Added type hint for Debug::getRefCount() which only support object. (#4429)

* Added type hint for `Debug::getRefCount()` which only support object.

* Update CHANGELOG-2.2.md

Author: limingxinleo

src/Debug.php

@@ -13,7 +13,10 @@
 
 class Debug
 {
-    public static function getRefCount($object): string
+    /**
+     * Get object's ref count.
+     */
+    public static function getRefCount(object $object): string
     {
         ob_start();
         debug_zval_dump($object);

tests/DebugTest.php

@@ -0,0 +1,36 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * This file is part of Hyperf.
+ *
+ * @link     https://www.hyperf.io
+ * @document https://hyperf.wiki
+ * @contact  [email protected]
+ * @license  https://github.com/hyperf/hyperf/blob/master/LICENSE
+ */
+namespace HyperfTest\Testing;
+
+use Hyperf\Testing\Debug;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * @internal
+ * @coversNothing
+ */
+class DebugTest extends TestCase
+{
+    public function testGetRefCount()
+    {
+        $this->assertSame('1', Debug::getRefCount(new \stdClass()));
+        $obj = new \stdClass();
+        $this->assertSame('2', Debug::getRefCount($obj));
+        $obj2 = new \stdClass();
+        $obj2->obj = $obj;
+        $this->assertSame('2', Debug::getRefCount($obj2));
+        $this->assertSame('3', Debug::getRefCount($obj));
+        $fun = static function () {};
+        $this->assertSame('2', Debug::getRefCount($fun));
+        $this->assertSame('1', Debug::getRefCount(function () {}));
+    }
+}