Angular2 Unit test Service that Emit value at Constructor Time

Writing a unit test for a component, that uses a Service with an emit inside the constructor, like this:

@Injectable()
export class Service1 {
  public onService1Done: EventEmitter<any> = new EventEmitter();
  public constructor(...) {
    this.onService1Done.emit(value);
  }
}

I notice that, according to what i have in the component.spec.ts:

beforeEachProviders(() => {
  return [
    provide(Service1, { useClass: MockService1 }),
    Component1
  ];
});

  it("check that XXX", inject(
    [Service1, Component1], (service1: Service1, component1: Component1) => {
    service1.onService1Done.subscribe({ next: () => DoSomething() });
    expect(DoSomething()).toEqual(IsDone);
  }));
});
}

The constructor of Service1, and so the emit, will be called before i could make the subscribe, inside the test;

there is a way to avoid this ?? to make the subscribe before the Constructor ?

As always, thanks in advance.