diff --git a/src/Config/Config.php b/src/Config/Config.php
index 5bb6375..b49a63c 100644
--- a/src/Config/Config.php
+++ b/src/Config/Config.php
@@ -22,7 +22,7 @@ class Config implements ArrayAccess, IteratorAggregate
      * @param array $options Configuration array containing routing settings
      */
     public function __construct(
-        private readonly array $options
+        private array $options
     ) {}
 
     /**
diff --git a/src/Router/RouteGroup.php b/src/Router/RouteGroup.php
index a4ec579..0176886 100644
--- a/src/Router/RouteGroup.php
+++ b/src/Router/RouteGroup.php
@@ -9,6 +9,8 @@ namespace Atlas\Router;
  */
 class RouteGroup
 {
+    use PathHelper;
+
     /**
      * Constructs a new RouteGroup instance.
      *
@@ -34,74 +36,131 @@ class RouteGroup
         return $self;
     }
 
-    /**
-     * Registers a GET route with group prefix.
-     *
-     * @param string $path URI path
-     * @param string|callable $handler Route handler
-     * @param string|null $name Optional route name
-     * @return self Fluent interface
-     */
-    public function get(string $path, string|callable $handler, string|null $name = null): self
+    public function get(string $path, mixed $handler, string|null $name = null): RouteDefinition
     {
         $fullPath = $this->buildFullPath($path);
-        return $this->router ? $this->router->get($fullPath, $handler, $name) : $this;
+        $middleware = $this->options['middleware'] ?? [];
+        $validation = $this->options['validation'] ?? [];
+        $defaults = $this->options['defaults'] ?? [];
+
+        if ($this->router) {
+            return $this->router->registerCustomRoute('GET', $fullPath, $handler, $name, $middleware, $validation, $defaults);
+        }
+        
+        return new RouteDefinition('GET', $fullPath, $fullPath, $handler, $name, $middleware, $validation, $defaults);
     }
 
-    /**
-     * Registers a POST route with group prefix.
-     *
-     * @param string $path URI path
-     * @param string|callable $handler Route handler
-     * @param string|null $name Optional route name
-     * @return self Fluent interface
-     */
-    public function post(string $path, string|callable $handler, string|null $name = null): self
+    public function post(string $path, mixed $handler, string|null $name = null): RouteDefinition
     {
         $fullPath = $this->buildFullPath($path);
-        return $this->router ? $this->router->post($fullPath, $handler, $name) : $this;
+        $middleware = $this->options['middleware'] ?? [];
+        $validation = $this->options['validation'] ?? [];
+        $defaults = $this->options['defaults'] ?? [];
+
+        if ($this->router) {
+            return $this->router->registerCustomRoute('POST', $fullPath, $handler, $name, $middleware, $validation, $defaults);
+        }
+        
+        return new RouteDefinition('POST', $fullPath, $fullPath, $handler, $name, $middleware, $validation, $defaults);
     }
 
-    /**
-     * Registers a PUT route with group prefix.
-     *
-     * @param string $path URI path
-     * @param string|callable $handler Route handler
-     * @param string|null $name Optional route name
-     * @return self Fluent interface
-     */
-    public function put(string $path, string|callable $handler, string|null $name = null): self
+    public function put(string $path, mixed $handler, string|null $name = null): RouteDefinition
     {
         $fullPath = $this->buildFullPath($path);
-        return $this->router ? $this->router->put($fullPath, $handler, $name) : $this;
+        $middleware = $this->options['middleware'] ?? [];
+        $validation = $this->options['validation'] ?? [];
+        $defaults = $this->options['defaults'] ?? [];
+
+        if ($this->router) {
+            return $this->router->registerCustomRoute('PUT', $fullPath, $handler, $name, $middleware, $validation, $defaults);
+        }
+        
+        return new RouteDefinition('PUT', $fullPath, $fullPath, $handler, $name, $middleware, $validation, $defaults);
     }
 
-    /**
-     * Registers a PATCH route with group prefix.
