#include<stdio.h>
//#include<stdlib.h>
int main()
{
int test,w,minus,a,b,tf=1,fin=0;
scanf("%d",&test);
while(test--)
{
scanf("%d",&w);
scanf("%d %d",&a,&b);
minus=a-b;
w--;
while(w--)
{
scanf("%d %d",&a,&b);
fin=a-b;
if(fin!=minus)
tf=0;
}
if(tf==1)
printf("yes\n\n");
else
printf("no\n\n");
}
//system("pause");
return 0;
}