import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    public static void main(String[] args) {
        Scanner scan=new Scanner(System.in);
        int q=scan.nextInt();
        int m=0;
        int n=0;
        int r=0;
        int s=0;
        int u=0;
        int v=0;
        int count=0;
        for(int i=0;i<q;i++){
            int num=scan.nextInt();
            for(int j=0;j<num;j++){
                int x=scan.nextInt();
                int y=scan.nextInt();
                if(x!=y ){
                    if(x<y){
                    m=x;
                    n=y;
                    }
                    else{
                       r=x;
                        s=y;
                    }
                }
                if(x==y){
                    if(count ==0)   
                    u=x;
                    else
                        v=x;
                }
            }
            if(m==s && n==r && (u==m || u==n))
                System.out.println("YES");
            else
                System.out.println("NO");
                
        }
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
    }
}