rot = {"A" : "B", "B" : "C", "C" : "A"}
t = int(input())
for i in range(t):
    n = int(input())
    s = list(input())
    f = 0
    for i in range(n):
        if (s[i] != "C") ^ (i & 1) == 0:
            s[i] = rot[s[i]]
            if (i & 1 == 1 and s[i] == "B"):
                break
        else:
            break
    print(*s, sep = "")