diff --git a/composer.json b/composer.json
index 882be1d0..f2b4b3db 100644
--- a/composer.json
+++ b/composer.json
@@ -26,7 +26,7 @@
         "symfony/asset": "^4.4|^5.0",
         "symfony/config": "^4.4|^5.0",
         "symfony/console": "^4.4|^5.0",
-        "symfony/translation-contracts": "^1.0",
+        "symfony/translation-contracts": "^1.1|^2.0",
         "symfony/dependency-injection": "^4.4|^5.0",
         "symfony/filesystem": "^4.4|^5.0",
         "symfony/finder": "^4.4|^5.0",
@@ -40,14 +40,14 @@
         "zendframework/zend-hydrator": "^2.2"
     },
     "require-dev": {
-        "matthiasnoback/symfony-config-test": "^4.0",
-        "matthiasnoback/symfony-dependency-injection-test": "^3.0",
+        "matthiasnoback/symfony-config-test": "^4.1",
+        "matthiasnoback/symfony-dependency-injection-test": "^4.1",
         "mikey179/vfsstream": "^1.6",
-        "phpspec/phpspec": "^5.0",
-        "phpstan/phpstan": "^0.11",
-        "phpstan/phpstan-phpunit": "^0.11",
-        "phpstan/phpstan-webmozart-assert": "^0.11",
-        "phpunit/phpunit": "^7.0",
+        "phpspec/phpspec": "^6.1",
+        "phpstan/phpstan": "^0.12",
+        "phpstan/phpstan-phpunit": "^0.12",
+        "phpstan/phpstan-webmozart-assert": "^0.12",
+        "phpunit/phpunit": "^8.5",
         "sylius-labs/coding-standard": "^3.0",
         "symfony/browser-kit": "^4.4|^5.0",
         "symfony/security-csrf": "^4.4|^5.0",
@@ -55,9 +55,6 @@
         "twig/twig": "^2.0",
         "vimeo/psalm": "^3.5"
     },
-    "conflict": {
-        "twig/twig": "^1.0"
-    },
     "autoload": {
         "psr-4": {
             "Sylius\\Bundle\\ThemeBundle\\": "src/"
diff --git a/phpstan.neon b/phpstan.neon
index eba38f28..2915116b 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -5,24 +5,19 @@ includes:
     - vendor/phpstan/phpstan-phpunit/rules.neon
 
 parameters:
+    checkMissingIterableValueType: false
     reportUnmatchedIgnoredErrors: false
-
-    specDir: 'spec/'
+    treatPhpDocTypesAsCertain: false
 
     excludes_analyse:
-        - %currentWorkingDirectory%/tests/Application/var/*
+        # Test dependencies
+        - %currentWorkingDirectory%/spec/
+        - %currentWorkingDirectory%/tests/Application/var/
 
     ignoreErrors:
         # PHPStan integration
         - '/Call to an undefined method Prophecy\\Prophecy\\MethodProphecy::getRealPath\(\)/'
 
