#include <bits/stdc++.h>

using namespace std;

typedef pair<int, int> pii;
typedef long long ll;
const int N = 2000010, MOD = 998244353, INF = 0x3f3f3f3f;
int n, m, w[N];

char s[N];
void solve() {
    if (n == 1) {
        puts("B");
        return;
    }
    if (s[1] == 'A') {
        int i = 1;
        if (s[i + 1] == 'B') {
            for (int k = i + 2; k < n + 1; k++) {
                if (s[k] == 'A') continue;
                for (int j = k; j < n + 1; j++)
                    if (s[j] == 'B') s[j] = 'A';
                    else break;
                break;
            }
        } else {
            s[i + 1] = 'B';
            for (int j = i + 2; j < n + 1; j++)
                if (s[j] == 'B') s[j] = 'A';
                else break;
        }
        s[1] = 'B';
        puts(s + 1);
    } else {
        if (s[2] == 'A') {
            s[2] = 'B';
            for (int i = 3; i < n + 1; i++)
                if (s[i] == 'B') s[i] = 'A';
                else break;
            }
        puts(s + 1);
    }
}

int main() {
    int T;
    scanf("%d", &T);
    while (T--) {
        scanf("%d%s", &n, s + 1);
        solve();
    }
    return 0;
}