diff --git a/.gitignore b/.gitignore
index 4a45ef5..af40440 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
 vendor
 composer.lock
 .php_cs.cache
+coverage
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index f0d8807..df4cef1 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -45,3 +45,11 @@ Good pull requests – patches, improvements, new features – are a fantastic h
 ```sh
 composer test
 ```
+
+To get code coverage information execute the following comand:
+
+```sh
+composer coverage
+```
+
+Then, open the `./coverage/index.html` file in your browser.
diff --git a/composer.json b/composer.json
index ca1722e..5676f25 100644
--- a/composer.json
+++ b/composer.json
@@ -41,9 +41,10 @@
     },
     "scripts": {
         "test": [
-            "phpunit",
+            "phpunit --coverage-text",
             "phpcs"
         ],
-        "cs-fix": "php-cs-fixer fix ."
+        "cs-fix": "php-cs-fixer fix .",
+        "coverage": "phpunit --coverage-html=coverage"
     }
 }
diff --git a/src/Factory.php b/src/Factory.php
index 48330cd..fc10b98 100644
--- a/src/Factory.php
+++ b/src/Factory.php
@@ -39,6 +39,7 @@ abstract class Factory
 
     /**
      * Set a custom ResponseFactory.
+     * @codeCoverageIgnore
      */
     public static function setResponseFactory(ResponseFactoryInterface $responseFactory)
     {
@@ -47,6 +48,7 @@ public static function setResponseFactory(ResponseFactoryInterface $responseFact
 
     /**
      * Set a custom StreamFactory.
+     * @codeCoverageIgnore
      */
     public static function setStreamFactory(StreamFactoryInterface $streamFactory)
     {
@@ -55,6 +57,7 @@ public static function setStreamFactory(StreamFactoryInterface $streamFactory)
 
     /**
      * Set a custom UriFactory.
+     * @codeCoverageIgnore
      */
     public static function setUriFactory(UriFactoryInterface $uriFactory)
     {
@@ -63,6 +66,7 @@ public static function setUriFactory(UriFactoryInterface $uriFactory)
 
     /**
      * Set a custom ServerRequestFactory.
+     * @codeCoverageIgnore
      */
     public static function setServerRequestFactory(ServerRequestFactoryInterface $serverRequestFactory)
     {
diff --git a/src/RequestHandlerContainer.php b/src/RequestHandlerContainer.php
index 8505111..f550dd8 100644
--- a/src/RequestHandlerContainer.php
+++ b/src/RequestHandlerContainer.php
@@ -10,7 +10,6 @@
 use Psr\Http\Server\RequestHandlerInterface;
 use ReflectionClass;
 use ReflectionMethod;
-use RuntimeException;
 
 /**
  * Resolve a callable using a container.
@@ -50,23 +49,19 @@ public function get($id)
     {
         try {
             $handler = $this->resolve($id);
+
+            if ($handler instanceof RequestHandlerInterface) {
+                return $handler;
+            }
+
+            return new CallableHandler($handler);
+        } catch (NotFoundExceptionInterface $exception) {
+            throw $exception;
         } catch (Exception $exception) {
             throw new class("Error getting the handler $id", 0, $exception)
                 extends Exception implements ContainerExceptionInterface {
             };
         }
-
-        if ($handler instanceof RequestHandlerInterface) {
-            return $handler;
-        }
-
-        if (is_callable($handler)) {
-            return new CallableHandler($handler);
-        }
-
-        throw new class("Handler $id not found or has not valid type", 0, $exception)
-            extends Exception implements NotFoundExceptionInterface {
-        };
     }
 
     /**
@@ -84,10 +79,6 @@ protected function resolve(string $handler)
             return function_exists($handler) ? $handler : $this->createClass($handler);
         }
 
-        if (!is_array($handler) || !is_string($handler[0])) {
-            return $handler;
-        }
-
         list($class, $method) = $handler;
 
         if ((new ReflectionMethod($class, $method))->isStatic()) {
@@ -105,7 +96,9 @@ protected function resolve(string $handler)
     protected function createClass(string $className)
     {
         if (!class_exists($className)) {
-            throw new RuntimeException("The class {$className} does not exists");
+            throw new class("The class $className does not exists")
+                extends Exception implements NotFoundExceptionInterface {
+            };
         }
 
         $reflection = new ReflectionClass($className);
@@ -120,7 +113,7 @@ protected function createClass(string $className)
     /**
      * Slit a string to an array
      *
-     * @return string|array
+     * @return string|string[]
      */
     protected function split(string $string)
     {
diff --git a/tests/ControllerStub.php b/tests/Assets/Controller.php
similarity index 52%
rename from tests/ControllerStub.php
rename to tests/Assets/Controller.php
index 3d0ab33..aafa3f0 100644
--- a/tests/ControllerStub.php
+++ b/tests/Assets/Controller.php
@@ -1,10 +1,14 @@
 <?php
 declare(strict_types = 1);
 
-namespace Middlewares\Tests;
+namespace Middlewares\Tests\Assets;
 
