import sys,random,bisect
from collections import deque,defaultdict
from heapq import heapify,heappop,heappush
from itertools import permutations
from math import log,gcd

input = lambda :sys.stdin.readline().rstrip()
mi = lambda :map(int,input().split())
li = lambda :list(mi())

for _ in range(int(input())):
    N = int(input())
    S = input()

    res = []
    for s in S[::-1]:
        if s=="B":
            res.append(s)
        else:
            if res and res[-1]=="B":
                if len(res) >= 2 and res[-2]=="B":
                    res.pop()
                else:
                    res.append("A")
            else:
                res.append("A")
    
    res = res[::-1]
    print("".join(res))