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

public class Solution {

    public static void main(String[] args) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
        Scanner in=new Scanner(System.in);
        int q=in.nextInt();
        for(int i=0;i<q;i++)
            {
            int n=in.nextInt();
            int a[][]=new int[n][2];
            for(int j=0;j<n;j++)
                {
                for(int k=0;k<2;k++)
                    {
                    a[j][k]=in.nextInt();
                }
            }
            Set<Integer> set = new HashSet<Integer>();
            Set<Integer> set2 = new HashSet<Integer>();
            int flag=1,count1=0,count2=0;
            for(int j=0;j<n-1;j++)
                {
                if(a[j][0]!=a[j+1][0])
                    set.add(a[j+1][0]);
                if(a[j][1]!=a[j+1][1])
                    set2.add(a[j+1][1]);
            }
            count1=set.size();
            count2=set2.size();
            if((count1<=2 && count2<=2))
                System.out.println("YES");
            else
                System.out.println("NO");
        }
    }
}