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


int main() 
{
    int q,n,x,y,i,j;
    bool flag;
    cin>>q;
    for(i=0;i<q;i++)
        {
        cin>>n;
        flag=true;
        for(j=0;j<n;j++)
            {
            cin>>x>>y;
            if(x>0&&y>0)
                {
                flag=false;
                cout<<"NO"<<"\n";
                break;
            }
        }
        if(flag==true)
            cout<<"YES"<<"\n";
    }
}