#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>

int main() {
    int q,n,u[1000],v[1000],i,j,k,flag,val;
    scanf("%d",&q);
    for(i=0;i<q;i++){
        scanf("%d",&n);
        for(j=0;j<n;j++){
            scanf ("%d %d",&u[j],&v[j]);
        }
        flag=0;
        val=u[0];
        for(j=i+1;j<n;j++){
            if(val==u[j]){
                flag++;
            }
        }
        for(j=0;j<n;j++){
            if(val==v[j]){
                flag++;
            }
        }
        if(flag==n){
            printf("YES\n");
        } else {
            printf("NO\n");
        }
    }

    /* Enter your code here. Read input from STDIN. Print output to STDOUT */    
    return 0;
}