public void Test_Method_LibraryBookDecreaseQuantity()
{
Book k = new Book();
k.Title = "Sto godina samoce";
k.ISBN = "ISBN 1-12345-123-1";
k.Publisher = "Sarajevo publishing";
LibraryBook lk = new LibraryBook(k);
lk.Quantity = 10;
lk.DecreaseQuantity();
Assert.AreEqual(Convert.ToUInt32(9), lk.Quantity);
}
