for Q in range(int(input())):
    n=int(input())
    x=[]
    y=[]
    for i in range(n):
        a,b=map(int,input().split())
        x.append(a)
        y.append(b)
    x=list(set(x))
    y=list(set(y))
    if(len(x)>2 or len(y)>2):
        print("NO")
    else:
        print("YES")