/* -*- coding: utf-8 -*-
 *
 * 3395.cc:  No.3395 Range Flipping Game - yukicoder
 */

#include<cstdio>
#include<algorithm>

using namespace std;

/* constant */

const int MAX_N = 250000;

/* typedef */

/* global variables */

char s[MAX_N + 4];

/* subroutines */

inline void flip(char &c) { c = 'A' + 'B' - c; }

/* main */

int main() {
  int tn;
  scanf("%d", &tn);

  while (tn--) {
    int n;
    scanf("%d%s", &n, s);

    for (int i = 0, f = 0; i < n; i++) {
      if (i == 0) {
	if (s[i] != 'A') flip(s[i]), f = 1;
      }
      else if (i == 1) {
	if (s[i] != 'B') flip(s[i]), f = 1;
	else if (f) break;
      }
      else {
	if (s[i] != 'A') flip(s[i]), f = 1;
	else if (f) break;
      }
    }

    for (int i = 0; i < n && s[i] == 'A'; i++) flip(s[i]);
    
    puts(s);
  }

  return 0;
}