-        # Symfony 3.4 support
-        - '/Method Symfony\\Component\\HttpKernel\\KernelInterface::getBundle\(\) invoked with 2 parameters, 1 required/'
-        - '/Method Symfony\\Component\\HttpKernel\\KernelInterface::getBundle\(\) invoked with 2 parameters, 0-1 required/'
-        - '/Call to function method_exists\(\) with .Symfony\\\\Component…. and .getRootNode. will always evaluate to false/'
-        - '/Call to an undefined method Symfony\\Component\\Config\\Definition\\Builder\\TreeBuilder::getRootNode\(\)/'
-        - '/Class Symfony\\Component\\Config\\Definition\\Builder\\TreeBuilder does not have a constructor and must be instantiated without any parameters/'
-
         # Symfony caveats
         - '/Parameter \#1 \$name of method Symfony\\Component\\Config\\FileLocatorInterface::locate\(\) expects string, Symfony\\Component\\Templating\\TemplateReferenceInterface given/'
         - '/Parameter \#1 \$translator of class Symfony\\Component\\Translation\\Formatter\\MessageFormatter constructor expects Symfony\\Contracts\\Translation\\TranslatorInterface|null, Symfony\\Component\\Translation\\MessageSelector given/'
@@ -30,3 +25,8 @@ parameters:
         # Symfony passes TemplateReference object instead of a string
         - "/Casting to string something that\\'s already string./"
         - '/Parameter \#1 \$name of method Twig\\Loader\\LoaderInterface::[A-Za-z]+\(\) expects string, string\|Symfony\\Component\\Templating\\TemplateReference given\./'
+
+        - '/Method Sylius\\Bundle\\ThemeBundle\\Filesystem\\FilesystemInterface::[A-Za-z]+\(\) has no return typehint specified./'
+        - '/Method Sylius\\Bundle\\ThemeBundle\\Translation\\ThemeAwareTranslator::__call\(\) has no return typehint specified./'
+        - '/Method Sylius\\Bundle\\ThemeBundle\\Translation\\ThemeAwareTranslator::trans\(\) has parameter \$[A-Za-z]+ with no typehint specified./'
+        - '/Method Sylius\\Bundle\\ThemeBundle\\Templating\\Locator\\TemplateFileLocator::unserialize\(\) has parameter \$serialized with no typehint specified./'
diff --git a/psalm.xml b/psalm.xml
index 263fea38..bad50e70 100644
--- a/psalm.xml
+++ b/psalm.xml
@@ -45,6 +45,7 @@
 
         <InvalidArgument>
             <errorLevel type="suppress">
+                <referencedFunction name="Symfony\Component\Config\FileLocatorInterface::locate" />
                 <referencedFunction name="Symfony\Component\EventDispatcher\EventDispatcherInterface::dispatch" />
             </errorLevel>
         </InvalidArgument>
diff --git a/src/Asset/Installer/AssetsInstaller.php b/src/Asset/Installer/AssetsInstaller.php
index 4a4f8341..dcd0ed02 100644
--- a/src/Asset/Installer/AssetsInstaller.php
+++ b/src/Asset/Installer/AssetsInstaller.php
@@ -20,7 +20,6 @@
 use Symfony\Component\Filesystem\Exception\IOException;
 use Symfony\Component\Filesystem\Filesystem;
 use Symfony\Component\Finder\Finder;
-use Symfony\Component\Finder\SplFileInfo;
 use Symfony\Component\HttpKernel\Bundle\BundleInterface;
 use Symfony\Component\HttpKernel\KernelInterface;
 
@@ -110,7 +109,6 @@ private function installThemedBundleAssets(ThemeInterface $theme, string $origin
         $finder = new Finder();
         $finder->sortByName()->ignoreDotFiles(false)->in($originDir);
 
-        /** @var SplFileInfo[] $finder */
         foreach ($finder as $originFile) {
             $targetFile = $targetDir . '/' . $originFile->getRelativePathname();
             $targetFile = $this->pathResolver->resolve($targetFile, $theme);
diff --git a/src/Asset/Package/PathPackage.php b/src/Asset/Package/PathPackage.php
index 71149289..d2192fd7 100644
--- a/src/Asset/Package/PathPackage.php
+++ b/src/Asset/Package/PathPackage.php
@@ -43,10 +43,7 @@ public function __construct(
         $this->pathResolver = $pathResolver;
     }
 
-    /**
-     * {@inheritdoc}
-     */
-    public function getUrl($path): string
+    public function getUrl(string $path): string
     {
         if ($this->isAbsoluteUrl($path)) {
             return $path;
diff --git a/src/Asset/Package/UrlPackage.php b/src/Asset/Package/UrlPackage.php
index 4c1cdff0..0981b4f6 100644
--- a/src/Asset/Package/UrlPackage.php
+++ b/src/Asset/Package/UrlPackage.php
@@ -67,10 +67,7 @@ public function __construct(
         $this->pathResolver = $pathResolver;
     }
 
