public void ReturnBookReadable()
        {
            var author = "Author";
            var title = "Title";
            var callNumber = "Call Number";
            var id = 1;

            var book = new Book(author, title, callNumber, id);

            var readable = $"ID:\t\t{book.ID}\nCall Number:\t{book.CallNumber}\nAuthor:\t\t{book.Author}\nTitle:\t\t{book.Title}";

            Assert.Equal(readable, book.ToString());
        }