Junit testing void against class type Java

If I have a public void createDeck and I have a public class Deck. Now I wish to create a new Deck, so Deck deck = new Deck() and in order to create a deck of class I call my deck.createDeck. How can I test this in Junit?

When I wish to test this I end up having a (Deck, void) and this can't be tested

Se link for code

http://ift.tt/1O2eBBA