#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    int q,n,i,j,count=0,count1=0;
    float a[10],b[10];
    scanf("%d",&q);
    for(i=0;i<q;i++)
        {
            scanf("%d",&n);
            for(j=0;j<n;j++)
                {   
                    
                    scanf("%f %f",&a[j],&b[j]);
                }
            for(j=0;j<n;j++)
                {
                    if(((b[j+1]-b[j])/(a[j+1]-a[j]))*((b[j+2]-b[j+1])/(a[j+2]-a[j+1])) == -1)
                        count++;
                    else
                        count1++;
                }
           if(count > 0)
                printf("NO\n");
            else
                printf("YES\n");
        }
    
    return 0;
}