diff --git a/src/Service/Ui.php b/src/Service/Ui.php
index c542f12..e9b2d78 100644
--- a/src/Service/Ui.php
+++ b/src/Service/Ui.php
@@ -172,6 +172,11 @@ public static function serverRequest(): ServerRequestInterface
     }
 
     public static function getQueryParamValue(string $param): ?string
+    {
+        return static::service()->returnQueryParamValue($param);
+    }
+
+    protected function returnQueryParamValue(string $param): ?string
     {
         $params = [];
         parse_str(static::service()->serverRequest()->getUri()->getQuery(), $params);
diff --git a/tests/Callback/CallbackTest.php b/tests/Callback/CallbackTest.php
index 48d57a7..a59f1f9 100644
--- a/tests/Callback/CallbackTest.php
+++ b/tests/Callback/CallbackTest.php
@@ -16,13 +16,14 @@
 use Fohn\Ui\HtmlTemplate;
 use Fohn\Ui\Js\Js;
 use Fohn\Ui\Service\Ui;
+use Fohn\Ui\Tests\UiTestService;
 use Fohn\Ui\View;
 
 class CallbackTest extends \PHPUnit\Framework\TestCase
 {
     protected function setUp(): void
     {
-        $ui = Ui::service();
+        $ui = UiTestService::service();
         $ui->setApp(new MockApp(['registerShutdown' => false]));
     }
 
diff --git a/tests/Callback/init-test-callback-ui.php b/tests/Callback/init-test-callback-ui.php
index 50c4e72..a0fb1ef 100644
--- a/tests/Callback/init-test-callback-ui.php
+++ b/tests/Callback/init-test-callback-ui.php
@@ -27,7 +27,7 @@
     Data::setDb($config['db']);
 
     $ui->environment = $config['env'];
-    $ui->displayformat = $config['format'];
+    $ui->setDisplayFormat($config['format']);
     $ui->timezone($config['timezone']);
 
     $ui->setApp($app);
diff --git a/tests/UiTestService.php b/tests/UiTestService.php
new file mode 100644
index 0000000..f75703a
--- /dev/null
+++ b/tests/UiTestService.php
@@ -0,0 +1,18 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * Ui Service setup for testing purpose.
+ */
+
+namespace Fohn\Ui\Tests;
+
+use Fohn\Ui\Service\Ui;
+
+class UiTestService extends Ui
+{
+    protected function returnQueryParamValue(string $param): ?string
+    {
+        return $_GET[$param] ?? null;
+    }
+}