-    /**
-     * {@inheritdoc}
-     */
-    public function getUrl($path): string
+    public function getUrl(string $path): string
     {
         if ($this->isAbsoluteUrl($path)) {
             return $path;
diff --git a/src/Configuration/ThemeConfiguration.php b/src/Configuration/ThemeConfiguration.php
index 70114bb3..d6d14bb3 100644
--- a/src/Configuration/ThemeConfiguration.php
+++ b/src/Configuration/ThemeConfiguration.php
@@ -24,28 +24,19 @@ final class ThemeConfiguration implements ConfigurationInterface
      */
     public function getConfigTreeBuilder(): TreeBuilder
     {
-        if (method_exists(TreeBuilder::class, 'getRootNode')) {
-            $treeBuilder = new TreeBuilder('sylius_theme');
-
-            /** @var ArrayNodeDefinition $rootNodeDefinition */
-            $rootNodeDefinition = $treeBuilder->getRootNode();
-        } else {
-            // BC layer for symfony/config 4.1 and older
-            $treeBuilder = new TreeBuilder();
-
-            /** @var ArrayNodeDefinition $rootNodeDefinition */
-            $rootNodeDefinition = $treeBuilder->root('sylius_theme');
-        }
-
-        $rootNodeDefinition->ignoreExtraKeys();
-
-        $this->addRequiredNameField($rootNodeDefinition);
-        $this->addOptionalTitleField($rootNodeDefinition);
-        $this->addOptionalDescriptionField($rootNodeDefinition);
-        $this->addOptionalPathField($rootNodeDefinition);
-        $this->addOptionalParentsList($rootNodeDefinition);
-        $this->addOptionalScreenshotsList($rootNodeDefinition);
-        $this->addOptionalAuthorsList($rootNodeDefinition);
+        $treeBuilder = new TreeBuilder('sylius_theme');
+        /** @var ArrayNodeDefinition $rootNode */
+        $rootNode = $treeBuilder->getRootNode();
+
+        $rootNode->ignoreExtraKeys();
+
+        $this->addRequiredNameField($rootNode);
+        $this->addOptionalTitleField($rootNode);
+        $this->addOptionalDescriptionField($rootNode);
+        $this->addOptionalPathField($rootNode);
+        $this->addOptionalParentsList($rootNode);
+        $this->addOptionalScreenshotsList($rootNode);
+        $this->addOptionalAuthorsList($rootNode);
 
         return $treeBuilder;
     }
diff --git a/src/DependencyInjection/Configuration.php b/src/DependencyInjection/Configuration.php
index 2616aaf9..6aa56bb1 100644
--- a/src/DependencyInjection/Configuration.php
+++ b/src/DependencyInjection/Configuration.php
@@ -36,25 +36,16 @@ public function __construct(array $configurationSourceFactories = [])
      */
     public function getConfigTreeBuilder(): TreeBuilder
     {
-        if (method_exists(TreeBuilder::class, 'getRootNode')) {
-            $treeBuilder = new TreeBuilder('sylius_theme');
+        $treeBuilder = new TreeBuilder('sylius_theme');
+        /** @var ArrayNodeDefinition $rootNode */
+        $rootNode = $treeBuilder->getRootNode();
 
-            /** @var ArrayNodeDefinition $rootNodeDefinition */
-            $rootNodeDefinition = $treeBuilder->getRootNode();
-        } else {
-            // BC layer for symfony/config 4.1 and older
-            $treeBuilder = new TreeBuilder();
+        $this->addSourcesConfiguration($rootNode);
 
