diff --git a/.travis.yml b/.travis.yml
index 6972a30a6..709e50500 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -15,25 +15,18 @@ matrix:
   fast_finish: true
   include:
     # Minimum supported dependencies with min and max PHP version
-    - php: 5.6
-      env: COMPOSER_FLAGS="--prefer-stable --prefer-lowest"
-    - php: 7.2
-      env: COMPOSER_FLAGS="--prefer-stable --prefer-lowest"
-    - php: 7.3
+    - php: 7.1
       env: COMPOSER_FLAGS="--prefer-stable --prefer-lowest"
 
     # Latest supported dependencies with each PHP version
-    - php: 5.6
-    - php: 7.0
     - php: 7.1
     - php: 7.2
-      env: COVERAGE=true PHPUNIT_FLAGS="-v --coverage-clover=coverage.clover"
     - php: 7.3
       env: COVERAGE=true PHPUNIT_FLAGS="-v --coverage-clover=coverage.clover"
 
     # Install all SF components in the same major version, see https://github.com/dunglas/symfony-lock
-    - php: 7.2
-      env: SYMFONY_VERSION="^3"
+    - php: 7.3
+      env: SYMFONY_VERSION="^4"
 
 before_install:
   - if [[ $COVERAGE != true ]]; then phpenv config-rm xdebug.ini || true; fi
@@ -51,9 +44,6 @@ install:
 
 before_script:
   - phpenv config-add .travis/php.ini
-  - if [ "$TRAVIS_PHP_VERSION" = "5.6" ]; then echo "extension = mongo.so" >> ~/.phpenv/versions/$(phpenv version-name)/etc/php.ini; fi;
-  - if [ "$TRAVIS_PHP_VERSION" = "5.6" ]; then composer require --dev --no-update doctrine/mongodb-odm=^1; fi;
-  - if [ "$TRAVIS_PHP_VERSION" = "7.0" ]; then echo "extension = mongodb.so" >> ~/.phpenv/versions/$(phpenv version-name)/etc/php.ini; fi;
   - if [ "$TRAVIS_PHP_VERSION" = "7.1" ]; then echo "extension = mongodb.so" >> ~/.phpenv/versions/$(phpenv version-name)/etc/php.ini; fi;
 
 script:
diff --git a/CHANGELOG-5.1.md b/CHANGELOG-5.1.md
new file mode 100644
index 000000000..71806bf1c
--- /dev/null
+++ b/CHANGELOG-5.1.md
@@ -0,0 +1,9 @@
+CHANGELOG for 5.1.x
+===================
+
+This changelog references the relevant changes (bug and security fixes) done
+in 5.1 versions.
+
+### 5.1.0 (2019-xx-xx)
+
+* Added compatibility with Symfony 4.2.
diff --git a/README.md b/README.md
index 6cd94259f..37b6832e7 100644
--- a/README.md
+++ b/README.md
@@ -31,9 +31,10 @@ The following table shows the compatibilities of different versions of the bundl
 
 | FOSElasticaBundle                                                                       | Elastica | Elasticsearch | Symfony    | PHP   |
 | --------------------------------------------------------------------------------------- | ---------| ------------- | ---------- | ----- |
-| [5.x](https://github.com/FriendsOfSymfony/FOSElasticaBundle/tree/master)                | ^5.2\|^6 | 5.\*\|6.\*    | ^3.2\|^4   | >=5.6 |
-| [4.x](https://github.com/FriendsOfSymfony/FOSElasticaBundle/tree/4.x) (unmaintained)    | 3.2.\*   | 2.\*          | ^2.8\|^3.2 | >=5.5 |
-| [3.2.x](https://github.com/FriendsOfSymfony/FOSElasticaBundle/tree/3.2.x) (unmaintained)| ^2.1     | 1.\*          | ^2.3\|^3   | >=5.3 |
+| [5.1] (master)                                                                          | ^5.3\|^6 | 5.\*\|6.\*    | ^3.4\|^4   | >=7.1 |
+| [5.0] (unmaintained)                                                                    | ^5.2\|^6 | 5.\*\|6.\*    | ^3.2\|^4   | >=5.6 |
+| [4.x] (unmaintained)                                                                    | 3.2.\*   | 2.\*          | ^2.8\|^3.2 | >=5.5 |
+| [3.2.x] (unmaintained)                                                                  | ^2.1     | 1.\*          | ^2.3\|^3   | >=5.3 |
 
