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

int main() {

    int q;
    scanf("%d",&q);/* Enter your code here. Read input from STDIN. Print output to STDOUT */    
    while(q--)
        {
        int n,i,j,f=0,c=0;
        scanf("%d",&n);
        int x[n],y[n];
        for(i=0;i<n;i++)
            scanf("%d %d",&x[i],&y[i]);
        for(i=0;i<n;i++)
            {f=0;
            for(j=0;j<n;j++)
                {
                if(j!=i)
                    {
                if(x[i]==x[j]||y[i]==y[j])
                    f=1;}
            }
            if (f==0)
                {c=1;
                break;}
        }
        if(c==0)
            printf("YES\n");
        else
            printf("NO\n");
    }
    return 0;
}