-     *
-     * @param string $path URI path
-     * @param string|callable $handler Route handler
-     * @param string|null $name Optional route name
-     * @return self Fluent interface
-     */
-    public function patch(string $path, string|callable $handler, string|null $name = null): self
+    public function patch(string $path, mixed $handler, string|null $name = null): RouteDefinition
     {
         $fullPath = $this->buildFullPath($path);
-        return $this->router ? $this->router->patch($fullPath, $handler, $name) : $this;
+        $middleware = $this->options['middleware'] ?? [];
+        $validation = $this->options['validation'] ?? [];
+        $defaults = $this->options['defaults'] ?? [];
+
+        if ($this->router) {
+            return $this->router->registerCustomRoute('PATCH', $fullPath, $handler, $name, $middleware, $validation, $defaults);
+        }
+        
+        return new RouteDefinition('PATCH', $fullPath, $fullPath, $handler, $name, $middleware, $validation, $defaults);
     }
 
-    /**
-     * Registers a DELETE route with group prefix.
-     *
-     * @param string $path URI path
-     * @param string|callable $handler Route handler
-     * @param string|null $name Optional route name
-     * @return self Fluent interface
-     */
-    public function delete(string $path, string|callable $handler, string|null $name = null): self
+    public function delete(string $path, mixed $handler, string|null $name = null): RouteDefinition
     {
         $fullPath = $this->buildFullPath($path);
-        return $this->router ? $this->router->delete($fullPath, $handler, $name) : $this;
+        $middleware = $this->options['middleware'] ?? [];
+        $validation = $this->options['validation'] ?? [];
+        $defaults = $this->options['defaults'] ?? [];
+
+        if ($this->router) {
+            return $this->router->registerCustomRoute('DELETE', $fullPath, $handler, $name, $middleware, $validation, $defaults);
+        }
+        
+        return new RouteDefinition('DELETE', $fullPath, $fullPath, $handler, $name, $middleware, $validation, $defaults);
+    }
+
+    public function redirect(string $path, string $destination, int $status = 302): RouteDefinition
+    {
+        $fullPath = $this->buildFullPath($path);
+        $middleware = $this->options['middleware'] ?? [];
+        $validation = $this->options['validation'] ?? [];
+        $defaults = $this->options['defaults'] ?? [];
+
+        if ($this->router) {
+            return $this->router->registerCustomRoute('REDIRECT', $fullPath, $destination, null, $middleware, $validation, $defaults)->attr('status', $status);
+        }
+
+        return (new RouteDefinition('REDIRECT', $fullPath, $fullPath, $destination, null, $middleware, $validation, $defaults))->attr('status', $status);
+    }
+
+    public function fallback(mixed $handler): self
+    {
+        $this->options['fallback'] = $handler;
+        
+        $prefix = $this->options['prefix'] ?? '/';
+        $middleware = $this->options['middleware'] ?? [];
+        
+        if ($this->router) {
+            $this->router->registerCustomRoute('FALLBACK', $this->joinPaths($prefix, '/_fallback'), $handler, null, $middleware)
+                 ->attr('_fallback', $handler)
+                 ->attr('_fallback_prefix', $this->normalizePath($prefix));
+        }
+
+        return $this;
+    }
+
+    public function registerCustomRoute(string $method, string $path, mixed $handler, string|null $name = null, array $middleware = [], array $validation = [], array $defaults = []): RouteDefinition
+    {
+        $fullPath = $this->buildFullPath($path);
+        $mergedMiddleware = array_merge($this->options['middleware'] ?? [], $middleware);
+        
+        $route = null;
+        if ($this->router) {
+            $route = $this->router->registerCustomRoute($method, $fullPath, $handler, $name, $mergedMiddleware);
+        } else {
+            $route = new RouteDefinition($method, $fullPath, $fullPath, $handler, $name, $mergedMiddleware);
+        }
+
+        // Apply group-level validation and defaults
+        $route->valid($this->options['validation'] ?? []);
+        foreach ($this->options['defaults'] ?? [] as $p => $v) {
+            $route->default($p, $v);
+        }
+
+        // Apply route-level validation and defaults
+        $route->valid($validation);
+        foreach ($defaults as $p => $v) {
+            $route->default($p, $v);
+        }
+
+        return $route;
     }
 
     /**
@@ -112,13 +171,72 @@ class RouteGroup
      */
     private function buildFullPath(string $path): string
     {
-        $prefix = $this->options['prefix'] ?? '';
+        return $this->joinPaths($this->options['prefix'] ?? '', $path);
+    }
 
-        if (empty($prefix)) {
-            return $path;
+    public function group(array $options): RouteGroup
+    {
+        $prefix = $this->options['prefix'] ?? '';
+        $newPrefix = $this->joinPaths($prefix, $options['prefix'] ?? '');
+        
+        $middleware = $this->options['middleware'] ?? [];
+        $newMiddleware = array_merge($middleware, $options['middleware'] ?? []);
+
+        $validation = $this->options['validation'] ?? [];
+        $newValidation = array_merge($validation, $options['validation'] ?? []);
+
+        $defaults = $this->options['defaults'] ?? [];
+        $newDefaults = array_merge($defaults, $options['defaults'] ?? []);
+        
+        $mergedOptions = array_merge($this->options, $options);
+        $mergedOptions['prefix'] = $newPrefix;
+        $mergedOptions['middleware'] = $newMiddleware;
+        $mergedOptions['validation'] = $newValidation;
+        $mergedOptions['defaults'] = $newDefaults;
+
+        return new RouteGroup($mergedOptions, $this->router);
+    }
+
+    /**
+     * Sets validation rules for parameters at the group level.
