public void ArticleInInventoryTest()
        {
            var article = new Article
            {
                ID = 2
            };
            var supplier = new Supplier1();

            supplier.AddArticle(article);

            Assert.True(supplier.ArticleInInventory(article.ID));
        }
        public void NoArticleInInventoryTest()
        {
            var article = new Article
            {
                ID = 2
            };
            var supplier = new Supplier1();

            supplier.AddArticle(article);

            Assert.False(supplier.ArticleInInventory(23));
        }
        public void SoldArticleInInventoryTest()
        {
            var article = new Article
            {
                ID = 2
            };

            article.Sell(12);
            var supplier = new Supplier1();

            supplier.AddArticle(article);

            Assert.False(supplier.ArticleInInventory(article.ID));
        }
        public void NoArticleInEmptyInventoryTest()
        {
            var supplier = new Supplier1();

            Assert.False(supplier.ArticleInInventory(23));
        }