add unit tests for user and auth

backend/tests/Unit/User/UserTest.php

@@ -0,0 +1,20 @@
+<?php
+
+namespace Tests\Unit\User;
+
+use App\Shared\ValueObject\EmailAddress;
+use App\User\User;
+use PHPUnit\Framework\TestCase;
+
+class UserTest extends TestCase
+{
+    public function testCreatesUserWithPasswordHash(): void
+    {
+        $email = new EmailAddress('test@example.com');
+        $user = new User(1, $email, 'hashed-password');
+
+        $this->assertSame(1, $user->getId());
+        $this->assertSame($email, $user->getEmail());
+        $this->assertSame('hashed-password', $user->getPasswordHash());
+    }
+}