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

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']);
    });
});