diff --git a/composer.json b/composer.json
index 657d21c..2c7ef0b 100644
--- a/composer.json
+++ b/composer.json
@@ -18,20 +18,20 @@
     ],
     "require": {
         "php": " >=8.3",
-        "ibexa/core": "~5.0.x-dev",
-        "symfony/asset": "^5.0",
-        "symfony/config": "^5.0",
-        "symfony/dependency-injection": "^5.0",
-        "symfony/filesystem": "^5.0",
-        "symfony/finder": "^5.0",
-        "symfony/http-foundation": "^5.0",
-        "symfony/http-kernel": "^5.0",
-        "symfony/templating": "^5.0",
+        "ibexa/core": "dev-ibx-8470-symfony-6 as 5.0.x-dev",
+        "symfony/asset": "^6.4",
+        "symfony/config": "^6.4",
+        "symfony/dependency-injection": "^6.4",
+        "symfony/filesystem": "^6.4",
+        "symfony/finder": "^6.4",
+        "symfony/http-foundation": "^6.4",
+        "symfony/http-kernel": "^6.4",
+        "symfony/templating": "^6.4",
         "twig/twig": "^3.0"
     },
     "require-dev": {
         "ibexa/code-style": "~2.0.0",
-        "ibexa/doctrine-schema": "~5.0.x-dev",
+        "ibexa/doctrine-schema": "dev-ibx-8470-symfony-6 as 5.0.x-dev",
         "mikey179/vfsstream": "^1.6",
         "phpunit/phpunit": "^9.6"
     },
diff --git a/src/bundle/DataCollector/TwigDataCollector.php b/src/bundle/DataCollector/TwigDataCollector.php
index f506b8b..c842b1f 100644
--- a/src/bundle/DataCollector/TwigDataCollector.php
+++ b/src/bundle/DataCollector/TwigDataCollector.php
@@ -9,18 +9,12 @@
 
 use Ibexa\DesignEngine\Templating\TemplatePathRegistryInterface;
 use Symfony\Bridge\Twig\DataCollector\TwigDataCollector as BaseCollector;
-use Symfony\Component\HttpFoundation\Request;
-use Symfony\Component\HttpFoundation\Response;
-use Symfony\Component\HttpKernel\DataCollector\LateDataCollectorInterface;
 use Twig\Environment;
 use Twig\Profiler\Profile;
 
-class TwigDataCollector extends BaseCollector implements LateDataCollectorInterface
+class TwigDataCollector extends BaseCollector
 {
-    /**
-     * @var \Ibexa\DesignEngine\Templating\TemplatePathRegistryInterface
-     */
-    private $templatePathRegistry;
+    private TemplatePathRegistryInterface $templatePathRegistry;
 
     public function __construct(Profile $profile, Environment $environment, TemplatePathRegistryInterface $templatePathRegistry)
     {
@@ -37,28 +31,13 @@ private function getTemplatePathRegistry()
         return $this->templatePathRegistry;
     }
 
-    public function collect(Request $request, Response $response, \Throwable $exception = null)
-    {
-        parent::collect($request, $response, $exception);
-    }
-
-    public function lateCollect()
+    public function lateCollect(): void
     {
         parent::lateCollect();
         $this->data['template_path_registry'] = serialize($this->templatePathRegistry);
     }
 
-    public function getTime()
-    {
-        return parent::getTime();
-    }
-
-    public function getTemplateCount()
-    {
-        return parent::getTemplateCount();
-    }
-
-    public function getTemplates()
+    public function getTemplates(): array
     {
         $registry = $this->getTemplatePathRegistry();
         $templates = [];
@@ -68,26 +47,4 @@ public function getTemplates()
 
