#include<bits/stdc++.h>

using namespace std;

#define rep(i, l, n) for(int i = int(l); i < int(n); i++)
#define ll long long
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()

template<class T> bool chmin(T &a, T b) {if(a > b) {a = b; return true;} return false;}
template<class T> bool chmax(T &a, T b) {if(a < b) {a = b; return true;} return false;}
template<class T> using spq = priority_queue<T, vector<T>, greater<T>>;

// bool -> Yes/No
string answer(bool b) {return b ? "Yes" : "No";}

void fix(int k) {cout << fixed << setprecision(k);}

const int inf = 2e9;
const long long INF = 2e18;
const long double eps = 1e-12;
const long double pi = acos(-1);
int dx[] = {0, -1, 0, 1, -1, -1, 1, 1}, dy[] = {1, 0, -1, 0, 1, -1, -1, 1};

void main_program() {
    int n; cin >> n;
    string s; cin >> s;
    int last_b = n;
    rep(i, 0, n) if(s[i] == 'B') last_b = i;
    rep(i, 0, last_b) {
        if(i & 1) s[i] = 'C';
        else s[i] = 'A';
    }
    cout << s << "\n";
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int T = 1;
    cin >> T;
    while(T--) {
        main_program();
    }
}