How can I unit test a component that uses the Router in Angular?

In Angular 2.0.0, I am unit testing a component that uses Router. However I get the 'Supplied parameters do not match any signature of call target.' error. In Visual studio code in spec.ts it is the new Router() that is highlighted in red

I really appreciate if someone could let me know what the correct syntax would be? Thanks in advance. My code as follows:

spec.ts

import { TestBed, async } from '@angular/core/testing';
import { NavToolComponent } from './nav-tool.component';
import { ComponentComm } from '../../shared/component-comm.service';
import { Router } from '@angular/router';

describe('Component: NavTool', () => {
    it('should create an instance', () => {
    let component = new NavToolComponent( new ComponentComm(), new Router());
    expect(component).toBeTruthy();
    });
});

Component constructor

constructor(private componentComm: ComponentComm, private router: Router) {}

You can also just use the RouterTestingModule and just spyOn the navigate function like this...

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

import { MyModule } from './my-module';
import { MyComponent } from './my-component';

describe('something', () => {

    let fixture: ComponentFixture<LandingComponent>;
    let router: Router;

    beforeEach(() => {

        TestBed.configureTestingModule({
            imports: [
                MyModule,
                RouterTestingModule.withRoutes([]),
            ],
        }).compileComponents();

        fixture = TestBed.createComponent(MyComponent);
        router = TestBed.get(Router); // TestBed.inject(Router) for Angular 9+

    });

    it('should navigate', () => {
        const component = fixture.componentInstance;
        const navigateSpy = spyOn(router, 'navigate');

        component.goSomewhere();
        expect(navigateSpy).toHaveBeenCalledWith(['/expectedUrl']);
    });
});

It's because the Route has some dependencies it expects passed to its constructor.

If you're using Angular components, you shouldn't be trying to do isolated tests. You should use the Angular testing infrastructure to prepare the test environment. This means letting Angular create the component, letting it inject all the required dependencies, instead of you trying to create everything.

To get you started, you should have something like

import { TestBed } from '@angular/core/testing';

describe('Component: NavTool', () => {
  let mockRouter = {
    navigate: jasmine.createSpy('navigate')
  };
  beforeEach(() => {
    TestBed.configureTestingModule({
      declarations: [ NavToolComponent ],
      providers: [
        { provide: Router, useValue: mockRouter },
        ComponentComm
      ]
    });
  });
  it('should click link', () => {
    let fixture = TestBed.createComponent(NavToolComponent);
    fixture.detectChanges();
    let component: NavToolComponent = fixture.componentInstance;
    component.clickLink('home');
    expect(mockRouter.navigate).toHaveBeenCalledWith(['/home']);
  });
});

Or something like that. You use the TestBed to configure a module from scratch for the testing. You configure it pretty much the same way with an @NgModule.

Here we are just mocking the router. Since we are just unit testing, we may not want the real routing facility. We just want to make sure that it is called with the right arguments. The mock and spy will be able to capture that call for us.

If you do want to use the real router, then you need to use the RouterTestingModule, where you can configure routes. See an example here and here

See Also:

• Angular docs on Testing for more examples using the Angular testing infrastructure.

Here an axample if we inject Route service in our component controller:

import { TestBed, async } from '@angular/core/testing';
import { RouterTestingModule } from '@angular/router/testing'; // Because we inject service in our component
import { Router } from '@angular/router'; // Just if we need to test Route Service functionality

import { AppComponent } from './app.component';
import { DummyLoginLayoutComponent } from '../../../testing/mock.components.spec'; // Because we inject service in your component

describe('AppComponent', () => {
  let router: Router; // Just if we need to test Route Service functionality

  beforeEach(async(() => {
    TestBed.configureTestingModule({
      declarations: [
        AppComponent,
        DummyLoginLayoutComponent // Because we inject service in our component
      ],
      imports: [
        RouterTestingModule.withRoutes([
          { path: 'login', component: DummyLoginLayoutComponent },
        ]) // Because we inject service in our component
      ],
    }).compileComponents();

    router = TestBed.get(Router); // Just if we need to test Route Service functionality
    router.initialNavigation(); // Just if we need to test Route Service functionality
  }));

  it('should create the app', async(() => {
    const fixture = TestBed.createComponent(AppComponent);
    const app = fixture.debugElement.componentInstance;
    expect(app).toBeTruthy();
  }));
});

We can also test other functionalitites such as navigate(). Just in case:

it('should call eventPage once with /register path if event is instanceof NavigationStart', fakeAsync(() => {
    spyOn(analyticService, 'eventPage');
    router.navigate(['register'])
      .then(() => {
        const baseUrl = window.location.origin;
        const url = `${baseUrl}/register`;
        expect(analyticService.eventPage).toHaveBeenCalledTimes(1);
        expect(analyticService.eventPage).toHaveBeenCalledWith(url);
      });
}));

My file with all mock components (mock.components.specs.ts)

import { Component } from '@angular/core';

@Component({
    selector: 'home',
    template: '<div>Dummy home component</div>',
    styleUrls: []
})

export class DummyHomeComponent { }

Jasmine goes one better with full spy objects...

describe('Test using router', () => {
    const router = jasmine.createSpyObj('Router', ['navigate']);
    ...
    beforeEach(async(() => {
        TestBed.configureTestingModule({
            providers: [  { provide: Router, useValue: router } ],
            ...
    });        
});