diff --git a/.gitignore b/.gitignore
index 9158da40b5..2a214a6888 100644
--- a/.gitignore
+++ b/.gitignore
@@ -8,4 +8,5 @@ phpunit.xml
 composer.lock
 vendor/
 .phpcs-cache
+.phpunit.result.cache
 phpcs.xml
diff --git a/composer.json b/composer.json
index 1c2766444f..364315ddba 100644
--- a/composer.json
+++ b/composer.json
@@ -39,7 +39,7 @@
         "doctrine/coding-standard": "^5.0",
         "jmikola/geojson": "^1.0",
         "phpstan/phpstan": "^0.10.3",
-        "phpunit/phpunit": "^7.4"
+        "phpunit/phpunit": "^8.2"
     },
     "autoload": {
         "psr-4": { "Doctrine\\ODM\\MongoDB\\": "lib/Doctrine/ODM/MongoDB" }
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Aggregation/Stage/GraphLookupTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Aggregation/Stage/GraphLookupTest.php
index 81802f91b4..699a95d00a 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Aggregation/Stage/GraphLookupTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Aggregation/Stage/GraphLookupTest.php
@@ -24,7 +24,7 @@ class GraphLookupTest extends BaseTest
 {
     use AggregationTestTrait;
 
-    public function setUp()
+    public function setUp() : void
     {
         parent::setUp();
         $this->requireMongoDB34('$graphLookup tests require at least MongoDB 3.4.0');
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Aggregation/Stage/LookupTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Aggregation/Stage/LookupTest.php
index 3e889f172c..7d780c4dbe 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Aggregation/Stage/LookupTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Aggregation/Stage/LookupTest.php
@@ -14,7 +14,7 @@
 
 class LookupTest extends BaseTest
 {
-    public function setUp()
+    public function setUp() : void
     {
         parent::setUp();
         $this->requireMongoDB32('$lookup tests require at least MongoDB 3.2.0');
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/BaseTest.php b/tests/Doctrine/ODM/MongoDB/Tests/BaseTest.php
index 5b55d05e1c..a24996aae4 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/BaseTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/BaseTest.php
@@ -28,13 +28,13 @@ abstract class BaseTest extends TestCase
     /** @var UnitOfWork */
     protected $uow;
 
-    public function setUp()
+    public function setUp() : void
     {
         $this->dm  = $this->createTestDocumentManager();
         $this->uow = $this->dm->getUnitOfWork();
     }
 
-    public function tearDown()
+    public function tearDown() : void
     {
         if (! $this->dm) {
             return;
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Functional/AtomicSetTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Functional/AtomicSetTest.php
index c2f4ace883..784c0fbe29 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Functional/AtomicSetTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Functional/AtomicSetTest.php
@@ -27,7 +27,7 @@ class AtomicSetTest extends BaseTest
     /** @var CommandLogger */
     private $logger;
 
-    public function setUp()
+    public function setUp() : void
     {
         parent::setUp();
 
@@ -35,11 +35,11 @@ public function setUp()
         $this->logger->register();
     }
 
-    public function tearDown()
+    public function tearDown() : void
     {
         $this->logger->unregister();
 
-        return parent::tearDown();
+        parent::tearDown();
     }
 
     public function testAtomicInsertAndUpdate()
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Functional/CommitImprovementTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Functional/CommitImprovementTest.php
index f28607e413..3b0ee7d6da 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Functional/CommitImprovementTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Functional/CommitImprovementTest.php
@@ -20,7 +20,7 @@ class CommitImprovementTest extends BaseTest
     /** @var CommandLogger */
     private $logger;
 
-    public function setUp()
+    public function setUp() : void
     {
         parent::setUp();
 
@@ -28,11 +28,11 @@ public function setUp()
         $this->logger->register();
     }
 
-    public function tearDown()
+    public function tearDown() : void
     {
         $this->logger->unregister();
 
