diff --git a/tests/Unit/Milestone11Test.php b/tests/Unit/Milestone11Test.php
new file mode 100644
index 0000000..7f3e567
--- /dev/null
+++ b/tests/Unit/Milestone11Test.php
@@ -0,0 +1,162 @@
+<?php
+
+namespace Atlas\Tests\Unit;
+
+use Atlas\Router\Router;
+use Atlas\Config\Config;
+use Atlas\Exception\RouteNotFoundException;
+use PHPUnit\Framework\TestCase;
+use Psr\Http\Message\ServerRequestInterface;
+use Psr\Http\Message\UriInterface;
+
+class Milestone11Test extends TestCase
+{
+    private Router $router;
+
+    protected function setUp(): void
+    {
+        $config = new Config(['modules_path' => ['/path/to/modules']]);
+        $this->router = new Router($config);
+    }
+
+    public function testRedirectSupport(): void
+    {
+        $this->router->redirect('/old', '/new', 301);
+        
+        $uri = $this->createMock(UriInterface::class);
+        $uri->method('getPath')->willReturn('/old');
+        $uri->method('getHost')->willReturn('localhost');
+        $uri->method('getScheme')->willReturn('http');
+        $uri->method('getPort')->willReturn(80);
+        
+        $request = $this->createMock(ServerRequestInterface::class);
+        $request->method('getMethod')->willReturn('GET');
+        $request->method('getUri')->willReturn($uri);
+        
+        $route = $this->router->match($request);
+        
+        $this->assertNotNull($route, 'Route should not be null for /old');
+        $this->assertSame('REDIRECT', $route->getMethod());
+        $this->assertSame('/new', $route->getHandler());
+        $this->assertSame(301, $route->getAttributes()['status']);
+    }
+
+    public function testUrlGenerationStrictChecks(): void
+    {
+        $this->router->get('/users/{{user_id}}', 'handler', 'user_detail');
+        
+        $this->expectException(\InvalidArgumentException::class);
+        $this->expectExceptionMessage('Missing required parameter "user_id"');
+        
+        $this->router->url('user_detail', []);
+    }
+
+    public function testUrlGenerationWithDefaultsAndOptional(): void
+    {
+        $this->router->get('/blog/{{slug?}}', 'handler', 'blog_post')->default('slug', 'index');
+        
+        $this->assertSame('/blog/index', $this->router->url('blog_post', []));
+        $this->assertSame('/blog/hello', $this->router->url('blog_post', ['slug' => 'hello']));
+    }
+
+    public function testFallbackAtGroupLevel(): void
+    {
+        $this->router->fallback('global_fallback');
+        
+        $group = $this->router->group(['prefix' => '/api']);
+        $group->fallback('api_fallback');
+        
+        // Request for /something-else -> global_fallback
+        $uri1 = $this->createMock(UriInterface::class);
+        $uri1->method('getPath')->willReturn('/something-else');
+        $uri1->method('getHost')->willReturn('localhost');
+        $uri1->method('getScheme')->willReturn('http');
+        $uri1->method('getPort')->willReturn(80);
+        
+        $request1 = $this->createMock(ServerRequestInterface::class);
+        $request1->method('getMethod')->willReturn('GET');
+        $request1->method('getUri')->willReturn($uri1);
+        
+        $route1 = $this->router->match($request1);
+        $this->assertNotNull($route1);
+        $this->assertSame('global_fallback', $route1->getHandler());
+
+        // Request for /api/nonexistent -> api_fallback
+        $uri2 = $this->createMock(UriInterface::class);
+        $uri2->method('getPath')->willReturn('/api/nonexistent');
+        $uri2->method('getHost')->willReturn('localhost');
+        $uri2->method('getScheme')->willReturn('http');
+        $uri2->method('getPort')->willReturn(80);
+        
+        $request2 = $this->createMock(ServerRequestInterface::class);
+        $request2->method('getMethod')->willReturn('GET');
+        $request2->method('getUri')->willReturn($uri2);
+        
+        $route2 = $this->router->match($request2);
+        $this->assertNotNull($route2);
+        $this->assertSame('api_fallback', $route2->getHandler());
+    }
+
+    public function testSubdomainConstraints(): void
+    {
+        $this->router->get('/test', 'handler')->attr('subdomain', 'api');
+        
+        $uri = $this->createMock(UriInterface::class);
+        $uri->method('getPath')->willReturn('/test');
+        $uri->method('getHost')->willReturn('api.example.com');
+        $uri->method('getScheme')->willReturn('http');
+        $uri->method('getPort')->willReturn(80);
+        
+        $request = $this->createMock(ServerRequestInterface::class);
+        $request->method('getMethod')->willReturn('GET');
+        $request->method('getUri')->willReturn($uri);
+        
+        $route = $this->router->match($request);
+        $this->assertNotNull($route);
+        
+        $uri2 = $this->createMock(UriInterface::class);
+        $uri2->method('getPath')->willReturn('/test');
+        $uri2->method('getHost')->willReturn('www.example.com');
+        $uri2->method('getScheme')->willReturn('http');
+        $uri2->method('getPort')->willReturn(80);
+        
+        $request2 = $this->createMock(ServerRequestInterface::class);
+        $request2->method('getMethod')->willReturn('GET');
+        $request2->method('getUri')->willReturn($uri2);
+        
+        $route2 = $this->router->match($request2);
+        $this->assertNull($route2);
+    }
+
+    public function testI18nSupport(): void
+    {
+        $this->router->get('/users', 'UserHandler', 'users')->attr('i18n', [
+            'fr' => '/utilisateurs',
+            'es' => '/usuarios'
+        ]);
+
+        // Default
+        $uri = $this->createMock(UriInterface::class);
+        $uri->method('getPath')->willReturn('/users');
+        $uri->method('getHost')->willReturn('localhost');
+        $uri->method('getScheme')->willReturn('http');
+        $uri->method('getPort')->willReturn(80);
+        $request = $this->createMock(ServerRequestInterface::class);
+        $request->method('getMethod')->willReturn('GET');
+        $request->method('getUri')->willReturn($uri);
+        $this->assertNotNull($this->router->match($request));
+
+        // French
+        $uriFr = $this->createMock(UriInterface::class);
+        $uriFr->method('getPath')->willReturn('/utilisateurs');
+        $uriFr->method('getHost')->willReturn('localhost');
+        $uriFr->method('getScheme')->willReturn('http');
+        $uriFr->method('getPort')->willReturn(80);
+        $requestFr = $this->createMock(ServerRequestInterface::class);
+        $requestFr->method('getMethod')->willReturn('GET');
+        $requestFr->method('getUri')->willReturn($uriFr);
+        $routeFr = $this->router->match($requestFr);
+        $this->assertNotNull($routeFr);
+        $this->assertSame('users', $routeFr->getName());
+    }
+}