-            /** @var ArrayNodeDefinition $rootNodeDefinition */
-            $rootNodeDefinition = $treeBuilder->root('sylius_theme');
-        }
-
-        $this->addSourcesConfiguration($rootNodeDefinition);
-
-        $rootNodeDefinition->children()->arrayNode('assets')->canBeDisabled();
-        $rootNodeDefinition->children()->arrayNode('templating')->canBeDisabled();
-        $rootNodeDefinition->children()->arrayNode('translations')->canBeDisabled();
-        $rootNodeDefinition->children()->scalarNode('context')->defaultValue('sylius.theme.context.settable')->cannotBeEmpty();
+        $rootNode->children()->arrayNode('assets')->canBeDisabled();
+        $rootNode->children()->arrayNode('templating')->canBeDisabled();
+        $rootNode->children()->arrayNode('translations')->canBeDisabled();
+        $rootNode->children()->scalarNode('context')->defaultValue('sylius.theme.context.settable')->cannotBeEmpty();
 
         return $treeBuilder;
     }
diff --git a/src/Filesystem/FilesystemInterface.php b/src/Filesystem/FilesystemInterface.php
index a73df8ff..2a7d953f 100644
--- a/src/Filesystem/FilesystemInterface.php
+++ b/src/Filesystem/FilesystemInterface.php
@@ -32,7 +32,7 @@ interface FilesystemInterface
      * @throws FileNotFoundException When originFile doesn't exist
      * @throws IOException           When copy fails
      */
-    public function copy($originFile, $targetFile, $override = false);
+    public function copy(string $originFile, string $targetFile, bool $override = false);
 
     /**
      * Creates a directory recursively.
@@ -42,7 +42,7 @@ public function copy($originFile, $targetFile, $override = false);
      *
      * @throws IOException On any directory creation failure
      */
-    public function mkdir($dirs, $mode = 0777);
+    public function mkdir($dirs, int $mode = 0777);
 
     /**
      * Checks the existence of files or directories.
@@ -62,7 +62,7 @@ public function exists($files);
      *
      * @throws IOException When touch fails
      */
-    public function touch($files, $time = null, $atime = null);
+    public function touch($files, int $time = null, int $atime = null);
 
     /**
      * Removes files or directories.
@@ -83,7 +83,7 @@ public function remove($files);
      *
      * @throws IOException When the change fail
      */
-    public function chmod($files, $mode, $umask = 0000, $recursive = false);
+    public function chmod($files, int $mode, int $umask = 0000, bool $recursive = false);
 
     /**
      * Change the owner of an array of files or directories.
@@ -94,7 +94,7 @@ public function chmod($files, $mode, $umask = 0000, $recursive = false);
      *
      * @throws IOException When the change fail
      */
-    public function chown($files, $user, $recursive = false);
+    public function chown($files, string $user, bool $recursive = false);
 
     /**
      * Change the group of an array of files or directories.
@@ -105,7 +105,7 @@ public function chown($files, $user, $recursive = false);
      *
      * @throws IOException When the change fail
      */
-    public function chgrp($files, $group, $recursive = false);
+    public function chgrp($files, string $group, bool $recursive = false);
 
     /**
      * Renames a file or a directory.
@@ -117,7 +117,7 @@ public function chgrp($files, $group, $recursive = false);
      * @throws IOException When target file or directory already exists
      * @throws IOException When origin cannot be renamed
      */
-    public function rename($origin, $target, $overwrite = false);
+    public function rename(string $origin, string $target, bool $overwrite = false);
 
     /**
      * Creates a symbolic link or copy a directory.
@@ -128,7 +128,7 @@ public function rename($origin, $target, $overwrite = false);
      *
      * @throws IOException When symlink fails
      */
-    public function symlink($originDir, $targetDir, $copyOnWindows = false);
+    public function symlink(string $originDir, string $targetDir, bool $copyOnWindows = false);
 
     /**
      * Mirrors a directory to another.
@@ -144,7 +144,7 @@ public function symlink($originDir, $targetDir, $copyOnWindows = false);
      *
      * @throws IOException When file type is unknown
      */
-    public function mirror($originDir, $targetDir, \Traversable $iterator = null, $options = []);
+    public function mirror(string $originDir, string $targetDir, \Traversable $iterator = null, array $options = []);
 
     /**
      * Given an existing path, convert it to a path relative to a given starting path.
@@ -154,7 +154,7 @@ public function mirror($originDir, $targetDir, \Traversable $iterator = null, $o
      *
      * @return string Path of target relative to starting path
      */
-    public function makePathRelative($endPath, $startPath);
+    public function makePathRelative(string $endPath, string $startPath);
 
