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
        else:
            if ANS[:-1] + S[i + 1:] > ANS + S[i:]:
                ANS = ANS[:-1]
            else:
                ANS += s
    print(ANS)