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

class node
    {
    public:
    int x,y;
    int flag;
    node()
        {
        flag=0;
    }
};

int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */
    int q,n,x,y,i,j,k,f;
    node *a;
    cin>>q;
    for(i=0;i<q;i++)
        {
        cin>>n;
        a=new node [n];
        for(j=0;j<n;j++)
            {
            cin>>x>>y;
            a[j].x=x;
            a[j].y=y;
        }
        
        for(k=0;k<n;k++)
            {
            for(f=k+1;f<n;f++)
                {
                if(a[f].flag!=1)
                    {
                if(a[k].y==a[f].y || a[k].x==a[f].x)
                    {
                    a[k].flag=1;
                    a[f].flag=1;
                }
                }
            }
        }
        f=0;
        for(k=0;k<n;k++)
            {
            if(a[k].flag==0){ cout<<"NO\n";
                        f=1;
                         break;
                       }
        }
        if(f==0) cout<<"YES\n";
        free(a);
    }
    return 0;
}