public static bool VerifyEnumerator(Stack<int>.Enumerator enumerator, int[] expectedValues)
 {
     bool retVal = true;
     int i = 0;
     while (enumerator.MoveNext())
     {
         if (enumerator.Current != expectedValues[i]) return false;
         ++i;
     };
     retVal = i == expectedValues.Length;
     return retVal;
 }