         return $templates;
     }
-
-    public function getBlockCount()
-    {
-        return parent::getBlockCount();
-    }
-
-    public function getMacroCount()
-    {
-        return parent::getMacroCount();
-    }
-
-    public function getHtmlCallGraph()
-    {
-        return parent::getHtmlCallGraph();
-    }
-
-    public function getProfile()
-    {
-        $profile = parent::getProfile();
-
-        return $profile;
-    }
 }
diff --git a/src/bundle/DependencyInjection/Compiler/AssetPathResolutionPass.php b/src/bundle/DependencyInjection/Compiler/AssetPathResolutionPass.php
index 8b38f9f..f719cd8 100644
--- a/src/bundle/DependencyInjection/Compiler/AssetPathResolutionPass.php
+++ b/src/bundle/DependencyInjection/Compiler/AssetPathResolutionPass.php
@@ -23,7 +23,10 @@
  */
 class AssetPathResolutionPass implements CompilerPassInterface
 {
-    public function process(ContainerBuilder $container)
+    /**
+     * @throws \Exception
+     */
+    public function process(ContainerBuilder $container): void
     {
         if ($container->getParameter('ibexa.design.assets.resolution.disabled')) {
             return;
@@ -39,7 +42,7 @@ public function process(ContainerBuilder $container)
         $container->setAlias('ibexadesign.asset_path_resolver', new Alias(ProvisionedPathResolver::class));
     }
 
-    private function preResolveAssetsPaths(AssetPathProvisionerInterface $provisioner, array $designPathMap)
+    private function preResolveAssetsPaths(AssetPathProvisionerInterface $provisioner, array $designPathMap): array
     {
         $resolvedPathsByDesign = [];
         foreach ($designPathMap as $design => $paths) {
diff --git a/src/bundle/DependencyInjection/Compiler/AssetThemePass.php b/src/bundle/DependencyInjection/Compiler/AssetThemePass.php
index bcf8489..858692e 100644
--- a/src/bundle/DependencyInjection/Compiler/AssetThemePass.php
+++ b/src/bundle/DependencyInjection/Compiler/AssetThemePass.php
@@ -15,7 +15,7 @@
 
 class AssetThemePass implements CompilerPassInterface
 {
-    public function process(ContainerBuilder $container)
+    public function process(ContainerBuilder $container): void
     {
         if (!($container->hasParameter('kernel.bundles') && $container->hasParameter('webroot_dir') && $container->hasDefinition('assets.packages'))) {
             return;
@@ -50,7 +50,7 @@ public function process(ContainerBuilder $container)
         if (is_dir($appLevelThemeDir)) {
             foreach ((new Finder())->directories()->in($appLevelThemeDir)->depth('== 0') as $directoryInfo) {
                 $theme = $directoryInfo->getBasename();
-                $themePaths = isset($themesPathMap[$theme]) ? $themesPathMap[$theme] : [];
+                $themePaths = $themesPathMap[$theme] ?? [];
                 // Application level paths are always top priority.
                 array_unshift($themePaths, 'assets/themes/' . $theme);
                 $themesPathMap[$theme] = $themePaths;
diff --git a/src/bundle/DependencyInjection/Compiler/TwigThemePass.php b/src/bundle/DependencyInjection/Compiler/TwigThemePass.php
index cddd5e4..159bf59 100644
--- a/src/bundle/DependencyInjection/Compiler/TwigThemePass.php
+++ b/src/bundle/DependencyInjection/Compiler/TwigThemePass.php
@@ -23,7 +23,10 @@
  */
 class TwigThemePass implements CompilerPassInterface
 {
-    public function process(ContainerBuilder $container)
+    /**
+     * @throws \ReflectionException
+     */
+    public function process(ContainerBuilder $container): void
     {
         if (!($container->hasParameter('kernel.bundles') && $container->hasDefinition(TwigThemeLoader::class))) {
             return;
@@ -50,7 +53,10 @@ public function process(ContainerBuilder $container)
 
