diff --git a/composer.json b/composer.json
index 748ba53..1ff4c84 100644
--- a/composer.json
+++ b/composer.json
@@ -23,6 +23,7 @@
   "prefer-stable": true,
   "require": {
     "php": "^7.0",
+    "doctrine/common": "^2.0",
     "doctrine/inflector": "^1.0",
     "zendframework/zend-paginator": "^2.6"
   },
@@ -32,6 +33,7 @@
     "humbug/humbug": "~1.0@dev",
     "phpmetrics/phpmetrics": "^2.0",
     "phpmd/phpmd": "^2.0",
+    "phpstan/phpstan": "~0.6",
     "phpunit/phpunit": "^4.5|^5.0",
     "phpunit/phpunit-mock-objects": "^3.2",
     "sebastian/phpcpd": "^2.0",
@@ -62,6 +64,7 @@
     "phpcs": "phpcs --standard=PSR2 src tests",
     "phpcs-lint": "php-cs-fixer fix --dry-run --verbose",
     "phpcpd": "phpcpd src",
+    "phpstan": "phpstan analyse --level 1 src tests",
     "phpmd": "phpmd src text unusedcode,naming,design,controversial,codesize",
     "phpmetrics": "phpmetrics --failure-condition='average.maintainabilityIndex < 50' src",
     "phpmetrics-report": "phpmetrics --report-html=build/metrics/index.html --offline src",
@@ -75,6 +78,7 @@
       "@phpcs-lint",
       "@phpcpd",
       "@phpmd",
+      "@phpstan",
       "@phpmetrics"
     ],
     "reports": [
diff --git a/src/EventsTrait.php b/src/EventsTrait.php
index d10dd09..d55fded 100644
--- a/src/EventsTrait.php
+++ b/src/EventsTrait.php
@@ -15,6 +15,7 @@
 
 use Doctrine\Common\EventManager;
 use Doctrine\Common\EventSubscriber;
+use Doctrine\Common\Persistence\ObjectManager;
 
 /**
  * Events trait.
@@ -75,7 +76,7 @@ public function restoreEventSubscribers()
      *
      * @param string $event
      */
-    public function disableEventListeners($event)
+    public function disableEventListeners(string $event)
     {
         if (!array_key_exists($event, $this->disabledListeners)) {
             $this->disabledListeners[$event] = [];
@@ -91,10 +92,12 @@ public function disableEventListeners($event)
     /**
      * Disable listener for an event.
      *
-     * @param string                                  $event
-     * @param \Doctrine\Common\EventSubscriber|string $subscriberClass
+     * @param string                 $event
+     * @param string|EventSubscriber $subscriberClass
+     *
+     * @throws \InvalidArgumentException
      */
-    public function disableEventListener($event, $subscriberClass)
+    public function disableEventListener(string $event, $subscriberClass)
     {
         $subscriberClass = $this->getSubscriberClassName($subscriberClass);
 
@@ -132,7 +135,7 @@ public function restoreAllEventListeners()
      *
      * @param string $event
      */
-    public function restoreEventListeners($event)
+    public function restoreEventListeners(string $event)
     {
         if (!array_key_exists($event, $this->disabledListeners) || empty($this->disabledListeners[$event])) {
             return;
@@ -157,7 +160,7 @@ public function restoreEventListeners($event)
      *
      * @return string
      */
-    protected function getSubscriberClassName($subscriberClass)
+    protected function getSubscriberClassName($subscriberClass): string
     {
         if (is_object($subscriberClass) && in_array(EventSubscriber::class, class_implements($subscriberClass))) {
             return get_class($subscriberClass);
@@ -178,7 +181,7 @@ protected function getSubscriberClassName($subscriberClass)
      *
      * @return array
      */
-    public function getRegisteredEvents()
+    public function getRegisteredEvents(): array
     {
         return array_keys($this->getEventManager()->getListeners());
     }
@@ -190,7 +193,7 @@ public function getRegisteredEvents()
      *
      * @return EventSubscriber[]
      */
-    protected function getEventListeners($event = null)
+    protected function getEventListeners($event = null): array
     {
         $eventManager = $this->getEventManager();
 
