Add extensive controller and model tests

tests/Unit/UploadControllerUnitTest.php

@@ -0,0 +1,14 @@
+<?php
+
+use App\Http\Controllers\UploadController;
+use Illuminate\Http\Request;
+
+it('returns unauthorized when storeAvatar has no user', function (): void {
+    $controller = new UploadController();
+    $request = Request::create('/api/user/avatar', 'POST');
+    $request->setUserResolver(fn () => null);
+
+    $response = $controller->storeAvatar($request);
+
+    expect($response->getStatusCode())->toBe(401);
+});