// (◕ᴗ◕✿)

// #pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define srep(i, s, n) for (ll i = s; i < (n); i++)
#define len(x) ((int)(x).size())
#define all(x) (x).begin(), (x).end()
using namespace std;
template<typename T> using vc = vector<T>;
template<typename T> using vv = vc<vc<T>>;
template<typename T> using vvv = vv<vc<T>>;
using vi = vc<int>;using vvi = vv<int>; using vvvi = vv<vi>;
using ll = long long;using vl = vc<ll>;using vvl = vv<ll>; using vvvl = vv<vl>;
using ld = long double; using vld = vc<ld>; using vvld = vc<vld>; using vvvld = vc<vvld>;
using uint = unsigned int;
using ull = unsigned long long;
const ld pi = acos(-1.0);
const int inf = 0x3f3f3f3f;
const ll INF = 0x3f3f3f3f3f3f3f3f;
// const ll mod = 1000000007;
const ll mod = 998244353;
inline bool inside(ll y, ll x, ll H, ll W) {return 0 <= (y) and (y) < (H) and 0 <= (x) and (x) < (W); }

#define debug(var) do { cerr << #var << " :\n"; view(var); } while(0)
template<typename T>void view(const T& e) {cerr << e;}
template<typename T1, typename T2>void view(const pair<T1, T2>& p) {cerr << "{" << p.first << ", " << p.second << "}";}
template<typename T>void view(const vc<T>& v) {for (const auto& e : v) {view(e);cerr << " ";} cerr << endl;}
template<typename T>void view(const vv<T>& vv) {for (const auto& v : vv) {view(v);} cerr << endl;}
template<typename T>void view(const set<T>& s) {for (const auto& e : s) {view(e);cerr << " ";} cerr << endl;}
template<typename T>void view(const multiset<T>& s) {for (const auto& e : s) {view(e);cerr << " ";} cerr << endl;}
template<typename T>void view(const unordered_set<T>& s) {for (const auto& e : s) {view(e);cerr << " ";} cerr << endl;}
template<typename T1, typename T2>void view(const map<T1, T2>& mp){for (const auto& e : mp) {view(e);cerr << " ";} cerr << endl;}

int main(){
    int T; cin >> T;
    while (T--){
        int N; cin >> N;
        string S; cin >> S;
        if (N < 3) cout << string(N, 'B') << endl;
        else if (S[0] == 'B'){
            if (S[1] == 'B') cout << S << endl;
            else{
                S[1] = 'B';
                srep(i, 2, N){
                    if (S[i] == 'B') S[i] = 'A';
                    else break;
                }
                cout << S << endl;
            }
        }else{
            S[0] = 'B';
            if (S[1] == 'B'){
                bool find = false;
                srep(i, 2, N){
                    if (S[i] == 'B'){
                        find = true;
                        S[i] = 'A';
                    }else if (find) break;
                }
                cout << S << endl;
            }else{
                S[1] = 'B';
                if (S[2] == 'B'){
                    S[2] = 'A';
                    srep(i, 3, N){
                        if (S[i] == 'B') S[i] = 'A';
                        else break;
                    }
                    cout << S << endl;
                }else{
                    cout << S << endl;
                }
            }

        }
    }
}