public void FindArticleByAuthorAndTitleTest()
        {
            Catalogue catalogue = new Catalogue();
            Article   article   = new Article("Einstein vs Weinstein", "Znany Profesor", 2019, 35);

            catalogue.Add(article);

            Article findArticle = catalogue.FindArticleByAuthorAndTitle("Znany Profesor", "Einstein vs Weinstein");

            Assert.AreSame(article, findArticle);
        }