         $twigLoaderDef = $container->findDefinition(TwigThemeLoader::class);
         // Now look for themes at application level
-        $appLevelThemesDir = $container->getParameter('twig.default_path') . '/themes';
+        $appLevelThemesDir = $container->getParameterBag()->resolveValue(
+            $container->getParameter('twig.default_path') . '/themes'
+        );
+
         if (is_dir($appLevelThemesDir)) {
             foreach ((new Finder())->directories()->in($appLevelThemesDir)->depth('== 0') as $directoryInfo) {
                 $theme = $directoryInfo->getBasename();
diff --git a/src/bundle/DependencyInjection/DesignConfigParser.php b/src/bundle/DependencyInjection/DesignConfigParser.php
index 7282e01..c1d83eb 100644
--- a/src/bundle/DependencyInjection/DesignConfigParser.php
+++ b/src/bundle/DependencyInjection/DesignConfigParser.php
@@ -13,22 +13,24 @@
 
 class DesignConfigParser implements ParserInterface
 {
-    public function mapConfig(array &$scopeSettings, $currentScope, ContextualizerInterface $contextualizer)
+    public function mapConfig(array &$scopeSettings, $currentScope, ContextualizerInterface $contextualizer): void
     {
         if (isset($scopeSettings['design'])) {
             $contextualizer->setContextualParameter('design', $currentScope, $scopeSettings['design']);
         }
     }
 
-    public function preMap(array $config, ContextualizerInterface $contextualizer)
+    public function preMap(array $config, ContextualizerInterface $contextualizer): void
     {
+        // Nothing to map
     }
 
-    public function postMap(array $config, ContextualizerInterface $contextualizer)
+    public function postMap(array $config, ContextualizerInterface $contextualizer): void
     {
+        // Nothing to map
     }
 
-    public function addSemanticConfig(NodeBuilder $nodeBuilder)
+    public function addSemanticConfig(NodeBuilder $nodeBuilder): void
     {
         $nodeBuilder
             ->scalarNode('design')
diff --git a/src/bundle/DependencyInjection/IbexaDesignEngineExtension.php b/src/bundle/DependencyInjection/IbexaDesignEngineExtension.php
index 849a21c..ae1887a 100644
--- a/src/bundle/DependencyInjection/IbexaDesignEngineExtension.php
+++ b/src/bundle/DependencyInjection/IbexaDesignEngineExtension.php
@@ -16,7 +16,7 @@
 
 class IbexaDesignEngineExtension extends Extension
 {
-    public const EXTENSION_NAME = 'ibexa_design_engine';
+    public const string EXTENSION_NAME = 'ibexa_design_engine';
 
     public function getAlias(): string
     {
@@ -28,20 +28,24 @@ public function getConfiguration(array $config, ContainerBuilder $container): ?C
         return new Configuration();
     }
 
-    public function load(array $configs, ContainerBuilder $container)
+    /**
+     * @throws \Exception
+     */
+    public function load(array $configs, ContainerBuilder $container): void
     {
         $loader = new Loader\YamlFileLoader($container, new FileLocator(__DIR__ . '/../Resources/config'));
         $loader->load('services.yaml');
         $loader->load('default_settings.yaml');
 
         $configuration = $this->getConfiguration($configs, $container);
+        assert(null !== $configuration);
         $config = $this->processConfiguration($configuration, $configs);
         $processor = new ConfigurationProcessor($container, 'ezdesign');
 
         $this->configureDesigns($config, $processor, $container);
     }
 
-    private function configureDesigns(array $config, ConfigurationProcessor $processor, ContainerBuilder $container)
+    private function configureDesigns(array $config, ConfigurationProcessor $processor, ContainerBuilder $container): void
     {
         // Always add "standard" design to the list (defaults to application level & override paths only)
         $config['design_list'] += ['standard' => []];
diff --git a/src/bundle/IbexaDesignEngineBundle.php b/src/bundle/IbexaDesignEngineBundle.php
index 6af98ac..065c3bb 100644
--- a/src/bundle/IbexaDesignEngineBundle.php
+++ b/src/bundle/IbexaDesignEngineBundle.php
@@ -4,6 +4,7 @@
  * @copyright Copyright (C) Ibexa AS. All rights reserved.
  * @license For full copyright and license information view LICENSE file distributed with this source code.
  */
+declare(strict_types=1);
 
 namespace Ibexa\Bundle\DesignEngine;
 
