from sys import stdin
input = stdin.readline

for _ in range(int(input())):
    N = int(input())
    S = list(input().rstrip("\n"))

    if N == 1:
        print("B")
        continue
    if N == 2:
        print("BB")
        continue

    if S[:3] == list("AAA"):
        S[0] = "B"
        S[1] = "B"
    elif S[:3] == list("AAB"):
        S[0] = "B"
        S[1] = "B"
        S[2] = "A"
        for i in range(3, N):
            if S[i] == "A":
                break
            S[i] = "A"
    elif S[:3] == list("ABA"):
        S[0] = "B"
        flag = False
        for i in range(3, N):
            if S[i] == "A" and flag:
                break
            if S[i] == "B":
                flag = True
            if S[i] == "B":
                S[i] = "A"
    elif S[:3] == list("ABB"):
        S[0] = "B"
        for i in range(2, N):
            if S[i] == "A":
                break
            S[i] = "A"
    elif S[:3] == list("BAA"):
        S[1] = "B"
    elif S[:3] == list("BAB"):
        S[1] = "B"
        S[2] = "A"
        for i in range(3, N):
            if S[i] == "A":
                break
            S[i] = "A"
    
    print("".join(S))