public void IsbnFilterWorksTest()
        {
            BookRepository repo     = new BookRepository();
            List <Book>    expected = new List <Book>();

            expected.Add(Book.CreateBook("1234", "Book nr 1's title", new Author("JK", "Rowling")));
            expected.Add(Book.CreateBook("9012", "Book nr 3's title", new Author("Xan", "BridgeBuilder")));

            CollectionAssert.AreEqual(expected, repo.searchBookISBN("12*"));
        }