#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include<bits/stdc++.h>
#define sqr sqrt
using namespace std;


struct pts{
    int x,y;
};

bool isRect(pts p[],int N){
    bool y = 0;
    for(int i = 0;i<N;++i){
        y = 0;
        for(int j = 0;j<N;++j){
            if(i!=j && (p[i].x == p[j].x || p[i].y == p[j].y)){
                y = 1;
                break;
            }
        }
        if(!y)return 0;
    }
    return 1;
}

int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int T;
    cin >> T;
    while(T--){
        int  N;
        cin >> N;
        pts p[N];
        for(int i = 0;i<N;++i){
            cin >> p[i].x >> p[i].y;
        }
        if(isRect(p,N)){
            cout << "YES" << endl;
        }
        else{
            cout << "NO" << endl;
        }
        
    }
    return 0;
}