diff --git a/CHANGELOG.md b/CHANGELOG.md
index 218cb8f25..7ce45c161 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 - Added missing `swiftmailer` dependency
 
 ### Changed
+- Risky code change for PHP 7
 - Made `sonata-project/google-authenticator` an optional dependency
 - Moved public methods of `User` to `UserInterface`
 - Lowered upper composer dependencies
diff --git a/src/Admin/Document/GroupAdmin.php b/src/Admin/Document/GroupAdmin.php
index bcc407ec7..235e2a047 100644
--- a/src/Admin/Document/GroupAdmin.php
+++ b/src/Admin/Document/GroupAdmin.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
diff --git a/src/Admin/Document/UserAdmin.php b/src/Admin/Document/UserAdmin.php
index 5033b37e2..adca51a76 100644
--- a/src/Admin/Document/UserAdmin.php
+++ b/src/Admin/Document/UserAdmin.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
diff --git a/src/Admin/Entity/GroupAdmin.php b/src/Admin/Entity/GroupAdmin.php
index 12ab13b5f..3859a1b57 100644
--- a/src/Admin/Entity/GroupAdmin.php
+++ b/src/Admin/Entity/GroupAdmin.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
diff --git a/src/Admin/Entity/UserAdmin.php b/src/Admin/Entity/UserAdmin.php
index eaddcbaba..2a138c40e 100644
--- a/src/Admin/Entity/UserAdmin.php
+++ b/src/Admin/Entity/UserAdmin.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
diff --git a/src/Admin/Model/GroupAdmin.php b/src/Admin/Model/GroupAdmin.php
index ae2a4190b..ab6edf883 100644
--- a/src/Admin/Model/GroupAdmin.php
+++ b/src/Admin/Model/GroupAdmin.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -39,7 +41,7 @@ public function getNewInstance()
     /**
      * {@inheritdoc}
      */
-    protected function configureListFields(ListMapper $listMapper)
+    protected function configureListFields(ListMapper $listMapper): void
     {
         $listMapper
             ->addIdentifier('name')
@@ -50,7 +52,7 @@ protected function configureListFields(ListMapper $listMapper)
     /**
      * {@inheritdoc}
      */
-    protected function configureDatagridFilters(DatagridMapper $datagridMapper)
+    protected function configureDatagridFilters(DatagridMapper $datagridMapper): void
     {
         $datagridMapper
             ->add('name')
@@ -60,7 +62,7 @@ protected function configureDatagridFilters(DatagridMapper $datagridMapper)
     /**
      * {@inheritdoc}
      */
-    protected function configureFormFields(FormMapper $formMapper)
+    protected function configureFormFields(FormMapper $formMapper): void
     {
         $formMapper
             ->tab('Group')
diff --git a/src/Admin/Model/UserAdmin.php b/src/Admin/Model/UserAdmin.php
index 21d075f00..6867edfcb 100644
--- a/src/Admin/Model/UserAdmin.php
+++ b/src/Admin/Model/UserAdmin.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -64,7 +66,7 @@ public function getExportFields()
     /**
      * {@inheritdoc}
      */
-    public function preUpdate($user)
+    public function preUpdate($user): void
     {
         $this->getUserManager()->updateCanonicalFields($user);
         $this->getUserManager()->updatePassword($user);
@@ -73,7 +75,7 @@ public function preUpdate($user)
     /**
      * @param UserManagerInterface $userManager
      */
-    public function setUserManager(UserManagerInterface $userManager)
+    public function setUserManager(UserManagerInterface $userManager): void
     {
         $this->userManager = $userManager;
     }
@@ -89,7 +91,7 @@ public function getUserManager()
     /**
      * {@inheritdoc}
      */
-    protected function configureListFields(ListMapper $listMapper)
+    protected function configureListFields(ListMapper $listMapper): void
     {
         $listMapper
             ->addIdentifier('username')
@@ -109,7 +111,7 @@ protected function configureListFields(ListMapper $listMapper)
     /**
      * {@inheritdoc}
      */
-    protected function configureDatagridFilters(DatagridMapper $filterMapper)
+    protected function configureDatagridFilters(DatagridMapper $filterMapper): void
     {
         $filterMapper
             ->add('id')
@@ -122,7 +124,7 @@ protected function configureDatagridFilters(DatagridMapper $filterMapper)
     /**
      * {@inheritdoc}
      */
-    protected function configureShowFields(ShowMapper $showMapper)
+    protected function configureShowFields(ShowMapper $showMapper): void
     {
         $showMapper
             ->with('General')
@@ -161,7 +163,7 @@ protected function configureShowFields(ShowMapper $showMapper)
     /**
      * {@inheritdoc}
      */
-    protected function configureFormFields(FormMapper $formMapper)
+    protected function configureFormFields(FormMapper $formMapper): void
     {
         // define group zoning
         $formMapper
diff --git a/src/Command/TwoStepVerificationCommand.php b/src/Command/TwoStepVerificationCommand.php
index 22f44a67d..9d6b02798 100644
--- a/src/Command/TwoStepVerificationCommand.php
+++ b/src/Command/TwoStepVerificationCommand.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -22,7 +24,7 @@ class TwoStepVerificationCommand extends ContainerAwareCommand
     /**
      * {@inheritdoc}
      */
-    public function configure()
+    public function configure(): void
     {
         $this->setName('sonata:user:two-step-verification');
         $this->addArgument('username', InputArgument::REQUIRED, 'The username to protect with a two step verification process');
@@ -33,7 +35,7 @@ public function configure()
     /**
      * {@inheritdoc}
      */
-    public function execute(InputInterface $input, OutputInterface $output)
+    public function execute(InputInterface $input, OutputInterface $output): void
     {
         if (!$this->getContainer()->has('sonata.user.google.authenticator.provider')) {
             throw new \RuntimeException('Two Step Verification process is not enabled');
diff --git a/src/Controller/AdminResettingController.php b/src/Controller/AdminResettingController.php
index b1918f19d..1f11cc7e2 100644
--- a/src/Controller/AdminResettingController.php
+++ b/src/Controller/AdminResettingController.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -173,7 +175,7 @@ public function resetAction(Request $request, $token)
      *
      * @param UserInterface $user
      */
-    private function sendResettingEmailMessage(UserInterface $user)
+    private function sendResettingEmailMessage(UserInterface $user): void
     {
         $url = $this->generateUrl('sonata_user_admin_resetting_reset', [
             'token' => $user->getConfirmationToken(),
diff --git a/src/Controller/AdminSecurityController.php b/src/Controller/AdminSecurityController.php
index 546ee9709..e23a5b535 100644
--- a/src/Controller/AdminSecurityController.php
+++ b/src/Controller/AdminSecurityController.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -73,12 +75,12 @@ public function loginAction(Request $request)
         ]);
     }
 
-    public function checkAction()
+    public function checkAction(): void
     {
         throw new \RuntimeException('You must configure the check path to be handled by the firewall using form_login in your security firewall configuration.');
     }
 
