How to unit test a component that depends on parameters from ActivatedRoute?

The simplest way to do this is to just use the useValue attribute and provide an Observable of the value you want to mock.

RxJS < 6

import { Observable } from 'rxjs/Observable';
import 'rxjs/add/observable/of';
...
{
  provide: ActivatedRoute,
  useValue: {
    params: Observable.of({id: 123})
  }
}

RxJS >= 6

import { of } from 'rxjs';
...
{
  provide: ActivatedRoute,
  useValue: {
    params: of({id: 123})
  }
}