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 = sc.nextInt();
        while(q-- >0){
            int n = sc.nextInt();
            boolean flag=false;
            for(int i=0;i<n;i++){
                int x = sc.nextInt();
                int y = sc.nextInt();
                if(x != 0 && y != 0) {
                    flag = true;
                    break;
                } 
            }
            if(flag) System.out.println("NO");
            else System.out.println("YES");
                
        }
    }
}