Merge remote-tracking branch 'MyIgel/templating'

57 files changed, 1801 insertions, 183 deletions

diff --git a/composer.json b/composer.json
index f38bb972..1f53e546 100644
--- a/composer.json
+++ b/composer.json
@@ -29,6 +29,8 @@
         "symfony/http-foundation": "^3.3",
         "symfony/psr-http-message-bridge": "^1.0",
         "twbs/bootstrap": "^3.3",
+        "twig/extensions": "^1.5",
+        "twig/twig": "^2.5",
         "zendframework/zend-diactoros": "^1.7"
     },
     "require-dev": {
diff --git a/config/app.php b/config/app.php
index 9af35eb4..e309abe4 100644
--- a/config/app.php
+++ b/config/app.php
@@ -13,8 +13,10 @@ return [
         \Engelsystem\Database\DatabaseServiceProvider::class,
         \Engelsystem\Http\RequestServiceProvider::class,
         \Engelsystem\Http\SessionServiceProvider::class,
+        \Engelsystem\Helpers\TranslationServiceProvider::class,
         \Engelsystem\Http\ResponseServiceProvider::class,
         \Engelsystem\Http\Psr7ServiceProvider::class,
+        \Engelsystem\Renderer\TwigServiceProvider::class,
         \Engelsystem\Middleware\RouteDispatcherServiceProvider::class,
         \Engelsystem\Middleware\RequestHandlerServiceProvider::class,
     ],
@@ -23,6 +25,8 @@ return [
     'middleware' => [
         \Engelsystem\Middleware\SendResponseHandler::class,
         \Engelsystem\Middleware\ExceptionHandler::class,
+        \Engelsystem\Middleware\SetLocale::class,
+        \Engelsystem\Middleware\ErrorHandler::class,
         \Engelsystem\Middleware\RouteDispatcher::class,
         \Engelsystem\Middleware\RequestHandler::class,
     ],
diff --git a/includes/engelsystem.php b/includes/engelsystem.php
index f7d813c5..4c096b43 100644
--- a/includes/engelsystem.php
+++ b/includes/engelsystem.php
@@ -16,18 +16,12 @@ require __DIR__ . '/includes.php';
  * Check for maintenance
  */
 if ($app->get('config')->get('maintenance')) {
-    echo file_get_contents(__DIR__ . '/../templates/maintenance.html');
+    echo file_get_contents(__DIR__ . '/../templates/layouts/maintenance.html');
     die();
 }
 
 
 /**
- * Init translations
- */
-gettext_init();
-
-
-/**
  * Init authorization
  */
 load_auth();
diff --git a/includes/helper/email_helper.php b/includes/helper/email_helper.php
index c223d026..8d1cb794 100644
--- a/includes/helper/email_helper.php
+++ b/includes/helper/email_helper.php
@@ -15,14 +15,16 @@ function engelsystem_email_to_user($recipient_user, $title, $message, $not_if_it
         return true;
     }
 
-    gettext_locale($recipient_user['Sprache']);
+    /** @var \Engelsystem\Helpers\Translator $translator */
+    $translator = app()->get('translator');
+    $locale = $translator->getLocale();
 
+    $translator->setLocale($recipient_user['Sprache']);
     $message = sprintf(_('Hi %s,'), $recipient_user['Nick']) . "\n\n"
         . _('here is a message for you from the engelsystem:') . "\n\n"
         . $message . "\n\n"
         . _('This email is autogenerated and has not been signed. You got this email because you are registered in the engelsystem.');
-
-    gettext_locale();
+    $translator->setLocale($locale);
 
     return engelsystem_email($recipient_user['email'], $title, $message);
 }
diff --git a/includes/helper/internationalization_helper.php b/includes/helper/internationalization_helper.php
deleted file mode 100644
index bb6d0abd..00000000
--- a/includes/helper/internationalization_helper.php
+++ /dev/null
@@ -1,80 +0,0 @@
-<?php
-
-/**
- * Return currently active locale
- *
- * @return string
- */
-function locale()
-{
-    return session()->get('locale');
-}
-
-/**
- * Returns two letter language code from currently active locale
- *
- * @return string
- */
-function locale_short()
-{
-    return substr(locale(), 0, 2);
-}
-
-/**
- * Initializes gettext for internationalization and updates the sessions locale to use for translation.
- */
-function gettext_init()
-{
-    $locales = config('locales');
-    $request = request();
-    $session = session();
-
-    if ($request->has('set_locale') && isset($locales[$request->input('set_locale')])) {
-        $session->set('locale', $request->input('set_locale'));
-    } elseif (!$session->has('locale')) {
-        $session->set('locale', config('default_locale'));
-    }
-
-    gettext_locale();
-    bindtextdomain('default', app('path.lang'));
-    bind_textdomain_codeset('default', 'UTF-8');
-    textdomain('default');
-}
-
-/**
- * Swich gettext locale.
- *
- * @param string $locale
- */
-function gettext_locale($locale = null)
-{
-    if (empty($locale)) {
-        $locale = session()->get('locale');
-    }
-
-    putenv('LC_ALL=' . $locale);
-    setlocale(LC_ALL, $locale);
-}
-
-/**
- * Renders language selection.
- *
- * @return array
- */
-function make_langselect()
-{
-    $request = app('request');
-
-    $items = [];
-    foreach (config('locales') as $locale => $name) {
-        $url = url($request->getPathInfo(), ['set_locale' => $locale]);
-
-        $items[] = toolbar_item_link(
-            htmlspecialchars($url),
-            '',
-            $name,
-            $locale == locale()
-        );
-    }
-    return $items;
-}
diff --git a/includes/includes.php b/includes/includes.php
index e316e550..7a68c3c9 100644
--- a/includes/includes.php
+++ b/includes/includes.php
@@ -61,7 +61,6 @@ $includeFiles = [
     __DIR__ . '/../includes/controller/user_worklog_controller.php',
 
     __DIR__ . '/../includes/helper/graph_helper.php',
-    __DIR__ . '/../includes/helper/internationalization_helper.php',
     __DIR__ . '/../includes/helper/message_helper.php',
     __DIR__ . '/../includes/helper/error_helper.php',
     __DIR__ . '/../includes/helper/email_helper.php',
diff --git a/includes/pages/guest_credits.php b/includes/pages/guest_credits.php
index db86132d..ecfa8f7c 100644
--- a/includes/pages/guest_credits.php
+++ b/includes/pages/guest_credits.php
@@ -13,5 +13,5 @@ function credits_title()
  */
 function guest_credits()
 {
-    return view(__DIR__ . '/../../templates/guest_credits.html');
+    return view(__DIR__ . '/../../templates/pages/credits.html');
 }
diff --git a/includes/pages/user_shifts.php b/includes/pages/user_shifts.php
index 186301db..020cfe54 100644
--- a/includes/pages/user_shifts.php
+++ b/includes/pages/user_shifts.php
@@ -224,7 +224,7 @@ function view_user_shifts()
     return page([
         div('col-md-12', [
             msg(),
-            view(__DIR__ . '/../../templates/user_shifts.html', [
+            view(__DIR__ . '/../../templates/pages/user-shifts.html', [
                 'title'         => shifts_title(),
                 'room_select'   => make_select($rooms, $shiftsFilter->getRooms(), 'rooms', _('Rooms')),
                 'start_select'  => html_select_key(
diff --git a/includes/sys_form.php b/includes/sys_form.php
index c974c1d1..cd1c84e6 100644
--- a/includes/sys_form.php
+++ b/includes/sys_form.php
@@ -66,6 +66,9 @@ function form_date($name, $label, $value, $start_date = '', $end_date = '')
     $value = is_numeric($value) ? date('Y-m-d', $value) : '';
     $start_date = is_numeric($start_date) ? date('Y-m-d', $start_date) : '';
     $end_date = is_numeric($end_date) ? date('Y-m-d', $end_date) : '';
+    $locale = $locale = session()->get('locale');
+    $shortLocale = substr($locale, 0, 2);
+
     return form_element($label, '
     <div class="input-group date" id="' . $dom_id . '">
       <input name="' . $name . '" class="form-control" value="' . htmlspecialchars($value) . '">'
@@ -73,13 +76,13 @@ function form_date($name, $label, $value, $start_date = '', $end_date = '')
     </div>
     <script type="text/javascript">
 			$(function(){
-        $(\'#' . $dom_id . '\').datepicker({
-				  language: \'' . locale_short() . '\',
-          todayBtn: \'linked\',
-          format: \'yyyy-mm-dd\',
-          startDate: \'' . $start_date . '\',
-          endDate: \'' . $end_date . '\',
-          orientation: \'bottom\'
+        $("#' . $dom_id . '").datepicker({
+				  language: "' . $shortLocale . '",
+          todayBtn: "linked",
+          format: "yyyy-mm-dd",
+          startDate: "' . $start_date . '",
+          endDate: "' . $end_date . '",
+          orientation: "bottom"
 			  });
       });
     </script>
diff --git a/includes/sys_menu.php b/includes/sys_menu.php
index fae94de5..5609c0ab 100644
--- a/includes/sys_menu.php
+++ b/includes/sys_menu.php
@@ -110,7 +110,7 @@ function make_user_submenu()
 {
     global $privileges, $page;
 
-    $user_submenu = make_langselect();
+    $user_submenu = make_language_select();
 
     if (in_array('user_settings', $privileges) || in_array('logout', $privileges)) {
         $user_submenu[] = toolbar_item_divider();
@@ -228,6 +228,30 @@ function make_room_navigation($menu)
 }
 
 /**
+ * Renders language selection.
+ *
+ * @return array
+ */
+function make_language_select()
+{
+    $request = app('request');
+    $activeLocale = session()->get('locale');
+
+    $items = [];
+    foreach (config('locales') as $locale => $name) {
+        $url = url($request->getPathInfo(), ['set-locale' => $locale]);
+
+        $items[] = toolbar_item_link(
+            htmlspecialchars($url),
+            '',
+            $name,
+            $locale == $activeLocale
+        );
+    }
+    return $items;
+}
+
+/**
  * @return string
  */
 function make_menu()
diff --git a/src/Application.php b/src/Application.php
index 6644a6cf..86397a2c 100644
--- a/src/Application.php
+++ b/src/Application.php
@@ -107,6 +107,7 @@ class Application extends Container
         $this->instance('path', $appPath);
         $this->instance('path.config', $appPath . DIRECTORY_SEPARATOR . 'config');
         $this->instance('path.lang', $appPath . DIRECTORY_SEPARATOR . 'locale');
+        $this->instance('path.views', $appPath . DIRECTORY_SEPARATOR . 'templates');
     }
 
