import scala.io.StdIn;
object Solution {
  def main(args : Array[String]) = {
    val t = StdIn.readInt()
    var result : List[String] = Nil
    for(k <- 0 until t) {
      val n = StdIn.readInt()
      var flag : Int = 0
      for(i <- 0 until n) {
        val Array(a,b) = StdIn.readLine().split(" ").map(_.toInt)
        if(a > 0 &&  b > 0) flag = 1
      }
      if(flag == 0) result = result :+ "YES"
      else result = result :+ "NO"

    }
    result.foreach(println(_))



  }

}