//code for xorpalindrome in Java
import java.util.*;
import java.lang.*;
import java.io.*;
class Xorpalindrome
{
public static void main (String[] args) throws java.lang.Exception
{
// your code goes here
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
BufferedWriter bw=new BufferedWriter(new OutputStreamWriter(System.out));
int t=Integer.parseInt(br.readLine());
StringBuffer sb=new StringBuffer();
while(t-->0)
{
int n=Integer.parseInt(br.readLine());
String s=br.readLine();
int count1=0,count2=0;
for(int i=0;i