from collections import deque
for _ in range(int(input())):
    n = int(input())
    s = list(input())
    res = deque()
    for i in range(n-1,-1,-1):
        if s[i] == "A":
            if len(res) >= 2:
                a,b = res.pop(),res.pop()
                if a == b == "B":
                    res.append("B")
                else:
                    res.append(b)
                    res.append(a)
                    res.append(s[i])
            else:
                res.append(s[i])
        else:
            res.append(s[i])

    res = list(res)[::-1]
    print("".join(res))