### Question:
MultiPageGui implements GUI { @Override public void displayTo(Player player) { playerPages.setPlayerPage(player.getUniqueId(), 1); player.openInventory(inventoryPages.getPage(1)); }  @Override void displayTo(Player player); @Override void clear(); @Override void addButton(InventoryItem inventoryItem, Executable executable); @Override void addItem(InventoryItem item); @Override void removeItem(int slot, int page);  }### Answer:
@Test public void displayTo() { MultiPageGui multiPageGui = new MultiPageGui(playerPages, inventoryPages, mock(SlotActions.class), mock(Server.class), playerPageRearranger); Player player = mock(Player.class); Inventory inventory = mock(Inventory.class); when(inventoryPages.getPage(eq(1))).thenReturn(inventory); multiPageGui.displayTo(player); verify(player).openInventory(same(inventory)); verify(playerPages).setPlayerPage(any(), eq(1)); }