public void Test_Merge()
{
TokenCollection a = Create(new[] { "mouse", "mouse", "mouse" });
TokenCollection b = Create(new[] { "mouse", "chicken", "chicken" });
TokenCollection merge = TokenCollection.Merge(a, b);
Assert.AreEqual(6, merge.Sum);
Assert.AreEqual(4, merge.get("mouse"));
Assert.AreEqual(2, merge.get("chicken"));
}