-        return parent::tearDown();
+        parent::tearDown();
     }
 
     public function testInsertIncludesAllNestedCollections()
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Functional/CustomTypeTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Functional/CustomTypeTest.php
index 256b273fe7..5c9fb68072 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Functional/CustomTypeTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Functional/CustomTypeTest.php
@@ -16,7 +16,7 @@
 
 class CustomTypeTest extends BaseTest
 {
-    public static function setUpBeforeClass()
+    public static function setUpBeforeClass() : void
     {
         Type::addType('date_collection', DateCollectionType::class);
     }
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Functional/DiscriminatorsDefaultValueTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Functional/DiscriminatorsDefaultValueTest.php
index d2a1c47e04..3c420b74f6 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Functional/DiscriminatorsDefaultValueTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Functional/DiscriminatorsDefaultValueTest.php
@@ -9,7 +9,7 @@
 
 class ReferenceDiscriminatorsDefaultValueTest extends BaseTest
 {
-    public function setUp()
+    public function setUp() : void
     {
         parent::setUp();
     }
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Functional/DocumentPersisterTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Functional/DocumentPersisterTest.php
index 388fb77404..c78107eae9 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Functional/DocumentPersisterTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Functional/DocumentPersisterTest.php
@@ -19,7 +19,7 @@ class DocumentPersisterTest extends BaseTest
     /** @var DocumentPersister */
     private $documentPersister;
 
-    public function setUp()
+    public function setUp() : void
     {
         parent::setUp();
 
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Functional/EcommerceTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Functional/EcommerceTest.php
index 6c564d1343..7d594a8a91 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Functional/EcommerceTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Functional/EcommerceTest.php
@@ -13,7 +13,7 @@
 
 class EcommerceTest extends BaseTest
 {
-    public function setUp()
+    public function setUp() : void
     {
         parent::setUp();
 
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Functional/EnsureShardingTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Functional/EnsureShardingTest.php
index 704c99f114..d867cd407f 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Functional/EnsureShardingTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Functional/EnsureShardingTest.php
@@ -16,7 +16,7 @@
  */
 class EnsureShardingTest extends BaseTest
 {
-    public function setUp()
+    public function setUp() : void
     {
         parent::setUp();
 
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Functional/FilterTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Functional/FilterTest.php
index 3730437095..7b1765dc5e 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Functional/FilterTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Functional/FilterTest.php
@@ -13,7 +13,7 @@
 
 class FilterTest extends BaseTest
 {
-    public function setUp()
+    public function setUp() : void
     {
         parent::setUp();
 
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Functional/PersistentCollectionCloneTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Functional/PersistentCollectionCloneTest.php
index 3cfd9439cb..8f1d34085d 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Functional/PersistentCollectionCloneTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Functional/PersistentCollectionCloneTest.php
@@ -14,7 +14,7 @@ class PersistentCollectionCloneTest extends BaseTest
     private $user1;
     private $user2;
 
-    public function setUp()
+    public function setUp() : void
     {
         parent::setUp();
 
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Functional/QueryTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Functional/QueryTest.php
index f5490a0ec8..23d73290ce 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Functional/QueryTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Functional/QueryTest.php
@@ -23,7 +23,7 @@
 
 class QueryTest extends BaseTest
 {
-    public function setUp()
+    public function setUp() : void
     {
         parent::setUp();
 
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Functional/ReadPreferenceTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Functional/ReadPreferenceTest.php
index fdab82296c..b006a4cf79 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Functional/ReadPreferenceTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Functional/ReadPreferenceTest.php
@@ -14,7 +14,7 @@
 
 class ReadPreferenceTest extends BaseTest
 {
-    public function setUp()
+    public function setUp() : void
     {
         parent::setUp();
 