 License
 -------
diff --git a/composer.json b/composer.json
index 5ba1b9a1b..5535a3591 100644
--- a/composer.json
+++ b/composer.json
@@ -12,30 +12,30 @@
         { "name": "Jeremy Mikola", "email": "jmikola@gmail.com" }
     ],
     "require": {
-        "php": "^5.6.0|^7.0",
-        "symfony/framework-bundle": "^3.2|^4",
-        "symfony/console": "^3.2|^4",
-        "symfony/dependency-injection": "^3.3|^4",
-        "symfony/property-access": "^3.2|^4",
+        "php": "^7.1",
+        "symfony/framework-bundle": "^3.4|^4",
+        "symfony/console": "^3.4|^4",
+        "symfony/dependency-injection": "^3.4|^4",
+        "symfony/property-access": "^3.4|^4",
         "pagerfanta/pagerfanta": "^1.0.5|^2.0",
         "psr/log": "^1.0",
-        "ruflin/elastica": "^5.2.1|^6.0"
+        "ruflin/elastica": "^5.3|^6.1"
     },
     "require-dev": {
         "doctrine/orm": "^2.5",
         "doctrine/doctrine-bundle": "^1.6",
-        "doctrine/phpcr-bundle": "^1.3",
+        "doctrine/phpcr-bundle": "^1.3|^2.0",
         "doctrine/phpcr-odm": "^1.4",
         "jackalope/jackalope-doctrine-dbal": "^1.2",
         "jms/serializer-bundle": "^2.2",
         "phpunit/phpunit": "^5.7.11|^6.5",
         "knplabs/knp-components": "^1.2",
-        "symfony/expression-language" : "^3.2|^4",
-        "symfony/twig-bundle": "^3.2|^4",
-        "symfony/serializer": "^3.2|^4",
-        "symfony/yaml": "^3.2|^4",
+        "symfony/expression-language" : "^3.4|^4",
+        "symfony/twig-bundle": "^3.4|^4",
+        "symfony/serializer": "^3.4|^4",
+        "symfony/yaml": "^3.4|^4",
         "friendsofphp/php-cs-fixer": "^2.2",
-        "symfony/web-profiler-bundle": "^3.0|^4.0",
+        "symfony/web-profiler-bundle": "^3.4|^4.0"
         "phpdocumentor/type-resolver": "~0.2.1"
     },
     "suggest": {
diff --git a/src/DependencyInjection/Configuration.php b/src/DependencyInjection/Configuration.php
index 0cb6d9d14..519174e4b 100644
--- a/src/DependencyInjection/Configuration.php
+++ b/src/DependencyInjection/Configuration.php
@@ -78,8 +78,7 @@ public function getConfigTreeBuilder()
      */
     public function getDynamicTemplateNode()
     {
-        $builder = new TreeBuilder();
-        $node = $builder->root('dynamic_templates');
+        $node = $this->createTreeBuilderNode('dynamic_templates');
 
         $node
             ->prototype('array')
@@ -109,8 +108,7 @@ public function getDynamicTemplateNode()
      */
     protected function getTypesNode()
     {
-        $builder = new TreeBuilder();
-        $node = $builder->root('types');
+        $node = $this->createTreeBuilderNode('types');
 
         $node
             ->useAttributeAsKey('name')
@@ -169,8 +167,7 @@ protected function getTypesNode()
      */
     protected function getPropertiesNode()
     {
-        $builder = new TreeBuilder();
-        $node = $builder->root('properties');
+        $node = $this->createTreeBuilderNode('properties');
 
         $node
             ->useAttributeAsKey('name')
@@ -185,8 +182,7 @@ protected function getPropertiesNode()
      */
     protected function getIdNode()
     {
-        $builder = new TreeBuilder();
-        $node = $builder->root('_id');
+        $node = $this->createTreeBuilderNode('_id');
 
         $node
             ->children()
@@ -202,8 +198,7 @@ protected function getIdNode()
      */
     protected function getSourceNode()
     {
-        $builder = new TreeBuilder();
-        $node = $builder->root('_source');
+        $node = $this->createTreeBuilderNode('_source');
 
         $node
             ->children()
@@ -229,8 +224,7 @@ protected function getSourceNode()
      */
     protected function getRoutingNode()
     {
-        $builder = new TreeBuilder();
-        $node = $builder->root('_routing');
+        $node = $this->createTreeBuilderNode('_routing');
 
         $node
             ->children()
@@ -247,8 +241,7 @@ protected function getRoutingNode()
      */
     protected function getParentNode()
     {
-        $builder = new TreeBuilder();
-        $node = $builder->root('_parent');
+        $node = $this->createTreeBuilderNode('_parent');
 
         $node
             ->children()
@@ -266,8 +259,7 @@ protected function getParentNode()
      */
     protected function getAllNode()
     {
-        $builder = new TreeBuilder();
-        $node = $builder->root('_all');
+        $node = $this->createTreeBuilderNode('_all');
 
         $node
             ->children()
@@ -284,8 +276,7 @@ protected function getAllNode()
      */
     protected function getPersistenceNode()
     {
-        $builder = new TreeBuilder();
-        $node = $builder->root('persistence');
+        $node = $this->createTreeBuilderNode('persistence');
 
         $node
             ->validate()
@@ -388,8 +379,7 @@ protected function getPersistenceNode()
      */
     protected function getSerializerNode()
     {
-        $builder = new TreeBuilder();
-        $node = $builder->root('serializer');
+        $node = $this->createTreeBuilderNode('serializer');
 
         $node
             ->addDefaultsIfNotSet()
@@ -540,6 +530,23 @@ private function addIndexesSection(ArrayNodeDefinition $rootNode)
         ;
     }
 
