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


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int test;
    cin >> test;
    
    while(test--){
        int n;
        cin >> n;
        long long int nodes[n][2];
        int graph[n][n];
        
        for(int i = 0; i < n; i++)
        for(int j = 0; j < n; j++)
            graph[i][j] = 0;
            
        for(int i = 0; i < n; i++)
            cin >> nodes[i][0] >> nodes[i][1];
            
        for(int i = 0; i < n; i++)
        for(int j = i+1; j < n; j++)
        if(nodes[i][1] - nodes[j][1] == 0 || nodes[i][0] - nodes[j][0] == 0){
            graph[i][j] = 1;
            graph[j][i] = 1;
        }
                
        queue<int> q;
        q.push(0);
        int visited[n];
        for(int i = 0; i < n; i++)
            visited[i] = 0;
        
        while(!q.empty()){
            int u = q.front();
            q.pop();
            for(int i = 0; i < n; i++){
                if(!visited[i] && graph[u][i] == 1)
                    q.push(i);
            }
            visited[u] = 1;
        }
        
        bool flag = true;
        for(int i = 0; i < n; i++)
            if(visited[i] == 0){
                flag = false;
                break;
            }
        
        if(flag)
            cout << "YES" << endl;
        else
            cout << "NO" << endl;
        
    }
    return 0;
}