@@ -19,7 +20,7 @@
 
 class IbexaDesignEngineBundle extends Bundle
 {
-    public function build(ContainerBuilder $container)
+    public function build(ContainerBuilder $container): void
     {
         parent::build($container);
 
diff --git a/src/contracts/DesignAwareInterface.php b/src/contracts/DesignAwareInterface.php
index 5cad927..de6ef46 100644
--- a/src/contracts/DesignAwareInterface.php
+++ b/src/contracts/DesignAwareInterface.php
@@ -4,12 +4,13 @@
  * @copyright Copyright (C) Ibexa AS. All rights reserved.
  * @license For full copyright and license information view LICENSE file distributed with this source code.
  */
+declare(strict_types=1);
 
 namespace Ibexa\Contracts\DesignEngine;
 
 interface DesignAwareInterface
 {
-    public const DESIGN_NAMESPACE = 'ibexadesign';
+    public const string DESIGN_NAMESPACE = 'ibexadesign';
 
     public function getCurrentDesign(): ?string;
 }
diff --git a/src/lib/Asset/AssetPathProvisionerInterface.php b/src/lib/Asset/AssetPathProvisionerInterface.php
index a33f0a9..589e380 100644
--- a/src/lib/Asset/AssetPathProvisionerInterface.php
+++ b/src/lib/Asset/AssetPathProvisionerInterface.php
@@ -11,12 +11,12 @@ interface AssetPathProvisionerInterface
 {
     /**
      * Pre-resolves assets paths for a given design from themes paths, where are stored physical assets.
-     * Returns an map with asset logical path as key and its resolved path (relative to webroot dir) as value.
+     * Returns a map with asset logical path as key and its resolved path (relative to webroot dir) as value.
      * Example => ['images/foo.png' => 'asset/themes/some_theme/images/foo.png'].
      *
-     * @param string $design
+     * @param string[] $assetsPaths
      *
-     * @return array
+     * @return array<string, string>
      */
-    public function provisionResolvedPaths(array $assetsPaths, $design);
+    public function provisionResolvedPaths(array $assetsPaths, string $design): array;
 }
diff --git a/src/lib/Asset/AssetPathResolver.php b/src/lib/Asset/AssetPathResolver.php
index 41e141c..e213299 100644
--- a/src/lib/Asset/AssetPathResolver.php
+++ b/src/lib/Asset/AssetPathResolver.php
@@ -12,20 +12,12 @@
 
 class AssetPathResolver implements AssetPathResolverInterface
 {
-    /**
-     * @var array
-     */
-    private $designPaths;
+    /** @var array<string, string> */
+    private array $designPaths;
 
-    /**
-     * @var string
-     */
-    private $webRootDir;
+    private string $webRootDir;
 
-    /**
-     * @var \Psr\Log\LoggerInterface
-     */
-    private $logger;
+    private ?LoggerInterface $logger;
 
     public function __construct(array $designPaths, $webRootDir, LoggerInterface $logger = null)
     {
@@ -34,7 +26,7 @@ public function __construct(array $designPaths, $webRootDir, LoggerInterface $lo
         $this->logger = $logger;
     }
 
-    public function resolveAssetPath($path, $design)
+    public function resolveAssetPath(string $path, string $design): string
     {
         if (!isset($this->designPaths[$design])) {
             throw new InvalidDesignException("Invalid design '$design'");
@@ -46,14 +38,12 @@ public function resolveAssetPath($path, $design)
             }
         }
 
