#include <bits/stdc++.h>

#include <atcoder/all>
using namespace std;
using i32 = int;
using u32 = unsigned int;
using i64 = long long;
using u64 = unsigned long long;
#define FAST_IO                \
  ios::sync_with_stdio(false); \
  cin.tie(0);
const i64 INF = 1001001001001001001;
using Modint = atcoder::static_modint<998244353>;

int main() {
  FAST_IO

  int T;
  cin >> T;
  while (T--) {
    int N;
    string S;
    cin >> N >> S;

    if (N == 1) {
      cout << "B" << "\n";
    } else {
      if (S[0] == 'B' && S[1] == 'B') {
        // none
      } else if (S[0] == 'B' && S[1] == 'A') {
        S[1] = 'B';
      } else if (S[0] == 'A' && S[1] == 'A') {
        S[0] = 'B';
        S[1] = 'B';
        int p = 2;
        while (p < N && S[p] == 'B') {
          S[p] = 'A';
        }
      } else {
        int s = -1, e = N;
        for (int i = 2; i < N; i++) {
          if (S[i] == 'B') {
            if (s < 0) {
              s = i;
            }
          }
          if (s >= 0 && S[i] == 'A') {
            e = i;
            break;
          }
        }
        if (s >= 0) {
          for (int i = s; i < e; i++) {
            S[i] = 'A';
          }
        }
        S[0] = 'B';
      }
      cout << S << "\n";
    }
  }
  // AAAABBBBAAAABBBB
}