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 sc=new Scanner(System.in);
        int q,x,y,n,x1,y1;
        boolean d;
        q=sc.nextInt();
        for(int i=1;i<=q;i++)
            {
            n=sc.nextInt();
            if(n==1)
                System.out.println("YES");
            else
                {
                    x=sc.nextInt();
                    y=sc.nextInt();
                d=true;
                for(int j=1;j<n;j++)
                    {
                    x1=sc.nextInt();
                    y1=sc.nextInt();
                    if(x!=x1 && y!=y1)
                        {
                        System.out.println("NO");
                        d=false;
                        break;
                    }
                    
                }
                if(d==true)
                        System.out.println("YES");
            }
        }
    }
}