-    public function logoutAction()
+    public function logoutAction(): void
     {
         throw new \RuntimeException('You must activate the logout in your security firewall configuration.');
     }
diff --git a/src/Controller/Api/GroupController.php b/src/Controller/Api/GroupController.php
index 90f30597a..a256545b5 100644
--- a/src/Controller/Api/GroupController.php
+++ b/src/Controller/Api/GroupController.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
diff --git a/src/Controller/Api/UserController.php b/src/Controller/Api/UserController.php
index 112f73869..279185939 100644
--- a/src/Controller/Api/UserController.php
+++ b/src/Controller/Api/UserController.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
diff --git a/src/DependencyInjection/Compiler/GlobalVariablesCompilerPass.php b/src/DependencyInjection/Compiler/GlobalVariablesCompilerPass.php
index 4b09e60b6..7d7ddbd4c 100644
--- a/src/DependencyInjection/Compiler/GlobalVariablesCompilerPass.php
+++ b/src/DependencyInjection/Compiler/GlobalVariablesCompilerPass.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -25,7 +27,7 @@ class GlobalVariablesCompilerPass implements CompilerPassInterface
     /**
      * {@inheritdoc}
      */
-    public function process(ContainerBuilder $container)
+    public function process(ContainerBuilder $container): void
     {
         $container->getDefinition('twig')
             ->addMethodCall('addGlobal', ['sonata_user', new Reference('sonata.user.twig.global')]);
diff --git a/src/DependencyInjection/Configuration.php b/src/DependencyInjection/Configuration.php
index 281ff8003..fe6c107e0 100644
--- a/src/DependencyInjection/Configuration.php
+++ b/src/DependencyInjection/Configuration.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
diff --git a/src/DependencyInjection/SonataUserExtension.php b/src/DependencyInjection/SonataUserExtension.php
index cc4469f14..de16ad23f 100644
--- a/src/DependencyInjection/SonataUserExtension.php
+++ b/src/DependencyInjection/SonataUserExtension.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -31,7 +33,7 @@ class SonataUserExtension extends Extension implements PrependExtensionInterface
     /**
      * {@inheritdoc}
      */
-    public function prepend(ContainerBuilder $container)
+    public function prepend(ContainerBuilder $container): void
     {
         if ($container->hasExtension('twig')) {
             // add custom form widgets
@@ -42,7 +44,7 @@ public function prepend(ContainerBuilder $container)
     /**
      * {@inheritdoc}
      */
-    public function load(array $configs, ContainerBuilder $container)
+    public function load(array $configs, ContainerBuilder $container): void
     {
         $processor = new Processor();
         $configuration = new Configuration();
@@ -165,7 +167,7 @@ public function configureGoogleAuthenticator($config, ContainerBuilder $containe
      * @param array            $config
      * @param ContainerBuilder $container
      */
-    public function configureClass($config, ContainerBuilder $container)
+    public function configureClass($config, ContainerBuilder $container): void
     {
         if ('orm' === $config['manager_type']) {
             $modelType = 'entity';
@@ -183,7 +185,7 @@ public function configureClass($config, ContainerBuilder $container)
      * @param array            $config
      * @param ContainerBuilder $container
      */
-    public function configureAdminClass($config, ContainerBuilder $container)
+    public function configureAdminClass($config, ContainerBuilder $container): void
     {
         $container->setParameter('sonata.user.admin.user.class', $config['admin']['user']['class']);
         $container->setParameter('sonata.user.admin.group.class', $config['admin']['group']['class']);
@@ -193,7 +195,7 @@ public function configureAdminClass($config, ContainerBuilder $container)
      * @param array            $config
      * @param ContainerBuilder $container
      */
-    public function configureTranslationDomain($config, ContainerBuilder $container)
+    public function configureTranslationDomain($config, ContainerBuilder $container): void
     {
         $container->setParameter('sonata.user.admin.user.translation_domain', $config['admin']['user']['translation']);
         $container->setParameter('sonata.user.admin.group.translation_domain', $config['admin']['group']['translation']);
@@ -203,7 +205,7 @@ public function configureTranslationDomain($config, ContainerBuilder $container)
      * @param array            $config
      * @param ContainerBuilder $container
      */
-    public function configureController($config, ContainerBuilder $container)
+    public function configureController($config, ContainerBuilder $container): void
     {
         $container->setParameter('sonata.user.admin.user.controller', $config['admin']['user']['controller']);
         $container->setParameter('sonata.user.admin.group.controller', $config['admin']['group']['controller']);
@@ -212,7 +214,7 @@ public function configureController($config, ContainerBuilder $container)
     /**
      * @param array $config
      */
-    public function registerDoctrineMapping(array $config)
+    public function registerDoctrineMapping(array $config): void
     {
         foreach ($config['class'] as $type => $class) {
             if (!class_exists($class)) {
@@ -250,7 +252,7 @@ public function registerDoctrineMapping(array $config)
      * @param ContainerBuilder $container
      * @param                  $managerType
      */
-    protected function aliasManagers(ContainerBuilder $container, $managerType)
+    protected function aliasManagers(ContainerBuilder $container, $managerType): void
     {
         $container->setAlias('sonata.user.user_manager', sprintf('sonata.user.%s.user_manager', $managerType));
         $container->setAlias('sonata.user.group_manager', sprintf('sonata.user.%s.group_manager', $managerType));
@@ -259,7 +261,7 @@ protected function aliasManagers(ContainerBuilder $container, $managerType)
     /**
      * @param array $config
      */
-    private function checkManagerTypeToModelTypeMapping(array $config)
+    private function checkManagerTypeToModelTypeMapping(array $config): void
     {
         $managerType = $config['manager_type'];
 
diff --git a/src/Document/BaseGroup.php b/src/Document/BaseGroup.php
index ff513eda4..c0bb72d8d 100644
--- a/src/Document/BaseGroup.php
+++ b/src/Document/BaseGroup.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
diff --git a/src/Document/BaseUser.php b/src/Document/BaseUser.php
index d494a51fd..aea1d510c 100644
--- a/src/Document/BaseUser.php
+++ b/src/Document/BaseUser.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -22,7 +24,7 @@ class BaseUser extends AbstractedUser implements UserInterface
     /**
      * Hook on pre-persist operations.
      */
-    public function prePersist()
+    public function prePersist(): void
     {
         $this->createdAt = new \DateTime();
         $this->updatedAt = new \DateTime();
@@ -31,7 +33,7 @@ public function prePersist()
     /**
      * Hook on pre-update operations.
      */
-    public function preUpdate()
+    public function preUpdate(): void
     {
         $this->updatedAt = new \DateTime();
     }
diff --git a/src/Document/GroupManager.php b/src/Document/GroupManager.php
index 42939f918..45c38795b 100644
--- a/src/Document/GroupManager.php
+++ b/src/Document/GroupManager.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -30,7 +32,7 @@ public function findGroupsBy(array $criteria = null, array $orderBy = null, $lim
     /**
      * {@inheritdoc}
      */
-    public function getPager(array $criteria, $page, $limit = 10, array $sort = [])
+    public function getPager(array $criteria, $page, $limit = 10, array $sort = []): void
     {
         new \RuntimeException('method not implemented');
     }
diff --git a/src/Document/UserManager.php b/src/Document/UserManager.php
index 399b1552a..f9e97ffc1 100644
--- a/src/Document/UserManager.php
+++ b/src/Document/UserManager.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -30,7 +32,7 @@ public function findUsersBy(array $criteria = null, array $orderBy = null, $limi
     /**
      * {@inheritdoc}
      */
-    public function getPager(array $criteria, $page, $limit = 10, array $sort = [])
+    public function getPager(array $criteria, $page, $limit = 10, array $sort = []): void
     {
         new \RuntimeException('method not implemented');
     }
diff --git a/src/Entity/BaseGroup.php b/src/Entity/BaseGroup.php
index 85db0ece2..63c9050c1 100644
--- a/src/Entity/BaseGroup.php
+++ b/src/Entity/BaseGroup.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
diff --git a/src/Entity/BaseUser.php b/src/Entity/BaseUser.php
index b945ee70b..272a13ad1 100644
--- a/src/Entity/BaseUser.php
+++ b/src/Entity/BaseUser.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -22,7 +24,7 @@ class BaseUser extends AbstractedUser
     /**
      * Hook on pre-persist operations.
      */
-    public function prePersist()
+    public function prePersist(): void
     {
         $this->createdAt = new \DateTime();
         $this->updatedAt = new \DateTime();
@@ -31,7 +33,7 @@ public function prePersist()
     /**
      * Hook on pre-update operations.
      */
-    public function preUpdate()
+    public function preUpdate(): void
     {
         $this->updatedAt = new \DateTime();
     }
diff --git a/src/Entity/GroupManager.php b/src/Entity/GroupManager.php
index 8a1342358..286da173b 100644
--- a/src/Entity/GroupManager.php
+++ b/src/Entity/GroupManager.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
diff --git a/src/Entity/UserManager.php b/src/Entity/UserManager.php
index c98f486d0..3bacb44e7 100644
--- a/src/Entity/UserManager.php
+++ b/src/Entity/UserManager.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -74,7 +76,7 @@ public function create()
     /**
      * {@inheritdoc}
      */
-    public function save($entity, $andFlush = true)
+    public function save($entity, $andFlush = true): void
     {
         if (!$entity instanceof UserInterface) {
             throw new \InvalidArgumentException('Save method expected entity of type UserInterface');
@@ -86,7 +88,7 @@ public function save($entity, $andFlush = true)
     /**
      * {@inheritdoc}
      */
-    public function delete($entity, $andFlush = true)
+    public function delete($entity, $andFlush = true): void
     {
         if (!$entity instanceof UserInterface) {
             throw new \InvalidArgumentException('Save method expected entity of type UserInterface');
diff --git a/src/Entity/UserManagerProxy.php b/src/Entity/UserManagerProxy.php
index 886c78520..813852362 100644
--- a/src/Entity/UserManagerProxy.php
+++ b/src/Entity/UserManagerProxy.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
diff --git a/src/Form/Transformer/RestoreRolesTransformer.php b/src/Form/Transformer/RestoreRolesTransformer.php
index 46996df72..542e54a98 100644
--- a/src/Form/Transformer/RestoreRolesTransformer.php
+++ b/src/Form/Transformer/RestoreRolesTransformer.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -37,7 +39,7 @@ public function __construct(EditableRolesBuilder $rolesBuilder)
     /**
      * @param array|null $originalRoles
      */
-    public function setOriginalRoles(array $originalRoles = null)
+    public function setOriginalRoles(array $originalRoles = null): void
     {
         $this->originalRoles = $originalRoles ?: [];
     }
diff --git a/src/Form/Type/ApiGroupType.php b/src/Form/Type/ApiGroupType.php
index 18de24bb1..44904d3cf 100644
--- a/src/Form/Type/ApiGroupType.php
+++ b/src/Form/Type/ApiGroupType.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
diff --git a/src/Form/Type/ApiUserType.php b/src/Form/Type/ApiUserType.php
index 5b484a6bd..92a756ab0 100644
--- a/src/Form/Type/ApiUserType.php
+++ b/src/Form/Type/ApiUserType.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
diff --git a/src/Form/Type/SecurityRolesType.php b/src/Form/Type/SecurityRolesType.php
index d7a531e49..1a9b48b8a 100644
--- a/src/Form/Type/SecurityRolesType.php
+++ b/src/Form/Type/SecurityRolesType.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -40,7 +42,7 @@ public function __construct(EditableRolesBuilder $rolesBuilder)
     /**
      * {@inheritdoc}
      */
-    public function buildForm(FormBuilderInterface $formBuilder, array $options)
+    public function buildForm(FormBuilderInterface $formBuilder, array $options): void
     {
         /*
          * The form shows only roles that the current user can edit for the targeted user. Now we still need to persist
@@ -52,12 +54,12 @@ public function buildForm(FormBuilderInterface $formBuilder, array $options)
         $transformer = new RestoreRolesTransformer($this->rolesBuilder);
 