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Functional/ReferenceDiscriminatorsTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Functional/ReferenceDiscriminatorsTest.php
index b3146b92dd..cb301089ed 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Functional/ReferenceDiscriminatorsTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Functional/ReferenceDiscriminatorsTest.php
@@ -9,7 +9,7 @@
 
 class ReferenceDiscriminatorsTest extends BaseTest
 {
-    public function setUp()
+    public function setUp() : void
     {
         parent::setUp();
         $this->dm->getSchemaManager()->ensureDocumentIndexes(CommentableAction::class);
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Functional/RepositoriesTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Functional/RepositoriesTest.php
index 163f35b387..76256a3880 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Functional/RepositoriesTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Functional/RepositoriesTest.php
@@ -10,7 +10,7 @@
 
 class RepositoriesTest extends BaseTest
 {
-    public function setUp()
+    public function setUp() : void
     {
         parent::setUp();
 
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Functional/ShardKeyTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Functional/ShardKeyTest.php
index 6228c354bb..43e3459566 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Functional/ShardKeyTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Functional/ShardKeyTest.php
@@ -19,7 +19,7 @@ class ShardKeyTest extends BaseTest
     /** @var CommandLogger */
     private $logger;
 
-    public function setUp()
+    public function setUp() : void
     {
         parent::setUp();
 
@@ -32,11 +32,11 @@ public function setUp()
         $this->logger->register();
     }
 
-    public function tearDown()
+    public function tearDown() : void
     {
         $this->logger->unregister();
 
-        return parent::tearDown();
+        parent::tearDown();
     }
 
     public function testUpdateAfterSave()
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Functional/SimpleReferencesTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Functional/SimpleReferencesTest.php
index 18151ab3ab..237876da04 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Functional/SimpleReferencesTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Functional/SimpleReferencesTest.php
@@ -18,7 +18,7 @@ class SimpleReferencesTest extends BaseTest
     private $user;
     private $test;
 
-    public function setUp()
+    public function setUp() : void
     {
         parent::setUp();
 
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Functional/Ticket/GH1138Test.php b/tests/Doctrine/ODM/MongoDB/Tests/Functional/Ticket/GH1138Test.php
index 88569464aa..5d1d9523f3 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Functional/Ticket/GH1138Test.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Functional/Ticket/GH1138Test.php
@@ -15,7 +15,7 @@ class GH1138Test extends BaseTest
     /** @var CommandLogger */
     private $logger;
 
-    public function setUp()
+    public function setUp() : void
     {
         parent::setUp();
 
@@ -23,11 +23,11 @@ public function setUp()
         $this->logger->register();
     }
 
-    public function tearDown()
+    public function tearDown() : void
     {
         $this->logger->unregister();
 
-        return parent::tearDown();
+        parent::tearDown();
     }
 
     public function testUpdatingDocumentBeforeItsInsertionShouldNotEntailMultipleQueries()
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Functional/Ticket/GH1229Test.php b/tests/Doctrine/ODM/MongoDB/Tests/Functional/Ticket/GH1229Test.php
index ac6c4a77e4..337cb39a28 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Functional/Ticket/GH1229Test.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Functional/Ticket/GH1229Test.php
@@ -21,7 +21,7 @@ class GH1229Test extends BaseTest
     /**
      * {@inheritdoc}
      */
-    public function setUp()
+    public function setUp() : void
     {
         parent::setUp();
 
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Functional/Ticket/GH593Test.php b/tests/Doctrine/ODM/MongoDB/Tests/Functional/Ticket/GH593Test.php
index 53f69429b6..15a13a1534 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Functional/Ticket/GH593Test.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Functional/Ticket/GH593Test.php
@@ -13,7 +13,7 @@
 
 class GH593Test extends BaseTest
 {
-    public function setUp()
+    public function setUp() : void
     {
         parent::setUp();
 
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Functional/Ticket/GH596Test.php b/tests/Doctrine/ODM/MongoDB/Tests/Functional/Ticket/GH596Test.php
index fbcbe41ddd..ac3d05f72c 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Functional/Ticket/GH596Test.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Functional/Ticket/GH596Test.php
@@ -9,7 +9,7 @@
 
 class GH596Test extends BaseTest
 {
-    public function setUp()
+    public function setUp() : void
     {
         parent::setUp();
 
