public void UnionTest()
{
Multiplicity <int> multiplicity1 = new Multiplicity <int>();
multiplicity1.Insert(1);
Multiplicity <int> multiplicity2 = new Multiplicity <int>();
Multiplicity <int> result = new Multiplicity <int>();
result.Union(multiplicity1, multiplicity2);
Assert.IsFalse(result.IsEmpty());
}