@@ -202,7 +205,7 @@ protected function getEventListeners($event = null)
      *
      * @return EventManager
      */
-    protected function getEventManager()
+    protected function getEventManager(): EventManager
     {
         return $this->getManager()->getEventManager();
     }
@@ -210,7 +213,7 @@ protected function getEventManager()
     /**
      * Get object manager.
      *
-     * @return \Doctrine\ORM\EntityManager|\Doctrine\ODM\MongoDB\DocumentManager|\Doctrine\ODM\CouchDB\DocumentManager
+     * @return ObjectManager
      */
-    abstract protected function getManager();
+    abstract protected function getManager(): ObjectManager;
 }
diff --git a/src/PaginatorTrait.php b/src/PaginatorTrait.php
index 96ae8c2..bab85d7 100644
--- a/src/PaginatorTrait.php
+++ b/src/PaginatorTrait.php
@@ -29,7 +29,7 @@ trait PaginatorTrait
      *
      * @return Paginator
      */
-    protected function getPaginator(AdapterInterface $adapter, $itemsPerPage)
+    protected function getPaginator(AdapterInterface $adapter, int $itemsPerPage): Paginator
     {
         $paginator = new Paginator($adapter);
         $paginator->setItemCountPerPage(max(-1, (int) $itemsPerPage));
diff --git a/src/Repository.php b/src/Repository.php
index fc416b9..c6997a8 100644
--- a/src/Repository.php
+++ b/src/Repository.php
@@ -14,6 +14,7 @@
 namespace Jgut\Doctrine\Repository;
 
 use Doctrine\Common\Persistence\ObjectRepository;
+use Zend\Paginator\Paginator;
 
 /**
  * Repository interface.
@@ -25,14 +26,14 @@ interface Repository extends ObjectRepository
      *
      * @return bool
      */
-    public function isAutoFlush();
+    public function isAutoFlush(): bool;
 
     /**
      * Set automatic manager flushing.
      *
      * @param bool $autoFlush
      */
-    public function setAutoFlush($autoFlush = false);
+    public function setAutoFlush(bool $autoFlush = false);
 
     /**
      * Manager flush.
@@ -63,15 +64,15 @@ public function restoreEventSubscribers();
      *
      * @param string $event
      */
-    public function disableEventListeners($event);
+    public function disableEventListeners(string $event);
 
     /**
      * Disable listener for an event.
      *
      * @param string                                  $event
-     * @param \Doctrine\Common\EventSubscriber|string $subscriberClass
+     * @param string|\Doctrine\Common\EventSubscriber $subscriberClass
      */
-    public function disableEventListener($event, $subscriberClass);
+    public function disableEventListener(string $event, $subscriberClass);
 
     /**
      * Restore all disabled listeners.
@@ -83,7 +84,14 @@ public function restoreAllEventListeners();
      *
      * @param string $event
      */
-    public function restoreEventListeners($event);
+    public function restoreEventListeners(string $event);
+
+    /**
+     * Get registered events.
+     *
+     * @return array
+     */
+    public function getRegisteredEvents(): array;
 
     /**
      * Return paginated elements filtered by criteria.
@@ -92,18 +100,18 @@ public function restoreEventListeners($event);
      * @param array                            $orderBy
      * @param int                              $itemsPerPage
      *
-     * @return \Zend\Paginator\Paginator
+     * @return Paginator
      */
-    public function findPaginatedBy($criteria, array $orderBy = [], $itemsPerPage = 10);
+    public function findPaginatedBy($criteria, array $orderBy = [], int $itemsPerPage = 10): Paginator;
 
     /**
      * Find one object by a set of criteria or create a new one.
      *
-     * @param array|\Doctrine\ORM\QueryBuilder|\Doctrine\ODM\MongoDB\Query\Builder $criteria
+     * @param array $criteria
      *
      * @return \stdClass
      */
-    public function findOneByOrGetNew($criteria);
+    public function findOneByOrGetNew(array $criteria);
 
