How to unit test a component that depends on parameters from ActivatedRoute?

Question

I am unit testing a component that is used to edit an object. The object has an unique id that is used in order to grab the specific object from an array of obj

Answer 1

Ran into the same issue while creating test suites for a routing path as:

{
   path: 'edit/:property/:someId',
   component: YourComponent,
   resolve: {
       yourResolvedValue: YourResolver
   }
}

In the component, I initialized the passed property as:

ngOnInit(): void {    
   this.property = this.activatedRoute.snapshot.params.property;
   ...
}

When running the tests, if you do not pass a property value in your mock ActivatedRoute "useValue", then you will get undefined when detecting changes using "fixture.detectChanges()". This is because the mock values for ActivatedRoute does not contain the property params.property. Then, it is required for the mock useValue to have those params in order for the fixture to initialize the 'this.property' in the component. You can add it as:

  let fixture: ComponentFixture;
  let component: YourComponent;
  let activatedRoute: ActivatedRoute; 

  beforeEach(done => {
        TestBed.configureTestingModule({
          declarations: [YourComponent],
          imports: [ YourImportedModules ],
          providers: [
            YourRequiredServices,
            {
              provide: ActivatedRoute,
              useValue: {
                snapshot: {
                  params: {
                    property: 'yourProperty',
                    someId: someId
                  },
                  data: {
                    yourResolvedValue: { data: mockResolvedData() }
                  }
                }
              }
            }
          ]
        })
          .compileComponents()
          .then(() => {
            fixture = TestBed.createComponent(YourComponent);
            component = fixture.debugElement.componentInstance;
            activatedRoute = TestBed.get(ActivatedRoute);
            fixture.detectChanges();
            done();
          });
      });

The you can start testing as for example:

it('should ensure property param is yourProperty', async () => {
   expect(activatedRoute.snapshot.params.property).toEqual('yourProperty');
   ....
});

Now, lets say you would like to test a different property value, then you can update your mock ActivatedRoute as:

  it('should ensure property param is newProperty', async () => {
    activatedRoute.snapshot.params.property = 'newProperty';
    fixture = TestBed.createComponent(YourComponent);
    component = fixture.debugElement.componentInstance;
    activatedRoute = TestBed.get(ActivatedRoute);
    fixture.detectChanges();

    expect(activatedRoute.snapshot.params.property).toEqual('newProperty');
});

Hope this helps!