public void SortedNumbersTest()
{
var listToSort = new List<int> { 1, 2, 3, 4, 5 };
var sorter = new MergeSorter<int>();
var actual = sorter.Mergesorter(listToSort).ToList();
var expected = new List<int> { 1, 2, 3, 4, 5 };
CollectionAssert.AreEqual(actual, expected);
}