#ifdef NACHIA
#define _GLIBCXX_DEBUG
#else
#define NDEBUG
#endif
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;
using ll = long long;
const ll INF = 1ll << 60;
#define REP(i,n) for(ll i=0; i<ll(n); i++)
template <class T> using V = vector<T>;
template <class A, class B> void chmax(A& l, const B& r){ if(l < r) l = r; }
template <class A, class B> void chmin(A& l, const B& r){ if(r < l) l = r; }

void testcase(){
    ll N; cin >> N;
    string S; cin >> S;
    if(N == 1){
        cout << "B\n";
    }
    else if(S[0] == 'B' && S[1] == 'B'){
        cout << S << "\n";
    }
    else if(S[0] == 'B' && S[1] == 'A'){
        S[1] = 'B';
        for(ll p=2; p<N && S[p] == 'B'; p++) S[p] = 'A';
        cout << S << "\n";
    }
    else if(S[0] == 'A' && S[1] == 'B'){
        S[0] = 'B';
        ll p = 2;
        while(p < N && S[p] == 'A') p++;
        while(p < N && S[p] == 'B') S[p++] = 'A';
        cout << S << "\n";
    }
    else {
        S[0] = S[1] = 'B';
        for(ll p=2; p<N && S[p] == 'B'; p++) S[p] = 'A';
        cout << S << "\n";
    }
}

int main(){
  cin.tie(0)->sync_with_stdio(0);
  ll T; cin >> T;
  REP(t,T)
  testcase();
  return 0;
}