Create a class to help test the Callable rule

With that, the tests will be more straightforward, and we won't need to
use the test class in the data providers. That will help us later
because, on PHPUnit 10, all data providers need to be static.

Signed-off-by: Henrique Moody <henriquemoody@gmail.com>

tests/library/Stubs/WithMethods.php

@@ -0,0 +1,21 @@
+<?php
+
+/*
+ * Copyright (c) Alexandre Gomes Gaigalas <alganet@gmail.com>
+ * SPDX-License-Identifier: MIT
+ */
+
+declare(strict_types=1);
+
+namespace Respect\Validation\Test\Stubs;
+
+final class WithMethods
+{
+    public function publicMethod(): void
+    {
+    }
+
+    public static function publicStaticMethod(): void
+    {
+    }
+}

tests/unit/Rules/CallableTypeTest.php

@@ -10,6 +10,7 @@ declare(strict_types=1);
 namespace Respect\Validation\Rules;
 
 use Respect\Validation\Test\RuleTestCase;
+use Respect\Validation\Test\Stubs\WithMethods;
 use stdClass;
 
 use const INF;
@@ -32,14 +33,10 @@ final class CallableTypeTest extends RuleTestCase
         $rule = new CallableType();
 
         return [
-            [
-                $rule,
-                static function (): void {
-                },
-            ],
+            [$rule, static fn() => null],
             [$rule, 'trim'],
-            [$rule, self::class . '::staticMethod'],
-            [$rule, [$this, __FUNCTION__]],
+            [$rule, WithMethods::class . '::publicStaticMethod'],
+            [$rule, [new WithMethods(), 'publicMethod']],
         ];
     }
 
@@ -58,9 +55,4 @@ final class CallableTypeTest extends RuleTestCase
             [$rule, null],
         ];
     }
-
-    public static function staticMethod(): void
-    {
-        // This is a static method example
-    }
 }