t.Fatalf("unexpected error: %v", err)
	}
	if err := ps.Subscribe(MaskAll, ch3, doneCh, nil); err == nil {
		t.Fatalf("unexpected nil err")
	}
}

func TestUnsubscribe(t *testing.T) {
	ps := New[Maskable, Maskable](2)
	ch1 := make(chan Maskable, 1)
	ch2 := make(chan Maskable, 1)
	doneCh1 := make(chan struct{})
	doneCh2 := make(chan struct{})