def main(N, S):
  if N == 1:
    return "B"
  if N == 2:
    return "BB"
  if S[:2] == list("AA"):
    for i in range(2, N):
      if S[i] == "B": S[i] = "A"
      else: break
    return "BB" + "".join(S[2:])
  if S[:2] == list("AB"):
    flag = False
    for i in range(2, N):
      if S[i] == "B":
        flag = True
        S[i] = "A"
      elif flag:
        break
    return "BB" + "".join(S[2:])
  if S[:2] == list("BA"):
    for i in range(2, N):
      if S[i] == "B": S[i] = "A"
      else: break
    return "BB" + "".join(S[2:])
  if S[:2] == list("BB"):
    return "".join(S)

T = int(input())
for _ in range(T):
  N = int(input())
  S = input()
  S = list(S)
  ans = main(N, S)
  print(ans)