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();

			int i = 0;
			label:
			while (i < n) {
				while (i < n) {
					if (s[i] == 'C') {
						break;
					} else {
						break label;
					}
				}
				if (i < n) {
					s[i] = 'A';
					i++;
				} else {
					break;
				}

				while (i < n) {
					if (s[i] == 'C') {
						break label;
					} else {
						break;
					}
				}
				if (i < n) {
					s[i]++;
					i++;
				} else {
					break;
				}
			}
			pw.println(s);
		}
		pw.flush();
		br.close();
	}
}