Não é possível ler a propriedade '_getPortal' de indefinida no teste de unidade iônica 2

Eu sou iniciante no teste de unidade iônica 2. Eu segui a documentação angular 2 (https://angular.io/docs/ts/latest/guide/testing.html) para testar minha aplicação iônica 2 com karma e jasmim.

Mas agora estou preso em um erro chamado

'Não é possível ler a propriedade' _getPortal 'de indefinido'

aqui está o meuLocationSearchModal.ts Arquivo

import { Component } from '@angular/core';
import { NavController, ViewController } from 'ionic-angular';
import { Location } from '../../services/domain/Location';
import { LocationService } from '../../services/LocationService';
import { LoadingController } from 'ionic-angular';

@Component({
  selector: 'location-search-modal',
  templateUrl: 'location-search-modal.html'
})
export class LocationSearchModal {
  locationList: Array<Location> = new Array<Location>();
  selectedLocation: number;
  temp: any = "test";

  constructor(public navCtrl: NavController, public locationService: LocationService, public viewController: ViewController, public loadingController: LoadingController) {
    this.filterLocationsForString();
  }

  filterLocations(event: any): void {
    const searchString: string = event.target.value;
    this.filterLocationsForString(searchString);
    console.log(this.filterLocationsForString(searchString));
  }

  filterLocationsForString(searchString?: string) {
    let loader = this.loadingController.create({
      content: "loading"
    });
    loader.present();
    this.locationService.getLocationsForLikeSearchString(searchString)
      .subscribe((result) => {
        loader.dismissAll();
        this.locationList = result
      });
    console.log(this.locationList);
  }

  closeLocationSearch() {
    this.locationService.getLocationById(this.selectedLocation)
      .subscribe((location) => this.viewController.dismiss(location[0]));
  }

}

e eu usei o serviço chamado locationService.ts lá e é esse serviço

import { Injectable } from '@angular/core';
import { Location } from './domain/Location';

import { DatabaseAccessor } from  '../database/DatabaseAccessor';
import { Observable } from 'rxjs/Rx';

@Injectable()
export class LocationService {
  locationList:Array<Location> = new Array<Location>();

  constructor(public databaseAccessor: DatabaseAccessor) {}

  getLocationsForLikeSearchString(searchString: string) : Observable<Array<Location>> {
    const searchValue = (searchString == null) ? '%' : searchString.trim() + '%';
    return <Observable<Array<Location>>> Observable.fromPromise(this.databaseAccessor.runSelectQuery(Location, new Location(), 'WHERE name LIKE ?', [searchValue]));
  }

  getLocationById(id: number): Observable<Location> {
    return <Observable<Location>> Observable.fromPromise(this.databaseAccessor.runSelectQuery(Location, new Location(), 'WHERE id = ?', [id]));
  }

  saveLocations(locations: Array<Location>){
    this.databaseAccessor.runInsertBatchQuery(Location.prototype, locations);
  }


}

Por fim, escrevi umspec.ts arquivo para teste de unidade e aqui está isso,

import { ComponentFixture, async } from '@angular/core/testing';
import { LocationSearchModal } from './LocationSearchModal';
import { LocationService } from '../../services/LocationService';
import { TestUtils } from '../../test';
import { TestBed } from '@angular/core/testing';
import { App, NavController, Platform, Config, Keyboard, Form, IonicModule, GestureController, ViewController, LoadingController }  from 'ionic-angular';
import { ConfigMock } from '../../mocks';
import { TranslateModule } from 'ng2-translate';
import { DatabaseAccessor } from  '../../database/DatabaseAccessor';

let comp: LocationSearchModal;
let fixture: ComponentFixture<LocationSearchModal>;
let instance: any = null;

describe('LocationSearchModal', () => {

  beforeEach(async(() => {

    TestBed.configureTestingModule({
      declarations: [LocationSearchModal], // declare the test component
      providers: [App, Platform, Form, Keyboard, NavController, GestureController, LoadingController, LocationService, DatabaseAccessor,
        { provide: ViewController, useClass: class { ViewController = jasmine.createSpy("viewController"); } },
        { provide: Config, useClass: ConfigMock },
      ],
      imports: [
        IonicModule,
        TranslateModule.forRoot(),
      ],
    });
    fixture = TestBed.createComponent(LocationSearchModal);
    comp = fixture.componentInstance;
  }));

  console.log(comp);
  it('Testing Location Component', () => {
    expect(comp.temp).toBe('test');
  })
});

Quando estou executando, o seguinte erro vem do terminal. (minha configuração de teste de unidade está correta e eu a testei com outro arquivo simp, le .spec.ts)

o erro

SUMMARY:
✔ 1 test completed
✖ 1 test failed

FAILED TESTS:
  LocationSearchModal
    ✖ Testing Location Component
      Chrome 54.0.2840 (Linux 0.0.0)
    Failed: Error in ./LocationSearchModal class LocationSearchModal_Host - inline template:0:0 caused by: Cannot read property '_getPortal' of undefined
    TypeError: Cannot read property '_getPortal' of undefined
        at App.present (webpack:/media/dilanka/Stuff/CODE%20BASE/Inspection/Unit%20Testing/Inspection-Rewrite/~/ionic-angular/components/app/app.js:78:0 <- src/test.ts:2091:35)
        at Loading.present (webpack:/media/dilanka/Stuff/CODE%20BASE/Inspection/Unit%20Testing/Inspection-Rewrite/~/ionic-angular/components/loading/loading.js:31:0 <- src/test.ts:38779:26)
        at LocationSearchModal.filterLocationsForString (webpack:/media/dilanka/Stuff/CODE%20BASE/Inspection/Unit%20Testing/Inspection-Rewrite/src/pages/location-search/LocationSearchModal.ts:9:4184 <- src/test.ts:18993:4170)
        at new LocationSearchModal (webpack:/media/dilanka/Stuff/CODE%20BASE/Inspection/Unit%20Testing/Inspection-Rewrite/src/pages/location-search/LocationSearchModal.ts:9:3407 <- src/test.ts:18993:3391)
        at new Wrapper_LocationSearchModal (/DynamicTestModule/LocationSearchModal/wrapper.ngfactory.js:7:18)
        at _View_LocationSearchModal_Host0.createInternal (/DynamicTestModule/LocationSearchModal/host.ngfactory.js:16:35)
        at _View_LocationSearchModal_Host0.AppView.create (webpack:/media/dilanka/Stuff/CODE%20BASE/Inspection/Unit%20Testing/Inspection-Rewrite/~/@angular/core/src/linker/view.js:84:0 <- src/test.ts:52350:21)
        at _View_LocationSearchModal_Host0.DebugAppView.create (webpack:/media/dilanka/Stuff/CODE%20BASE/Inspection/Unit%20Testing/Inspection-Rewrite/~/@angular/core/src/linker/view.js:294:0 <- src/test.ts:52560:44)
        at ComponentFactory.create (webpack:/media/dilanka/Stuff/CODE%20BASE/Inspection/Unit%20Testing/Inspection-Rewrite/~/@angular/core/src/linker/component_factory.js:152:0 <- src/test.ts:32035:36)
        at initComponent (webpack:/media/dilanka/Stuff/CODE%20BASE/Inspection/Unit%20Testing/Inspection-Rewrite/~/@angular/core/bundles/core-testing.umd.js:855:0 <- src/test.ts:7416:53)

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