# Enter your code here. Read input from STDIN. Print output to STDOUT

q = int(raw_input())

for i in range(q):
    n = int(raw_input())
    ans = 'YES'
    for j in range(n):
        a, b = map(int, raw_input().strip().split())
        if a != 0 and b != 0:
            ans = 'NO'
            continue
    print ans