+     *
+     * @param array|string $param Parameter name or array of rules
+     * @param array|string $rules Rules if first param is string
+     * @return self
+     */
+    public function valid(array|string $param, array|string $rules = []): self
+    {
+        if (!isset($this->options['validation'])) {
+            $this->options['validation'] = [];
         }
 
-        return rtrim($prefix, '/') . '/' . ltrim($path, '/');
+        if (is_array($param)) {
+            foreach ($param as $p => $r) {
+                $this->valid($p, $r);
+            }
+        } else {
+            $this->options['validation'][$param] = is_string($rules) ? [$rules] : $rules;
+        }
+
+        return $this;
+    }
+
+    /**
+     * Sets a default value for a parameter at the group level.
+     *
+     * @param string $param
+     * @param mixed $value
+     * @return self
+     */
+    public function default(string $param, mixed $value): self
+    {
+        if (!isset($this->options['defaults'])) {
+            $this->options['defaults'] = [];
+        }
+
+        $this->options['defaults'][$param] = $value;
+
+        return $this;
     }
 
     /**
@@ -139,8 +257,33 @@ class RouteGroup
      *
      * @return array Group options configuration
      */
+    public function module(string|array $identifier, string|null $prefix = null): self
+    {
+        if ($this->router) {
+            // We need to pass the group context to the module loading.
+            // But ModuleLoader uses the router directly.
+            // If we use $this->router->module(), it won't have the group prefix/middleware.
+            // We should probably allow ModuleLoader to take a "target" which can be a Router or RouteGroup.
+            
+            // For now, let's just use the router but we have a problem: inheritance.
+            // A better way is to make RouteGroup have a way to load modules.
+            
+            $moduleLoader = new ModuleLoader($this->router->getConfig(), $this);
+            $moduleLoader->load($identifier, $prefix);
+        }
+        return $this;
+    }
+
     public function getOptions(): array
     {
         return $this->options;
     }
+
+    /**
+     * @internal
+     */
+    public function getConfig(): Config
+    {
+        return $this->router->getConfig();
+    }
 }
\ No newline at end of file
diff --git a/tests/Integration/ModuleLoadingTest.php b/tests/Integration/ModuleLoadingTest.php
new file mode 100644
index 0000000..0b2e9e9
--- /dev/null
+++ b/tests/Integration/ModuleLoadingTest.php
@@ -0,0 +1,112 @@
+<?php
+
+namespace Atlas\Tests\Integration;
+
+use Atlas\Router\Router;
+use Atlas\Config\Config;
+use Atlas\Exception\MissingConfigurationException;
+use PHPUnit\Framework\TestCase;
+
+class ModuleLoadingTest extends TestCase
+{
+    private string $tempDir;
+
+    protected function setUp(): void
+    {
+        $this->tempDir = sys_get_temp_dir() . '/atlas_test_' . uniqid();
+        mkdir($this->tempDir);
+        mkdir($this->tempDir . '/User');
+    }
+
+    protected function tearDown(): void
+    {
+        $this->removeDirectory($this->tempDir);
+    }
+
+    private function removeDirectory(string $path): void
+    {
+        $files = array_diff(scandir($path), ['.', '..']);
+        foreach ($files as $file) {
+            (is_dir("$path/$file")) ? $this->removeDirectory("$path/$file") : unlink("$path/$file");
+        }
+        rmdir($path);
+    }
+
+    public function testModuleLoadsRoutesFromFilesystem(): void
+    {
+        $routesContent = '<?php return [["method" => "GET", "path" => "/profile", "handler" => "UserHandler", "name" => "user_profile"]];';
+        file_put_contents($this->tempDir . '/User/routes.php', $routesContent);
+
+        $config = new Config([
+            'modules_path' => [$this->tempDir],
+            'routes_file' => 'routes.php'
+        ]);
+
+        $router = new Router($config);
+        $router->module('User');
+
+        $routes = iterator_to_array($router->getRoutes());
+        $this->assertCount(1, $routes);
+        $this->assertSame('/profile', $routes[0]->getPath());
+        $this->assertSame('user_profile', $routes[0]->getName());
