#include <bits/stdc++.h>
using namespace std;


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int q;
    cin>>q;
    while(q--)
    {
        int n;
        cin>>n;
        vector<pair<int,int> > v;
        vector<pair<int,pair<int,int> > > slope;
        for(int i=0;i<n;i++)
        {
            int x,y;
            cin>>x>>y;
            v.push_back(make_pair(x,y));
        }
        //any pair which are perpendicular
        int c=0;
        for(int i=0;i<n;i++)
        {
            int f=0;
            for(int j=0;j<n;j++)
            {
                if(i!=j&&(v[i].first==v[j].first||v[i].second==v[j].second))
                {
                    f=1;
                    //cout<<"\n$$$$$$$$$$$\n";
                    //cout<<v[i].first<<" "<<v[i].second<<"\n";
                    //cout<<v[j].first<<" "<<v[j].second<<"\n";
                }
            }
            if(f==1)
            c++;
        }
        if(c==n)
        cout<<"YES\n";
        else
        cout<<"NO\n";

    }
    return 0;
}