import java.io.*;
import java.util.*;
import java.util.stream.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int t = sc.nextInt();
        StringBuilder sb = new StringBuilder();
        while (t-- > 0) {
            int n = sc.nextInt();
            char[] inputs = sc.next().toCharArray();
            int bCount = 0;
            StringBuilder tmp = new StringBuilder();
            for (int i = n - 1; i >= 0; i--) {
                if (inputs[i] == 'A') {
                    if (bCount > 1) {
                        tmp.deleteCharAt(tmp.length() - 1);
                        bCount--;
                    } else {
                        tmp.append("A");
                        bCount = 0;
                    }
                } else {
                    tmp.append("B");
                    bCount++;
                }
            }
            sb.append(tmp.reverse()).append("\n");
        }
        System.out.print(sb);
    }
}
class Utilities {
    static String arrayToLineString(Object[] arr) {
        return Arrays.stream(arr).map(x -> x.toString()).collect(Collectors.joining("\n"));
    }
    
    static String arrayToLineString(int[] arr) {
        return String.join("\n", Arrays.stream(arr).mapToObj(String::valueOf).toArray(String[]::new));
    }
}
class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    StringBuilder sb = new StringBuilder();
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public double nextDouble() throws Exception {
        return Double.parseDouble(next());
    }
    
    public int[] nextIntArray() throws Exception {
        return Stream.of(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray();
    }
    
    public String next() throws Exception {
        while (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
    
}