import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;

public class Main {
	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int t = Integer.parseInt(br.readLine());
		PrintWriter pw = new PrintWriter(System.out);
		for (int z = 0; z < t; z++) {
			int n = Integer.parseInt(br.readLine());
			char[] s = br.readLine().toCharArray();

			if (n == 1) {
				pw.println("B");
			} else {
				if (s[0] == 'A') {
					if (s[1] == 'B') {
						boolean flg = false;
						for (int i = 2; i < n; i++) {
							if (s[i] == 'B') {
								flg = true;
							}
							if (flg) {
								if (s[i] == 'A') {
									break;
								}
								s[i] = 'A';
							}
						}
					}
					s[0] = 'B';
					s[1] = 'B';
				} else {
					if (s[1] == 'A') {
						s[1] = 'B';
					}
				}
				pw.println(s);
			}
		}
		pw.flush();
		br.close();
	}
}