         // GET METHOD
-        $formBuilder->addEventListener(FormEvents::PRE_SET_DATA, function (FormEvent $event) use ($transformer) {
+        $formBuilder->addEventListener(FormEvents::PRE_SET_DATA, function (FormEvent $event) use ($transformer): void {
             $transformer->setOriginalRoles($event->getData());
         });
 
         // POST METHOD
-        $formBuilder->addEventListener(FormEvents::PRE_SUBMIT, function (FormEvent $event) use ($transformer) {
+        $formBuilder->addEventListener(FormEvents::PRE_SUBMIT, function (FormEvent $event) use ($transformer): void {
             $transformer->setOriginalRoles($event->getForm()->getData());
         });
 
@@ -67,7 +69,7 @@ public function buildForm(FormBuilderInterface $formBuilder, array $options)
     /**
      * {@inheritdoc}
      */
-    public function buildView(FormView $view, FormInterface $form, array $options)
+    public function buildView(FormView $view, FormInterface $form, array $options): void
     {
         $attr = $view->vars['attr'];
 
@@ -84,7 +86,7 @@ public function buildView(FormView $view, FormInterface $form, array $options)
     /**
      * {@inheritdoc}
      */
-    public function configureOptions(OptionsResolver $resolver)
+    public function configureOptions(OptionsResolver $resolver): void
     {
         $resolver->setDefaults([
             // make expanded default value
diff --git a/src/Form/Type/UserGenderListType.php b/src/Form/Type/UserGenderListType.php
index abd93e974..a5af54664 100644
--- a/src/Form/Type/UserGenderListType.php
+++ b/src/Form/Type/UserGenderListType.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
diff --git a/src/GoogleAuthenticator/Helper.php b/src/GoogleAuthenticator/Helper.php
index 9e5d6dba7..5854b9721 100644
--- a/src/GoogleAuthenticator/Helper.php
+++ b/src/GoogleAuthenticator/Helper.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
diff --git a/src/GoogleAuthenticator/InteractiveLoginListener.php b/src/GoogleAuthenticator/InteractiveLoginListener.php
index fa31dcf45..2bd0d9c2a 100644
--- a/src/GoogleAuthenticator/InteractiveLoginListener.php
+++ b/src/GoogleAuthenticator/InteractiveLoginListener.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -33,7 +35,7 @@ public function __construct(Helper $helper)
     /**
      * @param InteractiveLoginEvent $event
      */
-    public function onSecurityInteractiveLogin(InteractiveLoginEvent $event)
+    public function onSecurityInteractiveLogin(InteractiveLoginEvent $event): void
     {
         if (!$event->getAuthenticationToken() instanceof UsernamePasswordToken) {
             return;
diff --git a/src/GoogleAuthenticator/RequestListener.php b/src/GoogleAuthenticator/RequestListener.php
index 6210d8321..7d1a23d16 100644
--- a/src/GoogleAuthenticator/RequestListener.php
+++ b/src/GoogleAuthenticator/RequestListener.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -49,7 +51,7 @@ public function __construct(Helper $helper, TokenStorageInterface $tokenStorage,
     /**
      * @param GetResponseEvent $event
      */
-    public function onCoreRequest(GetResponseEvent $event)
+    public function onCoreRequest(GetResponseEvent $event): void
     {
         if (HttpKernel::MASTER_REQUEST != $event->getRequestType()) {
             return;
diff --git a/src/Model/GroupManagerInterface.php b/src/Model/GroupManagerInterface.php
index 48eb8f32b..61042948c 100644
--- a/src/Model/GroupManagerInterface.php
+++ b/src/Model/GroupManagerInterface.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
diff --git a/src/Model/User.php b/src/Model/User.php
index 48a32a233..37e7b5858 100644
--- a/src/Model/User.php
+++ b/src/Model/User.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
diff --git a/src/Model/UserInterface.php b/src/Model/UserInterface.php
index 1a950ed01..d558ba992 100644
--- a/src/Model/UserInterface.php
+++ b/src/Model/UserInterface.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
diff --git a/src/Model/UserManagerInterface.php b/src/Model/UserManagerInterface.php
index 25fe88cb2..882978e63 100644
--- a/src/Model/UserManagerInterface.php
+++ b/src/Model/UserManagerInterface.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
diff --git a/src/Security/Authorization/Voter/UserAclVoter.php b/src/Security/Authorization/Voter/UserAclVoter.php
index 282e1d1dc..43135916c 100644
--- a/src/Security/Authorization/Voter/UserAclVoter.php
+++ b/src/Security/Authorization/Voter/UserAclVoter.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
diff --git a/src/Security/EditableRolesBuilder.php b/src/Security/EditableRolesBuilder.php
index 4460d0f4a..8d88537b5 100644
--- a/src/Security/EditableRolesBuilder.php
+++ b/src/Security/EditableRolesBuilder.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -60,7 +62,7 @@ public function __construct(TokenStorageInterface $tokenStorage, AuthorizationCh
     /*
      * @param TranslatorInterface $translator
      */
-    public function setTranslator(TranslatorInterface $translator)
+    public function setTranslator(TranslatorInterface $translator): void
     {
         $this->translator = $translator;
     }
@@ -79,7 +81,7 @@ public function getRoles($domain = false, $expanded = true)
             return $roles;
         }
 
-        $this->iterateAdminRoles(function ($role, $isMaster) use ($domain, &$roles) {
+        $this->iterateAdminRoles(function ($role, $isMaster) use ($domain, &$roles): void {
             if ($isMaster) {
                 // if the user has the MASTER permission, allow to grant access the admin roles to other users
                 $roles[$role] = $this->translateRole($role, $domain);
@@ -122,7 +124,7 @@ public function getRolesReadOnly($domain = false)
             return $rolesReadOnly;
         }
 
