import java.io.*;
import java.util.*;

public class Solution {

    public static void main(String[] args) {
       Scanner in = new Scanner(System.in);
        int q = in.nextInt();
        for (int i = 0; i < q; i++) {
            int n = in.nextInt();
            int j = 0;
            HashSet<Integer> x = new HashSet<Integer>();
            HashSet<Integer> y = new HashSet<Integer>();
            boolean[] flags_x = new boolean[n];
            boolean[] flags_y = new boolean[n];
            in.nextLine();
            while (j < n && in.hasNextLine()) {
                String line = in.nextLine();
                String[] arr = line.split(" ");
                int first = Integer.parseInt(arr[0]);
                int second = Integer.parseInt(arr[1]);
                if (x.size() > 0) {
                    if (x.contains(first)) {
                        flags_x[j] = true;
                    } else {
                        flags_x[j] = false;
                        x.add(first);
                    }
                } else {
                    x.add(first);
                    flags_x[j] = true;
                }
                if (y.size() > 0) {
                    if (y.contains(second)) {
                        flags_y[j] = true;
                    } else {
                        flags_y[j] = false;
                        y.add(second);
                    }
                } else {
                    y.add(second);
                    flags_y[j] = true;
                }
                j++;
            }
            String answer = "YES";
            for (int k = 0; k < n; k++) {
                if ((flags_x[k] == false) && (flags_y[k] == false)) {
                    answer = "NO";                    
                }
            }
            System.out.println(answer);
        }
    }
}