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();
            int [] x = new int[n];
            int [] y = new int[n];
            int maxX = -10000;
            int maxY = -10000;
            int minX = 10000;
            int minY = 10000;
            for(int j=0;j<n;j++) {
                x[j] = in.nextInt();
                if(maxX<x[j]) {
                    maxX = x[j];
                }
                if(minX>x[j]) {
                    minX = x[j];
                }
                y[j] = in.nextInt();
                if(maxY<y[j]) {
                    maxY = y[j];
                }
                if(minY>y[j]) {
                    minY = y[j];
                }
            }
            Map<Integer, Integer> map = new HashMap<Integer, Integer>();
            if(n<=2) {
                System.out.println("YES");
            } else {
                map.put(maxX, 1);
                map.put(maxY, 1);
                map.put(minX, 1);
                map.put(minY, 1);
                boolean flag = false;
                for(int j=0;j<n;j++) {
                    if(!map.containsKey(x[j]) || !map.containsKey(y[j])) {
                        flag = true;
                    }
                }
                if(flag) {
                    System.out.println("NO");
                } else {
                    System.out.println("YES");
                }
            }
        }
    }
}