T = int(input())
ansls = []
for i in range(T):
    n = int(input())
    S = input()
    ans = []
    cntB = 0
    for j in range(n-1,-1,-1):
        if S[j] == 'B':
            cntB += 1
            ans.append('B')
        elif cntB > 1:
            cntB -= 1
            ans.pop()
        else:
            cntB = 0
            ans.append('A')
    ans.reverse()
    ansls.append(''.join(ans))
for ans in ansls:
    print(ans)