How to test multiple withLatestFrom store injections in NgRx-Effects?

In our angular webapp we have some NgRx-effects that use different information from different parts of our store. For this we are using the recommended withLatestFrom-approach:

withLatestFrom(
   this.store.pipe(select(...)),
   this.store.pipe(select(...)),
   ...
)

While this approach seems to be working fine in production, it feels horrible for unit testing the effects.

For our unit-tests we are currently using jasmine-marbles, jasmine spy-objects and the ngrx MockStore (NgRx 7+). The hard part is to provide the necessary store state, so that the selectors can work properly.

EXAMPLE-EFFECT, for which we do not have a unit-test:

@Effect()
getStammdatenDetails$: Observable<Action> = this.actions$.pipe(
   ofType(StammdatenItemDetailActionTypes.REQUEST_DETAILS),
   withLatestFrom(
      this.store.pipe(select(fromRoot.getMetadata)),
      this.store.pipe(select(fromRoot.getCustomerId)),
      this.store.pipe(select(fromRoot.getRouterParams))
   ),
   mergeMap(([action, metadata, customerId, params]) => {
      *effect logic*
   })
);

Maybe someone here can provide more insight or a useful link to a piece of documentation we are missing?

I would really appreciate any help in regards if there is a convenient method to unit tests such effects, or how to refactor those effects to be more "testable" (without moving the problem to another piece of code, which we cannot test afterwards).