     /**
diff --git a/src/Config/ConfigServiceProvider.php b/src/Config/ConfigServiceProvider.php
index 9fbccd68..63f43ced 100644
--- a/src/Config/ConfigServiceProvider.php
+++ b/src/Config/ConfigServiceProvider.php
@@ -13,6 +13,7 @@ class ConfigServiceProvider extends ServiceProvider
     public function register()
     {
         $config = $this->app->make(Config::class);
+        $this->app->instance(Config::class, $config);
         $this->app->instance('config', $config);
 
         foreach ($this->configFiles as $file) {
diff --git a/src/Helpers/TranslationServiceProvider.php b/src/Helpers/TranslationServiceProvider.php
new file mode 100644
index 00000000..9d86df7d
--- /dev/null
+++ b/src/Helpers/TranslationServiceProvider.php
@@ -0,0 +1,58 @@
+<?php
+
+namespace Engelsystem\Helpers;
+
+use Engelsystem\Config\Config;
+use Engelsystem\Container\ServiceProvider;
+use Symfony\Component\HttpFoundation\Session\Session;
+
+class TranslationServiceProvider extends ServiceProvider
+{
+    public function register()
+    {
+        /** @var Config $config */
+        $config = $this->app->get('config');
+        /** @var Session $session */
+        $session = $this->app->get('session');
+
+        $locales = $config->get('locales');
+        $locale = $config->get('default_locale');
+
+        $sessionLocale = $session->get('locale', $locale);
+        if (isset($locales[$sessionLocale])) {
+            $locale = $sessionLocale;
+        }
+
+        $this->initGettext();
+        $session->set('locale', $locale);
+
+        $translator = $this->app->make(
+            Translator::class,
+            ['locale' => $locale, 'locales' => $locales, 'localeChangeCallback' => [$this, 'setLocale']]
+        );
+        $this->app->instance(Translator::class, $translator);
+        $this->app->instance('translator', $translator);
+    }
+
+    /**
+     * @param string $textDomain
+     * @param string $encoding
+     * @codeCoverageIgnore
+     */
+    protected function initGettext($textDomain = 'default', $encoding = 'UTF-8')
+    {
+        bindtextdomain($textDomain, $this->app->get('path.lang'));
+        bind_textdomain_codeset($textDomain, $encoding);
+        textdomain($textDomain);
+    }
+
+    /**
+     * @param string $locale
+     * @codeCoverageIgnore
+     */
+    public function setLocale($locale)
+    {
+        putenv('LC_ALL=' . $locale);
+        setlocale(LC_ALL, $locale);
+    }
+}
diff --git a/src/Helpers/Translator.php b/src/Helpers/Translator.php
new file mode 100644
index 00000000..1e953a21
--- /dev/null
+++ b/src/Helpers/Translator.php
@@ -0,0 +1,105 @@
+<?php
+
+namespace Engelsystem\Helpers;
+
+class Translator
+{
+    /** @var string[] */
+    protected $locales;
+
+    /** @var string */
+    protected $locale;
+
+    /** @var callable */
+    protected $localeChangeCallback;
+
+    /**
+     * Translator constructor.
+     *
+     * @param string   $locale
+     * @param string[] $locales
+     * @param callable $localeChangeCallback
+     */
+    public function __construct(string $locale, array $locales = [], callable $localeChangeCallback = null)
+    {
+        $this->localeChangeCallback = $localeChangeCallback;
+
+        $this->setLocale($locale);
+        $this->setLocales($locales);
+    }
+
+    /**
+     * Get the translation for a given key
+     *
+     * @param string $key
+     * @param array  $replace
+     * @return string
+     */
+    public function translate(string $key, array $replace = []): string
+    {
+        $translated = $this->translateGettext($key);
+
+        if (!empty($replace)) {
+            $translated = call_user_func_array('sprintf', array_merge([$translated], $replace));
+        }
+
+        return $translated;
+    }
+
+    /**
+     * Translate the key via gettext
+     *
+     * @param string $key
+     * @return string
+     * @codeCoverageIgnore
+     */
+    protected function translateGettext(string $key): string
+    {
+        return _($key);
+    }
+
+    /**
+     * @return string
+     */
+    public function getLocale(): string
+    {
+        return $this->locale;
+    }
+
+    /**
+     * @param string $locale
+     */
+    public function setLocale(string $locale)
+    {
+        $this->locale = $locale;
+
+        if (is_callable($this->localeChangeCallback)) {
+            call_user_func_array($this->localeChangeCallback, [$locale]);
+        }
+    }
+
+    /**
+     * @return string[]
+     */
+    public function getLocales(): array
+    {
+        return $this->locales;
+    }
+
+    /**
+     * @param string $locale
+     * @return bool
+     */
+    public function hasLocale(string $locale): bool
+    {
+        return isset($this->locales[$locale]);
+    }
+
+    /**
+     * @param string[] $locales
+     */
+    public function setLocales(array $locales)
+    {
+        $this->locales = $locales;
+    }
+}
diff --git a/src/Http/Response.php b/src/Http/Response.php
index 9db6fa83..d79ab98b 100644
--- a/src/Http/Response.php
+++ b/src/Http/Response.php
@@ -2,6 +2,7 @@
 
 namespace Engelsystem\Http;
 
+use Engelsystem\Renderer\Renderer;
 use Psr\Http\Message\ResponseInterface;
 use Symfony\Component\HttpFoundation\Response as SymfonyResponse;
 
@@ -9,6 +10,25 @@ class Response extends SymfonyResponse implements ResponseInterface
 {
     use MessageTrait;
 
+    /** @var Renderer */
+    protected $view;
+
+    /**
+     * @param string   $content
+     * @param int      $status
+     * @param array    $headers
+     * @param Renderer $view
+     */
+    public function __construct(
+        $content = '',
+        int $status = 200,
+        array $headers = array(),
+        Renderer $view = null
+    ) {
+        $this->view = $view;
+        parent::__construct($content, $status, $headers);
+    }
+
     /**
      * Return an instance with the specified status code and, optionally, reason phrase.
      *
@@ -72,4 +92,25 @@ class Response extends SymfonyResponse implements ResponseInterface
 
         return $new;
     }
+
+    /**
+     * Return an instance with the rendered content.
+     *
+     * THis method retains the immutability of the message and returns
+     * an instance with the updated status and headers
+     *
+     * @param string              $view
+     * @param array               $data
+     * @param int                 $status
+     * @param string[]|string[][] $headers
+     * @return Response
+     */
+    public function withView($view, $data = [], $status = 200, $headers = [])
+    {
+        if (!$this->view instanceof Renderer) {
+            throw new \InvalidArgumentException('Renderer not defined');
+        }
+
+        return $this->create($this->view->render($view, $data), $status, $headers);
+    }
 }
diff --git a/src/Http/SessionServiceProvider.php b/src/Http/SessionServiceProvider.php
index 55e3f48b..59121a3b 100644
--- a/src/Http/SessionServiceProvider.php
+++ b/src/Http/SessionServiceProvider.php
@@ -17,6 +17,7 @@ class SessionServiceProvider extends ServiceProvider
         $this->app->bind(SessionStorageInterface::class, 'session.storage');
 
         $session = $this->app->make(Session::class);
+        $this->app->instance(Session::class, $session);
         $this->app->instance('session', $session);
 
         /** @var Request $request */
diff --git a/src/Http/UrlGeneratorServiceProvider.php b/src/Http/UrlGeneratorServiceProvider.php
index 37304076..9b9988aa 100644
--- a/src/Http/UrlGeneratorServiceProvider.php
+++ b/src/Http/UrlGeneratorServiceProvider.php
@@ -9,6 +9,7 @@ class UrlGeneratorServiceProvider extends ServiceProvider
     public function register()
     {
         $urlGenerator = $this->app->make(UrlGenerator::class);
+        $this->app->instance(UrlGenerator::class, $urlGenerator);
         $this->app->instance('http.urlGenerator', $urlGenerator);
     }
 }
diff --git a/src/Middleware/ErrorHandler.php b/src/Middleware/ErrorHandler.php
new file mode 100644
index 00000000..a7c4cfe6
--- /dev/null
+++ b/src/Middleware/ErrorHandler.php
@@ -0,0 +1,80 @@
+<?php
+
+namespace Engelsystem\Middleware;
+
+use Engelsystem\Http\Response;
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\ServerRequestInterface;
+use Psr\Http\Server\MiddlewareInterface;
+use Psr\Http\Server\RequestHandlerInterface;
+use Twig_LoaderInterface as TwigLoader;
+
+class ErrorHandler implements MiddlewareInterface
+{
+    /** @var TwigLoader */
+    protected $loader;
+
+    /** @var string */
+    protected $viewPrefix = 'errors/';
+
+    /**
+     * @param TwigLoader $loader
+     */
+    public function __construct(TwigLoader $loader)
+    {
+        $this->loader = $loader;
+    }
+
+    /**
+     * Handles any error messages
+     *
+     * Should be added at the beginning
+     *
+     * @param ServerRequestInterface  $request
+     * @param RequestHandlerInterface $handler
+     * @return ResponseInterface
+     */
+    public function process(
+        ServerRequestInterface $request,
+        RequestHandlerInterface $handler
+    ): ResponseInterface {
+        $response = $handler->handle($request);
+
+        $statusCode = $response->getStatusCode();
+        if ($statusCode < 400 || !$response instanceof Response) {
+            return $response;
+        }
+
+        $view = $this->selectView($statusCode);
+
+        return $response->withView(
+            $this->viewPrefix . $view,
+            [
+                'status'  => $statusCode,
+                'content' => $response->getContent(),
+            ],
+            $statusCode,
+            $response->getHeaders()
+        );
+    }
+
+    /**
+     * Select a view based on the given status code
+     *
+     * @param int $statusCode
+     * @return string
+     */
+    protected function selectView(int $statusCode): string
+    {
+        $hundreds = intdiv($statusCode, 100);
+
+        $viewsList = [$statusCode, $hundreds, $hundreds * 100];
+        foreach ($viewsList as $view) {
+            if ($this->loader->exists($this->viewPrefix . $view)) {
+                return $view;
+            }
+        }
+
+        return 'default';
+    }
+}
diff --git a/src/Middleware/LegacyMiddleware.php b/src/Middleware/LegacyMiddleware.php
index 276fb3ee..78132815 100644
--- a/src/Middleware/LegacyMiddleware.php
+++ b/src/Middleware/LegacyMiddleware.php
@@ -83,7 +83,7 @@ class LegacyMiddleware implements MiddlewareInterface
         }
 
         if (empty($title) and empty($content)) {
-            $page = '404';
+            $page = 404;
             $title = _('Page not found');
             $content = _('This page could not be found or you don\'t have permission to view it. You probably have to sign in or register in order to gain access!');
         }
@@ -277,29 +277,17 @@ class LegacyMiddleware implements MiddlewareInterface
             $parameters['meetings'] = 1;
         }
 
-        $status = 200;
-        if ($page == '404') {
-            $status = 404;
-            $content = info($content, true);
+        if (!empty($page) && is_int($page)) {
+            return response($content, (int)$page);
         }
 
