#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() {
    int v = 0;
    for (int i = 1; i < n + 1; i++) {
        if (i & 1) {
            if (!v && s[i] == 'C') s[i] = 'A';
            else break;
        } else {
            if (s[i] != 'C') s[i]++,  v |= s[i] == 'B';
            else break;
        }
    }
    puts(s + 1);
}

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