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


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */  
    int t;
    cin>>t;
    while(t--)
        {
        long long int n;
        cin>>n;
        long long int a[n][2];
        int i,j,k,l=0;
        for(i=0;i<n;i++)
            {for(j=0;j<2;j++)
              {cin>>a[i][j];}
            }
        if(n==1)
            {cout<<"YES"<<endl;}
        else if(n==2)
            {if(((a[0][0])-(a[1][0])==0) || ((a[0][1])-(a[1][1])==0))
             {cout<<"YES"<<endl;}}
        else{
            for(i=1;i<n-1;i++)
            {if(!((((a[i-1][0]-a[i][0])==0) || ((a[i-1][1]-a[i][1])==0)) ||(((a[i][0]-a[i+1][0])==0) || ((a[i][1]-a[i+1][1])==0))))
            {l++;
            }
            }
             if(l>0)
                 {cout<<"NO"<<endl;}
             else
                 {cout<<"YES"<<endl;}
        }
        
    }
    return 0;
}