Bug 442

Note: The given problem is for Version 2.

Steps to reproduce:
1. Initialize the warehouse
2. Add slots to the warehouse instance
3. Add an item with a negative value volume.

The test case given below demonstrates the current bug. When we try to add an item with a negative value volume, the program should deny the request. In reality, the program accepts the item and places it into the slot. 

@Test
	void testMoveToSlot_09() {
		Warehouse wh =  Warehouse.getInstance();
		ArrayList<Slot> slots = new ArrayList<>();
		slots.add(new Slot(1));
		slots.add(new Slot(2));
		slots.add(new Slot(3));
		slots.add(new Slot(4));
		slots.add(new Slot(5));
		
		wh.setSlots(slots);
		
		Item item1 = new Item(1,new Day("13-Oct-2020"),new Day("20-Oct-2020"));
		Item item2 = new Item(2,new Day("13-Oct-2020"),new Day("20-Oct-2020"));
		Item item3 = new Item(3,new Day("13-Oct-2020"),new Day("20-Oct-2020"));
		Item newItem = new Item(-2,new Day("13-Oct-2020"),new Day("23-Oct-2020"));
		
		boolean result = wh.testResult();
		String msg = "Checking when the size of an item is negative";
		assertEquals(false, result, msg);
	}