-        $this->iterateAdminRoles(function ($role, $isMaster) use ($domain, &$rolesReadOnly) {
+        $this->iterateAdminRoles(function ($role, $isMaster) use ($domain, &$rolesReadOnly): void {
             if (!$isMaster && $this->authorizationChecker->isGranted($role)) {
                 // although the user has no MASTER permission, allow the currently logged in user to view the role
                 $rolesReadOnly[$role] = $this->translateRole($role, $domain);
@@ -132,7 +134,7 @@ public function getRolesReadOnly($domain = false)
         return $rolesReadOnly;
     }
 
-    private function iterateAdminRoles(callable $func)
+    private function iterateAdminRoles(callable $func): void
     {
         // get roles from the Admin classes
         foreach ($this->pool->getAdminServiceIds() as $id) {
diff --git a/src/Serializer/UserSerializerHandler.php b/src/Serializer/UserSerializerHandler.php
index 2e04fa26b..c6919ab85 100644
--- a/src/Serializer/UserSerializerHandler.php
+++ b/src/Serializer/UserSerializerHandler.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
diff --git a/src/SonataUserBundle.php b/src/SonataUserBundle.php
index f86506449..a5567ea2c 100644
--- a/src/SonataUserBundle.php
+++ b/src/SonataUserBundle.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -21,7 +23,7 @@ class SonataUserBundle extends Bundle
     /**
      * {@inheritdoc}
      */
-    public function build(ContainerBuilder $container)
+    public function build(ContainerBuilder $container): void
     {
         $container->addCompilerPass(new GlobalVariablesCompilerPass());
 
@@ -31,7 +33,7 @@ public function build(ContainerBuilder $container)
     /**
      * {@inheritdoc}
      */
-    public function boot()
+    public function boot(): void
     {
         $this->registerFormMapping();
     }
@@ -39,7 +41,7 @@ public function boot()
     /**
      * Register form mapping information.
      */
-    public function registerFormMapping()
+    public function registerFormMapping(): void
     {
         FormHelper::registerFormTypeMapping([
             'fos_user_username' => 'FOS\UserBundle\Form\Type\UsernameFormType',
diff --git a/src/Twig/GlobalVariables.php b/src/Twig/GlobalVariables.php
index b3f6ac9e8..ca331daf7 100644
--- a/src/Twig/GlobalVariables.php
+++ b/src/Twig/GlobalVariables.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
diff --git a/tests/Admin/Document/GroupAdmin.php b/tests/Admin/Document/GroupAdmin.php
index f11594652..ced152028 100644
--- a/tests/Admin/Document/GroupAdmin.php
+++ b/tests/Admin/Document/GroupAdmin.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
diff --git a/tests/Admin/Document/UserAdmin.php b/tests/Admin/Document/UserAdmin.php
index 857e20cc0..b4554cec0 100644
--- a/tests/Admin/Document/UserAdmin.php
+++ b/tests/Admin/Document/UserAdmin.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
diff --git a/tests/Admin/Entity/UserAdmin.php b/tests/Admin/Entity/UserAdmin.php
index ea785797d..c2ddc0d38 100644
--- a/tests/Admin/Entity/UserAdmin.php
+++ b/tests/Admin/Entity/UserAdmin.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
diff --git a/tests/Admin/Model/GroupAdminTest.php b/tests/Admin/Model/GroupAdminTest.php
index 39c2f207d..7a110e174 100644
--- a/tests/Admin/Model/GroupAdminTest.php
+++ b/tests/Admin/Model/GroupAdminTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -19,7 +21,7 @@
  */
 final class GroupAdminTest extends TestCase
 {
-    public function testInstance()
+    public function testInstance(): void
     {
         $admin = new GroupAdmin('admin.group', 'Sonata\UserBundle\Model\Group', 'SonataAdminBundle:CRUD');
 
diff --git a/tests/Admin/Model/UserAdminTest.php b/tests/Admin/Model/UserAdminTest.php
index 4e05c389f..289406bc6 100644
--- a/tests/Admin/Model/UserAdminTest.php
+++ b/tests/Admin/Model/UserAdminTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -19,7 +21,7 @@
  */
 final class UserAdminTest extends TestCase
 {
-    public function testInstance()
+    public function testInstance(): void
     {
         $admin = new UserAdmin('admin.group', 'Sonata\UserBundle\Model\User', 'SonataAdminBundle:CRUD');
 
diff --git a/tests/Controller/AdminResettingControllerTest.php b/tests/Controller/AdminResettingControllerTest.php
index 9ae76a9f8..0a5012258 100644
--- a/tests/Controller/AdminResettingControllerTest.php
+++ b/tests/Controller/AdminResettingControllerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -18,12 +20,12 @@ class AdminResettingControllerTest extends TestCase
 {
     private $controller;
 
-    protected function setUp()
+    protected function setUp(): void
     {
         $this->controller = new AdminResettingController();
     }
 
-    public function testItIsInstantiable()
+    public function testItIsInstantiable(): void
     {
         $this->assertNotNull($this->controller);
     }
diff --git a/tests/Controller/AdminSecurityControllerTest.php b/tests/Controller/AdminSecurityControllerTest.php
index 3d7742962..75870d4ca 100644
--- a/tests/Controller/AdminSecurityControllerTest.php
+++ b/tests/Controller/AdminSecurityControllerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -18,12 +20,12 @@ class AdminSecurityControllerTest extends TestCase
 {
     private $controller;
 
-    protected function setUp()
+    protected function setUp(): void
     {
         $this->controller = new AdminSecurityController();
     }
 
-    public function testItIsInstantiable()
+    public function testItIsInstantiable(): void
     {
         $this->assertNotNull($this->controller);
     }
diff --git a/tests/Controller/Api/GroupControllerTest.php b/tests/Controller/Api/GroupControllerTest.php
index eeaef0963..caf44e439 100644
--- a/tests/Controller/Api/GroupControllerTest.php
+++ b/tests/Controller/Api/GroupControllerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -20,7 +22,7 @@
  */
 class GroupControllerTest extends TestCase
 {
-    public function testGetGroupsAction()
+    public function testGetGroupsAction(): void
     {
         $group = $this->createMock('FOS\UserBundle\Model\GroupInterface');
         $groupManager = $this->createMock('Sonata\UserBundle\Model\GroupManagerInterface');
@@ -35,13 +37,13 @@ public function testGetGroupsAction()
         $this->assertEquals([$group], $this->createGroupController(null, $groupManager)->getGroupsAction($paramFetcher));
     }
 
-    public function testGetGroupAction()
+    public function testGetGroupAction(): void
     {
         $group = $this->createMock('FOS\UserBundle\Model\GroupInterface');
         $this->assertEquals($group, $this->createGroupController($group)->getGroupAction(1));
     }
 
-    public function testGetGroupActionNotFoundException()
+    public function testGetGroupActionNotFoundException(): void
     {
         $this->expectException(\Symfony\Component\HttpKernel\Exception\NotFoundHttpException::class);
         $this->expectExceptionMessage('Group (42) not found');
@@ -49,7 +51,7 @@ public function testGetGroupActionNotFoundException()
         $this->createGroupController()->getGroupAction(42);
     }
 
-    public function testPostGroupAction()
+    public function testPostGroupAction(): void
     {
         $group = $this->createMock('FOS\UserBundle\Model\GroupInterface');
 
@@ -70,7 +72,7 @@ public function testPostGroupAction()
         $this->assertInstanceOf('FOS\RestBundle\View\View', $view);
     }
 
-    public function testPostGroupInvalidAction()
+    public function testPostGroupInvalidAction(): void
     {
         $groupManager = $this->createMock('Sonata\UserBundle\Model\GroupManagerInterface');
         $groupManager->expects($this->once())->method('getClass')->will($this->returnValue('Sonata\UserBundle\Entity\BaseGroup'));
@@ -87,7 +89,7 @@ public function testPostGroupInvalidAction()
         $this->assertInstanceOf('Symfony\Component\Form\FormInterface', $view);
     }
 
