def solve():
	N = int(input())
	S = list(input())
	for i in range(N):
		if i%2 == 0:
			if S[i] == 'C':
				S[i] = 'A'
			else:
				break
		else:
			if S[i] == 'A':
				S[i] = 'B'
			elif S[i] == 'B':
				S[i] = 'C'
			else:
				break
	print(*S, sep = "")

for _ in range(int(input())):
	solve()