def solve():
    N = int(input())
    S = input()

    if N == 1:
        print("B")

    elif S[:2] == "BB":
        print("BB" + S[2:])

    elif S[:2] == "AB":
        zero = min([i for i in range(2, N) if S[i] == "B"] + [N])
        one = min([i for i in range(zero + 1, N) if S[i] == "A"] + [N])
        print("BB" + "A" * (one - 2) + S[one:])

    else:
        one = min([i for i in range(2, N) if S[i] == "A"] + [N])
        print("BB" + "A" * (one - 2) + S[one:])


if __name__ == "__main__":
    T = int(input())

    for _ in range(T):
        solve()