-        return response(view(__DIR__ . '/../../templates/layout.html', [
-            'theme'          => isset($user) ? $user['color'] : config('theme'),
+        return response(view('layouts/app', [
             'title'          => $title,
-            'atom_link'      => ($page == 'news' || $page == 'user_meetings')
-                ? ' <link href="'
-                . page_link_to('atom', $parameters)
-                . '" type = "application/atom+xml" rel = "alternate" title = "Atom Feed">'
-                : '',
-            'start_page_url' => page_link_to('/'),
-            'credits_url'    => page_link_to('credits'),
+            'atom_feed'      => ($page == 'news' || $page == 'user_meetings') ? $parameters : [],
             'menu'           => make_menu(),
             'content'        => msg() . $content,
             'header_toolbar' => header_toolbar(),
-            'faq_url'        => config('faq_url'),
-            'contact_email'  => config('contact_email'),
-            'locale'         => locale(),
             'event_info'     => EventConfig_info($event_config) . ' <br />'
-        ]), $status);
+        ]), 200);
     }
 }
diff --git a/src/Middleware/SetLocale.php b/src/Middleware/SetLocale.php
new file mode 100644
index 00000000..86fa0b7f
--- /dev/null
+++ b/src/Middleware/SetLocale.php
@@ -0,0 +1,49 @@
+<?php
+
+namespace Engelsystem\Middleware;
+
+use Engelsystem\Helpers\Translator;
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\ServerRequestInterface;
+use Psr\Http\Server\MiddlewareInterface;
+use Psr\Http\Server\RequestHandlerInterface;
+use Symfony\Component\HttpFoundation\Session\Session;
+
+class SetLocale implements MiddlewareInterface
+{
+    /** @var Translator */
+    protected $translator;
+
+    /** @var Session */
+    protected $session;
+
+    /**
+     * @param Translator $translator
+     * @param Session    $session
+     */
+    public function __construct(Translator $translator, Session $session)
+    {
+        $this->translator = $translator;
+        $this->session = $session;
+    }
+
+    /**
+     * Process an incoming server request and setting the locale if required
+     *
+     * @param ServerRequestInterface  $request
+     * @param RequestHandlerInterface $handler
+     * @return ResponseInterface
+     */
+    public function process(ServerRequestInterface $request, RequestHandlerInterface $handler): ResponseInterface
+    {
+        $query = $request->getQueryParams();
+        if (isset($query['set-locale']) && $this->translator->hasLocale($query['set-locale'])) {
+            $locale = $query['set-locale'];
+
+            $this->translator->setLocale($locale);
+            $this->session->set('locale', $locale);
+        }
+
+        return $handler->handle($request);
+    }
+}
diff --git a/src/Renderer/RendererServiceProvider.php b/src/Renderer/RendererServiceProvider.php
index 3e8d69bc..2e41837b 100644
--- a/src/Renderer/RendererServiceProvider.php
+++ b/src/Renderer/RendererServiceProvider.php
@@ -24,12 +24,14 @@ class RendererServiceProvider extends ServiceProvider
     protected function registerRenderer()
     {
         $renderer = $this->app->make(Renderer::class);
+        $this->app->instance(Renderer::class, $renderer);
         $this->app->instance('renderer', $renderer);
     }
 
     protected function registerHtmlEngine()
     {
         $htmlEngine = $this->app->make(HtmlEngine::class);
+        $this->app->instance(HtmlEngine::class, $htmlEngine);
         $this->app->instance('renderer.htmlEngine', $htmlEngine);
         $this->app->tag('renderer.htmlEngine', ['renderer.engine']);
     }
diff --git a/src/Renderer/Twig/Extensions/Config.php b/src/Renderer/Twig/Extensions/Config.php
new file mode 100644
index 00000000..dbbe93e7
--- /dev/null
+++ b/src/Renderer/Twig/Extensions/Config.php
@@ -0,0 +1,31 @@
+<?php
+
+namespace Engelsystem\Renderer\Twig\Extensions;
+
+use Engelsystem\Config\Config as EngelsystemConfig;
+use Twig_Extension as TwigExtension;
+use Twig_Function as TwigFunction;
+
+class Config extends TwigExtension
+{
+    /** @var EngelsystemConfig */
+    protected $config;
+
+    /**
+     * @param EngelsystemConfig $config
+     */
+    public function __construct(EngelsystemConfig $config)
+    {
+        $this->config = $config;
+    }
+
+    /**
+     * @return TwigFunction[]
+     */
+    public function getFunctions()
+    {
+        return [
+            new TwigFunction('config', [$this->config, 'get']),
+        ];
+    }
+}
diff --git a/src/Renderer/Twig/Extensions/Globals.php b/src/Renderer/Twig/Extensions/Globals.php
new file mode 100644
index 00000000..f9bffbc8
--- /dev/null
+++ b/src/Renderer/Twig/Extensions/Globals.php
@@ -0,0 +1,23 @@
+<?php
+
+namespace Engelsystem\Renderer\Twig\Extensions;
+
+use Twig_Extension as TwigExtension;
+use Twig_Extension_GlobalsInterface as GlobalsInterface;
+
+class Globals extends TwigExtension implements GlobalsInterface
+{
+    /**
+     * Returns a list of global variables to add to the existing list.
+     *
+     * @return array An array of global variables
+     */
+    public function getGlobals()
+    {
+        global $user;
+
+        return [
+            'user' => isset($user) ? $user : [],
+        ];
+    }
+}
diff --git a/src/Renderer/Twig/Extensions/Session.php b/src/Renderer/Twig/Extensions/Session.php
new file mode 100644
index 00000000..4690f701
--- /dev/null
+++ b/src/Renderer/Twig/Extensions/Session.php
@@ -0,0 +1,31 @@
+<?php
+
+namespace Engelsystem\Renderer\Twig\Extensions;
+
+use Symfony\Component\HttpFoundation\Session\Session as SymfonySession;
+use Twig_Extension as TwigExtension;
+use Twig_Function as TwigFunction;
+
+class Session extends TwigExtension
+{
+    /** @var SymfonySession */
+    protected $session;
+
+    /**
+     * @param SymfonySession $session
+     */
+    public function __construct(SymfonySession $session)
+    {
+        $this->session = $session;
+    }
+
+    /**
+     * @return TwigFunction[]
+     */
+    public function getFunctions()
+    {
+        return [
+            new TwigFunction('session_get', [$this->session, 'get']),
+        ];
+    }
+}
diff --git a/src/Renderer/Twig/Extensions/Translation.php b/src/Renderer/Twig/Extensions/Translation.php
new file mode 100644
index 00000000..63f9800e
--- /dev/null
+++ b/src/Renderer/Twig/Extensions/Translation.php
@@ -0,0 +1,57 @@
+<?php
+
+namespace Engelsystem\Renderer\Twig\Extensions;
+
+use Engelsystem\Helpers\Translator;
+use Twig_Extension as TwigExtension;
+use Twig_Extensions_TokenParser_Trans as TranslationTokenParser;
+use Twig_Filter as TwigFilter;
+use Twig_Function as TwigFunction;
+use Twig_TokenParserInterface as TwigTokenParser;
+
+class Translation extends TwigExtension
+{
+    /** @var Translator */
+    protected $translator;
+
+    /** @var TranslationTokenParser */
+    protected $tokenParser;
+
+    /**
+     * @param Translator             $translator
+     * @param TranslationTokenParser $tokenParser
+     */
+    public function __construct(Translator $translator, TranslationTokenParser $tokenParser)
+    {
+        $this->translator = $translator;
+        $this->tokenParser = $tokenParser;
+    }
+
+    /**
+     * @return array
+     */
+    public function getFilters()
+    {
+        return [
+            new TwigFilter('trans', [$this->translator, 'translate']),
+        ];
+    }
+
+    /**
+     * @return TwigFunction[]
+     */
+    public function getFunctions()
+    {
+        return [
+            new TwigFunction('__', [$this->translator, 'translate']),
+        ];
+    }
+
+    /**
+     * @return TwigTokenParser[]
+     */
+    public function getTokenParsers()
+    {
+        return [$this->tokenParser];
+    }
+}
diff --git a/src/Renderer/Twig/Extensions/Url.php b/src/Renderer/Twig/Extensions/Url.php
new file mode 100644
index 00000000..62e59782
--- /dev/null
+++ b/src/Renderer/Twig/Extensions/Url.php
@@ -0,0 +1,43 @@
+<?php
+
+namespace Engelsystem\Renderer\Twig\Extensions;
+
+use Engelsystem\Http\UrlGenerator;
+use Twig_Extension as TwigExtension;
+use Twig_Function as TwigFunction;
+
+class Url extends TwigExtension
+{
+    /** @var UrlGenerator */
+    protected $urlGenerator;
+
+    /**
+     * @param UrlGenerator $urlGenerator
+     */
+    public function __construct(UrlGenerator $urlGenerator)
+    {
+        $this->urlGenerator = $urlGenerator;
+    }
+
+    /**
+     * @return TwigFunction[]
+     */
+    public function getFunctions()
+    {
+        return [
+            new TwigFunction('url', [$this, 'getUrl']),
+        ];
+    }
+
+    /**
+     * @param string $path
+     * @param array  $parameters
+     * @return UrlGenerator|string
+     */
+    public function getUrl($path, $parameters = [])
+    {
+        $path = str_replace('_', '-', $path);
+
+        return $this->urlGenerator->to($path, $parameters);
+    }
+}
diff --git a/src/Renderer/TwigEngine.php b/src/Renderer/TwigEngine.php
new file mode 100644
index 00000000..55a2e299
--- /dev/null
+++ b/src/Renderer/TwigEngine.php
@@ -0,0 +1,41 @@
+<?php
+
+namespace Engelsystem\Renderer;
+
+use Twig_Environment as Twig;
+use Twig_Error_Loader as LoaderError;
+use Twig_Error_Runtime as RuntimeError;
+use Twig_Error_Syntax as SyntaxError;
+
+class TwigEngine implements EngineInterface
+{
+    /** @var Twig */
+    protected $twig;
+
+    public function __construct(Twig $twig)
+    {
+        $this->twig = $twig;
+    }
+
+    /**
+     * Render a twig template
+     *
+     * @param string $path
+     * @param array  $data
+     * @return string
+     * @throws LoaderError|RuntimeError|SyntaxError
+     */
+    public function get($path, $data = [])
+    {
+        return $this->twig->render($path, $data);
+    }
+
+    /**
+     * @param string $path
+     * @return bool
+     */
+    public function canRender($path)
+    {
+        return $this->twig->getLoader()->exists($path);
+    }
+}
diff --git a/src/Renderer/TwigLoader.php b/src/Renderer/TwigLoader.php
new file mode 100644
index 00000000..154e6dbb
--- /dev/null
+++ b/src/Renderer/TwigLoader.php
@@ -0,0 +1,26 @@
+<?php
+
+namespace Engelsystem\Renderer;
+
+use Twig_Error_Loader;
+use Twig_Loader_Filesystem as FilesystemLoader;
+
+class TwigLoader extends FilesystemLoader
+{
+    /**
+     * @param string $name
+     * @param bool   $throw
+     * @return false|string
+     * @throws Twig_Error_Loader
+     */
+    public function findTemplate($name, $throw = true)
+    {
+        $extension = '.twig';
+        $extensionLength = strlen($extension);
+        if (substr($name, -$extensionLength, $extensionLength) !== $extension) {
+            $name .= $extension;
+        }
+
+        return parent::findTemplate($name, $throw);
+    }
+}
diff --git a/src/Renderer/TwigServiceProvider.php b/src/Renderer/TwigServiceProvider.php
new file mode 100644
index 00000000..0f453989
--- /dev/null
+++ b/src/Renderer/TwigServiceProvider.php
@@ -0,0 +1,77 @@
+<?php
+
+namespace Engelsystem\Renderer;
+
+use Engelsystem\Container\ServiceProvider;
+use Engelsystem\Renderer\Twig\Extensions\Config;
+use Engelsystem\Renderer\Twig\Extensions\Globals;
+use Engelsystem\Renderer\Twig\Extensions\Session;
+use Engelsystem\Renderer\Twig\Extensions\Translation;
+use Engelsystem\Renderer\Twig\Extensions\Url;
+use Twig_Environment as Twig;
+use Twig_LoaderInterface as TwigLoaderInterface;
+
+class TwigServiceProvider extends ServiceProvider
+{
+    /** @var array */
+    protected $extensions = [
+        'config'      => Config::class,
+        'globals'     => Globals::class,
+        'session'     => Session::class,
+        'url'         => Url::class,
+        'translation' => Translation::class,
+    ];
+
+    public function register()
+    {
+        $this->registerTwigEngine();
+
+        foreach ($this->extensions as $alias => $class) {
+            $this->registerTwigExtensions($class, $alias);
+        }
+    }
+
+    public function boot()
+    {
+        /** @var Twig $renderer */
+        $renderer = $this->app->get('twig.environment');
+
+        foreach ($this->app->tagged('twig.extension') as $extension) {
+            $renderer->addExtension($extension);
+        }
+    }
+
+    protected function registerTwigEngine()
+    {
+        $viewsPath = $this->app->get('path.views');
+
+        $twigLoader = $this->app->make(TwigLoader::class, ['paths' => $viewsPath]);
+        $this->app->instance(TwigLoader::class, $twigLoader);
+        $this->app->instance(TwigLoaderInterface::class, $twigLoader);
+        $this->app->instance('twig.loader', $twigLoader);
+
+        $twig = $this->app->make(Twig::class);
+        $this->app->instance(Twig::class, $twig);
+        $this->app->instance('twig.environment', $twig);
+
+        $twigEngine = $this->app->make(TwigEngine::class);
+        $this->app->instance('renderer.twigEngine', $twigEngine);
+        $this->app->tag('renderer.twigEngine', ['renderer.engine']);
+    }
+
+    /**
+     * @param string $class
+     * @param string $alias
+     */
+    protected function registerTwigExtensions($class, $alias)
+    {
+        $alias = 'twig.extension.' . $alias;
+
+        $extension = $this->app->make($class);
+
+        $this->app->instance($class, $extension);
+        $this->app->instance($alias, $extension);
+
+        $this->app->tag($alias, ['twig.extension']);
+    }
+}
diff --git a/src/helpers.php b/src/helpers.php
index 95571a40..84f26dfa 100644
--- a/src/helpers.php
+++ b/src/helpers.php
@@ -3,10 +3,11 @@
 
