#include<bits/stdc++.h>
using namespace std;
//#pragma GCC optimize("Ofast")

#define rep(i,n) for(ll i=0;i<n;i++)
#define repl(i,l,r) for(ll i=(l);i<(r);i++)
#define per(i,n) for(ll i=(n)-1;i>=0;i--)
#define perl(i,r,l) for(ll i=r-1;i>=l;i--)
#define all(x) (x).begin(),(x).end()
#define CST(x) cout<<fixed<<setprecision(x)
#define vtpl(x,y,z) vector<tuple<x,y,z>>
#define rev(x) reverse(x);
using ll=long long;
using vl=vector<ll>;
using vvl=vector<vector<ll>>;
using pl=pair<ll,ll>;
using vpl=vector<pl>;
using vvpl=vector<vpl>;
const ll MOD=1000000007;
const ll MOD9=998244353;
const int inf=1e9+10;
const ll INF=4e18;
const ll dy[9]={1,0,-1,0,1,1,-1,-1,0};
const ll dx[9]={0,1,0,-1,1,-1,1,-1,0};
template<class T> inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template<class T> inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}


int main(){
    ll t;cin >> t;
    while(t--){
        ll n;cin >> n;
        string s;cin >> s;
        ll bcnt=0,acnt=0;
        string ans;
        while(s.size()){
            while(s.size()&&s.back()=='B'){
                s.pop_back();bcnt++;
            }
            while(s.size()&&s.back()=='A'){
                s.pop_back();acnt++;
            }
            if(bcnt>acnt){
                bcnt-=acnt;acnt=0;
            }
            else{
                if(bcnt==0){
                    rep(_,acnt)ans+='A';
                    acnt=0;
                    continue;
                }
                ll f=bcnt-1;
                acnt-=f;bcnt-=f;
                rep(_,bcnt)ans+='B';
                rep(_,acnt)ans+='A';
                acnt=0;bcnt=0;
            }
        }
        rep(i,bcnt)ans+='B';
        rev(all(ans));
        cout << ans << endl;
    }
}