public void ShouldUnionTwoSet()
{
var set1 = new StringSet();
var set2 = new StringSet();
set1.Add("Test1");
set2.Add("Test2");
StringSet union = set1.Union(set2);
Assert.AreEqual(2, union.Count);
Assert.IsTrue( union.Contains("Test1"));
Assert.IsTrue( union.Contains("Test2"));
}