-    public function testPutGroupAction()
+    public function testPutGroupAction(): void
     {
         $group = $this->createMock('FOS\UserBundle\Model\GroupInterface');
 
@@ -109,7 +111,7 @@ public function testPutGroupAction()
         $this->assertInstanceOf('FOS\RestBundle\View\View', $view);
     }
 
-    public function testPutGroupInvalidAction()
+    public function testPutGroupInvalidAction(): void
     {
         $group = $this->createMock('FOS\UserBundle\Model\GroupInterface');
 
@@ -129,7 +131,7 @@ public function testPutGroupInvalidAction()
         $this->assertInstanceOf('Symfony\Component\Form\FormInterface', $view);
     }
 
-    public function testDeleteGroupAction()
+    public function testDeleteGroupAction(): void
     {
         $group = $this->createMock('FOS\UserBundle\Model\GroupInterface');
 
@@ -142,7 +144,7 @@ public function testDeleteGroupAction()
         $this->assertEquals(['deleted' => true], $view);
     }
 
-    public function testDeleteGroupInvalidAction()
+    public function testDeleteGroupInvalidAction(): void
     {
         $this->expectException('Symfony\Component\HttpKernel\Exception\NotFoundHttpException');
 
diff --git a/tests/Controller/Api/UserControllerTest.php b/tests/Controller/Api/UserControllerTest.php
index ad482b466..2f58b9749 100644
--- a/tests/Controller/Api/UserControllerTest.php
+++ b/tests/Controller/Api/UserControllerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -20,7 +22,7 @@
  */
 class UserControllerTest extends TestCase
 {
-    public function testGetUsersAction()
+    public function testGetUsersAction(): void
     {
         $userManager = $this->createMock('Sonata\UserBundle\Model\UserManagerInterface');
         $userManager->expects($this->once())->method('getPager')->will($this->returnValue([]));
@@ -34,13 +36,13 @@ public function testGetUsersAction()
         $this->assertEquals([], $this->createUserController(null, $userManager)->getUsersAction($paramFetcher));
     }
 
-    public function testGetUserAction()
+    public function testGetUserAction(): void
     {
         $user = $this->createMock('Sonata\UserBundle\Model\UserInterface');
         $this->assertEquals($user, $this->createUserController($user)->getUserAction(1));
     }
 
-    public function testGetUserActionNotFoundException()
+    public function testGetUserActionNotFoundException(): void
     {
         $this->expectException(\Symfony\Component\HttpKernel\Exception\NotFoundHttpException::class);
         $this->expectExceptionMessage('User (42) not found');
@@ -48,7 +50,7 @@ public function testGetUserActionNotFoundException()
         $this->createUserController()->getUserAction(42);
     }
 
-    public function testPostUserAction()
+    public function testPostUserAction(): void
     {
         $user = $this->createMock('FOS\UserBundle\Model\UserInterface');
 
@@ -68,7 +70,7 @@ public function testPostUserAction()
         $this->assertInstanceOf('FOS\RestBundle\View\View', $view);
     }
 
-    public function testPostUserInvalidAction()
+    public function testPostUserInvalidAction(): void
     {
         $userManager = $this->createMock('Sonata\UserBundle\Model\UserManagerInterface');
 
@@ -84,7 +86,7 @@ public function testPostUserInvalidAction()
         $this->assertInstanceOf('Symfony\Component\Form\FormInterface', $view);
     }
 
-    public function testPutUserAction()
+    public function testPutUserAction(): void
     {
         $user = $this->createMock('FOS\UserBundle\Model\UserInterface');
 
@@ -105,7 +107,7 @@ public function testPutUserAction()
         $this->assertInstanceOf('FOS\RestBundle\View\View', $view);
     }
 
-    public function testPutUserInvalidAction()
+    public function testPutUserInvalidAction(): void
     {
         $user = $this->createMock('FOS\UserBundle\Model\UserInterface');
 
@@ -124,7 +126,7 @@ public function testPutUserInvalidAction()
         $this->assertInstanceOf('Symfony\Component\Form\FormInterface', $view);
     }
 
-    public function testPostUserGroupAction()
+    public function testPostUserGroupAction(): void
     {
         $user = $this->createMock('Sonata\UserBundle\Entity\BaseUser');
         $user->expects($this->once())->method('hasGroup')->will($this->returnValue(false));
@@ -143,7 +145,7 @@ public function testPostUserGroupAction()
         $this->assertEquals(['added' => true], $view);
     }
 
-    public function testPostUserGroupInvalidAction()
+    public function testPostUserGroupInvalidAction(): void
     {
         $user = $this->createMock('Sonata\UserBundle\Entity\BaseUser');
         $user->expects($this->once())->method('hasGroup')->will($this->returnValue(true));
@@ -166,7 +168,7 @@ public function testPostUserGroupInvalidAction()
         $this->assertEquals(['error' => 'User "1" already has group "1"'], $data);
     }
 
-    public function testDeleteUserGroupAction()
+    public function testDeleteUserGroupAction(): void
     {
         $user = $this->createMock('Sonata\UserBundle\Entity\BaseUser');
         $user->expects($this->once())->method('hasGroup')->will($this->returnValue(true));
@@ -185,7 +187,7 @@ public function testDeleteUserGroupAction()
         $this->assertEquals(['removed' => true], $view);
     }
 
-    public function testDeleteUserGroupInvalidAction()
+    public function testDeleteUserGroupInvalidAction(): void
     {
         $user = $this->createMock('Sonata\UserBundle\Entity\BaseUser');
         $user->expects($this->once())->method('hasGroup')->will($this->returnValue(false));
@@ -208,7 +210,7 @@ public function testDeleteUserGroupInvalidAction()
         $this->assertEquals(['error' => 'User "1" has not group "1"'], $data);
     }
 
-    public function testDeleteUserAction()
+    public function testDeleteUserAction(): void
     {
         $user = $this->createMock('FOS\UserBundle\Model\UserInterface');
 
@@ -221,7 +223,7 @@ public function testDeleteUserAction()
         $this->assertEquals(['deleted' => true], $view);
     }
 
-    public function testDeleteUserInvalidAction()
+    public function testDeleteUserInvalidAction(): void
     {
         $this->expectException('Symfony\Component\HttpKernel\Exception\NotFoundHttpException');
 
diff --git a/tests/DependencyInjection/ConfigurationTest.php b/tests/DependencyInjection/ConfigurationTest.php
index b6bd5fcfd..236d242d3 100644
--- a/tests/DependencyInjection/ConfigurationTest.php
+++ b/tests/DependencyInjection/ConfigurationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -24,7 +26,7 @@ public function getConfiguration()
         return new Configuration();
     }
 
-    public function testDefault()
+    public function testDefault(): void
     {
         $this->assertProcessedConfigurationEquals([
             [],
diff --git a/tests/DependencyInjection/SonataUserExtensionTest.php b/tests/DependencyInjection/SonataUserExtensionTest.php
index 0eaf7672b..d71c90d89 100644
--- a/tests/DependencyInjection/SonataUserExtensionTest.php
+++ b/tests/DependencyInjection/SonataUserExtensionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -27,14 +29,14 @@ final class SonataUserExtensionTest extends AbstractExtensionTestCase
     /**
      * {@inheritdoc}
      */
-    protected function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
 
         $this->setParameter('kernel.bundles', ['SonataAdminBundle' => true]);
     }
 
-    public function testLoadDefault()
+    public function testLoadDefault(): void
     {
         $this->load();
 
@@ -49,7 +51,7 @@ public function testLoadDefault()
         );
     }
 
-    public function testTwigConfigParameterIsSetting()
+    public function testTwigConfigParameterIsSetting(): void
     {
         $fakeContainer = $this->getMockBuilder(ContainerBuilder::class)
             ->setMethods(['hasExtension', 'prependExtensionConfig'])
@@ -71,7 +73,7 @@ public function testTwigConfigParameterIsSetting()
         }
     }
 
-    public function testTwigConfigParameterIsSet()
+    public function testTwigConfigParameterIsSet(): void
     {
         $fakeTwigExtension = $this->getMockBuilder(TwigExtension::class)
             ->setMethods(['load', 'getAlias'])
@@ -95,7 +97,7 @@ public function testTwigConfigParameterIsSet()
         );
     }
 
