q = int(input())
for x in range(q):
    n = int(input())
    a = True
    for d in range(n):
        arr = [int(i) for i in input().split(" ")]
        if arr[0]!=0 and arr[1]!=0:
            a=False 
            break
    if a==True:
        print("YES")
    else:
        print("NO")