Added Decorator and observer Patterns along with UnitTest for Observer

tests/ObserverTest.php

@@ -0,0 +1,43 @@
+<?php
+
+/**
+ * @package: patterns
+ * @author: Yevhen Odynets
+ * @date: 2025-07-06
+ * @time: 13:31
+ */
+
+declare(strict_types = 1);
+
+namespace App\Tests;
+
+use Pattern\Behavioral\Observer\User;
+use Pattern\Behavioral\Observer\UserObserver;
+use PHPUnit\Framework\TestCase;
+
+class ObserverTest extends TestCase
+{
+    public function testObserver(): void
+    {
+        $user = new User();
+
+        /** These names will be skipped and not be added to the log of names */
+        $user->setName("Just a name");
+        $user->setName("Some new name");
+
+        $userObserver = new UserObserver();
+        $user->attach($userObserver);
+
+        /** After creating a new instance of UserObserver::class
+         * and attached it to User::class instance,
+         * these names will be added to the log of names */
+        $user->setName("Another new name");
+        $user->setName("Once again new name");
+        $user->setName("Possibly other new name");
+
+        $this->assertEquals(
+            ["Another new name", "Once again new name", "Possibly other new name"],
+            $userObserver->getNamesLog()
+        );
+    }
+}