-final class ControllerStub
+final class Controller
 {
+    public static function staticAction()
+    {
+    }
+
     public function action()
     {
     }
diff --git a/tests/Assets/ErrorController.php b/tests/Assets/ErrorController.php
new file mode 100644
index 0000000..c5a79b7
--- /dev/null
+++ b/tests/Assets/ErrorController.php
@@ -0,0 +1,18 @@
+<?php
+declare(strict_types = 1);
+
+namespace Middlewares\Tests\Assets;
+
+use Exception;
+
+final class ErrorController
+{
+    public function __construct()
+    {
+        throw new Exception('Error Processing Request');
+    }
+
+    public function __invoke()
+    {
+    }
+}
diff --git a/tests/Assets/RequestHandlerController.php b/tests/Assets/RequestHandlerController.php
new file mode 100644
index 0000000..d37ff29
--- /dev/null
+++ b/tests/Assets/RequestHandlerController.php
@@ -0,0 +1,15 @@
+<?php
+declare(strict_types = 1);
+
+namespace Middlewares\Tests\Assets;
+
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\ServerRequestInterface;
+use Psr\Http\Server\RequestHandlerInterface;
+
+final class RequestHandlerController implements RequestHandlerInterface
+{
+    public function handle(ServerRequestInterface $request): ResponseInterface
+    {
+    }
+}
diff --git a/tests/CallableHandlerTest.php b/tests/CallableHandlerTest.php
index 73d4e46..54ecaaf 100644
--- a/tests/CallableHandlerTest.php
+++ b/tests/CallableHandlerTest.php
@@ -19,6 +19,19 @@ public function testExecute()
         $this->assertEquals('Hello World', (string) $response->getBody());
     }
 
+    public function testExecuteHandler()
+    {
+        $callable = new CallableHandler(function ($request) {
+            echo $request->getHeaderLine('Foo');
+        });
+
+        $request = Factory::createServerRequest()->withHeader('Foo', 'Bar');
+        $response = $callable->handle($request);
+
+        $this->assertInstanceOf(ResponseInterface::class, $response);
+        $this->assertEquals('Bar', (string) $response->getBody());
+    }
+
     public function testOb()
     {
         $callable = new CallableHandler(function () {
diff --git a/tests/FactoryTest.php b/tests/FactoryTest.php
index 7c3540a..7d1be97 100644
--- a/tests/FactoryTest.php
+++ b/tests/FactoryTest.php
@@ -36,6 +36,20 @@ public function testStream()
         $this->assertTrue($stream->isSeekable());
     }
 
+    public function testStreamWithResource()
+    {
+        $resource = fopen('php://temp', 'r+');
+        fwrite($resource, 'Hello world');
+
+        $stream = Factory::createStream($resource);
+
+        $this->assertInstanceOf(StreamInterface::class, $stream);
+        $this->assertInstanceOf(Stream::class, $stream);
+        $this->assertTrue($stream->isWritable());
+        $this->assertTrue($stream->isSeekable());
+        $this->assertEquals('Hello world', (string) $stream);
+    }
+
     public function testUri()
     {
         $uri = Factory::createUri('http://example.com/my-path');
diff --git a/tests/RequestHandlerContainerTest.php b/tests/RequestHandlerContainerTest.php
index cebed0f..77ec86a 100644
--- a/tests/RequestHandlerContainerTest.php
+++ b/tests/RequestHandlerContainerTest.php
@@ -3,8 +3,13 @@
 
 namespace Middlewares\Tests;
 
+use Middlewares\Tests\Assets\Controller;
+use Middlewares\Tests\Assets\ErrorController;
+use Middlewares\Tests\Assets\RequestHandlerController;
 use Middlewares\Utils\RequestHandlerContainer;
 use PHPUnit\Framework\TestCase;
+use Psr\Container\ContainerExceptionInterface;
+use Psr\Container\NotFoundExceptionInterface;
 use Psr\Http\Server\RequestHandlerInterface;
 
 final class ReflectionResolverTest extends TestCase
@@ -13,9 +18,9 @@ public function testResolveClass()
     {
         $resolver = new RequestHandlerContainer();
 
-        $this->assertTrue($resolver->has(ControllerStub::class));
+        $this->assertTrue($resolver->has(Controller::class));
 
-        $callable = $resolver->get(ControllerStub::class);
+        $callable = $resolver->get(Controller::class);
 
         $this->assertInstanceOf(RequestHandlerInterface::class, $callable);
     }
@@ -24,9 +29,31 @@ public function testResolveClassCallable()
     {
         $resolver = new RequestHandlerContainer();
 
-        $this->assertTrue($resolver->has(ControllerStub::class.'::action'));
+        $this->assertTrue($resolver->has(Controller::class.'::action'));
 
-        $callable = $resolver->get(ControllerStub::class.'::action');
+        $callable = $resolver->get(Controller::class.'::action');
+
+        $this->assertInstanceOf(RequestHandlerInterface::class, $callable);
+    }
+
+    public function testResolveClassStaticCallable()
+    {
+        $resolver = new RequestHandlerContainer();
+
+        $this->assertTrue($resolver->has(Controller::class.'::staticAction'));
+
+        $callable = $resolver->get(Controller::class.'::staticAction');
+
+        $this->assertInstanceOf(RequestHandlerInterface::class, $callable);
+    }
+
+    public function testResolveRequestHandler()
+    {
+        $resolver = new RequestHandlerContainer();
+
+        $this->assertTrue($resolver->has(RequestHandlerController::class));
+
+        $callable = $resolver->get(RequestHandlerController::class);
 
         $this->assertInstanceOf(RequestHandlerInterface::class, $callable);
     }
@@ -41,4 +68,26 @@ public function testResolveFunction()
 
         $this->assertInstanceOf(RequestHandlerInterface::class, $callable);
     }
+
+    public function testContainerExceptionInterface()
+    {
+        $resolver = new RequestHandlerContainer();
+
+        $this->assertTrue($resolver->has(ErrorController::class));
+
+        $this->expectException(ContainerExceptionInterface::class);
+
+        $callable = $resolver->get(ErrorController::class);
+    }
+
+    public function testNotFoundException()
+    {
+        $resolver = new RequestHandlerContainer();
+
+        $this->assertFalse($resolver->has('foo'));
+
+        $this->expectException(NotFoundExceptionInterface::class);
+
+        $resolver->get('foo');
+    }
 }