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Functional/Ticket/MODM166Test.php b/tests/Doctrine/ODM/MongoDB/Tests/Functional/Ticket/MODM166Test.php
index 51c930f4b2..7e49100d8c 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Functional/Ticket/MODM166Test.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Functional/Ticket/MODM166Test.php
@@ -14,14 +14,13 @@
 
 class MODM166Test extends BaseTest
 {
-    public function setUp()
+    public function setUp() : void
     {
         parent::setUp();
 
         $this->listener = new MODM166EventListener();
         $evm            = $this->dm->getEventManager();
         $evm->addEventListener(Events::onFlush, $this->listener);
-        return $this->dm;
     }
 
     public function testUpdateCollectionDuringOnFlushAndRecomputSingleDocumentChangeSet()
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Functional/Ticket/MODM167Test.php b/tests/Doctrine/ODM/MongoDB/Tests/Functional/Ticket/MODM167Test.php
index 2bb6f5f1f3..689b00ddbc 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Functional/Ticket/MODM167Test.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Functional/Ticket/MODM167Test.php
@@ -12,14 +12,13 @@
 
 class MODM167Test extends BaseTest
 {
-    public function setUp()
+    public function setUp() : void
     {
         parent::setUp();
 
         $this->listener = new MODM167EventListener();
         $evm            = $this->dm->getEventManager();
         $evm->addEventListener(Events::onFlush, $this->listener);
-        return $this->dm;
     }
 
     public function testDetatchNewDocumentDuringOnFlush()
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Mapping/BasicInheritanceMappingTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Mapping/BasicInheritanceMappingTest.php
index 04aa34dcf7..769db0dc55 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Mapping/BasicInheritanceMappingTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Mapping/BasicInheritanceMappingTest.php
@@ -15,7 +15,7 @@ class BasicInheritanceMappingTest extends BaseTest
 {
     private $factory;
 
-    public function setUp()
+    public function setUp() : void
     {
         parent::setUp();
         $this->factory = new ClassMetadataFactory();
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Mapping/Driver/AbstractDriverTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Mapping/Driver/AbstractDriverTest.php
index 28dc9be579..a877a222c7 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Mapping/Driver/AbstractDriverTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Mapping/Driver/AbstractDriverTest.php
@@ -28,12 +28,12 @@ abstract class AbstractDriverTest extends TestCase
 {
     protected $driver;
 
-    public function setUp()
+    public function setUp() : void
     {
         // implement driver setup and metadata read
     }
 
-    public function tearDown()
+    public function tearDown() : void
     {
         unset($this->driver);
     }
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Mapping/Driver/XmlDriverTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Mapping/Driver/XmlDriverTest.php
index c22ebe27e6..2b56dad16e 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Mapping/Driver/XmlDriverTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Mapping/Driver/XmlDriverTest.php
@@ -14,7 +14,7 @@
 
 class XmlDriverTest extends AbstractDriverTest
 {
-    public function setUp()
+    public function setUp() : void
     {
         $this->driver = new XmlDriver(__DIR__ . '/fixtures/xml');
     }
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Mapping/ShardKeyInheritanceMappingTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Mapping/ShardKeyInheritanceMappingTest.php
index df8d8f7696..b324e2885a 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Mapping/ShardKeyInheritanceMappingTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Mapping/ShardKeyInheritanceMappingTest.php
@@ -13,7 +13,7 @@ class ShardKeyInheritanceMappingTest extends BaseTest
     /** @var ClassMetadataFactory */
     private $factory;
 
