T=int(input())
for _ in range(T):
    N=int(input())
    S=input()
    if N==2:
        print("BB")
        continue
    if N==1:
        print("B")
        continue
    if S[:3] == "AAA":
        print("BBA" + S[3:])
    elif S[:3] == "AAB":
        ans = "BB" + S[2:]
        ans = list(ans)
        for i in range(2,len(S)):
            if ans[i] == "B":
                break
        for i in range(i,len(S)):
            if ans[i] == "B":
                ans[i] = "A"
            else:
                break
        print("".join(ans))
    elif S[:2] == "AB":
        ans = "B" + S[1:]
        ans = list(ans)
        for i in range(2,len(S)):
            if ans[i] == "B":
                break
        for i in range(i,len(S)):
            if ans[i] == "B":
                ans[i] = "A"
            else:
                break
        print("".join(ans))
    elif S[:2] == "BB":
        print(S)
    elif S[:3] == "BAA":
        print("BBA" + S[3:])
    elif S[:3] == "BAB":
        ans = "BB" + S[2:]
        ans = list(ans)
        for i in range(2,len(S)):
            if ans[i] == "B":
                ans[i] = "A"
            else:
                break
        print("".join(ans))