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

q = gets.to_i
m = []
q.times do |i|
  m[i] = []
  n = gets.to_i
  n.times do |j|
    m[i][j] = gets.split(" ").map(&:to_i)
  end
end

m.each do |set|
  xs = []
  ys = []
  set.each do |point|
    x = point[0]
    y = point[1]
    if !xs.include? x
      xs << x
    end
    if !ys.include? y
      ys << y
    end
  end
  xs.length != 2 || ys.length != 2 ? puts("NO") : puts("YES")
end