How to mock route.snapshot.params?

Question

In my Angular 4 component I have something like:

constructor(private route: ActivatedRoute) {
}

ngOnInit() {
  this.myId = this.route.snapshot.params['myId'];
}

And I'm trying to create a mock that suppose to look like follows:

class MockActivatedRoute extends ActivatedRoute {
  public params = Observable.of({ myId: 123 });
}    

My test fails with:

TypeError: Cannot read property 'params' of undefined.

How do I suppose to mock it? Have I misunderstood the proper usage of ActivatedRoute and should better use router.subscribe in my component? I saw some complicated examples where people mocked snapshot itself, however for me it looks overcomplicated.

---

The test itself is quite simple:

describe('ngOnInit', () => {
it('should set up initial state properly',
  () => {
  const component = TestBed.createComponent(MyComponent).componentInstance;
    component.ngOnInit();
    expect(component.myId).toEqual('123');
  });
});

If I simply change a method under the test to something like follows - the test works:

ngOnInit() {
    //this.myId = this.route.snapshot.params['myId'];
    this.route.params.subscribe(params => {
    this.myId = params['myId'];
    });
}

Obviously I need to mock Activated snapshot, but is there a better approach?

Answer 1

Ok, I've found how to mock ActivatedRoute snapshot in the simple way. Something like this works for me:

providers: [MyComponent, {
  provide: ActivatedRoute,
  useValue: {snapshot: {params: {'myId': '123'}}}
}

Thanks :)