Fix: Correct PHPUnit test assertion and install PHPCS composer installer

composer.json

@@ -14,7 +14,7 @@
         "php": ">=7.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "^6.5",
+        "phpunit/phpunit": "^9.5",
         "10up/wp_mock": "0.3.0",
         "dealerdirect/phpcodesniffer-composer-installer": "^1.0",
         "wp-coding-standards/wpcs": "^3.0",

tests/test-admin.php

@@ -57,7 +57,7 @@ class AdminTest extends \WP_Mock\Tools\TestCase {
     public function test_constructor() {
         // Verify that the constructor initializes hooks
         $this->assertInstanceOf(Admin::class, $this->admin);
-        WP_Mock::assertActionAdded('admin_enqueue_scripts', [$this->admin, 'enqueue_admin_assets']);
+        WP_Mock::expectActionAdded('admin_enqueue_scripts', [$this->admin, 'enqueue_admin_assets']);
 
     }