#include <bits/stdc++.h>
using namespace std;
using ll = long long;


void solve(){
    int N; cin >> N;
    string S; cin >> S;
    if(N == 1){
        cout << 'B' << '\n';
        return;
    }
    if(S[0] == 'A'){
        if(S[1] == 'B'){
            for(int i = 2; i < N; ++i){
                if(S[i] == 'A') continue;
                else{
                    for(int j = i; j < N; ++j){
                        if(S[j] == 'B'){
                            S[j] = 'A';
                        }else{
                            break;
                        }
                    }
                    break;
                }
            }
            S[0] = 'B';
            cout << S << "\n";
        }else{
            S[1] = 'B';
            for(int i = 2; i < N; ++i){
                if(S[i] == 'B'){
                    S[i] = 'A';
                }else{
                    break;
                }
            }
            S[0] = 'B';
            cout << S << "\n";
        }
    }else{
        if(S[1] == 'B'){
            cout << S << "\n";
        }else{
            S[1] = 'B';
            for(int i = 2; i < N; ++i){
                if(S[i] == 'B'){
                    S[i] = 'A';
                }else{
                    break;
                }
            }
        }
    }
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << setprecision(10) << fixed;

    int T;
    //T = 1;
    cin >> T;
    for(;T--;) solve();
}