+    /**
+     * @return ArrayNodeDefinition|\Symfony\Component\Config\Definition\Builder\NodeDefinition
+     */
+    private function createTreeBuilderNode($name)
+    {
+        $builder = new TreeBuilder($name);
+
+        if (method_exists($builder, 'getRootNode')) {
+            $node = $builder->getRootNode();
+        } else {
+            // BC layer for symfony/config 4.1 and older
+            $node = $builder->root($name);
+        }
+
+        return $node;
+    }
+
     /**
      * Adds the configuration for the "index_templates" key.
      *
diff --git a/src/Transformer/AbstractElasticaToModelTransformer.php b/src/Transformer/AbstractElasticaToModelTransformer.php
index 6f3103ca1..c811bce27 100644
--- a/src/Transformer/AbstractElasticaToModelTransformer.php
+++ b/src/Transformer/AbstractElasticaToModelTransformer.php
@@ -31,22 +31,4 @@ public function setPropertyAccessor(PropertyAccessorInterface $propertyAccessor)
     {
         $this->propertyAccessor = $propertyAccessor;
     }
-
-    /**
-     * Returns a sorting closure to be used with usort() to put retrieved objects
-     * back in the order that they were returned by ElasticSearch.
-     *
-     * @param array  $idPos
-     * @param string $identifierPath
-     *
-     * @return callable
-     */
-    protected function getSortingClosure(array $idPos, $identifierPath)
-    {
-        $propertyAccessor = $this->propertyAccessor;
-
-        return function ($a, $b) use ($idPos, $identifierPath, $propertyAccessor) {
-            return $idPos[(string) $propertyAccessor->getValue($a, $identifierPath)] > $idPos[(string) $propertyAccessor->getValue($b, $identifierPath)];
-        };
-    }
 }
diff --git a/tests/Functional/TypeObj.php b/tests/Functional/TypeObj.php
index b047604b5..4daec76ae 100644
--- a/tests/Functional/TypeObj.php
+++ b/tests/Functional/TypeObj.php
@@ -9,15 +9,6 @@
  * file that was distributed with this source code.
  */
 
-/**
- * This file is part of the FOSElasticaBundle project.
- *
- * (c) Infinite Networks Pty Ltd <http://www.infinite.net.au>
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
-
 namespace FOS\ElasticaBundle\Tests\Functional;
 
 class TypeObj
diff --git a/tests/Functional/TypeObject.php b/tests/Functional/TypeObject.php
index 02ae9538a..b663d12f0 100644
--- a/tests/Functional/TypeObject.php
+++ b/tests/Functional/TypeObject.php
@@ -9,15 +9,6 @@
  * file that was distributed with this source code.
  */
 
-/**
- * This file is part of the FOSElasticaBundle project.
- *
- * (c) Infinite Networks Pty Ltd <http://www.infinite.net.au>
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
-
 namespace FOS\ElasticaBundle\Tests\Functional;
 
 class TypeObject
diff --git a/tests/Functional/app/ORM/IndexableService.php b/tests/Functional/app/ORM/IndexableService.php
index 5aecf0c50..cef885c11 100644
--- a/tests/Functional/app/ORM/IndexableService.php
+++ b/tests/Functional/app/ORM/IndexableService.php
@@ -9,15 +9,6 @@
  * file that was distributed with this source code.
  */
 
-/**
- * This file is part of the FOSElasticaBundle project.
- *
- * (c) Infinite Networks Pty Ltd <http://www.infinite.net.au>
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
-
 namespace FOS\ElasticaBundle\Tests\Functional\app\ORM;
 
 class IndexableService
diff --git a/tests/Unit/DataCollector/ElasticaDataCollectorTest.php b/tests/Unit/DataCollector/ElasticaDataCollectorTest.php
index 79ba03500..f288f9370 100644
--- a/tests/Unit/DataCollector/ElasticaDataCollectorTest.php
+++ b/tests/Unit/DataCollector/ElasticaDataCollectorTest.php
@@ -13,14 +13,14 @@
 
 use FOS\ElasticaBundle\DataCollector\ElasticaDataCollector;
 use FOS\ElasticaBundle\Logger\ElasticaLogger;
-use PHPUnit\Framework\TestCase;
+use FOS\ElasticaBundle\Tests\Unit\UnitTestHelper;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
 
 /**
  * @author Richard Miller <info@limethinking.co.uk>
  */
-class ElasticaDataCollectorTest extends TestCase
+class ElasticaDataCollectorTest extends UnitTestHelper
 {
     public function testCorrectAmountOfQueries()
     {
@@ -103,4 +103,17 @@ public function testName()
 