+    }
+
+    public function testModuleThrowsExceptionWhenModulesPathIsMissing(): void
+    {
+        $config = new Config([]);
+        $router = new Router($config);
+
+        $this->expectException(MissingConfigurationException::class);
+        $router->module('User');
+    }
+
+    public function testModuleSkipsWhenRoutesFileDoesNotExist(): void
+    {
+        $config = new Config([
+            'modules_path' => [$this->tempDir]
+        ]);
+
+        $router = new Router($config);
+        $router->module('NonExistent');
+
+        $this->assertCount(0, $router->getRoutes());
+    }
+
+    public function testModuleWithMultipleSearchPaths(): void
+    {
+        $secondPath = sys_get_temp_dir() . '/atlas_test_2_' . uniqid();
+        mkdir($secondPath);
+        mkdir($secondPath . '/Shared');
+        
+        $routesContent = '<?php return [["method" => "GET", "path" => "/shared", "handler" => "SharedHandler"]];';
+        file_put_contents($secondPath . '/Shared/routes.php', $routesContent);
+
+        $config = new Config([
+            'modules_path' => [$this->tempDir, $secondPath]
+        ]);
+
+        $router = new Router($config);
+        $router->module('Shared');
+
+        $routes = iterator_to_array($router->getRoutes());
+        $this->assertCount(1, $routes);
+        $this->assertSame('/shared', $routes[0]->getPath());
+
+        $this->removeDirectory($secondPath);
+    }
+
+    public function testModuleLoadsMultipleRoutes(): void
+    {
+        $routesContent = '<?php return [
+            ["method" => "GET", "path" => "/u1", "handler" => "h1"],
+            ["method" => "POST", "path" => "/u2", "handler" => "h2"]
+        ];';
+        file_put_contents($this->tempDir . '/User/routes.php', $routesContent);
+
+        $config = new Config(['modules_path' => $this->tempDir]);
+        $router = new Router($config);
+        $router->module('User');
+
+        $this->assertCount(2, $router->getRoutes());
+    }
+}
diff --git a/tests/Unit/ConfigTest.php b/tests/Unit/ConfigTest.php
new file mode 100644
index 0000000..588a5d5
--- /dev/null
+++ b/tests/Unit/ConfigTest.php
@@ -0,0 +1,103 @@
+<?php
+
+namespace Atlas\Tests\Unit;
+
+use Atlas\Config\Config;
+use PHPUnit\Framework\TestCase;
+
+class ConfigTest extends TestCase
+{
+    public function testGetReturnsValueOrPlaceholder(): void
+    {
+        $config = new Config(['key' => 'value']);
+        
+        $this->assertSame('value', $config->get('key'));
+        $this->assertSame('default', $config->get('non_existent', 'default'));
+        $this->assertNull($config->get('non_existent'));
+    }
+
+    public function testHasChecksExistence(): void
+    {
+        $config = new Config(['key' => 'value']);
+        
+        $this->assertTrue($config->has('key'));
+        $this->assertFalse($config->has('non_existent'));
+    }
+
+    public function testGetModulesPathNormalizesToArray(): void
+    {
+        $config1 = new Config(['modules_path' => '/single/path']);
+        $this->assertSame(['/single/path'], $config1->getModulesPath());
+
+        $config2 = new Config(['modules_path' => ['/path/1', '/path/2']]);
+        $this->assertSame(['/path/1', '/path/2'], $config2->getModulesPath());
+
+        $config3 = new Config([]);
+        $this->assertNull($config3->getModulesPath());
+    }
+
+    public function testGetModulesPathListAlwaysReturnsArray(): void
+    {
+        $config1 = new Config(['modules_path' => '/single/path']);
+        $this->assertSame(['/single/path'], $config1->getModulesPathList());
+
+        $config2 = new Config(['modules_path' => ['/path/1', '/path/2']]);
+        $this->assertSame(['/path/1', '/path/2'], $config2->getModulesPathList());
+
+        $config3 = new Config([]);
+        $this->assertSame([], $config3->getModulesPathList());
+    }
+
+    public function testGetRoutesFileWithDefault(): void
+    {
+        $config1 = new Config(['routes_file' => 'custom.php']);
+        $this->assertSame('custom.php', $config1->getRoutesFile());
+
+        $config2 = new Config([]);
+        $this->assertSame('routes.php', $config2->getRoutesFile());
+    }
+
