import sys
input = lambda :sys.stdin.readline()[:-1]
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES")
no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO")
#######################################################################
"""

Alice
- s[0] = A のとき終了する
- s[0] = C のとき s[0] = A にする

Bob
- s[0] = A のとき s[0] = B にする
- s[0] = C のとき終了する

f(A) = A
f(B) = B
f(C) = A




"""
mod = 998244353

def solve(n, s):
    if s[0] == "A":
        return s
    s = list(s)
    i = 0
    while i < len(s):
        if s[i] == "A" or s[i] == "B":
            return "".join(s)
        elif s[i] == "C":
            s[i] = "A"
            i += 1
            while i < n and s[i] == "C":
                i += 1

            if i == n:
                return "".join(s)
            if s[i] == "A":
                s[i] = "B"
                return "".join(s)
            elif s[i] == "B":
                s[i] = "C"
                i += 1
    return "".join(s)
            
        

for _ in range(ni()):
    n = ni()
    s = input()
    print(solve(n, s))