-        if ($this->logger) {
-            $this->logger->warning(
-                "Asset '$path' cannot be found in any configured themes.\nTried directories: " . implode(
-                    ', ',
-                    array_values($this->designPaths[$design])
-                )
-            );
-        }
+        $this->logger?->warning(
+            "Asset '$path' cannot be found in any configured themes.\nTried directories: " . implode(
+                ', ',
+                array_values($this->designPaths[$design])
+            )
+        );
 
         return $path;
     }
diff --git a/src/lib/Asset/AssetPathResolverInterface.php b/src/lib/Asset/AssetPathResolverInterface.php
index a08c9b6..3627cce 100644
--- a/src/lib/Asset/AssetPathResolverInterface.php
+++ b/src/lib/Asset/AssetPathResolverInterface.php
@@ -4,6 +4,7 @@
  * @copyright Copyright (C) Ibexa AS. All rights reserved.
  * @license For full copyright and license information view LICENSE file distributed with this source code.
  */
+declare(strict_types=1);
 
 namespace Ibexa\DesignEngine\Asset;
 
@@ -18,8 +19,6 @@ interface AssetPathResolverInterface
      *
      * @param string $path   Asset path to resolve
      * @param string $design Design to resolve path for
-     *
-     * @return string
      */
-    public function resolveAssetPath($path, $design);
+    public function resolveAssetPath(string $path, string $design): string;
 }
diff --git a/src/lib/Asset/ProvisionedPathResolver.php b/src/lib/Asset/ProvisionedPathResolver.php
index e91d7ec..a22a0b7 100644
--- a/src/lib/Asset/ProvisionedPathResolver.php
+++ b/src/lib/Asset/ProvisionedPathResolver.php
@@ -12,19 +12,13 @@
 class ProvisionedPathResolver implements AssetPathResolverInterface, AssetPathProvisionerInterface
 {
     /**
-     * @var array
+     * @var array<string, array<string, string>>
      */
-    private $resolvedPaths;
+    private array $resolvedPaths;
 
-    /**
-     * @var AssetPathResolverInterface
-     */
-    private $innerResolver;
+    private AssetPathResolverInterface $innerResolver;
 
-    /**
-     * @var string
-     */
-    private $webRootDir;
+    private string $webRootDir;
 
     public function __construct(array $resolvedPaths, AssetPathResolverInterface $innerResolver, $webRootDir)
     {
@@ -39,22 +33,19 @@ public function __construct(array $resolvedPaths, AssetPathResolverInterface $in
      *
      * {@inheritdoc}
      */
-    public function resolveAssetPath($path, $design)
+    public function resolveAssetPath(string $path, string $design): string
     {
-        if (!isset($this->resolvedPaths[$design][$path])) {
-            return $this->innerResolver->resolveAssetPath($path, $design);
-        }
-
-        return $this->resolvedPaths[$design][$path];
+        return $this->resolvedPaths[$design][$path] ?? $this->innerResolver->resolveAssetPath($path, $design);
     }
 
-    public function provisionResolvedPaths(array $assetsPaths, $design)
+    public function provisionResolvedPaths(array $assetsPaths, string $design): array
     {
         $webrootDir = $this->webRootDir;
         $assetsLogicalPaths = [];
         foreach ($assetsPaths as $path) {
-            $themePath = "$webrootDir/$path";
-            $assetsLogicalPaths = array_merge($assetsLogicalPaths, $this->computeLogicalPathFromPhysicalAssets($themePath));
+            foreach ($this->computeLogicalPathFromPhysicalAssets("$webrootDir/$path") as $logicalPath) {
+                $assetsLogicalPaths[] = $logicalPath;
+            }
         }
 
         $resolvedPaths = [];
@@ -72,11 +63,9 @@ public function provisionResolvedPaths(array $assetsPaths, $design)
      * This exclusion mainly applies to override directories,
      * e.g. "assets/", which is both an override dir and where app level themes can be defined.
      *
-     * @param string $themePath
-     *
-     * @return array
+     * @phpstan-return list<string>
      */
-    private function computeLogicalPathFromPhysicalAssets($themePath)
+    private function computeLogicalPathFromPhysicalAssets(string $themePath): array
     {
         if (!is_dir($themePath)) {
             return [];
diff --git a/src/lib/Asset/ThemePackage.php b/src/lib/Asset/ThemePackage.php
index 29feb91..c7e82b2 100644
--- a/src/lib/Asset/ThemePackage.php
+++ b/src/lib/Asset/ThemePackage.php
@@ -15,15 +15,9 @@ class ThemePackage implements PackageInterface, DesignAwareInterface
 {
     use DesignAwareTrait;
 
