n = int(input())
for i in range(n):
    q = int(input())
    xs, ys = [], []
    for j in range(q):
        x, y = [int(x) for x in input().split()]
        xs += [x]
        ys += [y]
    if len(set(xs))>2 or len(set(ys))>2:
        print('NO')
    else:
        print('YES')