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

public class Solution {

    public static boolean moreThanOnce(ArrayList<Integer> list, int searched) {

	    int numCount = 0;
	    boolean more = false;

	    for (int thisNum : list) {
	        if (thisNum == searched) {
	            numCount ++ ;
	        }
	    }

	    if (numCount > 1) {
	        more = true;
	    }

	    return more;
	}
	    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=sc.nextInt();
	        for(int i=0;i<q;i++){
	            int noofpoints=sc.nextInt();
	            int x[]= new int[noofpoints];int y[]= new int[noofpoints];
	            ArrayList< Integer> x2 = new ArrayList<Integer>(noofpoints);
	            ArrayList< Integer> y2 = new ArrayList<Integer>(noofpoints);
	            for(int j=0;j<noofpoints;j++){
	                x[j]=sc.nextInt();y[j]=sc.nextInt();
	                x2.add(x[j]); y2.add(y[j]);
	            }
	            
	            
	            
	            /*while(noofpoints!=-1){
	            	System.out.println(noofpoints);
	                if(x[noofpoints-1]==y[noofpoints-1]){
	                    noofpoints--;
	                    continue;
	                }
	                else
	                    break;
	                
	            }
	            if(noofpoints==-1)
	                System.out.println("Yes");
	            else
	                System.out.println("No");*/
	            int a=0;
	            for( a=0;a<noofpoints;a++){
	            	if(moreThanOnce(x2, x[a])){
	            		continue;
	            	}
	            	else{
	            		if(moreThanOnce(y2, y[a])){
	            			continue;
	            		}
	            		else{
	            			break;
	            		}
	            	}
	            	
	            }
	            if(a==noofpoints)
	            	System.out.println("YES");
	            else
	            	System.out.println("NO");
	            
	        }
	    }
}