Angular testing: Cannot read property 'nativeElement' of null

I am new in Angular testing and at the moment I am trying to test this piece of code but I'm getting an error concerning the event raised on the DOM:

<li class="list-group-item" *ngFor="let user of users">
  <a class="test-link"[routerLink]="['/detail', user.id]">
    {{user.userName}}
  </a>
</li>

The Test file:

beforeEach(async(() => {
  TestBed.configureTestingModule({
    declarations: [AdminComponent, UserDetailComponent],
    imports: [HttpClientModule,RouterTestingModule.withRoutes([
      {path:'detail/:id',
        component: UserDetailComponent}],
    )],
    providers: [UserService, AuthService]
  })
    .compileComponents();
}));

beforeEach(() => {
  router = TestBed.get(Router);
  location = TestBed.get(Location);

  fixture = TestBed.createComponent(AdminComponent);
  debugElement = fixture.debugElement;
  component = fixture.componentInstance;
  fixture.detectChanges();

});

it('test demands redirection', fakeAsync(() => {

  debugElement
    .query(By.css('.test-link'))
    .nativeElement.click();

  tick();

  expect(location.path()).toBe('/detail/testing/1');

}));

Why is click event on the native element is null?