     /**
      * Returns whether the file path is an absolute path.
@@ -163,7 +163,7 @@ public function makePathRelative($endPath, $startPath);
      *
      * @return bool
      */
-    public function isAbsolutePath($file);
+    public function isAbsolutePath(string $file);
 
     public function getFileContents(string $file): string;
 }
diff --git a/src/Loader/ThemeLoader.php b/src/Loader/ThemeLoader.php
index a6e08f86..1098c695 100644
--- a/src/Loader/ThemeLoader.php
+++ b/src/Loader/ThemeLoader.php
@@ -81,7 +81,6 @@ private function initializeThemes(array $configurations): array
     {
         $themes = [];
         foreach ($configurations as $configuration) {
-            /** @var ThemeInterface $theme */
             $themes[$configuration['name']] = $this->themeFactory->create($configuration['name'], $configuration['path']);
         }
 
diff --git a/src/Locator/BundleResourceLocator.php b/src/Locator/BundleResourceLocator.php
index b02922ac..91cea679 100644
--- a/src/Locator/BundleResourceLocator.php
+++ b/src/Locator/BundleResourceLocator.php
@@ -66,7 +66,7 @@ private function locateResourceBasedOnBundleNotation(string $resourcePath, Theme
 
         // Symfony 4.0+ always returns a single bundle
         /** @var BundleInterface|BundleInterface[] $bundles */
-        $bundles = $this->kernel->getBundle($bundleName, false);
+        $bundles = $this->kernel->getBundle($bundleName);
 
         // So we need to hack it to support both Symfony 3.4 and Symfony 4.0+
         if (!is_array($bundles)) {
diff --git a/src/Twig/ThemeFilesystemLoader.php b/src/Twig/ThemeFilesystemLoader.php
index 54614373..0a65432e 100644
--- a/src/Twig/ThemeFilesystemLoader.php
+++ b/src/Twig/ThemeFilesystemLoader.php
@@ -74,6 +74,7 @@ public function getCacheKey($name): string
 
     /**
      * @param string|TemplateReference $name
+     * @param int $time
      */
     public function isFresh($name, $time): bool
     {
diff --git a/tests/Application/Kernel.php b/tests/Application/Kernel.php
index f22160aa..54aef8cc 100644
--- a/tests/Application/Kernel.php
+++ b/tests/Application/Kernel.php
@@ -18,9 +18,6 @@
 
 final class Kernel extends HttpKernel
 {
-    /**
-     * {@inheritdoc}
-     */
     public function registerBundles()
     {
         return [
@@ -31,10 +28,7 @@ public function registerBundles()
         ];
     }
 
-    /**
-     * {@inheritdoc}
-     */
-    public function registerContainerConfiguration(LoaderInterface $loader)
+    public function registerContainerConfiguration(LoaderInterface $loader): void
     {
         $loader->load(__DIR__ . '/config/config.yml');
     }
diff --git a/tests/Application/TestBundle/DependencyInjection/TestExtension.php b/tests/Application/TestBundle/DependencyInjection/TestExtension.php
index 489b91c3..b0bced55 100644
--- a/tests/Application/TestBundle/DependencyInjection/TestExtension.php
+++ b/tests/Application/TestBundle/DependencyInjection/TestExtension.php
@@ -20,10 +20,7 @@
 
