public void CompareSortedOneEmptyTest()
        {
            //given
            var list1 = new List <int> ();
            var list2 = new List <int> {
                2, 3, 15, 20, 25
            };
            //when
            var listsComparer = new ListsComparer <int>(list1, list2);

            listsComparer.CompareSorted();
            //then
            CollectionAssert.IsEmpty(listsComparer.OnlyInList1);
            CollectionAssert.AreEqual(new List <int> {
                2, 3, 15, 20, 25
            }, listsComparer.OnlyInList2);
        }