use std::io::BufWriter;
use std::io::Write;

use proconio::{input, marker::Chars};

fn main() {
    input! { t: usize }
    let mut writer = BufWriter::new(std::io::stdout().lock());

    for _ in 0..t {
        input! {
            _n: usize, s: Chars,
        }
        let ans = solve(s);
        writeln!(writer, "{ans}").unwrap();
    }
}

fn solve(mut s: Vec<char>) -> String {
    let n = s.len();
    if n <= 2 {
        let ans = std::iter::repeat_n('B', n).collect();
        return ans;
    }

    match (s[0], s[1]) {
        ('A', 'A') | ('B', 'A') => {
            let r = (2..n).find(|&i| s[i] == 'A').unwrap_or(n);
            s[2..r].fill('A');
        }
        ('A', 'B') => {
            let l = (2..n).find(|&i| s[i] == 'B').unwrap_or(n);
            let r = (l..n).find(|&i| s[i] == 'A').unwrap_or(n);
            s[l..r].fill('A');
        }
        ('B', 'B') => (),
        _ => unreachable!(),
    }
    s[0..2].fill('B');

    s.iter().collect()
}

// ABxxxx
// BBxxxx