-    public function testTwigConfigParameterIsNotSet()
+    public function testTwigConfigParameterIsNotSet(): void
     {
         $this->load();
 
@@ -104,22 +106,22 @@ public function testTwigConfigParameterIsNotSet()
         $this->assertArrayNotHasKey(0, $twigConfigurations);
     }
 
-    public function testCorrectModelClass()
+    public function testCorrectModelClass(): void
     {
         $this->load(['class' => ['user' => 'Sonata\UserBundle\Tests\Entity\User']]);
     }
 
-    public function testCorrectModelClassWithLeadingSlash()
+    public function testCorrectModelClassWithLeadingSlash(): void
     {
         $this->load(['class' => ['user' => '\Sonata\UserBundle\Tests\Entity\User']]);
     }
 
-    public function testCorrectAdminClass()
+    public function testCorrectAdminClass(): void
     {
         $this->load(['admin' => ['user' => ['class' => '\Sonata\UserBundle\Tests\Admin\Entity\UserAdmin']]]);
     }
 
-    public function testCorrectModelClassWithNotDefaultManagerType()
+    public function testCorrectModelClassWithNotDefaultManagerType(): void
     {
         $this->load([
             'manager_type' => 'mongodb',
@@ -134,7 +136,7 @@ public function testCorrectModelClassWithNotDefaultManagerType()
         ]);
     }
 
-    public function testIncorrectModelClass()
+    public function testIncorrectModelClass(): void
     {
         $this->expectException('InvalidArgumentException');
 
@@ -143,7 +145,7 @@ public function testIncorrectModelClass()
         $this->load(['class' => ['user' => 'Foo\User']]);
     }
 
-    public function testNotCorrespondingModelClass()
+    public function testNotCorrespondingModelClass(): void
     {
         $this->expectException('InvalidArgumentException');
 
@@ -175,7 +177,7 @@ protected function getContainerExtensions()
     /**
      * {@inheritdoc}
      */
-    protected function load(array $configurationValues = [])
+    protected function load(array $configurationValues = []): void
     {
         $configs = [$this->getMinimalConfiguration(), $configurationValues];
 
diff --git a/tests/Document/BaseGroupTest.php b/tests/Document/BaseGroupTest.php
index 9c8f7a9d7..ebe7207f9 100644
--- a/tests/Document/BaseGroupTest.php
+++ b/tests/Document/BaseGroupTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -16,7 +18,7 @@
 
 class BaseGroupTest extends TestCase
 {
-    public function testToString()
+    public function testToString(): void
     {
         // Given
         $group = new BaseGroup('Group');
diff --git a/tests/Document/BaseUserTest.php b/tests/Document/BaseUserTest.php
index 11201c466..82d4fcd76 100644
--- a/tests/Document/BaseUserTest.php
+++ b/tests/Document/BaseUserTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -16,7 +18,7 @@
 
 class BaseUserTest extends TestCase
 {
-    public function testDateSetters()
+    public function testDateSetters(): void
     {
         // Given
         $user = new BaseUser();
@@ -34,7 +36,7 @@ public function testDateSetters()
         $this->assertEquals($today->format('U'), $user->getUpdatedAt()->format('U'), 'Should contain today\'s date');
     }
 
-    public function testDateWithPrePersist()
+    public function testDateWithPrePersist(): void
     {
         // Given
         $user = new BaseUser();
@@ -51,7 +53,7 @@ public function testDateWithPrePersist()
         $this->assertEquals($today->format('Y-m-d'), $user->getUpdatedAt()->format('Y-m-d'), 'Should be updated today');
     }
 
-    public function testDateWithPreUpdate()
+    public function testDateWithPreUpdate(): void
     {
         // Given
         $user = new BaseUser();
@@ -69,7 +71,7 @@ public function testDateWithPreUpdate()
         $this->assertEquals($today->format('Y-m-d'), $user->getUpdatedAt()->format('Y-m-d'), 'Should be updated today');
     }
 
-    public function testSettingMultipleGroups()
+    public function testSettingMultipleGroups(): void
     {
         // Given
         $user = new BaseUser();
@@ -87,7 +89,7 @@ public function testSettingMultipleGroups()
         $this->assertTrue($user->hasGroup('Group 2'), 'Should have a group named "Group 2"');
     }
 
-    public function testTwoStepVerificationCode()
+    public function testTwoStepVerificationCode(): void
     {
         // Given
         $user = new BaseUser();
@@ -99,7 +101,7 @@ public function testTwoStepVerificationCode()
         $this->assertEquals('123456', $user->getTwoStepVerificationCode(), 'Should return the two step verification code');
     }
 
-    public function testToStringWithName()
+    public function testToStringWithName(): void
     {
         // Given
         $user = new BaseUser();
@@ -112,7 +114,7 @@ public function testToStringWithName()
         $this->assertEquals('John', $string, 'Should return the username as string representation');
     }
 
-    public function testToStringWithoutName()
+    public function testToStringWithoutName(): void
     {
         // Given
         $user = new BaseUser();
diff --git a/tests/Document/Group.php b/tests/Document/Group.php
index e0049a6b4..0d2ca4a91 100644
--- a/tests/Document/Group.php
+++ b/tests/Document/Group.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
diff --git a/tests/Document/User.php b/tests/Document/User.php
index 02aa0949d..f90b5cffc 100644
--- a/tests/Document/User.php
+++ b/tests/Document/User.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
diff --git a/tests/Entity/BaseGroupTest.php b/tests/Entity/BaseGroupTest.php
index 2c048b1e6..5c169cc2e 100644
--- a/tests/Entity/BaseGroupTest.php
+++ b/tests/Entity/BaseGroupTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -16,7 +18,7 @@
 
 class BaseGroupTest extends TestCase
 {
-    public function testToString()
+    public function testToString(): void
     {
         // Given
         $group = new BaseGroup('Group');
diff --git a/tests/Entity/BaseUserTest.php b/tests/Entity/BaseUserTest.php
index 6d6c28ee7..b734ff679 100644
--- a/tests/Entity/BaseUserTest.php
+++ b/tests/Entity/BaseUserTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -16,7 +18,7 @@
 
 class BaseUserTest extends TestCase
 {
-    public function testDateSetters()
+    public function testDateSetters(): void
     {
         // Given
         $user = new BaseUser();
@@ -34,7 +36,7 @@ public function testDateSetters()
         $this->assertEquals($today->format('U'), $user->getUpdatedAt()->format('U'), 'Should contain today\'s date');
     }
 
-    public function testDateWithPrePersist()
+    public function testDateWithPrePersist(): void
     {
         // Given
         $user = new BaseUser();
@@ -51,7 +53,7 @@ public function testDateWithPrePersist()
         $this->assertEquals($today->format('Y-m-d'), $user->getUpdatedAt()->format('Y-m-d'), 'Should be updated today');
     }
 
-    public function testDateWithPreUpdate()
+    public function testDateWithPreUpdate(): void
     {
         // Given
         $user = new BaseUser();
@@ -69,7 +71,7 @@ public function testDateWithPreUpdate()
         $this->assertEquals($today->format('Y-m-d'), $user->getUpdatedAt()->format('Y-m-d'), 'Should be updated today');
     }
 
-    public function testSettingMultipleGroups()
+    public function testSettingMultipleGroups(): void
     {
         // Given
         $user = new BaseUser();
@@ -87,7 +89,7 @@ public function testSettingMultipleGroups()
         $this->assertTrue($user->hasGroup('Group 2'), 'Should have a group named "Group 2"');
     }
 
-    public function testTwoStepVerificationCode()
+    public function testTwoStepVerificationCode(): void
     {
         // Given
         $user = new BaseUser();
@@ -99,7 +101,7 @@ public function testTwoStepVerificationCode()
         $this->assertEquals('123456', $user->getTwoStepVerificationCode(), 'Should return the two step verification code');
     }
 
-    public function testToStringWithName()
+    public function testToStringWithName(): void
     {
         // Given
         $user = new BaseUser();
@@ -112,7 +114,7 @@ public function testToStringWithName()
         $this->assertEquals('John', $string, 'Should return the username as string representation');
     }
 
