t = int(input())
for _ in range(t):
    n = int(input())
    S = input()
    l = []
    for s in S:
        if s == "A":
            l.append(s)
            continue

        if len(l) < 2:
            l.append(s)
            continue
        # print(l)
        while len(l) >= 2:
            if l[-1] == "B" and l[-2] == "A":
                l.pop()
                l.pop()
            else:
                break
        l.append(s)
    # print("ans")
    print(*l,sep="")