from collections import defaultdict

queries = int(input())
for _ in range(queries):
    points = int(input())
    x_values = defaultdict(lambda: 0)
    y_values = defaultdict(lambda: 0)
    
    for x in range(points):
        x, y = [int(number) for number in input().split()]
        x_values[x] += 1
        y_values[y] += 1
    if len(x_values) > 2 or len(y_values) > 2:
        print('NO')
    else:
        print('YES')