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

public class Solution {

    private static Scanner in = new Scanner(System.in);

    public static void main(String[] args) {

        int numOfCases = in.nextInt();
        String[] answers = new String[numOfCases];
        for(int i = 0; i < answers.length; i++){
            answers[i] = solve();
        }

        for(String each : answers){
            System.out.println(each);
        }
    }

    private static String solve(){
        int q = in.nextInt();
        boolean result = true;
        for(int i = 0; i < q; i++){
            int firstPoint = in.nextInt();
            int nextPoint = in.nextInt();
            if(firstPoint == 0 || nextPoint == 0){
            }
            else if(result == true){
                result = false;
            }
        }

        if(result){
            return "YES";
        }
        else {
            return "NO";
        }

    }
}