Add API test to verify QR codes return a 404 for disabled short URLs

module/Core/test-api/Action/QrCodeTest.php

@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ShlinkioApiTest\Shlink\Core\Action;
+
+use PHPUnit\Framework\Attributes\Test;
+use Shlinkio\Shlink\TestUtils\ApiTest\ApiTestCase;
+
+class QrCodeTest extends ApiTestCase
+{
+    #[Test]
+    public function returnsNotFoundWhenShortUrlIsNotEnabled(): void
+    {
+        // The QR code successfully resolves at first
+        $response = $this->callShortUrl('custom/qr-code');
+        self::assertEquals(200, $response->getStatusCode());
+
+        // This short URL allow max 2 visits
+        $this->callShortUrl('custom');
+        $this->callShortUrl('custom');
+
+        // After 2 visits, the QR code should return a 404
+        $response = $this->callShortUrl('custom/qr-code');
+        self::assertEquals(404, $response->getStatusCode());
+    }
+}