Unit testing Angular 2 authGuard; spy method is not being called

Question

I'm trying to unit test my auth guard service. From this answer I was able to get this far, but now when I run the unit test for this, it says Expected spy navigate to have been called.

How to I get my spied router to be used as this.router in the service?

auth-guard.service.ts

import { Injectable } from '@angular/core';
import { Router, CanActivate } from '@angular/router';

@Injectable()
export class AuthGuardService {

  constructor(private router:Router) { }

  public canActivate() {
    const authToken = localStorage.getItem('auth-token');
    const tokenExp = localStorage.getItem('auth-token-exp');
    const hasAuth = (authToken && tokenExp);

    if(hasAuth && Date.now() < +tokenExp){
      return true;
    }
    this.router.navigate(['/login']);
    return false;
  }
}

auth-guard.service.spec.ts

import { TestBed, async, inject } from '@angular/core/testing';
import { RouterTestingModule } from '@angular/router/testing';

import { AuthGuardService } from './auth-guard.service';

describe('AuthGuardService', () => {
  let service:AuthGuardService = null;
  let router = {
    navigate: jasmine.createSpy('navigate')
  };

  beforeEach(() => {
    TestBed.configureTestingModule({
      providers: [
        AuthGuardService,
        {provide:RouterTestingModule, useValue:router}
      ],
      imports: [RouterTestingModule]
    });
  });

  beforeEach(inject([AuthGuardService], (agService:AuthGuardService) => {
    service = agService;
  }));

  it('checks if a user is valid', () => {
    expect(service.canActivate()).toBeFalsy();
    expect(router.navigate).toHaveBeenCalled();
  });
});

Replacing RouterTestingModule with Router like in the example answer throws Unexpected value 'undefined' imported by the module 'DynamicTestModule'.

Answer 1

Instead of stubbing Router, use dependency injection and spy on the router.navigate() method:

import { TestBed, async, inject } from '@angular/core/testing';
import { RouterTestingModule } from '@angular/router/testing';
import { Router } from '@angular/router';

import { AuthGuardService } from './auth-guard.service';

describe('AuthGuardService', () => {

  beforeEach(() => {
    TestBed.configureTestingModule({
      providers: [AuthGuardService],
      imports: [RouterTestingModule]
    });
  });

  it('checks if a user is valid',

    // inject your guard service AND Router
    async(inject([AuthGuardService, Router], (auth, router) => {

      // add a spy
      spyOn(router, 'navigate');

      expect(auth.canActivate()).toBeFalsy();
      expect(router.navigate).toHaveBeenCalled();
    })
  ));
});

https://plnkr.co/edit/GNjeJSQJkoelIa9AqqPp?p=preview