 use Engelsystem\Application;
 use Engelsystem\Config\Config;
+use Engelsystem\Helpers\Translator;
 use Engelsystem\Http\Request;
 use Engelsystem\Http\Response;
-use Engelsystem\Renderer\Renderer;
 use Engelsystem\Http\UrlGenerator;
+use Engelsystem\Renderer\Renderer;
 use Symfony\Component\HttpFoundation\Session\SessionInterface;
 
 /**
@@ -119,6 +120,40 @@ function session($key = null, $default = null)
 }
 
 /**
+ * Translate the given message
+ *
+ * @param  string $key
+ * @param  array  $replace
+ * @return string|Translator
+ */
+function trans($key = null, $replace = [])
+{
+    /** @var Translator $translator */
+    $translator = app('translator');
+
+    if (is_null($key)) {
+        return $translator;
+    }
+
+    return $translator->translate($key, $replace);
+}
+
+/**
+ * Translate the given message
+ *
+ * @param  string $key
+ * @param  array  $replace
+ * @return string
+ */
+function __($key, $replace = [])
+{
+    /** @var Translator $translator */
+    $translator = app('translator');
+
+    return $translator->translate($key, $replace);
+}
+
+/**
  * @param string $path
  * @param array  $parameters
  * @return UrlGeneratorInterface|string
@@ -139,7 +174,7 @@ function url($path = null, $parameters = [])
  * @param mixed[] $data
  * @return Renderer|string
  */
-function view($template = null, $data = null)
+function view($template = null, $data = [])
 {
     $renderer = app('renderer');
 
diff --git a/templates/errors/default.twig b/templates/errors/default.twig
new file mode 100644
index 00000000..5fb8bcbd
--- /dev/null
+++ b/templates/errors/default.twig
@@ -0,0 +1,7 @@
+{% extends "layouts/app.twig" %}
+
+{% block title %}{% if status == 404 %}{{ __("Page not found") }}{% else %}Error {{ status }}{% endif %}{% endblock %}
+
+{% block content %}
+    <div class="alert alert-info">{{ content }}</div>
+{% endblock %}
diff --git a/templates/layout.html b/templates/layout.html
deleted file mode 100644
index 832bdcf3..00000000
--- a/templates/layout.html
+++ /dev/null
@@ -1,46 +0,0 @@
-<!DOCTYPE html>
-<html lang="%locale%">
-<head>
-    <title>%title% - Engelsystem</title>
-    <meta charset="UTF-8"/>
-    <meta name="viewport" content="width=device-width, initial-scale=1">
-    <link rel="stylesheet" type="text/css" href="%start_page_url%assets/theme%theme%.css"/>
-    <script type="text/javascript" src="%start_page_url%assets/vendor.js"></script>
-    %atom_link%
-</head>
-<body>
-<div class="navbar navbar-default navbar-fixed-top">
-    <div class="container-fluid">
-        <div class="navbar-header">
-            <button type="button" class="navbar-toggle collapsed"
-                    data-toggle="collapse" data-target="#navbar-collapse-1">
-                <span class="sr-only">Toggle navigation</span>
-                <span class="icon-bar"></span>
-                <span class="icon-bar"></span>
-                <span class="icon-bar"></span>
-            </button>
-            <a class="navbar-brand" href="%start_page_url%">
-                <span class="icon-icon_angel"></span> <strong class="visible-lg-inline">ENGELSYSTEM</strong>
-            </a>
-        </div>
-        <div class="collapse navbar-collapse" id="navbar-collapse-1">%menu% %header_toolbar%</div>
-    </div>
-</div>
-<div class="container-fluid">
-    <div class="row">%content%</div>
-    <div class="row" id="footer">
-        <div class="col-md-12">
-            <hr/>
-            <div class="text-center footer" style="margin-bottom: 10px;">
-                %event_info%
-                <a href="%faq_url%">FAQ</a>
-                · <a href="%contact_email%"><span class="glyphicon glyphicon-envelope"></span> Contact</a>
-                · <a href="https://github.com/engelsystem/engelsystem/issues">Bugs / Features</a>
-                · <a href="https://github.com/engelsystem/engelsystem/">Development Platform</a>
-                · <a href="%credits_url%">Credits</a>
-            </div>
-        </div>
-    </div>
-</div>
-</body>
-</html>
diff --git a/templates/layouts/app.twig b/templates/layouts/app.twig
new file mode 100644
index 00000000..42d5610c
--- /dev/null
+++ b/templates/layouts/app.twig
@@ -0,0 +1,87 @@
+{% set theme = user.color|default(config('theme')) %}
+<!DOCTYPE html>
+<html>
+<head>
+    {% block head %}
+        <title>{% block title %}{{ title }}{% endblock %} - Engelsystem</title>
+        <meta charset="UTF-8"/>
+        <meta name="viewport" content="width=device-width, initial-scale=1">
+        <link rel="stylesheet" type="text/css" href="css/theme{{ theme }}.css"/>
+        <link rel="stylesheet" type="text/css" href="vendor/icomoon/style.css"/>
+        <link rel="stylesheet" type="text/css" href="vendor/bootstrap-datepicker-1.7.1/css/bootstrap-datepicker3.min.css"/>
+        <script type="text/javascript" src="vendor/jquery-2.1.1.min.js"></script>
+        <script type="text/javascript" src="vendor/jquery-ui.min.js"></script>
+        {% if atom_feed -%}
+            <link href="{{ url('atom', atom_feed) }}" type="application/atom+xml" rel="alternate" title="Atom Feed">
+        {% endif %}
+    {% endblock %}
+</head>
+<body>
+
+{% block body %}
+    <div class="navbar navbar-default navbar-fixed-top">
+        {% block header %}
+            <div class="container-fluid">
+                <div class="navbar-header">
+                    <button type="button" class="navbar-toggle collapsed"
+                            data-toggle="collapse" data-target="#navbar-collapse-1">
+                        <span class="sr-only">Toggle navigation</span>
+                        <span class="icon-bar"></span>
+                        <span class="icon-bar"></span>
+                        <span class="icon-bar"></span>
+                    </button>
+                    <a class="navbar-brand" href="{{ url('/') }}">
+                        <span class="icon-icon_angel"></span> <strong class="visible-lg-inline">ENGELSYSTEM</strong>
+                    </a>
+                </div>
+
+                {% block navbar %}
+                    <div class="collapse navbar-collapse" id="navbar-collapse-1">
+                        {{ menu|raw }}
+                        {{ header_toolbar|raw }}
+                    </div>
+                {% endblock %}
+            </div>
+        {% endblock %}
+    </div>
+
+    <div class="container-fluid">
+        <div class="row">{% block content %}{{ content|raw }}{% endblock %}</div>
+        <div class="row" id="footer">
+            {% block footer %}
+                <div class="col-md-12">
+                    <hr/>
+                    <div class="text-center footer" style="margin-bottom: 10px;">
+                        {% block eventinfo %}
+                            {{ event_info|raw }}
+                        {% endblock %}
+                        <a href="{{ config('faq_url') }}">FAQ</a>
+                        · <a href="{{ config('contact_email') }}">
+                            <span class="glyphicon glyphicon-envelope"></span>Contact
+                          </a>
+                        · <a href="https://github.com/engelsystem/engelsystem/issues">Bugs / Features</a>
+                        · <a href="https://github.com/engelsystem/engelsystem/">Development Platform</a>
+                        · <a href="{{ url('credits') }}">Credits</a>
+                    </div>
+                </div>
+            {% endblock %}
+        </div>
+    </div>
+
+    <script type="text/javascript" src="vendor/bootstrap/js/bootstrap.min.js"></script>
+    <script type="text/javascript" src="vendor/bootstrap-datepicker-1.7.1/js/bootstrap-datepicker.min.js"></script>
+    <script type="text/javascript" src="vendor/bootstrap-datepicker-1.7.1/locales/bootstrap-datepicker.de.min.js"></script>
+    <script type="text/javascript" src="vendor/Chart.min.js"></script>
+    <script type="text/javascript" src="js/forms.js"></script>
+    <script type="text/javascript" src="vendor/moment-with-locales.min.js"></script>
+    <script type="text/javascript">
+        $(function () {
+            moment.locale("{{ session_get('locale')|escape('js') }}");
+        });
+    </script>
+    <script type="text/javascript" src="js/moment-countdown.js"></script>
+    <script type="text/javascript" src="js/sticky-headers.js"></script>
+{% endblock %}
+
+</body>
+</html>
diff --git a/templates/maintenance.html b/templates/layouts/maintenance.html
index f7ab5772..f7ab5772 100644
--- a/templates/maintenance.html
+++ b/templates/layouts/maintenance.html
diff --git a/templates/guest_credits.html b/templates/pages/credits.html
index db7fac57..4e247113 100644
--- a/templates/guest_credits.html
+++ b/templates/pages/credits.html
@@ -6,15 +6,15 @@
             <p>
                 The original system was written by <a href="https://github.com/cookieBerlin/engelsystem">cookie</a>.
                 It was then completely rewritten and enhanced by
-                <a href="http://notrademark.de/">msquare</a> (maintainer),
-                <a href="http://myigel.name/">MyIgel</a>,
-                <a href="http://mortzu.de/">mortzu</a>,
-                <a href="http://jplitza.de/">jplitza</a> and
-                gnomus.
+                <a href="https://notrademark.de">msquare</a> (maintainer),
+                <a href="https://myigel.name">MyIgel</a>,
+                <a href="https://mortzu.de">mortzu</a>,
+                <a href="https://jplitza.de">jplitza</a> and
+                <a href="https://github.com/gnomus">gnomus</a>.
             </p>
             <p>
-                Please look at the <a href="https://github.com/engelsystem/engelsystem/graphs/contributors">contributor
-                list on github</a> for a more complete version.
+                Please look at the <a href="https://github.com/engelsystem/engelsystem/graphs/contributors">
+                contributor list on github</a> for a more complete version.
             </p>
         </div>
         <div class="col-md-4">
@@ -22,8 +22,8 @@
             <p>
                 Webspace, development platform and domain on <a href="https://engelsystem.de">engelsystem.de</a>
                 is currently provided by <a href="https://www.wybt.net/">would you buy this?</a> (ichdasich)
-                and adminstrated by <a href="http://mortzu.de/">mortzu</a>,
-                <a href="http://derf.homelinux.org/">derf</a> and ichdasich.
+                and adminstrated by <a href="https://mortzu.de">mortzu</a>,
+                <a href="http://derf.homelinux.org">derf</a> and ichdasich.
             </p>
         </div>
         <div class="col-md-4">
diff --git a/templates/user_shifts.html b/templates/pages/user-shifts.html
index 2fdade29..2fdade29 100644
--- a/templates/user_shifts.html
+++ b/templates/pages/user-shifts.html
diff --git a/tests/Unit/ApplicationTest.php b/tests/Unit/ApplicationTest.php
index 866eb957..012226b2 100644
--- a/tests/Unit/ApplicationTest.php
+++ b/tests/Unit/ApplicationTest.php
@@ -48,6 +48,7 @@ class ApplicationTest extends TestCase
         $this->assertTrue($app->has('path'));
         $this->assertTrue($app->has('path.config'));
         $this->assertTrue($app->has('path.lang'));
+        $this->assertTrue($app->has('path.views'));
 