         $this->assertSame('elastica', $elasticaDataCollector->getName());
     }
+
+    public function testReset()
+    {
+        /** @var $loggerMock \PHPUnit_Framework_MockObject_MockObject|ElasticaLogger */
+        $loggerMock = $this->createMock(ElasticaLogger::class);
+        $loggerMock->expects($this->once())
+            ->method('reset')
+            ->willReturn('foo');
+
+        $elasticaDataCollector = new ElasticaDataCollector($loggerMock);
+        $elasticaDataCollector->reset();
+        $this->assertSame([], $this->getProtectedProperty($elasticaDataCollector, 'data'));
+    }
 }
diff --git a/tests/Unit/Event/IndexEventTest.php b/tests/Unit/Event/IndexEventTest.php
new file mode 100644
index 000000000..f22d4e9ed
--- /dev/null
+++ b/tests/Unit/Event/IndexEventTest.php
@@ -0,0 +1,33 @@
+<?php
+
+/*
+ * This file is part of the FOSElasticaBundle package.
+ *
+ * (c) FriendsOfSymfony <http://friendsofsymfony.github.com/>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace FOS\ElasticaBundle\Tests\Unit\Event;
+
+use FOS\ElasticaBundle\Event\IndexEvent;
+use PHPUnit\Framework\TestCase;
+
+class IndexEventTest extends TestCase
+{
+    /**
+     * @var IndexEvent
+     */
+    private $event;
+
+    protected function setUp()
+    {
+        $this->event = new IndexEvent('index');
+    }
+
+    public function testIndex()
+    {
+        $this->assertEquals('index', $this->event->getIndex());
+    }
+}
diff --git a/tests/Unit/Event/IndexPopulateEventTest.php b/tests/Unit/Event/IndexPopulateEventTest.php
new file mode 100644
index 000000000..c400800f4
--- /dev/null
+++ b/tests/Unit/Event/IndexPopulateEventTest.php
@@ -0,0 +1,55 @@
+<?php
+
+/*
+ * This file is part of the FOSElasticaBundle package.
+ *
+ * (c) FriendsOfSymfony <http://friendsofsymfony.github.com/>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace FOS\ElasticaBundle\Tests\Unit\Event;
+
+use FOS\ElasticaBundle\Event\IndexPopulateEvent;
+use PHPUnit\Framework\TestCase;
+
+class IndexPopulateEventTest extends TestCase
+{
+    /**
+     * @var IndexPopulateEvent
+     */
+    private $event;
+
+    protected function setUp()
+    {
+        $this->event = new IndexPopulateEvent('index', false, []);
+    }
+
+    public function testReset()
+    {
+        $this->assertFalse($this->event->isReset());
+        $this->event->setReset(true);
+        $this->assertTrue($this->event->isReset());
+    }
+
+    public function testOptions()
+    {
+        $this->event->setOption('name', 'value');
+        $this->assertEquals(['name' => 'value'], $this->event->getOptions());
+    }
+
+    public function testOptionValid()
+    {
+        $this->event->setOption('name', 'value');
+        $this->assertEquals('value', $this->event->getOption('name'));
+    }
+
+    public function testOptionInvalid()
+    {
+        $this->expectException(\InvalidArgumentException::class);
+        $this->event->getOption('name');
+        $this->event->setOption('name', 'value');
+        $this->assertEquals('value', $this->event->getOption('name'));
+    }
+}
diff --git a/tests/Unit/Event/IndexResetEventTest.php b/tests/Unit/Event/IndexResetEventTest.php
new file mode 100644
index 000000000..5dfac08c0
--- /dev/null
+++ b/tests/Unit/Event/IndexResetEventTest.php
@@ -0,0 +1,39 @@
+<?php
+
+/*
+ * This file is part of the FOSElasticaBundle package.
+ *
+ * (c) FriendsOfSymfony <http://friendsofsymfony.github.com/>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace FOS\ElasticaBundle\Tests\Unit\Event;
+
+use FOS\ElasticaBundle\Event\IndexResetEvent;
+use PHPUnit\Framework\TestCase;
+
+class IndexResetEventTest extends TestCase
+{
+    public function testForce()
+    {
+        $event = new IndexResetEvent('index', false, true);
+        $this->assertTrue($event->isForce());
+
+        $event = new IndexResetEvent('index', false, false);
+        $this->assertFalse($event->isForce());
+
+        $event->setForce(true);
+        $this->assertTrue($event->isForce());
+    }
+
+    public function testPopulating()
+    {
+        $event = new IndexResetEvent('index', true, false);
+        $this->assertTrue($event->isPopulating());
+
+        $event = new IndexResetEvent('index', false, false);
+        $this->assertFalse($event->isPopulating());
+    }
+}
diff --git a/tests/Unit/Event/TransformEventTest.php b/tests/Unit/Event/TransformEventTest.php
new file mode 100644
index 000000000..5aae506c8
--- /dev/null
+++ b/tests/Unit/Event/TransformEventTest.php
@@ -0,0 +1,56 @@
+<?php
+
+/*
+ * This file is part of the FOSElasticaBundle package.
+ *
+ * (c) FriendsOfSymfony <http://friendsofsymfony.github.com/>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace FOS\ElasticaBundle\Tests\Unit\Event;
+
+use Elastica\Document;
+use FOS\ElasticaBundle\Event\TransformEvent;
+use PHPUnit\Framework\TestCase;
+
+class TransformEventTest extends TestCase
+{
+    /**
+     * @var TransformEvent
+     */
+    private $event;
+
+    protected function setUp()
+    {
+        $document = new Document();
+        $object = (object) [];
+        $this->event = new TransformEvent($document, [], $object);
+    }
+
+    public function testDocument()
+    {
+        $this->assertNotNull($this->event->getDocument());
+        $document = new Document();
+        $this->event->setDocument($document);
+        $this->assertEquals($document, $this->event->getDocument());
+    }
+
+    public function testFields()
+    {
+        $document = new Document();
+        $object = (object) [];
+        $fields = ['abc', '123'];
+        $event = new TransformEvent($document, $fields, $object);
+        $this->assertEquals($fields, $event->getFields());
+    }
+
+    public function testObject()
+    {
+        $document = new Document();
+        $object = (object) ['abc', '123'];
+        $event = new TransformEvent($document, [], $object);
+        $this->assertEquals($object, $event->getObject());
+    }
+}
diff --git a/tests/Unit/Event/TypePopulateEventTest.php b/tests/Unit/Event/TypePopulateEventTest.php
new file mode 100644
index 000000000..d8536a62f
--- /dev/null