-    /**
-     * @var AssetPathResolverInterface
-     */
-    private $pathResolver;
+    private AssetPathResolverInterface $pathResolver;
 
-    /**
-     * @var \Symfony\Component\Asset\PackageInterface
-     */
-    private $innerPackage;
+    private PackageInterface $innerPackage;
 
     public function __construct(AssetPathResolverInterface $pathResolver, PackageInterface $innerPackage)
     {
@@ -31,12 +25,12 @@ public function __construct(AssetPathResolverInterface $pathResolver, PackageInt
         $this->innerPackage = $innerPackage;
     }
 
-    public function getUrl($path)
+    public function getUrl(string $path): string
     {
         return $this->innerPackage->getUrl($this->pathResolver->resolveAssetPath($path, $this->getCurrentDesign()));
     }
 
-    public function getVersion($path)
+    public function getVersion(string $path): string
     {
         return $this->innerPackage->getVersion($this->pathResolver->resolveAssetPath($path, $this->getCurrentDesign()));
     }
diff --git a/src/lib/DesignAwareTrait.php b/src/lib/DesignAwareTrait.php
index 45ae87b..feb1bd2 100644
--- a/src/lib/DesignAwareTrait.php
+++ b/src/lib/DesignAwareTrait.php
@@ -4,6 +4,7 @@
  * @copyright Copyright (C) Ibexa AS. All rights reserved.
  * @license For full copyright and license information view LICENSE file distributed with this source code.
  */
+declare(strict_types=1);
 
 namespace Ibexa\DesignEngine;
 
@@ -11,10 +12,7 @@
 
 trait DesignAwareTrait
 {
-    /**
-     * @var \Ibexa\Contracts\Core\SiteAccess\ConfigResolverInterface
-     */
-    private $configResolver;
+    private ConfigResolverInterface $configResolver;
 
     public function setConfigResolver(ConfigResolverInterface $configResolver): void
     {
diff --git a/src/lib/Templating/TemplateNameResolverInterface.php b/src/lib/Templating/TemplateNameResolverInterface.php
index 93880fe..b452ed3 100644
--- a/src/lib/Templating/TemplateNameResolverInterface.php
+++ b/src/lib/Templating/TemplateNameResolverInterface.php
@@ -15,27 +15,15 @@
  */
 interface TemplateNameResolverInterface extends DesignAwareInterface
 {
-    /**
-     * @deprecated since Ibexa 4.0. Use
-     * {@see \Ibexa\Contracts\DesignEngine\DesignAwareInterface::DESIGN_NAMESPACE} instead.
-     */
-    public const EZ_DESIGN_NAMESPACE = 'ezdesign';
-
     /**
      * Resolves provided template name within current design and returns properly namespaced template name.
      *
      * @param string $name Template name to resolve
-     *
-     * @return string
      */
-    public function resolveTemplateName($name);
+    public function resolveTemplateName(string $name): string;
 
     /**
-     * Checks if provided template name is using @ibexadesign namespace.
-     *
-     * @param string $name
-     *
-     * @return bool
+     * Checks if provided template name is using `@ibexadesign` namespace.
      */
-    public function isTemplateDesignNamespaced($name);
+    public function isTemplateDesignNamespaced(string $name): bool;
 }
diff --git a/src/lib/Templating/TemplatePathRegistry.php b/src/lib/Templating/TemplatePathRegistry.php
index 9cddb81..81e8d80 100644
--- a/src/lib/Templating/TemplatePathRegistry.php
+++ b/src/lib/Templating/TemplatePathRegistry.php
@@ -12,37 +12,36 @@
 class TemplatePathRegistry implements TemplatePathRegistryInterface, Serializable
 {
     /** @var array<string, string> */
-    private $pathMap = [];
+    private array $pathMap = [];
 
