<?php
$_fp = fopen("php://stdin", "r");
/* Enter your code here. Read input from STDIN. Print output to STDOUT */
fscanf($_fp,"%d",$q);
while($q) {
    fscanf($_fp,"%d",$nbak);
    //echo $n,"\n\n";
    $cs = [];
      $n = $nbak;
    while ($n) {
        $s = fgets($_fp);
        $s = explode(' ',trim($s));
        $cs[] = array_map('intval', $s);
        $n--;
    }
    if($nbak < 4) {
        echo "YES\n";
        $q--;
        continue;
    }
   // var_dump($cs);
    $xmin = $xmax = $cs[0][0];
    $ymin = $ymax = $cs[0][1];
    foreach($cs as $c) {
        if($c[0] > $xmax)
            $xmax = $c[0];
        elseif($c[0] < $xmin)
            $xmin = $c[0];
        if($c[1] > $ymax)
            $ymax = $c[1];
        elseif($c[1] < $ymin)
            $ymin = $c[1];
    }
    //echo "$xmin, $xmax, $ymin, $ymax";
    $rec = true;
    foreach ($cs as $c) {
       if($c[0] >= $xmin && $c[0] <= $xmax && ($c[1] == $ymin || $c[1] == $ymax))
            $rec  = true;
        elseif(($c[0] == $xmin || $c[0] == $xmax) && $c[1] >= $ymin && $c[1] <= $ymax)
        	$rec  = true;
        else {
            $rec = false;
            break;
        }
    }
    if($rec)
        echo "YES\n";
    else
        echo "NO\n";
    $q--;
}

?>