public void CopyToMs()
{
char[] chars = new char[] { 'a', 'a', 'b', 'c', 'd', 'e' };
var ms = new MultiSet <char>(chars);
char[] outputArr = new char[chars.Length];
ms.CopyTo(outputArr, 0);
Assert.AreEqual(string.Concat(chars), string.Concat(outputArr));
}