-    /** @var string */
-    private $kernelRootDir;
+    private string $kernelRootDir;
 
     public function __construct($kernelRootDir)
     {
         $this->kernelRootDir = $kernelRootDir;
     }
 
-    public function mapTemplatePath($templateName, $path)
+    public function mapTemplatePath(string $templateName, string $path): void
     {
         $this->pathMap[$templateName] = str_replace($this->kernelRootDir . '/', '', $path);
     }
 
-    public function getTemplatePath($templateName)
+    public function getTemplatePath(string $templateName): string
     {
-        return isset($this->pathMap[$templateName]) ? $this->pathMap[$templateName] : $templateName;
+        return $this->pathMap[$templateName] ?? $templateName;
     }
 
-    public function getPathMap()
+    public function getPathMap(): array
     {
         return $this->pathMap;
     }
 
-    public function serialize()
+    public function serialize(): ?string
     {
         return serialize([$this->pathMap, $this->kernelRootDir]);
     }
 
-    public function unserialize($serialized)
+    public function unserialize($serialized): void
     {
         [$this->pathMap, $this->kernelRootDir] = unserialize($serialized);
     }
diff --git a/src/lib/Templating/TemplatePathRegistryInterface.php b/src/lib/Templating/TemplatePathRegistryInterface.php
index 3994b09..4900692 100644
--- a/src/lib/Templating/TemplatePathRegistryInterface.php
+++ b/src/lib/Templating/TemplatePathRegistryInterface.php
@@ -4,6 +4,7 @@
  * @copyright Copyright (C) Ibexa AS. All rights reserved.
  * @license For full copyright and license information view LICENSE file distributed with this source code.
  */
+declare(strict_types=1);
 
 namespace Ibexa\DesignEngine\Templating;
 
@@ -19,21 +20,14 @@ interface TemplatePathRegistryInterface
      * @param string $templateName The template logical name
      * @param string $path         Template path
      */
-    public function mapTemplatePath($templateName, $path);
+    public function mapTemplatePath(string $templateName, string $path): void;
 
-    /**
-     * Returns path for given template.
-     *
-     * @param string $templateName
-     *
-     * @return string
-     */
-    public function getTemplatePath($templateName);
+    public function getTemplatePath(string $templateName): string;
 
     /**
      * Returns the whole hash map.
      *
-     * @return array
+     * @return array<string, string>
      */
-    public function getPathMap();
+    public function getPathMap(): array;
 }
diff --git a/src/lib/Templating/ThemeTemplateNameResolver.php b/src/lib/Templating/ThemeTemplateNameResolver.php
index ae68dc5..333792d 100644
--- a/src/lib/Templating/ThemeTemplateNameResolver.php
+++ b/src/lib/Templating/ThemeTemplateNameResolver.php
@@ -17,16 +17,16 @@ class ThemeTemplateNameResolver implements TemplateNameResolverInterface
     /**
      * Collection of already resolved template names.
      *
-     * @var array
+     * @var array<string, string>
      */
-    private $resolvedTemplateNames = [];
+    private array $resolvedTemplateNames = [];
 
     public function __construct(ConfigResolverInterface $configResolver)
     {
         $this->setConfigResolver($configResolver);
     }
 
-    public function resolveTemplateName($name)
+    public function resolveTemplateName(string $name): string
     {
         if (!$this->isTemplateDesignNamespaced($name)) {
             return $name;
@@ -39,8 +39,9 @@ public function resolveTemplateName($name)
         ));
     }
 