-    public function setUp()
+    public function setUp() : void
     {
         parent::setUp();
         $this->factory = new ClassMetadataFactory();
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Mapping/Symfony/AbstractDriverTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Mapping/Symfony/AbstractDriverTest.php
index d33499f276..66f71eb0ca 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Mapping/Symfony/AbstractDriverTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Mapping/Symfony/AbstractDriverTest.php
@@ -64,13 +64,13 @@ public function testFindMappingNamespaceNotFound()
         $driver->getLocator()->findMappingFile('MyOtherNamespace\MySubnamespace\Document\Foo');
     }
 
-    protected function setUp()
+    protected function setUp() : void
     {
         $this->dir = sys_get_temp_dir() . '/abstract_driver_test';
         @mkdir($this->dir, 0775, true);
     }
 
-    protected function tearDown()
+    protected function tearDown() : void
     {
         $iterator = new RecursiveIteratorIterator(new RecursiveDirectoryIterator($this->dir), RecursiveIteratorIterator::CHILD_FIRST);
 
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/PersistentCollection/DefaultPersistentCollectionGeneratorTest.php b/tests/Doctrine/ODM/MongoDB/Tests/PersistentCollection/DefaultPersistentCollectionGeneratorTest.php
index 3f818dc4fd..57d05d1c78 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/PersistentCollection/DefaultPersistentCollectionGeneratorTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/PersistentCollection/DefaultPersistentCollectionGeneratorTest.php
@@ -16,7 +16,7 @@ class DefaultPersistentCollectionGeneratorTest extends BaseTest
     /** @var DefaultPersistentCollectionGenerator */
     private $generator;
 
-    public function setUp()
+    public function setUp() : void
     {
         parent::setUp();
         $this->generator = new DefaultPersistentCollectionGenerator(
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Persisters/PersistenceBuilderTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Persisters/PersistenceBuilderTest.php
index d84d6a98d2..110a5eed67 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Persisters/PersistenceBuilderTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Persisters/PersistenceBuilderTest.php
@@ -21,13 +21,13 @@ class PersistenceBuilderTest extends BaseTest
 {
     private $pb;
 
-    public function setUp()
+    public function setUp() : void
     {
         parent::setUp();
         $this->pb = $this->dm->getUnitOfWork()->getPersistenceBuilder();
     }
 
-    public function tearDown()
+    public function tearDown() : void
     {
         unset($this->pb);
         parent::tearDown();
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Query/QueryExpressionVisitorTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Query/QueryExpressionVisitorTest.php
index 66dbdb4825..b82137898f 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Query/QueryExpressionVisitorTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Query/QueryExpressionVisitorTest.php
@@ -19,7 +19,7 @@ class QueryExpressionVisitorTest extends BaseTest
     private $queryBuilder;
     private $visitor;
 
-    public function setUp()
+    public function setUp() : void
     {
         parent::setUp();
         $this->queryBuilder = $this->dm->createQueryBuilder(Bar::class);
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/SchemaManagerTest.php b/tests/Doctrine/ODM/MongoDB/Tests/SchemaManagerTest.php
index cb51159f34..7f5968785d 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/SchemaManagerTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/SchemaManagerTest.php
@@ -55,7 +55,7 @@ class SchemaManagerTest extends BaseTest
     /** @var SchemaManager */
     private $schemaManager;
 
-    public function setUp()
+    public function setUp() : void
     {
         parent::setUp();
 
@@ -89,7 +89,7 @@ public function setUp()
         $this->schemaManager = $this->dm->getSchemaManager();
     }
 
-    public function tearDown()
+    public function tearDown() : void
     {
         // do not call parent, client here is mocked and there's nothing to tidy up in the database
     }
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Tools/ResolveTargetDocumentListenerTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Tools/ResolveTargetDocumentListenerTest.php
index 1695088951..7a08624682 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Tools/ResolveTargetDocumentListenerTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Tools/ResolveTargetDocumentListenerTest.php
@@ -22,7 +22,7 @@ class ResolveTargetDocumentListenerTest extends BaseTest
     /** @var ClassMetadataFactory */
     private $factory;
 
-    public function setUp()
+    public function setUp() : void
     {
         parent::setUp();