#include <iostream>
#include <algorithm>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
//#define endl "\n";
int main(){
  ll Q;
  cin >> Q;
  for(int q = 1; q <= Q; q++){
    ll N;
    cin >> N;
    string S;
    cin >> S;
    if(N <= 2){
      //全部B
      for(int i = 0; i < N; i++) cout << "B";
      cout << endl;
      continue;
    }
    //先頭3文字で場合分け
    if(S[0] == 'A'){
      if(S[1] == 'A'){
        if(S[2] == 'A'){
          //AAA
          cout << "BB";
          for(int i = 2; i < N; i++) cout << S[i];
          cout << endl;
          continue;
        }else{
          //AAB
          cout << "BB";
          ll pos = 2;
          while(pos < N && S[pos] == 'B'){
            cout << 'A';
            pos++;
          }
          for(int i = pos; i < N; i++) cout << S[i];
          cout << endl;
          continue;
        }
      }else{
        if(S[2] == 'A'){
          //ABA
          cout << "BB";
          ll pos = 2;
          while(pos < N && S[pos] == 'A'){
            cout << 'A';
            pos++;
          }
          while(pos < N && S[pos] == 'B'){
            cout << 'A';
            pos++;
          }
          for(int i = pos; i < N; i++) cout << S[i];
          cout << endl;
          continue;
        }else{
          //ABB
          cout << "BB";
          ll pos = 2;
          while(pos < N && S[pos] == 'B'){
            cout << 'A';
            pos++;
          }
          for(int i = pos; i < N; i++) cout << S[i];
          cout << endl;
          continue;
        }
      }
    }else{
      if(S[1] == 'A'){
        if(S[2] == 'A'){
          //BAA
          cout << "BB";
          for(int i = 2; i < N; i++) cout << S[i];
          cout << endl;
          continue;
        }else{
          //BAB
          cout << "BB";
          ll pos = 2;
          while(pos < N && S[pos] == 'B'){
            cout << 'A';
            pos++;
          }
          for(int i = pos; i < N; i++) cout << S[i];
          cout << endl;
          continue;
        }
      }else{
        if(S[2] == 'A'){
          //BBA
          cout << "BB";
          for(int i = 2; i < N; i++) cout << S[i];
          cout << endl;
          continue;
        }else{
          //BBB
          cout << "BB";
          for(int i = 2; i < N; i++) cout << S[i];
          cout << endl;
          continue;
        }
      }
    }
  }
  return 0;
}