-    public function isTemplateDesignNamespaced($name)
+    public function isTemplateDesignNamespaced(string $name): bool
     {
-        return (strpos($name, '@' . static::DESIGN_NAMESPACE) !== false) || (strpos($name, '@' . $this->getCurrentDesign()) !== false);
+        return str_contains($name, '@' . static::DESIGN_NAMESPACE)
+            || (str_contains($name, '@' . $this->getCurrentDesign()));
     }
 }
diff --git a/src/lib/Templating/Twig/TwigThemeLoader.php b/src/lib/Templating/Twig/TwigThemeLoader.php
index 58e281e..1097db2 100644
--- a/src/lib/Templating/Twig/TwigThemeLoader.php
+++ b/src/lib/Templating/Twig/TwigThemeLoader.php
@@ -22,38 +22,30 @@ class TwigThemeLoader implements LoaderInterface
     /**
      * @var \Ibexa\DesignEngine\Templating\TemplateNameResolverInterface
      */
-    private $nameResolver;
+    private TemplateNameResolverInterface $nameResolver;
 
     /**
      * @var \Ibexa\DesignEngine\Templating\TemplatePathRegistryInterface
      */
-    private $pathRegistry;
+    private TemplatePathRegistryInterface $pathRegistry;
 
-    /**
-     * @var \Twig\Loader\FilesystemLoader
-     */
-    private $innerFilesystemLoader;
+    private FilesystemLoader $innerFilesystemLoader;
 
     public function __construct(
         TemplateNameResolverInterface $templateNameResolver,
         TemplatePathRegistryInterface $templatePathRegistry,
-        LoaderInterface $innerFilesystemLoader
+        FilesystemLoader $innerFilesystemLoader
     ) {
         $this->innerFilesystemLoader = $innerFilesystemLoader;
         $this->nameResolver = $templateNameResolver;
         $this->pathRegistry = $templatePathRegistry;
     }
 
-    public function exists($name)
+    public function exists(string $name): bool
     {
         return $this->innerFilesystemLoader->exists($this->nameResolver->resolveTemplateName($name));
     }
 
-    public function getSource($name)
-    {
-        return $this->innerFilesystemLoader->getSource($this->nameResolver->resolveTemplateName($name));
-    }
-
     public function getSourceContext(string $name): Source
     {
         $source = $this->innerFilesystemLoader->getSourceContext($this->nameResolver->resolveTemplateName((string)$name));
@@ -72,27 +64,36 @@ public function isFresh(string $name, int $time): bool
         return $this->innerFilesystemLoader->isFresh($this->nameResolver->resolveTemplateName($name), $time);
     }
 
-    public function getPaths($namespace = FilesystemLoader::MAIN_NAMESPACE)
+    public function getPaths(string $namespace = FilesystemLoader::MAIN_NAMESPACE): array
     {
         return $this->innerFilesystemLoader->getPaths($namespace);
     }
 
-    public function getNamespaces()
+    public function getNamespaces(): array
     {
         return $this->innerFilesystemLoader->getNamespaces();
     }
 
-    public function setPaths($paths, $namespace = FilesystemLoader::MAIN_NAMESPACE)
+    /**
+     * @param string|string[] $paths
+     */
+    public function setPaths(string|array $paths, $namespace = FilesystemLoader::MAIN_NAMESPACE): void
     {
         $this->innerFilesystemLoader->setPaths($paths, $namespace);
     }
 
-    public function addPath($path, $namespace = FilesystemLoader::MAIN_NAMESPACE)
+    /**
+     * @throws \Twig\Error\LoaderError
+     */
+    public function addPath(string $path, string $namespace = FilesystemLoader::MAIN_NAMESPACE): void
     {
         $this->innerFilesystemLoader->addPath($path, $namespace);
     }
 
-    public function prependPath($path, $namespace = FilesystemLoader::MAIN_NAMESPACE)
+    /**
+     * @throws \Twig\Error\LoaderError
+     */
+    public function prependPath(string $path, string $namespace = FilesystemLoader::MAIN_NAMESPACE): void
     {
         $this->innerFilesystemLoader->prependPath($path, $namespace);
     }
diff --git a/tests/bundle/.gitkeep b/tests/bundle/.gitkeep
new file mode 100644
index 0000000..e69de29