How to unit test a Angular 4 component which uses router.paramMap

Question

I m new to angular 4 and trying to test one of the angular 4 feature router.paramMap from unit tests, Reading route params in fallowing way and working as expected in my applica

Answer 1

For anyone needing tests on a component for when it does have a certain route param, and when it does not have it (as in /product and /product/:id ), the following works for me:

The component:

export class PageProductComponent implements OnInit {
    id: string | null = null;

    constructor(private readonly activatedRoute: ActivatedRoute) { }

    ngOnInit(): void {
        this.id = this.activatedRoute.snapshot.paramMap.get('id');
    }
}

The tests:

describe('PageProductComponent ', () => {
    let component: PageProductComponent ;
    let fixture: ComponentFixture;
    let debugEl: DebugElement;

    const makeCompiledTestBed = (provider?: object): void => {
        const moduleDef: TestModuleMetadata = {
            imports: [
                RouterTestingModule,
            ],
            declarations: [ PageProductComponent ],
            providers: [ ]
        };
        if (moduleDef.providers && provider) {
            moduleDef.providers.push(provider);
        }
        TestBed.configureTestingModule(moduleDef).compileComponents();
    };

    const setupTestVars = (): void => {
        fixture = TestBed.createComponent(PageProductComponent );
        component = fixture.componentInstance;
        debugEl = fixture.debugElement;
        fixture.detectChanges();
    };

    describe('When an ID is NOT provided in the URL param', () => {
        beforeEach(async(makeCompiledTestBed));
        beforeEach(setupTestVars);

        it('should list all products', () => {
            //...
        });

    });

    describe('When an ID is provided in the URL param', () => {
        beforeEach(async(() => {
            makeCompiledTestBed({
                provide: ActivatedRoute,
                useValue: {
                    snapshot: {
                        paramMap: convertToParamMap({id: 1234})
                    }
                }
            });
        }));

        beforeEach(setupTestVars);

        it('should show a specific product', () => {
            //...
        });
    });
});