#include <bits/stdc++.h>
using namespace std;
using ll = long long;

void solve(){
    int n;
    string s;
    cin >> n >> s;
    for(int i = 0; i < n; i++){
        if(i % 2 == 0){
            if(s[i] == 'A' || s[i] == 'B') break;
            s[i] = 'A';
        }else{
            if(s[i] == 'C') break;
            s[i]++;
        }
    }
    cout << s << '\n';
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    int T;
    cin >> T;
    while(T--) solve();
}