 final class TestExtension extends Extension
 {
-    /**
-     * {@inheritdoc}
-     */
-    public function load(array $configs, ContainerBuilder $container)
+    public function load(array $configs, ContainerBuilder $container): void
     {
         $loader = new XmlFileLoader($container, new FileLocator(__DIR__ . '/../Resources/config'));
         $loader->load('services.xml');
diff --git a/tests/DependencyInjection/ConfigurationTest.php b/tests/DependencyInjection/ConfigurationTest.php
index 76e276dc..8ac71fc4 100644
--- a/tests/DependencyInjection/ConfigurationTest.php
+++ b/tests/DependencyInjection/ConfigurationTest.php
@@ -66,7 +66,7 @@ public function its_context_can_be_overridden(): void
     /**
      * @test
      */
-    public function assets_support_is_enabled_by_default()
+    public function assets_support_is_enabled_by_default(): void
     {
         $this->assertProcessedConfigurationEquals([[]], ['assets' => ['enabled' => true]], 'assets');
     }
@@ -74,7 +74,7 @@ public function assets_support_is_enabled_by_default()
     /**
      * @test
      */
-    public function assets_support_may_be_toggled()
+    public function assets_support_may_be_toggled(): void
     {
         $this->assertProcessedConfigurationEquals([['assets' => ['enabled' => true]]], ['assets' => ['enabled' => true]], 'assets');
         $this->assertProcessedConfigurationEquals([['assets' => []]], ['assets' => ['enabled' => true]], 'assets');
@@ -87,7 +87,7 @@ public function assets_support_may_be_toggled()
     /**
      * @test
      */
-    public function templating_support_is_enabled_by_default()
+    public function templating_support_is_enabled_by_default(): void
     {
         $this->assertProcessedConfigurationEquals([[]], ['templating' => ['enabled' => true]], 'templating');
     }
@@ -95,7 +95,7 @@ public function templating_support_is_enabled_by_default()
     /**
      * @test
      */
-    public function templating_support_may_be_toggled()
+    public function templating_support_may_be_toggled(): void
     {
         $this->assertProcessedConfigurationEquals([['templating' => ['enabled' => true]]], ['templating' => ['enabled' => true]], 'templating');
         $this->assertProcessedConfigurationEquals([['templating' => []]], ['templating' => ['enabled' => true]], 'templating');
@@ -108,7 +108,7 @@ public function templating_support_may_be_toggled()
     /**
      * @test
      */
-    public function translations_support_is_enabled_by_default()
+    public function translations_support_is_enabled_by_default(): void
     {
         $this->assertProcessedConfigurationEquals([[]], ['translations' => ['enabled' => true]], 'translations');
     }
@@ -116,7 +116,7 @@ public function translations_support_is_enabled_by_default()
     /**
      * @test
      */
-    public function translations_support_may_be_toggled()
+    public function translations_support_may_be_toggled(): void
     {
         $this->assertProcessedConfigurationEquals([['translations' => ['enabled' => true]]], ['translations' => ['enabled' => true]], 'translations');
         $this->assertProcessedConfigurationEquals([['translations' => []]], ['translations' => ['enabled' => true]], 'translations');
@@ -126,9 +126,6 @@ public function translations_support_may_be_toggled()
         $this->assertProcessedConfigurationEquals([['translations' => false]], ['translations' => ['enabled' => false]], 'translations');
     }
 
-    /**
-     * {@inheritdoc}
-     */
     protected function getConfiguration(): ConfigurationInterface
     {
         return new Configuration();
diff --git a/tests/Functional/AssetTest.php b/tests/Functional/AssetTest.php
index ddc814c7..a45f79e7 100644
--- a/tests/Functional/AssetTest.php
+++ b/tests/Functional/AssetTest.php
@@ -107,7 +107,7 @@ private function createWebDirectory(): string
         return $webDirectory;
     }
 
-    private function assertFileContent($lines, $webDirectory): void
+    private function assertFileContent(array $lines, string $webDirectory): void
     {
         foreach ($lines as $line) {
             if (empty($line)) {
diff --git a/tests/Translation/DependencyInjection/Compiler/TranslatorFallbackLocalesPassTest.php b/tests/Translation/DependencyInjection/Compiler/TranslatorFallbackLocalesPassTest.php
index 0e1defab..42a3efd6 100644
--- a/tests/Translation/DependencyInjection/Compiler/TranslatorFallbackLocalesPassTest.php
+++ b/tests/Translation/DependencyInjection/Compiler/TranslatorFallbackLocalesPassTest.php
@@ -103,10 +103,7 @@ public function it_does_not_force_symfony_translator_to_have_any_method_calls():
         $this->assertContainerBuilderHasService('sylius.theme.translation.translator');
     }
 
