T=int(input())
for _ in range(T):
  n=int(input())
  s=list(input())
  if n==1:
    print("B")
    continue
  if s[:2]==["A","A"]:
    s[:2]=["B","B"]
    if s[2]=="B":
      for i in range(2,n):
        if s[i]=="B":
          for j in range(i,n):
            if s[j]=="B":
              s[j]="A"
            else:
              break
          break
  elif s[:2]==["A","B"]:
    for i in range(2,n):
      if s[i]=="B":
        for j in range(i,n):
          if s[j]=="B":
            s[j]="A"
          else:
            break
        break
    s[0]="B"
  elif s[:2]==["B","A"]:
    s[1]="B"
    if n>=3:
      if s[2]=="A":
        s[2]="B"
        for i in range(3,n):
          if s[i]=="B":
            for j in range(i,n):
              if s[j]=="B":
                s[j]="A"
              else:
                break
            break
  elif s[:2]==["B","B"]:
    pass
  print("".join(s))