def main():
	n = int(input())
	S = input()
	if n == 1:
		return "B"
	elif n == 2:
		return "BB"
	else:
		Ans = [S[i] for i in range(n)]
		if S[:2] in "BAA":
			now = 2
			while now < n and Ans[now] == "B":
				Ans[now] = "A"
				now += 1
			Ans[0] = "B"
			Ans[1] = "B"
		elif S[:2] == "AB":
			now = 2
			while now < n and Ans[now] == "A":
				now += 1
			while now < n and Ans[now] == "B":
				Ans[now] = "A"
				now += 1
			Ans[0] = "B"
		return "".join(Ans)

for _ in range(int(input())):
	print(main())