/* -*- coding: utf-8 -*-
 *
 * 3374.cc:  No.3374 Caesar Shift Game - yukicoder
 */

#include<cstdio>
#include<algorithm>

using namespace std;

/* constant */

const int MAX_N = 500000;

/* typedef */

/* global variables */

char s[MAX_N + 4];

/* subroutines */

/* main */

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

  while (tn--) {
    int n;
    scanf("%d%s", &n, s);
    
    for (int i = 0; i < n; i++) {
      if (! (i & 1)) { // A's turn
	if (s[i] == 'C') s[i] = 'A';
	else break;
      }
      else { // B's turn
	if (s[i] != 'C') s[i]++;
	else break;
      }
    }

    puts(s);
  }

  return 0;
}