public void SearchTest()
        {
            // empty search
            string         search_value = "";
            List <Contact> expected     = new List <Contact> {
                c1, c2, c3, c4
            };
            List <Contact> actual = adb.Search(search_value);

            CollectionAssert.AreEqual(expected, actual);

            // name search
            search_value = "Jarn";
            expected     = new List <Contact> {
                c1
            };
            actual = adb.Search(search_value);
            CollectionAssert.AreEqual(expected, actual);

            // email search
            search_value = "meesters@";
            expected     = new List <Contact> {
                c2
            };
            actual = adb.Search(search_value);
            CollectionAssert.AreEqual(expected, actual);

            // search multiple contacts
            search_value = "@hotmail";
            expected     = new List <Contact> {
                c2, c3
            };
            actual = adb.Search(search_value);
            CollectionAssert.AreEqual(expected, actual);
        }