#!/usr/bin/env python2

num_queries = int(raw_input())

for i in range(num_queries):
    n_points = int(raw_input())
    points = []
    for j in range(n_points):
        points.append(tuple(int(coord) for coord in raw_input().split()))

    if n_points <= 2:
        if points[0][0] != points[1][0] and points[0][1] != points[1][1]:
            # nondegenerate
            print 'YES'
        else:
            # degenerate
            print 'NO'
        continue

    xs = set(point[0] for point in points)
    ys = set(point[1] for point in points)

    if len(xs) != 2 or len(ys) != 2:
        print 'NO'
        continue

    print 'YES'