+++ b/tests/Unit/Event/TypePopulateEventTest.php
@@ -0,0 +1,24 @@
+<?php
+
+/*
+ * This file is part of the FOSElasticaBundle package.
+ *
+ * (c) FriendsOfSymfony <http://friendsofsymfony.github.com/>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace FOS\ElasticaBundle\Tests\Unit\Event;
+
+use FOS\ElasticaBundle\Event\TypePopulateEvent;
+use PHPUnit\Framework\TestCase;
+
+class TypePopulateEventTest extends TestCase
+{
+    public function testType()
+    {
+        $event = new TypePopulateEvent('index', 'type', false, []);
+        $this->assertEquals('type', $event->getType());
+    }
+}
diff --git a/tests/Unit/Event/TypeResetEventTest.php b/tests/Unit/Event/TypeResetEventTest.php
new file mode 100644
index 000000000..197a38d26
--- /dev/null
+++ b/tests/Unit/Event/TypeResetEventTest.php
@@ -0,0 +1,24 @@
+<?php
+
+/*
+ * This file is part of the FOSElasticaBundle package.
+ *
+ * (c) FriendsOfSymfony <http://friendsofsymfony.github.com/>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace FOS\ElasticaBundle\Tests\Unit\Event;
+
+use FOS\ElasticaBundle\Event\TypeResetEvent;
+use PHPUnit\Framework\TestCase;
+
+class TypeResetEventTest extends TestCase
+{
+    public function testType()
+    {
+        $event = new TypeResetEvent('index', 'type');
+        $this->assertEquals('type', $event->getType());
+    }
+}
diff --git a/tests/Unit/EventListener/PopulateListenerTest.php b/tests/Unit/EventListener/PopulateListenerTest.php
new file mode 100644
index 000000000..f5260d6c8
--- /dev/null
+++ b/tests/Unit/EventListener/PopulateListenerTest.php
@@ -0,0 +1,60 @@
+<?php
+
+/*
+ * This file is part of the FOSElasticaBundle package.
+ *
+ * (c) FriendsOfSymfony <http://friendsofsymfony.github.com/>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace FOS\ElasticaBundle\Tests\Unit\Event;
+
+use FOS\ElasticaBundle\EventListener\PopulateListener;
+use FOS\ElasticaBundle\Event\IndexPopulateEvent;
+use FOS\ElasticaBundle\Index\Resetter;
+use PHPUnit\Framework\TestCase;
+
+class PopulateListenerTest extends TestCase
+{
+    private function mockResetter($numberOfCalls, $indexName, $deleteOption)
+    {
+        $stub = $this
+            ->getMockBuilder(Resetter::class)
+            ->disableOriginalConstructor()
+            ->getMock()
+        ;
+
+        $stub
+            ->expects($this->exactly($numberOfCalls))
+            ->method('switchIndexAlias')
+            ->with($indexName, $deleteOption);
+
+        return $stub;
+    }
+
+    public function testOnPostIndexPopulateWithReset()
+    {
+        $indexName = 'index';
+        $deleteOption = true;
+
+        $stub = $this->mockResetter(1, $indexName, $deleteOption);
+        $listener = new PopulateListener($stub);
+
+        $event = new IndexPopulateEvent($indexName, true, ['delete' => $deleteOption]);
+        $listener->onPostIndexPopulate($event);
+    }
+
+    public function testOnPostIndexPopulateWithoutReset()
+    {
+        $indexName = 'index';
+        $deleteOption = true;
+
+        $stub = $this->mockResetter(0, $indexName, $deleteOption);
+        $listener = new PopulateListener($stub);
+
+        $event = new IndexPopulateEvent($indexName, false, ['delete' => $deleteOption]);
+        $listener->onPostIndexPopulate($event);
+    }
+}
diff --git a/tests/Unit/Exception/AliasIsIndexExceptionTest.php b/tests/Unit/Exception/AliasIsIndexExceptionTest.php
new file mode 100644
index 000000000..6eaf30d49
--- /dev/null
+++ b/tests/Unit/Exception/AliasIsIndexExceptionTest.php
@@ -0,0 +1,23 @@
+<?php
+
+/*
+ * This file is part of the FOSElasticaBundle package.
+ *
+ * (c) FriendsOfSymfony <http://friendsofsymfony.github.com/>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace FOS\ElasticaBundle\Tests\Unit\Event;
+
+use FOS\ElasticaBundle\Exception\AliasIsIndexException;
+use PHPUnit\Framework\TestCase;
+
+class AliasIsIndexExceptionTest extends TestCase
+{
+    public function testConstruct()
+    {
+        $exception = new AliasIsIndexException('indexName');
+    }
+}
diff --git a/tests/Unit/Exception/InvalidArgumentTypeExceptionTest.php b/tests/Unit/Exception/InvalidArgumentTypeExceptionTest.php
new file mode 100644
index 000000000..6aecdc800
--- /dev/null
+++ b/tests/Unit/Exception/InvalidArgumentTypeExceptionTest.php
@@ -0,0 +1,23 @@
+<?php
+
+/*
+ * This file is part of the FOSElasticaBundle package.
+ *
+ * (c) FriendsOfSymfony <http://friendsofsymfony.github.com/>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace FOS\ElasticaBundle\Tests\Unit\Event;
+
+use FOS\ElasticaBundle\Exception\InvalidArgumentTypeException;
+use PHPUnit\Framework\TestCase;
+
+class InvalidArgumentTypeExceptionTest extends TestCase
+{
+    public function testConstruct()
+    {
+        $exception = new InvalidArgumentTypeException('value', 'expectedType');
+    }
+}
diff --git a/tests/Unit/Paginator/FantaPaginatorAdapterTest.php b/tests/Unit/Paginator/FantaPaginatorAdapterTest.php
new file mode 100644
index 000000000..36d954731
--- /dev/null
+++ b/tests/Unit/Paginator/FantaPaginatorAdapterTest.php
@@ -0,0 +1,99 @@
+<?php
+
+/*
+ * This file is part of the FOSElasticaBundle package.
+ *
+ * (c) FriendsOfSymfony <http://friendsofsymfony.github.com/>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace FOS\ElasticaBundle\Tests\Unit\Event;
+
+use FOS\ElasticaBundle\Paginator\FantaPaginatorAdapter;
+use FOS\ElasticaBundle\Paginator\PaginatorAdapterInterface;
+use FOS\ElasticaBundle\Paginator\PartialResultsInterface;
+use PHPUnit\Framework\TestCase;
+
+class FantaPaginatorAdapterTest extends TestCase
+{
+    private function mockPartialResults($results)
+    {
+        $mock = $this
+            ->getMockBuilder(PartialResultsInterface::class)
+            ->getMock();
+        $mock
+            ->expects($this->exactly(1))
+            ->method('toArray')
+            ->willReturn($results);
+        return $mock;
+    }
+
+    private function mockPaginatorAdapter()
+    {
+        $mock = $this
+            ->getMockBuilder(PaginatorAdapterInterface::class)
+            ->getMock();
+        return $mock;
+    }
+
+    public function testGetNbResults()
+    {
