Add a test to reproduce the issue

Author: mpdude

tests/Tests/ORM/Functional/Ticket/GH12183Test.php

@@ -0,0 +1,46 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Doctrine\Tests\ORM\Functional\Ticket;
+
+use Doctrine\ORM\Tools\Pagination\Paginator;
+use Doctrine\Tests\Models\CMS\CmsArticle;
+use Doctrine\Tests\OrmFunctionalTestCase;
+
+final class GH12183Test extends OrmFunctionalTestCase
+{
+    protected function setUp(): void
+    {
+        $this->useModelSet('cms');
+
+        parent::setUp();
+
+        $article = new CmsArticle();
+
+        $article->topic = 'Loomings';
+        $article->text = 'Call me Ishmael.';
+
+        $this->_em->persist($article);
+        $this->_em->flush();
+        $this->_em->clear();
+    }
+
+    public function testPaginatorCountWithOutputWalkerAfterQueryHasBeenExecuted(): void
+    {
+        $query = $this->_em->createQuery('SELECT a FROM Doctrine\Tests\Models\CMS\CmsArticle a');
+
+        // Paginator::count is right when the query has not yet been executed
+        $paginator = new Paginator($query);
+        $paginator->setUseOutputWalkers(false);
+        self::assertSame(1, $paginator->count());
+
+        // Execute the query
+        $result = $query->getResult();
+        self::assertCount(1, $result);
+
+        $paginator = new Paginator($query);
+        $paginator->setUseOutputWalkers(false);
+        self::assertSame(1, $paginator->count());
+    }
+}