#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic warning "-Wunused-function"
using namespace std;
using namespace atcoder;
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; i--)
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
template<class T> bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; } else return false; }
template<class T> bool chmin(T& a, const T& b) { if (b < a) { a = b; return true; } else return false; }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int tt;
  cin >> tt;
  while (tt--) {
    int n;
    string s;
    cin >> n >> s;
    if (n <= 2) {
      rep(_, 2) cout << 'B';
      cout << '\n';
      continue;
    }
    auto t = s.substr(0, 3);
    if (t == "AAA" || t == "BAA" || t == "BBA") {
      s[0] = s[1] = 'B';
    } else if (t == "AAB" || t == "ABB" || t == "BAB") {
      s[0] = s[1] = 'B';
      s[2] = 'A';
      for (int i = 3; i < n; i++) {
        if (s[i] == 'A') break;
        s[i] = 'A';
      }
    } else if (t == "ABA") {
      s[0] = 'B';
      for (int i = 3; i < n; i++) {
        if (s[i] == 'A') continue;
        while (i < n && s[i] == 'B') {
          s[i++] = 'A';
        }
        break;
      }
    } else {
      assert(t == "BBB");
    }
    cout << s << '\n';
  }
}