     /**
      * Get a new managed object instance.
@@ -118,14 +126,14 @@ public function getNew();
      * @param \stdClass|\stdClass[] $objects
      * @param bool                  $flush
      */
-    public function add($objects, $flush = false);
+    public function add($objects, bool $flush = false);
 
     /**
      * Remove all objects.
      *
      * @param bool $flush
      */
-    public function removeAll($flush = false);
+    public function removeAll(bool $flush = false);
 
     /**
      * Remove object filtered by a set of criteria.
@@ -133,7 +141,7 @@ public function removeAll($flush = false);
      * @param array $criteria
      * @param bool  $flush
      */
-    public function removeBy(array $criteria, $flush = false);
+    public function removeBy(array $criteria, bool $flush = false);
 
     /**
      * Remove first object filtered by a set of criteria.
@@ -141,7 +149,7 @@ public function removeBy(array $criteria, $flush = false);
      * @param array $criteria
      * @param bool  $flush
      */
-    public function removeOneBy(array $criteria, $flush = false);
+    public function removeOneBy(array $criteria, bool $flush = false);
 
     /**
      * Remove objects.
@@ -149,21 +157,21 @@ public function removeOneBy(array $criteria, $flush = false);
      * @param \stdClass|\stdClass[]|string|int $objects
      * @param bool                             $flush
      */
-    public function remove($objects, $flush = false);
+    public function remove($objects, bool $flush = false);
 
     /**
      * Get all objects count.
      *
      * @return int
      */
-    public function countAll();
+    public function countAll(): int;
 
     /**
      * Get object count filtered by a set of criteria.
      *
-     * @param array|\Doctrine\ORM\QueryBuilder $criteria
+     * @param mixed $criteria
      *
      * @return int
      */
-    public function countBy($criteria);
+    public function countBy($criteria): int;
 }
diff --git a/src/RepositoryTrait.php b/src/RepositoryTrait.php
index 7bf2a79..4f77fdd 100644
--- a/src/RepositoryTrait.php
+++ b/src/RepositoryTrait.php
@@ -13,6 +13,8 @@
 
 namespace Jgut\Doctrine\Repository;
 
+use Doctrine\Common\Persistence\Mapping\ClassMetadata;
+use Doctrine\Common\Persistence\ObjectManager;
 use Doctrine\Common\Util\Inflector;
 
 /**
@@ -27,7 +29,7 @@ trait RepositoryTrait
      *
      * @return bool
      */
-    public function isAutoFlush()
+    public function isAutoFlush(): bool
     {
         return $this->autoFlush;
     }
@@ -37,7 +39,7 @@ public function isAutoFlush()
      *
      * @param bool $autoFlush
      */
-    public function setAutoFlush($autoFlush = true)
+    public function setAutoFlush(bool $autoFlush = true)
     {
         $this->autoFlush = $autoFlush === true;
     }
@@ -53,11 +55,11 @@ public function flush()
     /**
      * Find one object by a set of criteria or create a new one.
      *
-     * @param array|\Doctrine\ORM\QueryBuilder|\Doctrine\ODM\MongoDB\Query\Builder $criteria
+     * @param array $criteria
      *
-     * @return \stdClass
+     * @return object
      */
-    public function findOneByOrGetNew($criteria)
+    public function findOneByOrGetNew(array $criteria)
     {
         $object = $this->findOneBy($criteria);
 
@@ -71,7 +73,7 @@ public function findOneByOrGetNew($criteria)
     /**
      * Get a new managed object instance.
      *
-     * @return \stdClass
+     * @return object
      */
     public function getNew()
     {
@@ -88,7 +90,7 @@ public function getNew()
      *
      * @throws \InvalidArgumentException
      */
-    public function add($objects, $flush = false)
+    public function add($objects, bool $flush = false)
     {
         if (!is_array($objects)) {
             $objects = [$objects];
@@ -114,7 +116,7 @@ public function add($objects, $flush = false)
      *
      * @param bool $flush
      */
-    public function removeAll($flush = false)
+    public function removeAll(bool $flush = false)
     {
         $manager = $this->getManager();
 