+    public function testGetModulesGlob(): void
+    {
+        $config1 = new Config(['modules_glob' => 'src/*/routes.php']);
+        $this->assertSame('src/*/routes.php', $config1->getModulesGlob());
+
+        $config2 = new Config([]);
+        $this->assertNull($config2->getModulesGlob());
+    }
+
+    public function testToArray(): void
+    {
+        $options = ['a' => 1, 'b' => 2];
+        $config = new Config($options);
+        
+        $this->assertSame($options, $config->toArray());
+    }
+
+    public function testArrayAccess(): void
+    {
+        $config = new Config(['key' => 'value']);
+        
+        $this->assertTrue(isset($config['key']));
+        $this->assertSame('value', $config['key']);
+        
+        $config['new'] = 'val';
+        $this->assertSame('val', $config['new']);
+        
+        unset($config['key']);
+        $this->assertFalse(isset($config['key']));
+    }
+
+    public function testIteratorAggregate(): void
+    {
+        $options = ['a' => 1, 'b' => 2];
+        $config = new Config($options);
+        
+        $result = [];
+        foreach ($config as $key => $value) {
+            $result[$key] = $value;
+        }
+        
+        $this->assertSame($options, $result);
+    }
+}
diff --git a/tests/Unit/RouteGroupTest.php b/tests/Unit/RouteGroupTest.php
new file mode 100644
index 0000000..21137c5
--- /dev/null
+++ b/tests/Unit/RouteGroupTest.php
@@ -0,0 +1,99 @@
+<?php
+
+namespace Atlas\Tests\Unit;
+
+use Atlas\Router\Router;
+use Atlas\Router\RouteGroup;
+use Atlas\Config\Config;
+use PHPUnit\Framework\TestCase;
+
+class RouteGroupTest extends TestCase
+{
+    private Router $router;
+
+    protected function setUp(): void
+    {
+        $config = new Config(['modules_path' => ['/path/to/modules']]);
+        $this->router = new Router($config);
+    }
+
+    public function testGroupAppliesPrefixToRoutes(): void
+    {
+        $group = $this->router->group(['prefix' => '/api']);
+        
+        $group->get('/users', 'Handler');
+        
+        $routes = iterator_to_array($this->router->getRoutes());
+        $this->assertCount(1, $routes);
+        $this->assertSame('/api/users', $routes[0]->getPath());
+    }
+
+    public function testGroupAppliesPrefixWithLeadingSlashToRoutes(): void
+    {
+        $group = $this->router->group(['prefix' => 'api']);
+        
+        $group->get('users', 'Handler');
+        
+        $routes = iterator_to_array($this->router->getRoutes());
+        $this->assertCount(1, $routes);
+        $this->assertSame('/api/users', $routes[0]->getPath());
+    }
+
+    public function testGroupWithTrailingSlashInPrefix(): void
+    {
+        $group = $this->router->group(['prefix' => '/api/']);
+        
+        $group->get('/users', 'Handler');
+        
+        $routes = iterator_to_array($this->router->getRoutes());
+        $this->assertCount(1, $routes);
+        $this->assertSame('/api/users', $routes[0]->getPath());
+    }
+
+    public function testAllHttpMethodsInGroup(): void
+    {
+        $group = $this->router->group(['prefix' => '/api']);
+        
+        $group->get('/test', 'handler');
+        $group->post('/test', 'handler');
+        $group->put('/test', 'handler');
+        $group->patch('/test', 'handler');
+        $group->delete('/test', 'handler');
+        
+        $routes = iterator_to_array($this->router->getRoutes());
+        $this->assertCount(5, $routes);
+        
+        foreach ($routes as $route) {
+            $this->assertSame('/api/test', $route->getPath());
+        }
+    }
+
+    public function testGroupReturnsSameInstanceForChaining(): void
+    {
+        $group = $this->router->group(['prefix' => '/api']);
+        
+        $group->get('/users', 'Handler');
+        $group->post('/users', 'Handler');
+        
+        $routes = iterator_to_array($this->router->getRoutes());
+        $this->assertCount(2, $routes);
+    }
+
+    public function testGroupCanBeCreatedWithoutRouterAndStillWorks(): void
+    {
+        // This tests the case where RouteGroup might be used partially or in isolation
+        // although buildFullPath is the main logic.