         $this->assertEquals(realpath('.'), $app->path());
         $this->assertEquals(realpath('.') . '/config', $app->get('path.config'));
diff --git a/tests/Unit/Config/ConfigServiceProviderTest.php b/tests/Unit/Config/ConfigServiceProviderTest.php
index 998c0ba1..925854be 100644
--- a/tests/Unit/Config/ConfigServiceProviderTest.php
+++ b/tests/Unit/Config/ConfigServiceProviderTest.php
@@ -24,8 +24,13 @@ class ConfigServiceProviderTest extends ServiceProviderTest
         Application::setInstance($app);
 
         $this->setExpects($app, 'make', [Config::class], $config);
-        $this->setExpects($app, 'instance', ['config', $config]);
         $this->setExpects($app, 'get', ['path.config'], __DIR__ . '/../../../config', $this->atLeastOnce());
+        $app->expects($this->exactly(2))
+            ->method('instance')
+            ->withConsecutive(
+                [Config::class, $config],
+                ['config', $config]
+            );
 
         $this->setExpects($config, 'set', null, null, $this->exactly(2));
         $config->expects($this->exactly(3))
@@ -60,7 +65,12 @@ class ConfigServiceProviderTest extends ServiceProviderTest
         Application::setInstance($app);
 
         $this->setExpects($app, 'make', [Config::class], $config);
-        $this->setExpects($app, 'instance', ['config', $config]);
+        $app->expects($this->exactly(2))
+            ->method('instance')
+            ->withConsecutive(
+              [Config::class, $config],
+              ['config', $config]
+            );
         $this->setExpects($app, 'get', ['path.config'], __DIR__ . '/not_existing', $this->atLeastOnce());
 
         $this->setExpects($config, 'set', null, null, $this->never());
diff --git a/tests/Unit/Helpers/TranslationServiceProviderTest.php b/tests/Unit/Helpers/TranslationServiceProviderTest.php
new file mode 100644
index 00000000..c5ba7386
--- /dev/null
+++ b/tests/Unit/Helpers/TranslationServiceProviderTest.php
@@ -0,0 +1,86 @@
+<?php
+
+namespace Engelsystem\Test\Unit\Helpers;
+
+use Engelsystem\Config\Config;
+use Engelsystem\Helpers\TranslationServiceProvider;
+use Engelsystem\Helpers\Translator;
+use Engelsystem\Test\Unit\ServiceProviderTest;
+use PHPUnit\Framework\MockObject\MockObject;
+use Symfony\Component\HttpFoundation\Session\Session;
+
+class TranslationServiceProviderTest extends ServiceProviderTest
+{
+    /**
+     * @covers \Engelsystem\Helpers\TranslationServiceProvider::register()
+     */
+    public function testRegister()
+    {
+        $app = $this->getApp(['make', 'instance', 'get']);
+        /** @var Config|MockObject $config */
+        $config = $this->createMock(Config::class);
+        /** @var Session|MockObject $session */
+        $session = $this->createMock(Session::class);
+        /** @var Translator|MockObject $translator */
+        $translator = $this->createMock(Translator::class);
+
+        /** @var TranslationServiceProvider|MockObject $serviceProvider */
+        $serviceProvider = $this->getMockBuilder(TranslationServiceProvider::class)
+            ->setConstructorArgs([$app])
+            ->setMethods(['initGettext', 'setLocale'])
+            ->getMock();
+
+        $serviceProvider->expects($this->once())
+            ->method('initGettext');
+
+        $app->expects($this->exactly(2))
+            ->method('get')
+            ->withConsecutive(['config'], ['session'])
+            ->willReturnOnConsecutiveCalls($config, $session);
+
+        $defaultLocale = 'fo_OO';
+        $locale = 'te_ST.WTF-9';
+        $locales = ['fo_OO' => 'Foo', 'fo_OO.BAR' => 'Foo (Bar)', 'te_ST.WTF-9' => 'WTF\'s Testing?'];
+        $config->expects($this->exactly(2))
+            ->method('get')
+            ->withConsecutive(
+                ['locales'],
+                ['default_locale']
+            )
+            ->willReturnOnConsecutiveCalls(
+                $locales,
+                $defaultLocale
+            );
+
+        $session->expects($this->once())
+            ->method('get')
+            ->with('locale', $defaultLocale)
+            ->willReturn($locale);
+        $session->expects($this->once())
+            ->method('set')
+            ->with('locale', $locale);
+
+        $app->expects($this->once())
+            ->method('make')
+            ->with(
+                Translator::class,
+                [
+                    'locale'               => $locale,
+                    'locales'              => $locales,
+                    'localeChangeCallback' => [$serviceProvider, 'setLocale']
+                ]
+            )
+            ->willReturn($translator);
+
+        $app->expects($this->exactly(2))
+            ->method('instance')
+            ->withConsecutive(
+                [Translator::class, $translator],
+                ['translator', $translator]
+            );
+
+        $serviceProvider->register();
+    }
+}
+
+
diff --git a/tests/Unit/Helpers/TranslatorTest.php b/tests/Unit/Helpers/TranslatorTest.php
new file mode 100644
index 00000000..396d2b65
--- /dev/null
+++ b/tests/Unit/Helpers/TranslatorTest.php
@@ -0,0 +1,69 @@
+<?php
+
+namespace Engelsystem\Test\Unit\Helpers;
+
+use Engelsystem\Helpers\Translator;
+use Engelsystem\Test\Unit\ServiceProviderTest;
+use PHPUnit\Framework\MockObject\MockObject;
+use stdClass;
+
+class TranslatorTest extends ServiceProviderTest
+{
+    /**
+     * @covers \Engelsystem\Helpers\Translator::__construct()
+     * @covers \Engelsystem\Helpers\Translator::setLocale()
+     * @covers \Engelsystem\Helpers\Translator::setLocales()
+     * @covers \Engelsystem\Helpers\Translator::getLocale()
+     * @covers \Engelsystem\Helpers\Translator::getLocales()
+     * @covers \Engelsystem\Helpers\Translator::hasLocale()
+     */
+    public function testInit()
+    {
+        $locales = ['te_ST.ER-01' => 'Tests', 'fo_OO' => 'SomeFOO'];
+        $locale = 'te_ST.ER-01';
+
+        /** @var callable|MockObject $callable */
+        $callable = $this->getMockBuilder(stdClass::class)
+            ->setMethods(['__invoke'])
+            ->getMock();
+        $callable->expects($this->exactly(2))
+            ->method('__invoke')
+            ->withConsecutive(['te_ST.ER-01'], ['fo_OO']);
+
+        $translator = new Translator($locale, $locales, $callable);
+
+        $this->assertEquals($locales, $translator->getLocales());
+        $this->assertEquals($locale, $translator->getLocale());
+
+        $translator->setLocale('fo_OO');
+        $this->assertEquals('fo_OO', $translator->getLocale());
+
+        $newLocales = ['lo_RM' => 'Lorem', 'ip_SU-M' => 'Ipsum'];
+        $translator->setLocales($newLocales);
+        $this->assertEquals($newLocales, $translator->getLocales());
+
+        $this->assertTrue($translator->hasLocale('ip_SU-M'));
+        $this->assertFalse($translator->hasLocale('te_ST.ER-01'));
+    }
+
+    /**
+     * @covers \Engelsystem\Helpers\Translator::translate()
+     */
+    public function testTranslate()
+    {
+        /** @var Translator|MockObject $translator */
+        $translator = $this->getMockBuilder(Translator::class)
+            ->setConstructorArgs(['de_DE.UTF-8', ['de_DE.UTF-8' => 'Deutsch']])
+            ->setMethods(['translateGettext'])
+            ->getMock();
+        $translator->expects($this->once())
+            ->method('translateGettext')
+            ->with('My favourite number is %u!')
+            ->willReturn('Meine Lieblingszahl ist die %u!');
+
+        $return = $translator->translate('My favourite number is %u!', [3]);
+        $this->assertEquals('Meine Lieblingszahl ist die 3!', $return);
+    }
+}
+
+
diff --git a/tests/Unit/HelpersTest.php b/tests/Unit/HelpersTest.php
index fb9e6f00..b9cedd30 100644
--- a/tests/Unit/HelpersTest.php
+++ b/tests/Unit/HelpersTest.php
@@ -5,10 +5,10 @@ namespace Engelsystem\Test\Unit;
 use Engelsystem\Application;
 use Engelsystem\Config\Config;
 use Engelsystem\Container\Container;
+use Engelsystem\Helpers\Translator;
 use Engelsystem\Http\Request;
 use Engelsystem\Http\Response;
 use Engelsystem\Renderer\Renderer;
-use Engelsystem\Http\UrlGenerator;
 use Engelsystem\Http\UrlGeneratorInterface;
 use PHPUnit\Framework\TestCase;
 use PHPUnit_Framework_MockObject_MockObject as MockObject;
@@ -196,6 +196,29 @@ class HelpersTest extends TestCase
     }
 
