#!/usr/bin/env PyPy3

from collections import Counter, defaultdict, deque
import itertools
import re
import math
from functools import reduce
import operator
import bisect
import heapq
import functools
mod=10**9+7

import sys
input=sys.stdin.readline

t = int(input())
for _ in range(t):
    n=int(input())
    s=input().rstrip()
    ans = []
    for i in range(n):
        if ans:
            if ans[-1] == 'A' and s[i] == 'B':
                if i + 1 < n and s[i+1] == 'B':
                    ans.pop()
                    while len(ans) >= 2 and ans[-2] == 'A' and ans[-1] == 'B':
                        ans.pop()
                        ans.pop()
                else:
                    ans.append(s[i])
            else:
                ans.append(s[i])
        else:
            ans.append(s[i])
    print(''.join(ans))