Add test

[MAILPOET-1571]

lib/Models/NewsletterLink.php

@@ -5,4 +5,19 @@ if(!defined('ABSPATH')) exit;
 
 class NewsletterLink extends Model {
   public static $_table = MP_NEWSLETTER_LINKS_TABLE;
+
+  static function findTopLinkForNewsletter(Newsletter $newsletter) {
+    return self::selectExpr('links.*')
+      ->selectExpr('count(*)', 'clicksCount')
+      ->tableAlias('links')
+      ->innerJoin(StatisticsClicks::$_table,
+        array('clicks.link_id', '=', 'links.id'),
+        'clicks')
+      ->where('newsletter_id', $newsletter->id())
+      ->groupBy('links.id')
+      ->orderByDesc('clicksCount')
+      ->limit(1)
+      ->findOne();
+  }
+
 }

lib/Models/ScheduledTask.php

@@ -32,6 +32,15 @@ class ScheduledTask extends Model {
     );
   }
 
+  /** @return StatsNotification */
+  function statsNotification() {
+    return $this->hasOne(
+      StatsNotification::class,
+      'task_id',
+      'id'
+    );
+  }
+
   function pause() {
     $this->set('status', self::STATUS_PAUSED);
     $this->save();

lib/Models/StatsNotification.php

@@ -5,6 +5,15 @@ namespace MailPoet\Models;
 class StatsNotification extends Model {
   public static $_table = MP_STATS_NOTIFICATIONS_TABLE;
 
+  /** @return Newsletter */
+  public function newsletter() {
+    return $this->hasOne(
+      Newsletter::class,
+      'id',
+      'newsletter_id'
+    );
+  }
+
   /** @return StatsNotification */
   static function createOrUpdate($data = array()) {
     $model = null;