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

struct Point {
    int x, y;
};

int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */ 
    const int N = 10;
    int q, n;
    Point p[N];
    string result;
    
    cin >> q;
    for (int qi = 0; qi < q; qi++) {
        cin >> n;
        for (int ni = 0; ni < n; ni++) {
            cin >> p[ni].x >> p[ni].y;
        }
        result = "YES";
        for (int i = 0; i < n; i++) {
            Point p0 = p[i];
            int j;
            for (j = 0; j < n; j++) {
                if (j == i) continue;
                
                if (p0.x == p[j].x || p0.y == p[j].y) {
                    // point ok
                    break;
                }
            }
            
            if (j == n) {
                result = "NO";
                break;
            }
        }
        
        cout << result << endl;
    }
    return 0;
}