+        $mock = $this->mockPaginatorAdapter();
+        $mock
+            ->expects($this->exactly(1))
+            ->method('getTotalHits')
+            ->willReturn(123);
+        $adapter = new FantaPaginatorAdapter($mock);
+        $this->assertEquals(123, $adapter->getNbResults());
+    }
+
+    public function testGetAggregations()
+    {
+        $mock = $this->mockPaginatorAdapter();
+        $mock
+            ->expects($this->exactly(1))
+            ->method('getAggregations')
+            ->willReturn([]);
+        $adapter = new FantaPaginatorAdapter($mock);
+        $this->assertEquals([], $adapter->getAggregations());
+    }
+
+    public function testGetSuggests()
+    {
+        $mock = $this->mockPaginatorAdapter();
+        $mock
+            ->expects($this->exactly(1))
+            ->method('getSuggests')
+            ->willReturn([]);
+        $adapter = new FantaPaginatorAdapter($mock);
+        $this->assertEquals([], $adapter->getSuggests());
+    }
+
+    public function testGetGetSlice()
+    {
+        $results = [];
+        $resultsMock = $this->mockPartialResults($results);
+
+        $mock = $this->mockPaginatorAdapter();
+        $mock
+            ->expects($this->exactly(1))
+            ->method('getResults')
+            ->with(1, 10)
+            ->willReturn($resultsMock);
+        $adapter = new FantaPaginatorAdapter($mock);
+        $this->assertEquals($results, $adapter->getSlice(1, 10));
+    }
+
+    public function testGetMaxScore()
+    {
+        $mock = $this->mockPaginatorAdapter();
+        $mock
+            ->expects($this->exactly(1))
+            ->method('getMaxScore')
+            ->willReturn(123);
+        $adapter = new FantaPaginatorAdapter($mock);
+        $this->assertEquals(123, $adapter->getMaxScore());
+    }
+}
diff --git a/tests/Unit/Paginator/RawPaginatorAdapterTest.php b/tests/Unit/Paginator/RawPaginatorAdapterTest.php
new file mode 100644
index 000000000..13e3e2893
--- /dev/null
+++ b/tests/Unit/Paginator/RawPaginatorAdapterTest.php
@@ -0,0 +1,130 @@
+<?php
+
+/*
+ * This file is part of the FOSElasticaBundle package.
+ *
+ * (c) FriendsOfSymfony <http://friendsofsymfony.github.com/>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace FOS\ElasticaBundle\Tests\Unit\Event;
+
+use FOS\ElasticaBundle\Paginator\RawPaginatorAdapter;
+use Elastica\Query;
+use Elastica\ResultSet;
+use Elastica\SearchableInterface;
+use InvalidArgumentException;
+use PHPUnit\Framework\TestCase;
+
+class RawPaginatorAdapterTest extends TestCase
+{
+    private function mockResultSet()
+    {
+        $methods = ['getTotalHits', 'getAggregations', 'getSuggests', 'getMaxScore'];
+        $mock = $this
+            ->getMockBuilder(ResultSet::class)
+            ->disableOriginalConstructor()
+            ->setMethods($methods)
+            ->getMock();
+        return $mock;
+    }
+
+    private function mockSearchable()
+    {
+        $mock = $this
+            ->getMockBuilder(SearchableInterface::class)
+            ->getMock();
+        return $mock;
+    }
+
+    private function createAdapterWithSearch($methodName, $value)
+    {
+        $resultSet = $this->mockResultSet();
+        $resultSet
+            ->expects($this->exactly(1))
+            ->method($methodName)
+            ->willReturn($value);
+
+        $query = new Query();
+        $options = [];
+        $searchable = $this->mockSearchable();
+        $searchable
+            ->expects($this->exactly(1))
+            ->method('search')
+            ->with($query)
+            ->willReturn($resultSet);
+
+        $adapter = new RawPaginatorAdapter($searchable, $query, $options);
+        return $adapter;
+    }
+
+    private function createAdapterWithCount($totalHits, $querySize = null)
+    {
+        $query = new Query();
+        if ($querySize) {
+            $query->setParam('size', $querySize);
+        }
+        $options = [];
+        $searchable = $this->mockSearchable();
+        $searchable
+            ->expects($this->exactly(1))
+            ->method('count')
+            ->willReturn($totalHits);
+
+        $adapter = new RawPaginatorAdapter($searchable, $query, $options);
+        return $adapter;
+    }
+
+    public function testGetTotalHits()
+    {
+        $adapter = $this->createAdapterWithCount(123);
+        $this->assertEquals(123, $adapter->getTotalHits());
+
+        $adapter = $this->createAdapterWithCount(123, 100);
+        $this->assertEquals(100, $adapter->getTotalHits());
+    }
+
+    public function testGetTotalHitsGenuineTotal()
+    {
+        $adapter = $this->createAdapterWithCount(123);
+        $this->assertEquals(123, $adapter->getTotalHits(true));
+
+        $adapter = $this->createAdapterWithCount(123, 100);
+        $this->assertEquals(123, $adapter->getTotalHits(true));
+    }
+
+    public function testGetAggregations()
+    {
+        $value = [];
+        $adapter = $this->createAdapterWithSearch('getAggregations', $value);
+        $this->assertEquals($value, $adapter->getAggregations());
+    }
+
+    public function testGetSuggests()
+    {
+        $value = [];
+        $adapter = $this->createAdapterWithSearch('getSuggests', $value);
+        $this->assertEquals($value, $adapter->getSuggests());
+    }
+
+    public function testGetMaxScore()
+    {
+        $value = 1.0;
+        $adapter = $this->createAdapterWithSearch('getMaxScore', $value);
+        $this->assertEquals($value, $adapter->getMaxScore());
+    }
+
+    public function testGetQuery()
+    {
+        $resultSet = $this->mockResultSet();
+
+        $query = new Query();
+        $options = [];
+        $searchable = $this->mockSearchable($query);
+
+        $adapter = new RawPaginatorAdapter($searchable, $query, $options);
+        $this->assertEquals($query, $adapter->getQuery());
+    }
+}
diff --git a/tests/Unit/Provider/IndexableTest.php b/tests/Unit/Provider/IndexableTest.php
index 5aac883bd..99f241936 100644
--- a/tests/Unit/Provider/IndexableTest.php
+++ b/tests/Unit/Provider/IndexableTest.php
@@ -9,15 +9,6 @@
  * file that was distributed with this source code.
  */
 
