#include <iostream>
#include <vector>
#include <algorithm>
#include <set>

using namespace std;

void solve()
{
  int n;
  cin >> n;
  string s;
  cin >> s;
  if (n == 1)
  {
    cout << "B" << endl;
    return;
  }
  if (s.substr(0, 2) == "AA")
  {
    int id = 2;
    s[1] = 'B';
    while (id < n && s[id] == 'B')
    {
      s[id] = 'A';
      ++id;
    }
    s[0] = 'B';
  }
  else if (s.substr(0, 2) == "AB")
  {
    for (int i = 2; i < n; ++i)
    {
      if (s[i] == 'B')
      {
        int id = i;
        while (id < n && s[id] == 'B')
        {
          s[id] = 'A';
          ++id;
        }
        break;
      }
    }
    s[0] = 'B';
  }
  else if (s.substr(0, 2) == "BA")
  {
    int id = 2;
    s[1] = 'B';
    while (id < n && s[id] == 'B')
    {
      s[id] = 'A';
      ++id;
    }
    s[0] = 'B';
  }
  cout << s << endl;
}

int main()
{
    int t;
    cin >> t;
    while (t--) solve();
}