     /**
+     * @covers \__
+     * @covers \trans
+     */
+    public function testTrans()
+    {
+        /** @var Translator|MockObject $translator */
+        $translator = $this->getMockBuilder(Translator::class)
+            ->disableOriginalConstructor()
+            ->getMock();
+
+        $this->getAppMock('translator', $translator);
+
+        $translator->expects($this->exactly(2))
+            ->method('translate')
+            ->with('Lorem %s Ipsum', ['foo'])
+            ->willReturn('Lorem foo Ipsum');
+
+        $this->assertEquals($translator, trans());
+        $this->assertEquals('Lorem foo Ipsum', trans('Lorem %s Ipsum', ['foo']));
+        $this->assertEquals('Lorem foo Ipsum', __('Lorem %s Ipsum', ['foo']));
+    }
+
+    /**
      * @covers \url
      */
     public function testUrl()
diff --git a/tests/Unit/Http/ResponseTest.php b/tests/Unit/Http/ResponseTest.php
index f6c24767..d7dc37c0 100644
--- a/tests/Unit/Http/ResponseTest.php
+++ b/tests/Unit/Http/ResponseTest.php
@@ -3,6 +3,8 @@
 namespace Engelsystem\Test\Unit\Http;
 
 use Engelsystem\Http\Response;
+use Engelsystem\Renderer\Renderer;
+use PHPUnit\Framework\MockObject\MockObject;
 use PHPUnit\Framework\TestCase;
 use Psr\Http\Message\ResponseInterface;
 use Symfony\Component\HttpFoundation\Response as SymfonyResponse;
@@ -46,4 +48,37 @@ class ResponseTest extends TestCase
         $this->assertNotEquals($response, $newResponse);
         $this->assertEquals('Lorem Ipsum?', $newResponse->getContent());
     }
-}
+
+    /**
+     * @covers \Engelsystem\Http\Response::withView
+     */
+    public function testWithView()
+    {
+        /** @var REnderer|MockObject $renderer */
+        $renderer = $this->createMock(Renderer::class);
+
+        $renderer->expects($this->once())
+            ->method('render')
+            ->with('foo', ['lorem' => 'ipsum'])
+            ->willReturn('Foo ipsum!');
+
+        $response = new Response('', 200, [], $renderer);
+        $newResponse = $response->withView('foo', ['lorem' => 'ipsum'], 505, ['test' => 'er']);
+
+        $this->assertNotEquals($response, $newResponse);
+        $this->assertEquals('Foo ipsum!', $newResponse->getContent());
+        $this->assertEquals(505, $newResponse->getStatusCode());
+        $this->assertArraySubset(['test' => ['er']], $newResponse->getHeaders());
+    }
+
+    /**
+     * @covers \Engelsystem\Http\Response::withView
+     */
+    public function testWithViewNoRenderer()
+    {
+        $this->expectException(\InvalidArgumentException::class);
+
+        $response = new Response();
+        $response->withView('foo');
+    }
+}
\ No newline at end of file
diff --git a/tests/Unit/Http/SessionServiceProviderTest.php b/tests/Unit/Http/SessionServiceProviderTest.php
index a78b4f72..d0125bc2 100644
--- a/tests/Unit/Http/SessionServiceProviderTest.php
+++ b/tests/Unit/Http/SessionServiceProviderTest.php
@@ -54,6 +54,7 @@ class SessionServiceProviderTest extends ServiceProviderTest
             ->method('instance')
             ->withConsecutive(
                 ['session.storage', $sessionStorage],
+                [Session::class, $session],
                 ['session', $session]
             );
 
@@ -88,10 +89,11 @@ class SessionServiceProviderTest extends ServiceProviderTest
                 $sessionStorage,
                 $session
             );
-        $app->expects($this->exactly(2))
+        $app->expects($this->exactly(3))
             ->method('instance')
             ->withConsecutive(
                 ['session.storage', $sessionStorage],
+                [Session::class, $session],
                 ['session', $session]
             );
 
diff --git a/tests/Unit/Http/UrlGeneratorServiceProviderTest.php b/tests/Unit/Http/UrlGeneratorServiceProviderTest.php
index 874268b0..720af631 100644
--- a/tests/Unit/Http/UrlGeneratorServiceProviderTest.php
+++ b/tests/Unit/Http/UrlGeneratorServiceProviderTest.php
@@ -21,7 +21,12 @@ class UrlGeneratorServiceProviderTest extends ServiceProviderTest
         $app = $this->getApp();
 
         $this->setExpects($app, 'make', [UrlGenerator::class], $urlGenerator);
-        $this->setExpects($app, 'instance', ['http.urlGenerator', $urlGenerator]);
+        $app->expects($this->exactly(2))
+            ->method('instance')
+            ->withConsecutive(
+                [UrlGenerator::class, $urlGenerator],
+                ['http.urlGenerator', $urlGenerator]
+            );
 
         $serviceProvider = new UrlGeneratorServiceProvider($app);
         $serviceProvider->register();
diff --git a/tests/Unit/Middleware/ErrorHandlerTest.php b/tests/Unit/Middleware/ErrorHandlerTest.php
new file mode 100644
index 00000000..abf9c52f
--- /dev/null
+++ b/tests/Unit/Middleware/ErrorHandlerTest.php
@@ -0,0 +1,88 @@
+<?php
+
+namespace Engelsystem\Test\Unit\Middleware;
+
+use Engelsystem\Http\Response;
+use Engelsystem\Middleware\ErrorHandler;
+use Engelsystem\Test\Unit\Middleware\Stub\ReturnResponseMiddlewareHandler;
+use PHPUnit\Framework\MockObject\MockObject;
+use PHPUnit\Framework\TestCase;
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\ServerRequestInterface;
+use Twig_LoaderInterface as TwigLoader;
+
+class ErrorHandlerTest extends TestCase
+{
+    /**
+     * @covers \Engelsystem\Middleware\ErrorHandler::__construct
+     * @covers \Engelsystem\Middleware\ErrorHandler::process
+     * @covers \Engelsystem\Middleware\ErrorHandler::selectView
+     */
+    public function testProcess()
+    {
+        /** @var TwigLoader|MockObject $twigLoader */
+        $twigLoader = $this->createMock(TwigLoader::class);
+        /** @var ServerRequestInterface|MockObject $request */
+        $request = $this->createMock(ServerRequestInterface::class);
+        /** @var ResponseInterface|MockObject $psrResponse */
+        $psrResponse = $this->getMockForAbstractClass(ResponseInterface::class);
+        $returnResponseHandler = new ReturnResponseMiddlewareHandler($psrResponse);
+
+        $psrResponse->expects($this->once())
+            ->method('getStatusCode')
+            ->willReturn(505);
+
+        $errorHandler = new ErrorHandler($twigLoader);
+
+        $return = $errorHandler->process($request, $returnResponseHandler);
+        $this->assertEquals($psrResponse, $return, 'Plain PSR-7 Response should be passed directly');
+
+        /** @var Response|MockObject $response */
+        $response = $this->createMock(Response::class);
+
+        $response->expects($this->exactly(3))
+            ->method('getStatusCode')
+            ->willReturnOnConsecutiveCalls(
+                200,
+                418,
+                505
+            );
+
+        $returnResponseHandler->setResponse($response);
+        $return = $errorHandler->process($request, $returnResponseHandler);
+        $this->assertEquals($response, $return, 'Only Responses >= 400 should be processed');
+
+        $twigLoader->expects($this->exactly(4))
+            ->method('exists')
+            ->withConsecutive(
+                ['errors/418'],
+                ['errors/4'],
+                ['errors/400'],
+                ['errors/505']
+            )
+            ->willReturnOnConsecutiveCalls(
+                false,
+                false,
+                false,
+                true
+            );
+
+        $response->expects($this->exactly(2))
+            ->method('getContent')
+            ->willReturnOnConsecutiveCalls(
+                'Teapot',
+                'Internal Error!'
+            );
+
+        $response->expects($this->exactly(2))
+            ->method('withView')
+            ->withConsecutive(
+                ['errors/default', ['status' => 418, 'content' => 'Teapot'], 418],
+                ['errors/505', ['status' => 505, 'content' => 'Internal Error!'], 505]
+            )
+            ->willReturn($response);
+
+        $errorHandler->process($request, $returnResponseHandler);
+        $errorHandler->process($request, $returnResponseHandler);
+    }
+}
diff --git a/tests/Unit/Middleware/SetLocaleTest.php b/tests/Unit/Middleware/SetLocaleTest.php
new file mode 100644
index 00000000..c4e9d2a4
--- /dev/null
+++ b/tests/Unit/Middleware/SetLocaleTest.php
@@ -0,0 +1,71 @@
+<?php
+
+namespace Engelsystem\Test\Unit\Middleware;
+
+use Engelsystem\Helpers\Translator;
+use Engelsystem\Middleware\SetLocale;
+use PHPUnit\Framework\TestCase;
+use PHPUnit_Framework_MockObject_MockObject as MockObject;
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\ServerRequestInterface;
+use Psr\Http\Server\RequestHandlerInterface;
+use Symfony\Component\HttpFoundation\Session\Session;
+
+class SetLocaleTest extends TestCase
+{
+    /**
+     * @covers \Engelsystem\Middleware\SetLocale::__construct
+     * @covers \Engelsystem\Middleware\SetLocale::process
+     */
+    public function testRegister()
+    {
+        /** @var Translator|MockObject $translator */
+        $translator = $this->createMock(Translator::class);
+        /** @var Session|MockObject $session */
+        $session = $this->createMock(Session::class);
+        /** @var ServerRequestInterface|MockObject $request */
+        $request = $this->getMockForAbstractClass(ServerRequestInterface::class);
+        /** @var RequestHandlerInterface|MockObject $handler */
+        $handler = $this->getMockForAbstractClass(RequestHandlerInterface::class);
+        /** @var ResponseInterface|MockObject $response */
+        $response = $this->getMockForAbstractClass(ResponseInterface::class);
+
+        $locale = 'te_ST.UTF8';
+
+        $request->expects($this->exactly(3))
+            ->method('getQueryParams')
+            ->willReturnOnConsecutiveCalls(
+                [],
+                ['set-locale' => 'en_US.UTF8'],
+                ['set-locale' => $locale]
+            );
+
+        $translator->expects($this->exactly(2))
+            ->method('hasLocale')
+            ->withConsecutive(
+                ['en_US.UTF8'],
+                [$locale]
+            )
+            ->willReturnOnConsecutiveCalls(
+                false,
+                true
+            );
+        $translator->expects($this->once())
+            ->method('setLocale')
+            ->with($locale);
+
+        $session->expects($this->once())
+            ->method('set')
+            ->with('locale', $locale);
+
+        $handler->expects($this->exactly(3))
+            ->method('handle')
+            ->with($request)
+            ->willReturn($response);
+
+        $middleware = new SetLocale($translator, $session);
+        $middleware->process($request, $handler);
+        $middleware->process($request, $handler);
+        $middleware->process($request, $handler);
+    }
+}
diff --git a/tests/Unit/Middleware/Stub/ReturnResponseMiddlewareHandler.php b/tests/Unit/Middleware/Stub/ReturnResponseMiddlewareHandler.php
index 323e07b4..370187dd 100644
--- a/tests/Unit/Middleware/Stub/ReturnResponseMiddlewareHandler.php
+++ b/tests/Unit/Middleware/Stub/ReturnResponseMiddlewareHandler.php
@@ -27,4 +27,14 @@ class ReturnResponseMiddlewareHandler implements RequestHandlerInterface
     {
         return $this->response;
     }
+
+    /**
+     * Set the response
+     *
+     * @param ResponseInterface $response
+     */
+    public function setResponse(ResponseInterface $response)
+    {
+        $this->response = $response;
+    }
 }
diff --git a/tests/Unit/Renderer/RendererServiceProviderTest.php b/tests/Unit/Renderer/RendererServiceProviderTest.php
index 3826da7e..6cdf4363 100644
--- a/tests/Unit/Renderer/RendererServiceProviderTest.php
+++ b/tests/Unit/Renderer/RendererServiceProviderTest.php
@@ -37,10 +37,12 @@ class RendererServiceProviderTest extends ServiceProviderTest
                 $htmlEngine
             );
 
