#include <bits/stdc++.h>
#define f first
#define s second
#define mp make_pair
#define pb push_back
#define all(c) (c).begin(), (c).end()
#define sqr(x) (x)*(x)
#define fname ""

using namespace std;

typedef long long ll;
const double eps = 1e-9;
const double PI = acos(-1.0);
const int inf = int (1e9+7);
const ll INF = (ll) 8e18+7;
const int mod = int (1e9+7);     
const int N = int (2e5+7);    

int q, n;
pair <int, int> a[N];

bool check() {
	sort(a, a + n);
	n = unique(a, a + n) - a;
	int x1 = inf, x2 = -inf;
	for(int i = 0; i < n; i ++)
		x1 = min(x1, a[i].s), x2 = max(x2, a[i].s);
	for(int i = 0; i < n; i ++) {
		int j = i;
		while(j < n && a[j].f == a[i].f)
			j ++;
		if(i > 0 && j < n) {
			for(int k = i; k < j; k ++)
				if(a[k].s != x1 && a[k].s != x2)
					return 0;
		}
		if(j > i)
			i = j - 1;
	}
	return 1;
}

int main () { 
   	//freopen(fname".in", "r", stdin);
   	//freopen(fname".out", "w", stdout);
   	ios_base::sync_with_stdio(0);
	cin.tie(0);
	
	cin >> q;
	while(q --) {
		bool ok = 0;
		cin >> n;
		for(int i = 0; i < n; i ++)
			cin >> a[i].f >> a[i].s;
		if(check()) 
			ok = 1;
		if(ok)
			cout << "YES\n";
		else
			cout << "NO\n";
	}
	return 0;
}