-/**
- * This file is part of the FOSElasticaBundle project.
- *
- * (c) Infinite Networks Pty Ltd <http://www.infinite.net.au>
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
-
 namespace FOS\ElasticaBundle\Tests\Unit\Provider;
 
 use FOS\ElasticaBundle\Provider\Indexable;
diff --git a/tests/Unit/Provider/PagerProviderRegistryTest.php b/tests/Unit/Provider/PagerProviderRegistryTest.php
new file mode 100644
index 000000000..70a08fe65
--- /dev/null
+++ b/tests/Unit/Provider/PagerProviderRegistryTest.php
@@ -0,0 +1,81 @@
+<?php
+
+/*
+ * This file is part of the FOSElasticaBundle package.
+ *
+ * (c) FriendsOfSymfony <http://friendsofsymfony.github.com/>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace FOS\ElasticaBundle\Tests\Unit\Provider;
+
+use FOS\ElasticaBundle\Provider\PagerProviderRegistry;
+use Symfony\Component\DependencyInjection\Container;
+use PHPUnit\Framework\TestCase;
+
+class PagerProviderRegistryTest extends TestCase
+{
+    protected function mockPagerProviderRegistry(array $providers, $service = null)
+    {
+        $container = new Container();
+        $container->set('the_service_id', $service);
+
+        $registry = new PagerProviderRegistry($providers);
+        $registry->setContainer($container);
+        return $registry;
+    }
+
+    public function testGetAllProviders()
+    {
+        $providers = [
+            'index' => [
+                'type' => 'the_service_id',
+            ],
+        ];
+        $service = new \stdClass();
+        $registry = $this->mockPagerProviderRegistry($providers, $service);
+        $this->assertEquals(['index/type' => $service], $registry->getAllProviders('index', 'type'));
+    }
+
+    public function testGetIndexProvidersValid()
+    {
+        $providers = [
+            'index' => [
+                'type' => 'the_service_id',
+            ],
+        ];
+        $service = new \stdClass();
+        $registry = $this->mockPagerProviderRegistry($providers, $service);
+        $this->assertEquals(['type' => $service], $registry->getIndexProviders('index', 'type'));
+    }
+
+    public function testGetIndexProvidersInvalid()
+    {
+        $registry = $this->mockPagerProviderRegistry([]);
+        $this->expectException(\InvalidArgumentException::class);
+        $this->expectExceptionMessage('No providers were registered for index "index".');
+        $registry->getIndexProviders('index');
+    }
+
+    public function testGetProviderValid()
+    {
+        $providers = [
+            'index' => [
+                'type' => 'the_service_id',
+            ],
+        ];
+        $service = new \stdClass();
+        $registry = $this->mockPagerProviderRegistry($providers, $service);
+        $this->assertEquals($service, $registry->getProvider('index', 'type'));
+    }
+
+    public function testGetProviderInvalid()
+    {
+        $registry = $this->mockPagerProviderRegistry([]);
+        $this->expectException(\InvalidArgumentException::class);
+        $this->expectExceptionMessage('No provider was registered for index "index" and type "type".');
+        $registry->getProvider('index', 'type');
+    }
+}
diff --git a/tests/Unit/RepositoryTest.php b/tests/Unit/RepositoryTest.php
index 93601bdf5..163911b46 100644
--- a/tests/Unit/RepositoryTest.php
+++ b/tests/Unit/RepositoryTest.php
@@ -20,59 +20,67 @@
  */
 class RepositoryTest extends TestCase
 {
-    public function testThatFindCallsFindOnFinder()
+    public function testFind()
     {
         $testQuery = 'Test Query';
 
