t = int(input())
for _ in range(t):
    n = int(input())
    S = input()
    ANS = ''
    res = 0
    for i in range(n):
        s = S[i]
        if s == 'A':
            ANS += s
        elif s == 'B' and len(ANS) > 0 and ANS[-1] == 'A':
            if i < n - 1 and ANS[:-1] + S[i + 1] > ANS + S[i:i + 2]:
                ANS = ANS[:-1]
            else:
                ANS += s
        else:
            ANS += s
    res = 0
    for i in range(0, len(ANS), 2):
        if ANS[i:i + 2] == 'AB':
            res += 2
        else:
            break
    if len(ANS) != res:
        ANS = ANS[res:]
    print(ANS)