public void Sum ()
{
#region Sum
IEnumerable<uint> s = null;
Assert.Throws<ArgumentNullException>(() => s.Sum ());
s = new []{1U, 2U, 3U};
Assert.AreEqual (6U, s.Sum ());
Assert.AreEqual (6U, s.Sum (null));
IEnumerable<SimpleNumber> s2 = new[]{
new SimpleNumber (1),
new SimpleNumber (2),
new SimpleNumber (3),
};
Assert.AreEqual (new SimpleNumber (6), s2.Sum (new SimpleNumberMath ()));
#endregion
}