Hot vs Cold Observables

Recently I noticed the following code In the tests of some effect:

   const action = new fromActions.LoadPosts();
   actions$.stream = hot('-a', { a: action });
   const expected = cold('-b', { b: completion });
   
   expect(effects.loadPosts$).toBeObservable(expected);

This effect purpose is to activate request in response of "load posts" action:
Here is the effect code:

   loadPosts$ = this.actions$.ofType(postActions.LOAD_POSTS).pipe(
    switchMap(() => {
      return this.postService
        .getPosts()
        .pipe(map(posts => new postActions.LoadPostsSuccess(posts)));
    })
  );

According to Ben Lesh's explanation here: "observable is cold if its underlying producer is created and activated during the subscription"
In our case - the producer is Ajax request to "/post" API.
Since request is NOT made until someone subscribed to it - it considered cold
Unlike "loadPosts" action - which is hot:

export class LoadPosts implements Action {
  readonly type = LOAD_POSTS;
}

And here is what the test us checking - is in response to hot action, the cold request is following