#include <iostream>
#include <iomanip>//小数点出力用
//cout << fixed << setprecision(10) << ans;
#include <cmath>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <unordered_map>
using ll = long long;
using namespace std;
#define modPHash (ll)((1LL<<61)-1)
#define modP (ll)998244353
bool chkrng0idx(int pos, int sup) { return (0 <= pos && pos < sup); }
int clk4(int num) { return (num - 2) * (num % 2); }
void yn(bool tf) { cout << (tf ? "Yes\n" : "No\n"); }

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int T;
    cin >> T;
    while (T--) {
        int N;
        cin >> N;
        string S;
        cin >> S;
        if (N == 1) {
            cout << "B\n";
        }
        else if(N == 2){
            cout << "BB\n";
        }
        else {
            if (S.substr(0,3) == "AAA") {
                cout << "BBA";
                cout << S.substr(3) << "\n";
            }
            else if (S.substr(0, 3) == "AAB") {
                int i = 2;
                while (i != N && S[i] == 'B') {
                    S[i] = 'A';
                    i++;
                }
                S[0] = 'B';
                S[1] = 'B';
                cout << S << "\n";
            }
            else if (S.substr(0, 3) == "ABA") {
                int i = 2;
                while (i != N && S[i] == 'A')i++;
                while (i != N && S[i] == 'B') {
                    S[i] = 'A';
                    i++;
                }
                S[0] = 'B';
                cout << S << "\n";
            }
            else if (S.substr(0, 3) == "ABB") {
                int i = 2;
                while (i != N && S[i] == 'B') {
                    S[i] = 'A';
                    i++;
                }
                S[0] = 'B';
                cout << S << "\n";
            }
            else if (S.substr(0, 3) == "BAA") {
                cout << "BB";
                cout << S.substr(2) << "\n";
            }
            else if (S.substr(0, 3) == "BAB") {
                int i = 2;
                while (i != N && S[i] == 'B') {
                    S[i] = 'A';
                    i++;
                }
                S[0] = 'B';
                S[1] = 'B';
                cout << S << "\n";
            }
            else if (S.substr(0, 3) == "BBA") {
                cout << S << "\n";
            }
            else if (S.substr(0, 3) == "BBB") {
                cout << S << "\n";
            }
        }
    }
}