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

class point
    {
    int x,y;
}



public class Solution {

    public static void main(String[] args) {
        Scanner s= new Scanner(System.in);
        int q=s.nextInt();
        while(q-->0)
            {
            int n=s.nextInt();
            point p[] = new point[n];
            for(int x=0;x<n;x++)
            {
                p[x]=new point();
                p[x].x=s.nextInt();
                p[x].y=s.nextInt();
            }
            int x,y;
            boolean f=false;
            for(x=0;x<n;x++)
                {
                f=false;
                for(y=0;y<n;y++)
                    {
                    if(p[x].x==p[y].x && x!=y)break;
                }
                if(y==n)
                    {
                    
                    for(int z=0;z<n;z++)
                        if(p[x].y==p[z].y && x!=z){f=true;break;}
                    if(f)continue;
                else break;
                           }
                
            }
            if(x!=n){System.out.println("NO");continue;}
            
            for(x=0;x<n;x++)
                {
                f=false;
                for(y=0;y<n;y++)
                    {
                    if(p[x].y==p[y].y && x!=y)break;
                }
                if(y==n){
                    for(int z=0;z<n;z++)
                        if(p[x].x==p[z].x && x!=z){f=true;break;}
                    if(f)continue;
                else break;
                           }
                
            }
            if(x!=n){System.out.println("NO");}
            else System.out.println("YES");
            
            
        }
    }
}