using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Hack1
{
	struct Point
	{
		public int x, y;

		public static Point Read()
		{
			var ss = Console.ReadLine().Split( ' ' ).Select( s => int.Parse( s ) ).ToArray();
			return new Point { x = ss[ 0 ], y = ss[ 1 ] };
		}
	}

	class Program
	{
		const int Z = int.MaxValue;
		static void Main( string[] args )
		{
			var N = int.Parse( Console.ReadLine() );
			for (int n = 0; n < N; ++n)
			{
				var Q = int.Parse( Console.ReadLine() );
				var lps = new List<Point>();
				for (int q = 0; q < Q; ++q)
					lps.Add( Point.Read() );

				var x1 = lps.Min( p => p.x );
				var x2 = lps.Max( p => p.x );
				var y1 = lps.Min( p => p.y );
				var y2 = lps.Max( p => p.y );

				bool ok = true;
				foreach (var p in lps)
				{
					if (p.x >= x1 && p.x <= x2 && (p.y == y1 || p.y == y2))
						continue;
					if (p.y >= y1 && p.y <= y2 && (p.x == x1 || p.x == x2))
						continue;
					ok = false;
					break;
				}
				Console.WriteLine( ok ? "YES" : "NO" );
			}
		}
	}
}