import java.io.*;
import java.util.*;

public class Solution {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int q = in.nextInt();
        for (int i=0; i < q; i++) {
            int n = in.nextInt();
            Set<Integer> ys = new HashSet<Integer>();
            Set<Integer> xs = new HashSet<>();

            Set<Integer> rx = new HashSet<>();
            Set<Integer> ry = new HashSet<>();
            Set<Integer> zz = new HashSet<>();
            
            for (int j=0; j < n; j++) {
                int x = in.nextInt();
                int y = in.nextInt();
                if (xs.contains(x)) {
                    rx.add(x);
                } else if (ys.contains(y)) {
                    ry.add(y);
                } else {
                    zz.add(x);
                }
                xs.add(x);
                ys.add(y);
            }
            
                //System.out.println(zz.size());
            if (ry.size() > 2 || rx.size() > 2 || zz.size() > 1) {
                System.out.println("NO");
            } else {
                System.out.println("YES");                
            }
        }
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
    }
}