import collections
T = int(input())
for _ in range(T):
    N=int(input())
    S = list(input())
    d = collections.deque()
    d.append('x')
    d.append('x')
    bcnt = 0
    for s in S[::-1]:
        d.append(s)
        if d[-1]=='B' and d[-2]=='B':
            bcnt+=1
        while d[-1]=='A' and d[-2]=='B' and bcnt>=1:
            d.pop()
            d.pop()
            bcnt-=1

    ANS = list(d)[::-1]
    print(''.join(map(str, ANS[:len(ANS)-2])))