unit testing spyOn observable service in angular2

Question

I have a service (ChildService) which depends on another service (InteractWithServerService). The latter service (InteractWithServerService) is used to make server calls and

Answer 1

However, the test case doesn't work and throws "Error: No provider for Http!".

Because you still have the service in the providers, so Angular is trying to create it still

providers: [
 InteractWithServerService,
    ChildService],

What you can do instead of creating a mock class is to just do something like

providers: [
  { 
    provide: InteractWithServerService,
    useValue: { get: Observable.of(..) }
  }
]

Here's you're using useValue which provide any object. That will be the value used when injected. In the case above, it is just some arbitrary object with your mock method.

If you want to spy so that you can provide different values, you could inject the InteractWithServerService, and then do

spyOn(service, 'get').and.returnValue(Observable.of(...))
// do test

Another thing you could do is mock the Http with a dummy object

{ provide: Http, useValue: {} }

Now the InteractWithServerService will work (just adding the class to the providers` like you currently have). And you can just spy on it

let service = TestBed.get(InteractWithServerService);
spyOn(service, 'get').and.returnValue(..)
// do test