-        $finderMock = $this->getFinderMock($testQuery);
+        $finderMock = $this->mockTransformedFinder('find', [$testQuery]);
         $repository = new Repository($finderMock);
         $repository->find($testQuery);
     }
 
-    public function testThatFindCallsFindOnFinderWithLimit()
+    public function testFindWithLimit()
     {
         $testQuery = 'Test Query';
         $testLimit = 20;
 
-        $finderMock = $this->getFinderMock($testQuery, $testLimit);
+        $finderMock = $this->mockTransformedFinder('find', [$testQuery, $testLimit]);
         $repository = new Repository($finderMock);
         $repository->find($testQuery, $testLimit);
     }
 
-    public function testThatFindPaginatedCallsFindPaginatedOnFinder()
+    public function testFindPaginated()
     {
         $testQuery = 'Test Query';
 
-        $finderMock = $this->getFinderMock($testQuery, [], 'findPaginated');
+        $finderMock = $this->mockTransformedFinder('findPaginated', [$testQuery, []]);
         $repository = new Repository($finderMock);
         $repository->findPaginated($testQuery);
     }
 
-    public function testThatCreatePaginatorCreatesAPaginatorViaFinder()
+    public function testCreatePagitatorAdapter()
     {
         $testQuery = 'Test Query';
 
-        $finderMock = $this->getFinderMock($testQuery, [], 'createPaginatorAdapter');
+        $finderMock = $this->mockTransformedFinder('createPaginatorAdapter', [$testQuery, []]);
         $repository = new Repository($finderMock);
         $repository->createPaginatorAdapter($testQuery);
     }
 
-    public function testThatFindHybridCallsFindHybridOnFinder()
+    public function testCreateHybridPaginatorAdapter()
     {
         $testQuery = 'Test Query';
 
-        $finderMock = $this->getFinderMock($testQuery, null, 'findHybrid');
+        $finderMock = $this->mockTransformedFinder('createHybridPaginatorAdapter', [$testQuery]);
+        $repository = new Repository($finderMock);
+        $repository->createHybridPaginatorAdapter($testQuery);
+    }
+
+    public function testFindHybrid()
+    {
+        $testQuery = 'Test Query';
+
+        $finderMock = $this->mockTransformedFinder('findHybrid', [$testQuery, null, []]);
         $repository = new Repository($finderMock);
         $repository->findHybrid($testQuery);
     }
 
-    private function getFinderMock($testQuery, $testLimit = null, $method = 'find')
+    private function mockTransformedFinder($name, $arguments)
     {
         $finderMock = $this->createMock(TransformedFinder::class);
         $finderMock->expects($this->once())
-            ->method($method)
-            ->with($this->equalTo($testQuery), $this->equalTo($testLimit));
-
+            ->method($name)
+            ->withConsecutive($arguments);
         return $finderMock;
     }
 }
diff --git a/tests/Unit/Transformer/AbstractElasticaToModelTransformerTest.php b/tests/Unit/Transformer/AbstractElasticaToModelTransformerTest.php
new file mode 100644
index 000000000..f9e462e26
--- /dev/null
+++ b/tests/Unit/Transformer/AbstractElasticaToModelTransformerTest.php
@@ -0,0 +1,41 @@
+<?php
+
+/*
+ * This file is part of the FOSElasticaBundle package.
+ *
+ * (c) FriendsOfSymfony <http://friendsofsymfony.github.com/>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace FOS\ElasticaBundle\Tests\Unit\Transformer;
+
+use FOS\ElasticaBundle\Transformer\AbstractElasticaToModelTransformer;
+use Symfony\Component\PropertyAccess\PropertyAccessorInterface;
+use FOS\ElasticaBundle\Tests\Unit\UnitTestHelper;
+
+class AbstractElasticaToModelTransformerTest extends UnitTestHelper
+{
+    public function testSetPropertyAccessor()
+    {
+        $propertyAccessor = $this->mockPropertyAccesor();
+        $transformer = $this->mockAbstractElasticaToModelTransformer();
+        $transformer->setPropertyAccessor($propertyAccessor);
+        $this->assertEquals($propertyAccessor, $this->getProtectedProperty($transformer, 'propertyAccessor'));
+    }
+
+    protected function mockAbstractElasticaToModelTransformer()
+    {
+        $mock = $this
+            ->getMockBuilder(AbstractElasticaToModelTransformer::class)
+            ->getMockForAbstractClass();
+        return $mock;
+    }
+
+    protected function mockPropertyAccesor()
+    {
+        $mock = $this->createMock(PropertyAccessorInterface::class);
+        return $mock;
+    }
+}
diff --git a/tests/Unit/UnitTestHelper.php b/tests/Unit/UnitTestHelper.php
new file mode 100644
index 000000000..0519a9d6a
--- /dev/null
+++ b/tests/Unit/UnitTestHelper.php
@@ -0,0 +1,32 @@
+<?php
+
+/*
+ * This file is part of the FOSElasticaBundle package.
+ *
+ * (c) FriendsOfSymfony <http://friendsofsymfony.github.com/>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace FOS\ElasticaBundle\Tests\Unit;
+
+use PHPUnit\Framework\TestCase;
+
+class UnitTestHelper extends TestCase
+{
+    /**
+     * Gets a protected property on a given object via reflection.
+     *
+     * @param object $object   instance in which protected value is being modified
+     * @param string $property property on instance being modified
+     */
+    protected function getProtectedProperty($object, string $property)
+    {
+        $reflection = new \ReflectionClass($object);
+        $reflectionProperty = $reflection->getProperty($property);
+        $reflectionProperty->setAccessible(true);
+
+        return $reflectionProperty->getValue($object);
+    }
+}