#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, s, t) for (ll i = (ll)s; i < (ll)(t); i++)
#define rrep(i, s, t) for (ll i = (ll)(t) - 1; i >= (ll)(s); i--)
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)

#define TT template <typename T>
template <class T1, class T2>
bool chmin(T1& x, T2 y) { return x > y ? (x = y, true) : false; }
template <class T1, class T2>
bool chmax(T1& x, T2 y) { return x < y ? (x = y, true) : false; }

struct io_setup {
    io_setup() {
        ios::sync_with_stdio(false);
        std::cin.tie(nullptr);
        cout << fixed << setprecision(15);
        srand(time(NULL));
    }
} io_setup;

void solve() {
    int N;
    string S;
    cin >> N >> S;
    int l = 0;
    while (l < N && S[l] == 'B') l++;
    if (l == N) {
        cout << S << endl;
        return;
    }
    int r = l;
    while (r < N && S[r] == 'A') r++;
    if (l >= 2) {
        cout << S << endl;
    } else if (l == 1) {
        S[1] = 'B';
        cout << S << endl;
    } else if (r - l >= 2) {
        rep(i, l, l + 2) S[i] = 'B';
        cout << S << endl;
    } else {
        int n = r + 1;
        while (n < N && S[n] == 'A') n++;
        while (n < N && S[n] == 'B') {
            S[n] = 'A';
            n++;
        }
        rep(i, l, r) S[i] = 'B';
        cout << S << endl;
    }
}

int main() {
    int T;
    cin >> T;
    while (T--) {
        solve();
    }
}