q = int(input())
x, y = set(), set()

for i in range(q):
    n = int(input())
    for j in range(n):
        points = input().split()
        x.add(points[0])
        y.add(points[1])

    if len(x) == 2 and len(y) == 2:
        print("YES")
    else:
        print("NO")
    x.clear()
    y.clear()