-    /**
-     * {@inheritdoc}
-     */
-    protected function registerCompilerPass(ContainerBuilder $container)
+    protected function registerCompilerPass(ContainerBuilder $container): void
     {
         $container->addCompilerPass(new TranslatorFallbackLocalesPass());
     }
diff --git a/tests/Translation/DependencyInjection/Compiler/TranslatorLoaderProviderPassTest.php b/tests/Translation/DependencyInjection/Compiler/TranslatorLoaderProviderPassTest.php
index 7f5ae43e..7e3c4cb7 100644
--- a/tests/Translation/DependencyInjection/Compiler/TranslatorLoaderProviderPassTest.php
+++ b/tests/Translation/DependencyInjection/Compiler/TranslatorLoaderProviderPassTest.php
@@ -98,10 +98,7 @@ public function it_does_not_force_the_existence_of_translation_loaders(): void
         );
     }
 
-    /**
-     * {@inheritdoc}
-     */
-    protected function registerCompilerPass(ContainerBuilder $container)
+    protected function registerCompilerPass(ContainerBuilder $container): void
     {
         $container->addCompilerPass(new TranslatorLoaderProviderPass());
     }
diff --git a/tests/Translation/DependencyInjection/Compiler/TranslatorResourceProviderPassTest.php b/tests/Translation/DependencyInjection/Compiler/TranslatorResourceProviderPassTest.php
index f8f36dbf..591570dd 100644
--- a/tests/Translation/DependencyInjection/Compiler/TranslatorResourceProviderPassTest.php
+++ b/tests/Translation/DependencyInjection/Compiler/TranslatorResourceProviderPassTest.php
@@ -144,10 +144,7 @@ public function it_does_not_crash_if_definition_does_not_have_resource_files_at_
         );
     }
 
-    /**
-     * {@inheritdoc}
-     */
-    protected function registerCompilerPass(ContainerBuilder $container)
+    protected function registerCompilerPass(ContainerBuilder $container): void
     {
         $container->addCompilerPass(new TranslatorResourceProviderPass());
     }
diff --git a/tests/Translation/TranslatorTest.php b/tests/Translation/TranslatorTest.php
index fe910305..a9a6bda6 100644
--- a/tests/Translation/TranslatorTest.php
+++ b/tests/Translation/TranslatorTest.php
@@ -51,7 +51,7 @@ public function it_instantiates_with_valid_options(array $options): void
      * @dataProvider getInvalidLocalesTests
      * @expectedException \InvalidArgumentException
      */
-    public function it_throws_exception_on_instantiating_with_invalid_locale($locale): void
+    public function it_throws_exception_on_instantiating_with_invalid_locale(string $locale): void
     {
         $this->createTranslator($locale);
     }
@@ -60,7 +60,7 @@ public function it_throws_exception_on_instantiating_with_invalid_locale($locale
      * @test
      * @dataProvider getAllValidLocalesTests
      */
-    public function it_instantiates_with_valid_locale($locale): void
+    public function it_instantiates_with_valid_locale(string $locale): void
     {
         $translator = $this->createTranslator($locale);
 
