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

int main() {
    int q;
    scanf("%d",&q);
    while(q--)
        {
        int n,t=0;
        scanf("%d",&n);
        while(n--)
            {
            int x,y;
            scanf("%d%d",&x,&y);
            if(x!=0 && y!=0 )
                t=1;
        }
        if(t==0)
            printf("YES\n");
        else
            printf("NO\n");
    }
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */    
    return 0;
}