import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

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();
            HashSet<Integer> xvals = new HashSet<>();
            HashSet<Integer> yvals = new HashSet<>();
            boolean works = true;
            for (int j = 0; j < n; j++) {
                int x = in.nextInt();
                int y = in.nextInt();
                if (!xvals.contains(x) && xvals.size() == 2) {
                    works = false;
                    break;
                }
                else if (!xvals.contains(x)) {
                    xvals.add(x);
                }
                if (!yvals.contains(y) && yvals.size() == 2) {
                    works = false;
                    break;
                }
                else if (!yvals.contains(y)) {
                    yvals.add(y);
                }
            }
            if (works) {
                System.out.println("YES");
            }
            else {
                System.out.println("NO");
            }
        }
    }
}