09:50:07Z

-1

Add spyOn(component, 'getMenu'); in beforeEach block after you are assigning component variable.

The error is telling you that it is not getting the required method that you want to spy on.

PS- Too late for this answer, but maybe it will help someone else

answered Dec 24, 2020 at 9:50

Ankit Choudhary

1652 silver badges13 bronze badges

2 Comments

PMO1948 Over a year ago

That would not solve the issue - it would just test that the function was called, but not actually test the function itself

Ankit Choudhary Over a year ago

you can chain it with .and.callThrough() if you want to call the real function

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