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

public class Solution {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int q = sc.nextInt();
        while(q-- > 0){
            int n = sc.nextInt() , xi[] = new int[n] ,  yi[] = new int[n];
            for(int i = 0 ; i < n ; i++){
                xi[i] = sc.nextInt() ; yi[i] = sc.nextInt();
            }
            boolean poss = true;
            for(int i = 1 ; i < n ; i++){
                boolean deg = false;
                for(int j = i - 1 ; j >= 0 ; j--){
                    if(xi[i] == xi[j] || yi[i] == yi[j]){
                        deg = true;
                        break;
                    }
                }
                if(!deg){poss = false; break;}
            }
            if(poss) System.out.println("YES"); else System.out.println("NO");
        }
    }
}