-        $app->expects($this->exactly(2))
+        $app->expects($this->exactly(4))
             ->method('instance')
             ->withConsecutive(
+                [Renderer::class, $renderer],
                 ['renderer', $renderer],
+                [HtmlEngine::class, $htmlEngine],
                 ['renderer.htmlEngine', $htmlEngine]
             );
 
diff --git a/tests/Unit/Renderer/Twig/Extensions/ConfigTest.php b/tests/Unit/Renderer/Twig/Extensions/ConfigTest.php
new file mode 100644
index 00000000..6a9cb78a
--- /dev/null
+++ b/tests/Unit/Renderer/Twig/Extensions/ConfigTest.php
@@ -0,0 +1,25 @@
+<?php
+
+namespace Engelsystem\Test\Unit\Renderer\Twig\Extensions;
+
+use Engelsystem\Config\Config as EngelsystemConfig;
+use Engelsystem\Renderer\Twig\Extensions\Config;
+use PHPUnit\Framework\MockObject\MockObject;
+
+class ConfigTest extends ExtensionTest
+{
+    /**
+     * @covers \Engelsystem\Renderer\Twig\Extensions\Config::__construct
+     * @covers \Engelsystem\Renderer\Twig\Extensions\Config::getFunctions
+     */
+    public function testGetFunctions()
+    {
+        /** @var EngelsystemConfig|MockObject $config */
+        $config = $this->createMock(EngelsystemConfig::class);
+
+        $extension = new Config($config);
+        $functions = $extension->getFunctions();
+
+        $this->assertExtensionExists('config', [$config, 'get'], $functions);
+    }
+}
diff --git a/tests/Unit/Renderer/Twig/Extensions/ExtensionTest.php b/tests/Unit/Renderer/Twig/Extensions/ExtensionTest.php
new file mode 100644
index 00000000..e1c5a378
--- /dev/null
+++ b/tests/Unit/Renderer/Twig/Extensions/ExtensionTest.php
@@ -0,0 +1,84 @@
+<?php
+
+namespace Engelsystem\Test\Unit\Renderer\Twig\Extensions;
+
+use PHPUnit\Framework\TestCase;
+use Twig_Function as TwigFunction;
+
+abstract class ExtensionTest extends TestCase
+{
+    /**
+     * Assert that a twig filter was registered
+     *
+     * @param string         $name
+     * @param callable       $callback
+     * @param TwigFunction[] $functions
+     */
+    protected function assertFilterExists($name, $callback, $functions)
+    {
+        foreach ($functions as $function) {
+            if ($function->getName() != $name) {
+                continue;
+            }
+
+            $this->assertEquals($callback, $function->getCallable());
+            return;
+        }
+
+        $this->fail(sprintf('Filter %s not found', $name));
+    }
+
+    /**
+     * Assert that a twig function was registered
+     *
+     * @param string         $name
+     * @param callable       $callback
+     * @param TwigFunction[] $functions
+     */
+    protected function assertExtensionExists($name, $callback, $functions)
+    {
+        foreach ($functions as $function) {
+            if ($function->getName() != $name) {
+                continue;
+            }
+
+            $this->assertEquals($callback, $function->getCallable());
+            return;
+        }
+
+        $this->fail(sprintf('Function %s not found', $name));
+    }
+
+    /**
+     * Assert that a global exists
+     *
+     * @param string  $name
+     * @param mixed   $value
+     * @param mixed[] $globals
+     */
+    protected function assertGlobalsExists($name, $value, $globals)
+    {
+        if (isset($globals[$name])) {
+            $this->assertArraySubset([$name => $value], $globals);
+
+            return;
+        }
+
+        $this->fail(sprintf('Global %s not found', $name));
+    }
+
+    /**
+     * Assert that a token parser was set
+     *
+     * @param $tokenParser
+     * @param $tokenParsers
+     */
+    protected function assertTokenParserExists($tokenParser, $tokenParsers)
+    {
+        $this->assertArraySubset(
+            [$tokenParser],
+            $tokenParsers,
+            sprintf('Token parser %s not found', get_class($tokenParser))
+        );
+    }
+}
diff --git a/tests/Unit/Renderer/Twig/Extensions/GlobalsTest.php b/tests/Unit/Renderer/Twig/Extensions/GlobalsTest.php
new file mode 100644
index 00000000..6cc3a4da
--- /dev/null
+++ b/tests/Unit/Renderer/Twig/Extensions/GlobalsTest.php
@@ -0,0 +1,25 @@
+<?php
+
+namespace Engelsystem\Test\Unit\Renderer\Twig\Extensions;
+
+use Engelsystem\Renderer\Twig\Extensions\Globals;
+
+class GlobalsTest extends ExtensionTest
+{
+    /**
+     * @covers \Engelsystem\Renderer\Twig\Extensions\Globals::getGlobals
+     */
+    public function testGetGlobals()
+    {
+        $extension = new Globals();
+        $globals = $extension->getGlobals();
+
+        $this->assertGlobalsExists('user', [], $globals);
+
+        global $user;
+        $user['foo'] = 'bar';
+
+        $globals = $extension->getGlobals();
+        $this->assertGlobalsExists('user', ['foo' => 'bar'], $globals);
+    }
+}
diff --git a/tests/Unit/Renderer/Twig/Extensions/SessionTest.php b/tests/Unit/Renderer/Twig/Extensions/SessionTest.php
new file mode 100644
index 00000000..7ce4dc3a
--- /dev/null
+++ b/tests/Unit/Renderer/Twig/Extensions/SessionTest.php
@@ -0,0 +1,25 @@
+<?php
+
+namespace Engelsystem\Test\Unit\Renderer\Twig\Extensions;
+
+use Engelsystem\Renderer\Twig\Extensions\Session;
+use PHPUnit\Framework\MockObject\MockObject;
+use Symfony\Component\HttpFoundation\Session\Session as SymfonySession;
+
+class SessionTest extends ExtensionTest
+{
+    /**
+     * @covers \Engelsystem\Renderer\Twig\Extensions\Session::__construct
+     * @covers \Engelsystem\Renderer\Twig\Extensions\Session::getFunctions
+     */
+    public function testGetGlobals()
+    {
+        /** @var SymfonySession|MockObject $session */
+        $session = $this->createMock(SymfonySession::class);
+
+        $extension = new Session($session);
+        $functions = $extension->getFunctions();
+
+        $this->assertExtensionExists('session_get', [$session, 'get'], $functions);
+    }
+}
diff --git a/tests/Unit/Renderer/Twig/Extensions/TranslationTest.php b/tests/Unit/Renderer/Twig/Extensions/TranslationTest.php
new file mode 100644
index 00000000..f1548604
--- /dev/null
+++ b/tests/Unit/Renderer/Twig/Extensions/TranslationTest.php
@@ -0,0 +1,60 @@
+<?php
+
+namespace Engelsystem\Test\Unit\Renderer\Twig\Extensions;
+
+use Engelsystem\Helpers\Translator;
+use Engelsystem\Renderer\Twig\Extensions\Translation;
+use PHPUnit\Framework\MockObject\MockObject;
+use Twig_Extensions_TokenParser_Trans as TranslationTokenParser;
+
+class TranslationTest extends ExtensionTest
+{
+    /**
+     * @covers \Engelsystem\Renderer\Twig\Extensions\Translation::__construct
+     * @covers \Engelsystem\Renderer\Twig\Extensions\Translation::getFilters
+     */
+    public function testGeFilters()
+    {
+        /** @var Translator|MockObject $translator */
+        $translator = $this->createMock(Translator::class);
+        /** @var TranslationTokenParser|MockObject $parser */
+        $parser = $this->createMock(TranslationTokenParser::class);
+
+        $extension = new Translation($translator, $parser);
+        $filters = $extension->getFilters();
+
+        $this->assertExtensionExists('trans', [$translator, 'translate'], $filters);
+    }
+
+    /**
+     * @covers \Engelsystem\Renderer\Twig\Extensions\Translation::getFunctions
+     */
+    public function testGetFunctions()
+    {
+        /** @var Translator|MockObject $translator */
+        $translator = $this->createMock(Translator::class);
+        /** @var TranslationTokenParser|MockObject $parser */
+        $parser = $this->createMock(TranslationTokenParser::class);
+
+        $extension = new Translation($translator, $parser);
+        $functions = $extension->getFunctions();
+
+        $this->assertExtensionExists('__', [$translator, 'translate'], $functions);
+    }
+
+    /**
+     * @covers \Engelsystem\Renderer\Twig\Extensions\Translation::getTokenParsers
+     */
+    public function testGetTokenParsers()
+    {
+        /** @var Translator|MockObject $translator */
+        $translator = $this->createMock(Translator::class);
+        /** @var TranslationTokenParser|MockObject $parser */
+        $parser = $this->createMock(TranslationTokenParser::class);
+
+        $extension = new Translation($translator, $parser);
+        $tokenParsers = $extension->getTokenParsers();
+
+        $this->assertTokenParserExists($parser, $tokenParsers);
+    }
+}
diff --git a/tests/Unit/Renderer/Twig/Extensions/UrlTest.php b/tests/Unit/Renderer/Twig/Extensions/UrlTest.php
new file mode 100644
index 00000000..c7e40bea
--- /dev/null
+++ b/tests/Unit/Renderer/Twig/Extensions/UrlTest.php
@@ -0,0 +1,64 @@
+<?php
+
+namespace Engelsystem\Test\Unit\Renderer\Twig\Extensions;
+
+use Engelsystem\Http\UrlGenerator;
+use Engelsystem\Renderer\Twig\Extensions\Url;
+use PHPUnit\Framework\MockObject\MockObject;
+
+class UrlTest extends ExtensionTest
+{
+    /**
+     * @covers \Engelsystem\Renderer\Twig\Extensions\Url::__construct
+     * @covers \Engelsystem\Renderer\Twig\Extensions\Url::getFunctions
+     */
+    public function testGetGlobals()
+    {
+        /** @var UrlGenerator|MockObject $urlGenerator */
+        $urlGenerator = $this->createMock(UrlGenerator::class);
+
+        $extension = new Url($urlGenerator);
+        $functions = $extension->getFunctions();
+
+        $this->assertExtensionExists('url', [$extension, 'getUrl'], $functions);
+    }
+
+    /**
+     * @return string[][]
+     */
+    public function getUrls()
+    {
+        return [
+            ['/', '/', 'http://foo.bar/'],
+            ['/foo', '/foo', 'http://foo.bar/foo'],
