public void TestMapShouldReturnDescendingValues(string value, double?expected)
{
var strings = new List <string> {
"Apple", "Elephant", "Monkey", "Tiger", "Zebra"
};
var map = new StringToAxisMap(strings, 0d, 1d, SortOrder.Descending);
var result = map.Map(value);
Assert.That(result, Is.EqualTo(expected));
}