-    public function testToStringWithoutName()
+    public function testToStringWithoutName(): void
     {
         // Given
         $user = new BaseUser();
diff --git a/tests/Entity/GroupManagerTest.php b/tests/Entity/GroupManagerTest.php
index 359e7caa1..b27ac46e4 100644
--- a/tests/Entity/GroupManagerTest.php
+++ b/tests/Entity/GroupManagerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -17,11 +19,11 @@
 
 class GroupManagerTest extends TestCase
 {
-    public function testGetPager()
+    public function testGetPager(): void
     {
         $self = $this;
         $this
-            ->getUserManager(function ($qb) use ($self) {
+            ->getUserManager(function ($qb) use ($self): void {
                 $qb->expects($self->once())->method('getRootAliases')->will($self->returnValue(['g']));
                 $qb->expects($self->never())->method('andWhere');
                 $qb->expects($self->once())->method('orderBy')->with(
@@ -33,14 +35,14 @@ public function testGetPager()
             ->getPager([], 1);
     }
 
-    public function testGetPagerWithInvalidSort()
+    public function testGetPagerWithInvalidSort(): void
     {
         $this->expectException(\RuntimeException::class);
         $this->expectExceptionMessage('Invalid sort field \'invalid\' in \'className\' class');
 
         $self = $this;
         $this
-            ->getUserManager(function ($qb) use ($self) {
+            ->getUserManager(function ($qb) use ($self): void {
                 $qb->expects($self->never())->method('andWhere');
                 $qb->expects($self->never())->method('orderBy');
                 $qb->expects($self->never())->method('setParameters');
@@ -48,11 +50,11 @@ public function testGetPagerWithInvalidSort()
             ->getPager([], 1, 10, ['invalid' => 'ASC']);
     }
 
-    public function testGetPagerWithEnabledUsers()
+    public function testGetPagerWithEnabledUsers(): void
     {
         $self = $this;
         $this
-            ->getUserManager(function ($qb) use ($self) {
+            ->getUserManager(function ($qb) use ($self): void {
                 $qb->expects($self->once())->method('getRootAliases')->will($self->returnValue(['g']));
                 $qb->expects($self->once())->method('andWhere')->with($self->equalTo('g.enabled = :enabled'));
                 $qb->expects($self->once())->method('orderBy')->with(
@@ -64,11 +66,11 @@ public function testGetPagerWithEnabledUsers()
             ->getPager(['enabled' => true], 1);
     }
 
-    public function testGetPagerWithDisabledUsers()
+    public function testGetPagerWithDisabledUsers(): void
     {
         $self = $this;
         $this
-            ->getUserManager(function ($qb) use ($self) {
+            ->getUserManager(function ($qb) use ($self): void {
                 $qb->expects($self->once())->method('getRootAliases')->will($self->returnValue(['g']));
                 $qb->expects($self->once())->method('andWhere')->with($self->equalTo('g.enabled = :enabled'));
                 $qb->expects($self->once())->method('orderBy')->with(
diff --git a/tests/Entity/User.php b/tests/Entity/User.php
index e5123d258..ef6c8f7ff 100644
--- a/tests/Entity/User.php
+++ b/tests/Entity/User.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
diff --git a/tests/Entity/UserManagerProxyTest.php b/tests/Entity/UserManagerProxyTest.php
index d17164750..afcdcb083 100644
--- a/tests/Entity/UserManagerProxyTest.php
+++ b/tests/Entity/UserManagerProxyTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -16,7 +18,7 @@
 
 class UserManagerProxyTest extends TestCase
 {
-    public function testProxy()
+    public function testProxy(): void
     {
         $doctrine = $this->getMockBuilder('Doctrine\Common\Persistence\ManagerRegistry')->disableOriginalConstructor()->getMock();
 
diff --git a/tests/Entity/UserManagerTest.php b/tests/Entity/UserManagerTest.php
index d32c9c2f3..de4cdf545 100644
--- a/tests/Entity/UserManagerTest.php
+++ b/tests/Entity/UserManagerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -17,11 +19,11 @@
 
 class UserManagerTest extends TestCase
 {
-    public function testGetPager()
+    public function testGetPager(): void
     {
         $self = $this;
         $this
-            ->getUserManager(function ($qb) use ($self) {
+            ->getUserManager(function ($qb) use ($self): void {
                 $qb->expects($self->once())->method('getRootAliases')->will($self->returnValue(['u']));
                 $qb->expects($self->never())->method('andWhere');
                 $qb->expects($self->once())->method('orderBy')->with(
@@ -32,14 +34,14 @@ public function testGetPager()
             ->getPager([], 1);
     }
 
-    public function testGetPagerWithInvalidSort()
+    public function testGetPagerWithInvalidSort(): void
     {
         $this->expectException(\RuntimeException::class);
         $this->expectExceptionMessage('Invalid sort field \'invalid\' in \'Sonata\UserBundle\Entity\BaseUser\' class');
 
         $self = $this;
         $this
-            ->getUserManager(function ($qb) use ($self) {
+            ->getUserManager(function ($qb) use ($self): void {
                 $qb->expects($self->never())->method('andWhere');
                 $qb->expects($self->never())->method('orderBy');
                 $qb->expects($self->never())->method('setParameters');
@@ -47,11 +49,11 @@ public function testGetPagerWithInvalidSort()
             ->getPager([], 1, 10, ['invalid' => 'ASC']);
     }
 
-    public function testGetPagerWithValidSortDesc()
+    public function testGetPagerWithValidSortDesc(): void
     {
         $self = $this;
         $this
-            ->getUserManager(function ($qb) use ($self) {
+            ->getUserManager(function ($qb) use ($self): void {
                 $qb->expects($self->once())->method('getRootAliases')->will($self->returnValue(['u']));
                 $qb->expects($self->once())->method('andWhere')->with($self->equalTo('u.enabled = :enabled'));
                 $qb->expects($self->once())->method('setParameter')->with(
@@ -66,11 +68,11 @@ public function testGetPagerWithValidSortDesc()
             ->getPager(['enabled' => true], 1, 10, ['email' => 'DESC']);
     }
 
-    public function testGetPagerWithEnabledUsers()
+    public function testGetPagerWithEnabledUsers(): void
     {
         $self = $this;
         $this
-            ->getUserManager(function ($qb) use ($self) {
+            ->getUserManager(function ($qb) use ($self): void {
                 $qb->expects($self->once())->method('getRootAliases')->will($self->returnValue(['u']));
                 $qb->expects($self->once())->method('andWhere')->with($self->equalTo('u.enabled = :enabled'));
                 $qb->expects($self->once())->method('setParameter')->with(
@@ -85,11 +87,11 @@ public function testGetPagerWithEnabledUsers()
             ->getPager(['enabled' => true], 1);
     }
 
-    public function testGetPagerWithDisabledUsers()
+    public function testGetPagerWithDisabledUsers(): void
     {
         $self = $this;
         $this
-            ->getUserManager(function ($qb) use ($self) {
+            ->getUserManager(function ($qb) use ($self): void {
                 $qb->expects($self->once())->method('getRootAliases')->will($self->returnValue(['u']));
                 $qb->expects($self->once())->method('andWhere')->with($self->equalTo('u.enabled = :enabled'));
                 $qb->expects($self->once())->method('setParameter')->with(
diff --git a/tests/Form/Transformer/RestoreRolesTransformerTest.php b/tests/Form/Transformer/RestoreRolesTransformerTest.php
index 7113ffd13..4afa5ee9e 100644
--- a/tests/Form/Transformer/RestoreRolesTransformerTest.php
+++ b/tests/Form/Transformer/RestoreRolesTransformerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -17,7 +19,7 @@
 
 class RestoreRolesTransformerTest extends TestCase
 {
-    public function testInvalidStateTransform()
+    public function testInvalidStateTransform(): void
     {
         $this->expectException(\RuntimeException::class);
 
@@ -27,7 +29,7 @@ public function testInvalidStateTransform()
         $transformer->transform([]);
     }
 
-    public function testInvalidStateReverseTransform()
+    public function testInvalidStateReverseTransform(): void
     {
         $this->expectException(\RuntimeException::class);
 
@@ -37,7 +39,7 @@ public function testInvalidStateReverseTransform()
         $transformer->reverseTransform([]);
     }
 