+        $group = new RouteGroup(['prefix' => '/api']);
+        
+        // Use reflection or just check options if public (it is protected/private)
+        $this->assertSame(['prefix' => '/api'], $group->getOptions());
+    }
+
+    public function testSetOptionOnGroup(): void
+    {
+        $group = new RouteGroup();
+        $group->setOption('prefix', '/test');
+        
+        $this->assertSame(['prefix' => '/test'], $group->getOptions());
+    }
+}
diff --git a/tests/Unit/RouterFallbackTest.php b/tests/Unit/RouterFallbackTest.php
new file mode 100644
index 0000000..8ff2f64
--- /dev/null
+++ b/tests/Unit/RouterFallbackTest.php
@@ -0,0 +1,36 @@
+<?php
+
+namespace Atlas\Tests\Unit;
+
+use Atlas\Router\Router;
+use Atlas\Config\Config;
+use PHPUnit\Framework\TestCase;
+
+class RouterFallbackTest extends TestCase
+{
+    public function testFallbackHandlerCanBeSet(): void
+    {
+        $config = new Config(['modules_path' => ['/path/to/modules']]);
+        $router = new Router($config);
+        
+        $handler = function() { return '404'; };
+        $router->fallback($handler);
+        
+        // Use reflection to check if fallbackHandler is set correctly since there is no getter
+        $reflection = new \ReflectionClass($router);
+        $property = $reflection->getProperty('fallbackHandler');
+        $property->setAccessible(true);
+        
+        $this->assertSame($handler, $property->getValue($router));
+    }
+
+    public function testFallbackReturnsRouterInstanceForChaining(): void
+    {
+        $config = new Config(['modules_path' => ['/path/to/modules']]);
+        $router = new Router($config);
+        
+        $result = $router->fallback('Handler');
+        
+        $this->assertSame($router, $result);
+    }
+}
diff --git a/tests/Unit/RouterUrlTest.php b/tests/Unit/RouterUrlTest.php
new file mode 100644
index 0000000..c4d3f32
--- /dev/null
+++ b/tests/Unit/RouterUrlTest.php
@@ -0,0 +1,67 @@
+<?php
+
+namespace Atlas\Tests\Unit;
+
+use Atlas\Router\Router;
+use Atlas\Config\Config;
+use Atlas\Exception\RouteNotFoundException;
+use PHPUnit\Framework\TestCase;
+
+class RouterUrlTest extends TestCase
+{
+    private Router $router;
+
+    protected function setUp(): void
+    {
+        $config = new Config(['modules_path' => ['/path/to/modules']]);
+        $this->router = new Router($config);
+    }
+
+    public function testUrlGeneratesForStaticRoute(): void
+    {
+        $this->router->get('/users', 'handler', 'user_list');
+        
+        $url = $this->router->url('user_list');
+        
+        $this->assertSame('/users', $url);
+    }
+
+    public function testUrlGeneratesWithParameters(): void
+    {
+        $this->router->get('/users/{{user_id}}', 'handler', 'user_detail');
+        
+        $url = $this->router->url('user_detail', ['user_id' => 42]);
+        
+        $this->assertSame('/users/42', $url);
+    }
+
+    public function testUrlGeneratesWithMultipleParameters(): void
+    {
+        $this->router->get('/posts/{{post_id}}/comments/{{comment_id}}', 'handler', 'comment_detail');
+        
+        $url = $this->router->url('comment_detail', [
+            'post_id' => 10,
+            'comment_id' => 5
+        ]);
+        
+        $this->assertSame('/posts/10/comments/5', $url);
+    }
+
+    public function testUrlThrowsExceptionWhenRouteNotFound(): void
+    {
+        $this->expectException(RouteNotFoundException::class);
+        $this->expectExceptionMessage('Route "non_existent" not found');
+        
+        $this->router->url('non_existent');
+    }
+
+    public function testUrlWithMissingParametersThrowsException(): 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', []);
+    }
+}