@@ -72,7 +72,7 @@ public function it_instantiates_with_valid_locale($locale): void
      * @dataProvider getInvalidLocalesTests
      * @expectedException \InvalidArgumentException
      */
-    public function its_throws_exception_on_setting_invalid_fallback_locales($locale): void
+    public function its_throws_exception_on_setting_invalid_fallback_locales(string $locale): void
     {
         $translator = $this->createTranslator('fr');
         $translator->setFallbackLocales(['fr', $locale]);
@@ -82,7 +82,7 @@ public function its_throws_exception_on_setting_invalid_fallback_locales($locale
      * @test
      * @dataProvider getAllValidLocalesTests
      */
-    public function its_fallback_locales_can_be_set_only_if_valid($locale): void
+    public function its_fallback_locales_can_be_set_only_if_valid(string $locale): void
     {
         $translator = $this->createTranslator('fr');
         $translator->setFallbackLocales(['fr', $locale]);
@@ -94,7 +94,7 @@ public function its_fallback_locales_can_be_set_only_if_valid($locale): void
      * @test
      * @dataProvider getAllValidLocalesTests
      */
-    public function it_adds_resources_with_valid_locales($locale): void
+    public function it_adds_resources_with_valid_locales(string $locale): void
     {
         $translator = $this->createTranslator('fr');
         $translator->addLoader('array', new ArrayLoader());
@@ -107,7 +107,7 @@ public function it_adds_resources_with_valid_locales($locale): void
      * @test
      * @dataProvider getAllValidLocalesTests
      */
-    public function it_translates_valid_locales($locale): void
+    public function it_translates_valid_locales(string $locale): void
     {
         $translator = $this->createTranslator($locale);
         $translator->addLoader('array', new ArrayLoader());
@@ -153,7 +153,7 @@ public function it_can_have_multiple_fallback_locales(): void
      * @test
      * @dataProvider getThemelessLocalesTests
      */
-    public function it_gets_catalogue_with_fallback_catalogues_of_a_simple_locale($locale): void
+    public function it_gets_catalogue_with_fallback_catalogues_of_a_simple_locale(string $locale): void
     {
         $translator = $this->createTranslator($locale);
         $catalogue = new MessageCatalogue($locale);
@@ -165,7 +165,7 @@ public function it_gets_catalogue_with_fallback_catalogues_of_a_simple_locale($l
      * @test
      * @dataProvider getThemedLocalesTests
      */
-    public function it_gets_catalogue_with_fallback_catalogues_of_a_themed_locale($locale): void
+    public function it_gets_catalogue_with_fallback_catalogues_of_a_themed_locale(string $locale): void
     {
         $translator = $this->createTranslator($locale);
 
@@ -269,10 +269,7 @@ public function it_creates_a_nested_catalogue_with_fallback_translations(): void
         $this->assertEquals($catalogue, $translator->getCatalogue());
     }
 
-    /**
-     * @return array
-     */
-    public function getInvalidLocalesTests()
+    public function getInvalidLocalesTests(): array
     {
         return [
             ['fr FR'],
@@ -289,10 +286,7 @@ public function getInvalidLocalesTests()
         ];
     }
 
-    /**
-     * @return array
-     */
-    public function getAllValidLocalesTests()
+    public function getAllValidLocalesTests(): array
     {
         return array_merge(
             $this->getThemedLocalesTests(),
@@ -300,10 +294,7 @@ public function getAllValidLocalesTests()
         );
     }
 
-    /**
-     * @return array
-     */
-    public function getThemedLocalesTests()
+    public function getThemedLocalesTests(): array
     {
         return [
             ['fr@heron'],
@@ -316,10 +307,7 @@ public function getThemedLocalesTests()
         ];
     }
 
-    /**
-     * @return array
-     */
-    public function getThemelessLocalesTests()
+    public function getThemelessLocalesTests(): array
     {
         return [
             [''],
@@ -333,10 +321,7 @@ public function getThemelessLocalesTests()
         ];
     }
 
-    /**
-     * @return array
-     */
-    public function getValidOptionsTests()
+    public function getValidOptionsTests(): array
     {
         return [
             [['cache_dir' => null, 'debug' => false]],
@@ -347,10 +332,7 @@ public function getValidOptionsTests()
         ];
     }
 
-    /**
-     * @return array
-     */
-    public function getInvalidOptionsTests()
+    public function getInvalidOptionsTests(): array
     {
         return [
             [['heron' => '']],
@@ -360,10 +342,9 @@ public function getInvalidOptionsTests()
     }
 
     /**
-     * @param string $locale
      * @param string[] $options
      */
-    private function createTranslator($locale = 'en', $options = []): Translator
+    private function createTranslator(string $locale = 'en', array $options = []): Translator
     {
         $loaderProvider = new TranslatorLoaderProvider();
         $resourceProvider = new TranslatorResourceProvider();