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

int main() {
    int q;
    cin>>q;
    while(q--){
        int n,a,b;
        cin>>n;
        vector<pair<int,int> > vec;
        for(int i=0;i<n;i++){
            cin>>a>>b;
            vec.push_back({a,b});
        }
        bool ans=true;
        int count;
        for(int i=0;i<n;i++){
            count=0;
            for(int j=0;j<n;j++){
                if((vec[i].first-vec[j].first)==0||(vec[i].second-vec[j].second)==0){
                    count++;
                }
            }
            if(count<2){
                cout<<"NO"<<endl;
                ans=false;
                break;
            }
        }
        if(ans==true)
            cout<<"YES"<<endl;
    }
    return 0;
}