"""

https://yukicoder.me/problems/no/3395

後手に AB で渡したい

AA,BA = 3文字目スタートで後は自由
AB = 完全自由
BB = そのまま

"""

import sys
from sys import stdin

TT = int(stdin.readline())

ANS = []

for loop in range(TT):

    N = int(stdin.readline())
    S = stdin.readline()[:-1]

    if N == 1:
        print ("B")
        continue
    elif N == 2:
        print ("BB")
        continue
    elif S[:2] == "BB":
        print (S)
        continue

    elif S[:2] == "AB":
        state = 0
        ans = [ "BB" ]
        
        for i in range(2,N):
            
            if state == 0:
                if S[i] == "B":
                    state = 1
                    ans.append("A")
                else:
                    ans.append(S[i])
            elif state == 1:
                if S[i] == "B":
                    ans.append("A")
                else:
                    ans.append(S[i])
                    state = 2
            else:
                ans.append(S[i])
        print ("".join(ans))
        
    else:
        state = 1
        ans = ["BB"]
        for i in range(2,N):
            
            if state == 0:
                if S[i] == "B":
                    state = 1
                    ans.append("A")
                else:
                    ans.append(S[i])
            elif state == 1:
                if S[i] == "B":
                    ans.append("A")
                else:
                    ans.append(S[i])
                    state = 2
            else:
                ans.append(S[i])
        print ("".join(ans))