+            ['foo_bar', 'foo-bar', 'http://foo.bar/foo-bar'],
+            ['dolor', 'dolor', 'http://foo.bar/dolor?lorem_ipsum=dolor', ['lorem_ipsum' => 'dolor']],
+        ];
+    }
+
+    /**
+     * @dataProvider getUrls
+     *
+     * @param string $url
+     * @param string $return
+     * @param string $urlTo
+     * @param array  $parameters
+     *
+     * @covers       \Engelsystem\Renderer\Twig\Extensions\Url::getUrl
+     */
+    public function testGetUrl($url, $urlTo, $return, $parameters = [])
+    {
+        /** @var UrlGenerator|MockObject $urlGenerator */
+        $urlGenerator = $this->createMock(UrlGenerator::class);
+
+        $urlGenerator->expects($this->once())
+            ->method('to')
+            ->with($urlTo, $parameters)
+            ->willReturn($return);
+
+        $extension = new Url($urlGenerator);
+        $generatedUrl = $extension->getUrl($url, $parameters);
+
+        $this->assertEquals($return, $generatedUrl);
+    }
+}
diff --git a/tests/Unit/Renderer/TwigEngineTest.php b/tests/Unit/Renderer/TwigEngineTest.php
new file mode 100644
index 00000000..9d0618f1
--- /dev/null
+++ b/tests/Unit/Renderer/TwigEngineTest.php
@@ -0,0 +1,60 @@
+<?php
+
+namespace Engelsystem\Test\Unit\Renderer;
+
+use Engelsystem\Renderer\TwigEngine;
+use PHPUnit\Framework\MockObject\MockObject;
+use PHPUnit\Framework\TestCase;
+use Twig_Environment as Twig;
+use Twig_LoaderInterface as LoaderInterface;
+
+class TwigEngineTest extends TestCase
+{
+    /**
+     * @covers \Engelsystem\Renderer\TwigEngine::__construct
+     * @covers \Engelsystem\Renderer\TwigEngine::get
+     */
+    public function testGet()
+    {
+        /** @var Twig|MockObject $twig */
+        $twig = $this->createMock(Twig::class);
+
+        $path = 'foo.twig';
+        $data = ['lorem' => 'ipsum'];
+
+        $twig->expects($this->once())
+            ->method('render')
+            ->with($path, $data)
+            ->willReturn('LoremIpsum!');
+
+        $engine = new TwigEngine($twig);
+        $return = $engine->get($path, $data);
+        $this->assertEquals('LoremIpsum!', $return);
+    }
+
+
+    /**
+     * @covers \Engelsystem\Renderer\TwigEngine::canRender
+     */
+    public function testCanRender()
+    {
+        /** @var Twig|MockObject $twig */
+        $twig = $this->createMock(Twig::class);
+        /** @var LoaderInterface|MockObject $loader */
+        $loader = $this->getMockForAbstractClass(LoaderInterface::class);
+
+        $path = 'foo.twig';
+
+        $twig->expects($this->once())
+            ->method('getLoader')
+            ->willReturn($loader);
+        $loader->expects($this->once())
+            ->method('exists')
+            ->with($path)
+            ->willReturn(true);
+
+        $engine = new TwigEngine($twig);
+        $return = $engine->canRender($path);
+        $this->assertTrue($return);
+    }
+}
diff --git a/tests/Unit/Renderer/TwigLoaderTest.php b/tests/Unit/Renderer/TwigLoaderTest.php
new file mode 100644
index 00000000..e6867643
--- /dev/null
+++ b/tests/Unit/Renderer/TwigLoaderTest.php
@@ -0,0 +1,31 @@
+<?php
+
+namespace Engelsystem\Test\Unit\Renderer;
+
+use Engelsystem\Renderer\TwigLoader;
+use PHPUnit\Framework\TestCase;
+use ReflectionClass as Reflection;
+
+class TwigLoaderTest extends TestCase
+{
+    /**
+     * @covers \Engelsystem\Renderer\TwigLoader::findTemplate
+     */
+    public function testFindTemplate()
+    {
+        $loader = new TwigLoader();
+
+        $reflection = new Reflection(get_class($loader));
+        $property = $reflection->getProperty('cache');
+        $property->setAccessible(true);
+
+        $realPath = __DIR__ . '/Stub/foo.twig';
+        $property->setValue($loader, ['Stub/foo.twig' => $realPath]);
+
+        $return = $loader->findTemplate('Stub/foo.twig');
+        $this->assertEquals($realPath, $return);
+
+        $return = $loader->findTemplate('Stub/foo');
+        $this->assertEquals($realPath, $return);
+    }
+}
diff --git a/tests/Unit/Renderer/TwigServiceProviderTest.php b/tests/Unit/Renderer/TwigServiceProviderTest.php
new file mode 100644
index 00000000..3cd0da4d
--- /dev/null
+++ b/tests/Unit/Renderer/TwigServiceProviderTest.php
@@ -0,0 +1,155 @@
+<?php
+
+namespace Engelsystem\Test\Unit\Renderer;
+
+use Engelsystem\Renderer\TwigEngine;
+use Engelsystem\Renderer\TwigLoader;
+use Engelsystem\Renderer\TwigServiceProvider;
+use Engelsystem\Test\Unit\ServiceProviderTest;
+use PHPUnit\Framework\MockObject\MockObject;
+use ReflectionClass as Reflection;
+use stdClass;
+use Twig_Environment as Twig;
+use Twig_ExtensionInterface as ExtensionInterface;
+use Twig_LoaderInterface as TwigLoaderInterface;
+
+class TwigServiceProviderTest extends ServiceProviderTest
+{
+    /**
+     * @covers \Engelsystem\Renderer\TwigServiceProvider::register
+     * @covers \Engelsystem\Renderer\TwigServiceProvider::registerTwigExtensions
+     */
+    public function testRegister()
+    {
+        $app = $this->getApp(['make', 'instance', 'tag']);
+        $class = $this->createMock(stdClass::class);
+
+        $className = 'Foo\Bar\Class';
+        $classAlias = 'twig.extension.foo';
+
+        $app->expects($this->once())
+            ->method('make')
+            ->with('Foo\Bar\Class')
+            ->willReturn($class);
+
+        $app->expects($this->exactly(2))
+            ->method('instance')
+            ->withConsecutive(
+                [$className, $class],
+                [$classAlias, $class]
+            );
+
+        $app->expects($this->once())
+            ->method('tag')
+            ->with($classAlias, ['twig.extension']);
+
+        /** @var TwigServiceProvider|MockObject $serviceProvider */
+        $serviceProvider = $this->getMockBuilder(TwigServiceProvider::class)
+            ->setConstructorArgs([$app])
+            ->setMethods(['registerTwigEngine'])
+            ->getMock();
+        $serviceProvider->expects($this->once())
+            ->method('registerTwigEngine');
+        $this->setExtensionsTo($serviceProvider, ['foo' => 'Foo\Bar\Class']);
+
+        $serviceProvider->register();
+    }
+
+    /**
+     * @covers \Engelsystem\Renderer\TwigServiceProvider::boot
+     */
+    public function testBoot()
+    {
+        /** @var Twig|MockObject $twig */
+        $twig = $this->createMock(Twig::class);
+        /** @var ExtensionInterface|MockObject $firsExtension */
+        $firsExtension = $this->getMockForAbstractClass(ExtensionInterface::class);
+        /** @var ExtensionInterface|MockObject $secondExtension */
+        $secondExtension = $this->getMockForAbstractClass(ExtensionInterface::class);
+
+        $app = $this->getApp(['get', 'tagged']);
+
+        $app->expects($this->once())
+            ->method('get')
+            ->with('twig.environment')
+            ->willReturn($twig);
+        $app->expects($this->once())
+            ->method('tagged')
+            ->with('twig.extension')
+            ->willReturn([$firsExtension, $secondExtension]);
+
+        $twig->expects($this->exactly(2))
+            ->method('addExtension')
+            ->withConsecutive($firsExtension, $secondExtension);
+
+        $serviceProvider = new TwigServiceProvider($app);
+        $serviceProvider->boot();
+    }
+
+    /**
+     * @covers \Engelsystem\Renderer\TwigServiceProvider::registerTwigEngine
+     */
+    public function testRegisterTWigEngine()
+    {
+        /** @var TwigEngine|MockObject $htmlEngine */
+        $twigEngine = $this->createMock(TwigEngine::class);
+        /** @var TwigLoader|MockObject $twigLoader */
+        $twigLoader = $this->createMock(TwigLoader::class);
+        /** @var Twig|MockObject $twig */
+        $twig = $this->createMock(Twig::class);
+
+        $app = $this->getApp(['make', 'instance', 'tag', 'get']);
+
+        $viewsPath = __DIR__ . '/Stub';
+
+        $app->expects($this->exactly(3))
+            ->method('make')
+            ->withConsecutive(
+                [TwigLoader::class, ['paths' => $viewsPath]],
+                [Twig::class],
+                [TwigEngine::class]
+            )->willReturnOnConsecutiveCalls(
+                $twigLoader,
+                $twig,
+                $twigEngine
+            );
+
+        $app->expects($this->exactly(6))
+            ->method('instance')
+            ->withConsecutive(
+                [TwigLoader::class, $twigLoader],
+                [TwigLoaderInterface::class, $twigLoader],
+                ['twig.loader', $twigLoader],
+                [Twig::class, $twig],
+                ['twig.environment', $twig],
+                ['renderer.twigEngine', $twigEngine]
+            );
+
+        $app->expects($this->once())
+            ->method('get')
+            ->with('path.views')
+            ->willReturn($viewsPath);
+
+        $this->setExpects($app, 'tag', ['renderer.twigEngine', ['renderer.engine']]);
+
+        $serviceProvider = new TwigServiceProvider($app);
+        $this->setExtensionsTo($serviceProvider, []);
+
+        $serviceProvider->register();
+    }
+
+    /**
+     * @param TwigServiceProvider $serviceProvider
+     * @param array               $extensions
+     * @throws \ReflectionException
+     */
+    protected function setExtensionsTo($serviceProvider, $extensions)
+    {
+        $reflection = new Reflection(get_class($serviceProvider));
+
+        $property = $reflection->getProperty('extensions');
+        $property->setAccessible(true);
+
+        $property->setValue($serviceProvider, $extensions);
+    }
+}