@@ -133,7 +135,7 @@ public function removeAll($flush = false)
      * @param array $criteria
      * @param bool  $flush
      */
-    public function removeBy(array $criteria, $flush = false)
+    public function removeBy(array $criteria, bool $flush = false)
     {
         $manager = $this->getManager();
 
@@ -152,7 +154,7 @@ public function removeBy(array $criteria, $flush = false)
      * @param array $criteria
      * @param bool  $flush
      */
-    public function removeOneBy(array $criteria, $flush = false)
+    public function removeOneBy(array $criteria, bool $flush = false)
     {
         $object = $this->findOneBy($criteria);
 
@@ -170,12 +172,12 @@ public function removeOneBy(array $criteria, $flush = false)
     /**
      * Remove objects.
      *
-     * @param \stdClass|\stdClass[]|string|int $objects
-     * @param bool                             $flush
+     * @param object|object[]|string|int $objects
+     * @param bool                       $flush
      *
      * @throws \InvalidArgumentException
      */
-    public function remove($objects, $flush = false)
+    public function remove($objects, bool $flush = false)
     {
         $manager = $this->getManager();
 
@@ -207,7 +209,7 @@ public function remove($objects, $flush = false)
      *
      * @return int
      */
-    public function countAll()
+    public function countAll(): int
     {
         return $this->countBy([]);
     }
@@ -215,11 +217,11 @@ public function countAll()
     /**
      * Get object count filtered by a set of criteria.
      *
-     * @param array|\Doctrine\ORM\QueryBuilder|\Doctrine\ODM\MongoDB\Query\Builder $criteria
+     * @param mixed $criteria
      *
      * @return int
      */
-    abstract public function countBy($criteria);
+    abstract public function countBy($criteria): int;
 
     /**
      * Adds support for magic finders and removers.
@@ -229,9 +231,9 @@ abstract public function countBy($criteria);
      *
      * @throws \BadMethodCallException
      *
-     * @return array|object
+     * @return mixed
      */
-    public function __call($method, $arguments)
+    public function __call(string $method, array $arguments)
     {
         static $supportedMethods = ['findBy', 'findOneBy', 'findPaginatedBy', 'removeBy', 'removeOneBy'];
 
@@ -268,9 +270,9 @@ public function __call($method, $arguments)
      *
      * @throws \BadMethodCallException
      *
-     * @return array|object
+     * @return mixed
      */
-    protected function callSupportedMethod($method, $fieldName, array $arguments)
+    protected function callSupportedMethod(string $method, string $fieldName, array $arguments)
     {
         $classMetadata = $this->getClassMetadata();
 
@@ -300,27 +302,29 @@ protected function callSupportedMethod($method, $fieldName, array $arguments)
      *
      * @return bool
      */
-    protected function canBeManaged($object)
+    protected function canBeManaged($object): bool
     {
         return is_object($object) && is_a($object, $this->getClassName());
     }
 
     /**
      * Get Class name.
+     *
+     * @return string
      */
-    abstract public function getClassName();
+    abstract public function getClassName(): string;
 
     /**
      * Get object manager.
      *
-     * @return \Doctrine\ORM\EntityManager|\Doctrine\ODM\MongoDB\DocumentManager|\Doctrine\ODM\CouchDB\DocumentManager
+     * @return ObjectManager
      */
-    abstract protected function getManager();
+    abstract protected function getManager(): ObjectManager;
 