-    public function testValidTransform()
+    public function testValidTransform(): void
     {
         $roleBuilder = $this->createMock(EditableRolesBuilder::class);
 
@@ -49,7 +51,7 @@ public function testValidTransform()
         $this->assertEquals($data, $transformer->transform($data));
     }
 
-    public function testValidReverseTransform()
+    public function testValidReverseTransform(): void
     {
         $roleBuilder = $this->createMock(EditableRolesBuilder::class);
 
@@ -63,7 +65,7 @@ public function testValidReverseTransform()
         $this->assertEquals(['ROLE_FOO', 'ROLE_HIDDEN'], $transformer->reverseTransform($data));
     }
 
-    public function testTransformAllowEmptyOriginalRoles()
+    public function testTransformAllowEmptyOriginalRoles(): void
     {
         $roleBuilder = $this->createMock(EditableRolesBuilder::class);
 
@@ -75,7 +77,7 @@ public function testTransformAllowEmptyOriginalRoles()
         $this->assertEquals($data, $transformer->transform($data));
     }
 
-    public function testReverseTransformAllowEmptyOriginalRoles()
+    public function testReverseTransformAllowEmptyOriginalRoles(): void
     {
         $roleBuilder = $this->createMock(EditableRolesBuilder::class);
 
@@ -89,7 +91,7 @@ public function testReverseTransformAllowEmptyOriginalRoles()
         $this->assertEquals(['ROLE_FOO'], $transformer->reverseTransform($data));
     }
 
-    public function testReverseTransformRevokedHierarchicalRole()
+    public function testReverseTransformRevokedHierarchicalRole(): void
     {
         $roleBuilder = $this->createMock(EditableRolesBuilder::class);
 
@@ -114,7 +116,7 @@ public function testReverseTransformRevokedHierarchicalRole()
         $this->assertNotContains($revokedRole, $processedRoles);
     }
 
-    public function testReverseTransformHiddenRole()
+    public function testReverseTransformHiddenRole(): void
     {
         $roleBuilder = $this->createMock(EditableRolesBuilder::class);
 
diff --git a/tests/Form/Type/SecurityRolesTypeTest.php b/tests/Form/Type/SecurityRolesTypeTest.php
index cc679053a..43b9cd395 100755
--- a/tests/Form/Type/SecurityRolesTypeTest.php
+++ b/tests/Form/Type/SecurityRolesTypeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -24,7 +26,7 @@ class SecurityRolesTypeTest extends TypeTestCase
 {
     protected $roleBuilder;
 
-    public function testGetDefaultOptions()
+    public function testGetDefaultOptions(): void
     {
         $type = new SecurityRolesType($this->roleBuilder);
 
@@ -35,7 +37,7 @@ public function testGetDefaultOptions()
         $this->assertCount(3, $options['choices']);
     }
 
-    public function testGetParent()
+    public function testGetParent(): void
     {
         $type = new SecurityRolesType($this->roleBuilder);
         $this->assertEquals(
@@ -44,7 +46,7 @@ public function testGetParent()
         );
     }
 
-    public function testSubmitValidData()
+    public function testSubmitValidData(): void
     {
         $form = $this->factory->create($this->getSecurityRolesTypeName(), null, [
             'multiple' => true,
@@ -59,7 +61,7 @@ public function testSubmitValidData()
         $this->assertTrue(in_array('ROLE_FOO', $form->getData()));
     }
 
-    public function testSubmitInvalidData()
+    public function testSubmitInvalidData(): void
     {
         $form = $this->factory->create($this->getSecurityRolesTypeName(), null, [
             'multiple' => true,
@@ -73,7 +75,7 @@ public function testSubmitInvalidData()
         $this->assertNull($form->getData());
     }
 
-    public function testSubmitWithHiddenRoleData()
+    public function testSubmitWithHiddenRoleData(): void
     {
         $originalRoles = ['ROLE_SUPER_ADMIN', 'ROLE_USER'];
 
diff --git a/tests/Resources/XliffTest.php b/tests/Resources/XliffTest.php
index cfbd494be..a56bc8c0f 100644
--- a/tests/Resources/XliffTest.php
+++ b/tests/Resources/XliffTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
diff --git a/tests/Security/Authorization/Voter/UserAclVoterTest.php b/tests/Security/Authorization/Voter/UserAclVoterTest.php
index a4fff45c1..40a8bdf28 100644
--- a/tests/Security/Authorization/Voter/UserAclVoterTest.php
+++ b/tests/Security/Authorization/Voter/UserAclVoterTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -18,7 +20,7 @@
 
 class UserAclVoterTest extends TestCase
 {
-    public function testVoteWillAbstainWhenAUserIsLoggedInAndASuperAdmin()
+    public function testVoteWillAbstainWhenAUserIsLoggedInAndASuperAdmin(): void
     {
         // Given
         $user = $this->createMock('FOS\UserBundle\Model\UserInterface');
@@ -44,7 +46,7 @@ public function testVoteWillAbstainWhenAUserIsLoggedInAndASuperAdmin()
         $this->assertEquals(VoterInterface::ACCESS_ABSTAIN, $decision, 'Should abstain from voting');
     }
 
-    public function testVoteWillDenyAccessWhenAUserIsLoggedInAndNotASuperAdmin()
+    public function testVoteWillDenyAccessWhenAUserIsLoggedInAndNotASuperAdmin(): void
     {
         // Given
         $user = $this->createMock('FOS\UserBundle\Model\UserInterface');
@@ -70,7 +72,7 @@ public function testVoteWillDenyAccessWhenAUserIsLoggedInAndNotASuperAdmin()
         $this->assertEquals(VoterInterface::ACCESS_DENIED, $decision, 'Should deny access');
     }
 
-    public function testVoteWillAbstainWhenAUserIsNotAvailable()
+    public function testVoteWillAbstainWhenAUserIsNotAvailable(): void
     {
         // Given
         $user = $this->createMock('FOS\UserBundle\Model\UserInterface');
@@ -95,7 +97,7 @@ public function testVoteWillAbstainWhenAUserIsNotAvailable()
         $this->assertEquals(VoterInterface::ACCESS_ABSTAIN, $decision, 'Should abstain from voting');
     }
 
-    public function testVoteWillAbstainWhenAUserIsLoggedInButIsNotAFOSUser()
+    public function testVoteWillAbstainWhenAUserIsLoggedInButIsNotAFOSUser(): void
     {
         // Given
         $user = $this->createMock('FOS\UserBundle\Model\UserInterface');
diff --git a/tests/Security/EditableRolesBuilderTest.php b/tests/Security/EditableRolesBuilderTest.php
index 26bc49299..b0283480d 100644
--- a/tests/Security/EditableRolesBuilderTest.php
+++ b/tests/Security/EditableRolesBuilderTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *
@@ -21,7 +23,7 @@ class EditableRolesBuilderTest extends TestCase
     /**
      * @group legacy
      */
-    public function testRolesFromHierarchy()
+    public function testRolesFromHierarchy(): void
     {
         $token = $this->createMock('Symfony\Component\Security\Core\Authentication\Token\TokenInterface');
 
@@ -71,7 +73,7 @@ public function testRolesFromHierarchy()
         $this->assertEquals($expected, $roles);
     }
 
-    public function testRolesFromAdminWithMasterAdmin()
+    public function testRolesFromAdminWithMasterAdmin(): void
     {
         $securityHandler = $this->createMock('Sonata\AdminBundle\Security\Handler\SecurityHandlerInterface');
         $securityHandler->expects($this->exactly(2))->method('getBaseRole')->will($this->returnValue('ROLE_FOO_%s'));
@@ -111,7 +113,7 @@ public function testRolesFromAdminWithMasterAdmin()
         $this->assertEquals($expected, $roles);
     }
 
-    public function testWithNoSecurityToken()
+    public function testWithNoSecurityToken(): void
     {
         $tokenStorage = $this->createMock(TokenStorageInterface::class);
         $tokenStorage->expects($this->any())->method('getToken')->will($this->returnValue(null));
diff --git a/tests/bootstrap.php b/tests/bootstrap.php
index 771a59651..e14c4dd4d 100644
--- a/tests/bootstrap.php
+++ b/tests/bootstrap.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the Sonata Project package.
  *