#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */  
    int n,m,l,k,i,j,flag;
    cin>>n;
    for(i=0;i<n;i++)
        {
        cin>>m;
        for(j=0;j<m;j++)
            {
            cin>>k>>l;
            if(i==k && i==l)
                {
                  flag=1;  
            }
            else
                flag=2;
        }
        if(flag==1)
            cout<<"NO\n";
        if(flag==2)
            cout<<"YES\n";
        
    }
    return 0;
}