     /**
      * Get class metadata.
      *
-     * @return \Doctrine\Common\Persistence\Mapping\ClassMetadata
+     * @return ClassMetadata
      */
-    abstract protected function getClassMetadata();
+    abstract protected function getClassMetadata(): ClassMetadata;
 }
diff --git a/tests/Repository/Stubs/BlankEventStub.php b/tests/Repository/Stubs/BlankEventStub.php
index f611593..d3eecda 100644
--- a/tests/Repository/Stubs/BlankEventStub.php
+++ b/tests/Repository/Stubs/BlankEventStub.php
@@ -20,7 +20,10 @@
  */
 class BlankEventStub implements EventSubscriber
 {
-    public function getSubscribedEvents()
+    /**
+     * {@inheritdoc}
+     */
+    public function getSubscribedEvents(): array
     {
         return [];
     }
diff --git a/tests/Repository/Stubs/EventStub.php b/tests/Repository/Stubs/EventStub.php
index 30e2391..3654811 100644
--- a/tests/Repository/Stubs/EventStub.php
+++ b/tests/Repository/Stubs/EventStub.php
@@ -20,7 +20,10 @@
  */
 class EventStub implements EventSubscriber
 {
-    public function getSubscribedEvents()
+    /**
+     * {@inheritdoc}
+     */
+    public function getSubscribedEvents(): array
     {
         return [
             'prePersist',
diff --git a/tests/Repository/Stubs/PaginatorTraitStub.php b/tests/Repository/Stubs/PaginatorTraitStub.php
index 5b3a4e6..ec87f08 100644
--- a/tests/Repository/Stubs/PaginatorTraitStub.php
+++ b/tests/Repository/Stubs/PaginatorTraitStub.php
@@ -15,6 +15,7 @@
 
 use Jgut\Doctrine\Repository\PaginatorTrait;
 use Zend\Paginator\Adapter\ArrayAdapter;
+use Zend\Paginator\Paginator;
 
 /**
  * Paginator trait stub.
@@ -29,9 +30,9 @@ class PaginatorTraitStub
      * @param array $items
      * @param int   $limit
      *
-     * @return \Zend\Paginator\Paginator
+     * @return Paginator
      */
-    public function getPaginated(array $items, $limit)
+    public function getPaginated(array $items, $limit): Paginator
     {
         return $this->getPaginator(new ArrayAdapter($items), $limit);
     }
diff --git a/tests/Repository/Stubs/RepositoryStub.php b/tests/Repository/Stubs/RepositoryStub.php
index cf26b9b..76a35aa 100644
--- a/tests/Repository/Stubs/RepositoryStub.php
+++ b/tests/Repository/Stubs/RepositoryStub.php
@@ -13,10 +13,12 @@
 
 namespace Jgut\Doctrine\Repository\Tests\Stubs;
 
+use Doctrine\Common\Persistence\Mapping\ClassMetadata;
 use Doctrine\ORM\EntityManager;
 use Jgut\Doctrine\Repository\EventsTrait;
 use Jgut\Doctrine\Repository\Repository;
 use Jgut\Doctrine\Repository\RepositoryTrait;
+use Zend\Paginator\Paginator;
 
 /**
  * Repository stub.
@@ -51,7 +53,7 @@ public function __construct(EntityManager $entityManager, array $entities = [])
     /**
      * {@inheritdoc}
      */
-    protected function getManager()
+    protected function getManager(): EntityManager
     {
         return $this->entityManager;
     }
@@ -59,7 +61,7 @@ protected function getManager()
     /**
      * {@inheritdoc}
      */
-    public function getClassName()
+    public function getClassName(): string
     {
         return EntityStub::class;
     }
@@ -67,14 +69,17 @@ public function getClassName()
     /**
      * {@inheritdoc}
      */
-    public function countBy($criteria)
+    public function countBy($criteria): int
     {
         return count($this->entities);
     }
 
-    public function findPaginatedBy($criteria, array $orderBy = null, $itemsPerPage = 10)
+    /**
+     * {@inheritdoc}
+     */
+    public function findPaginatedBy($criteria, array $orderBy = null, int $itemsPerPage = 10): Paginator
     {
-        // TODO: Implement findPaginatedBy() method.
+        // Implementation not needed
     }
 
     /**
@@ -92,7 +97,7 @@ public function find($id)
     /**
      * {@inheritdoc}
      */
-    public function findAll()
+    public function findAll(): array
     {
         return $this->entities;
     }
@@ -118,7 +123,7 @@ public function findOneBy(array $criteria)
      *
      * @return \Doctrine\Common\Persistence\Mapping\ClassMetadata
      */
-    protected function getClassMetadata()
+    protected function getClassMetadata(): ClassMetadata
     {
         return new \Doctrine\ORM\Mapping\ClassMetadataInfo('EntityDocumentStub');
     }