diff --git a/composer.json b/composer.json
index 67f0bed..753a8d4 100644
--- a/composer.json
+++ b/composer.json
@@ -20,7 +20,7 @@
     },
     "require-dev": {
         "graylog2/gelf-php": "~1.1",
-        "phpunit/phpunit": "~5.4",
+        "phpunit/phpunit": "^6.0.12",
         "satooshi/php-coveralls": "dev-master"
     },
     "autoload": {
diff --git a/tests/Factory/FormatterPluginManagerFactoryTest.php b/tests/Factory/FormatterPluginManagerFactoryTest.php
index f3d49d6..adaf4ca 100644
--- a/tests/Factory/FormatterPluginManagerFactoryTest.php
+++ b/tests/Factory/FormatterPluginManagerFactoryTest.php
@@ -4,10 +4,10 @@
 use MonologModule\Factory\FormatterPluginManagerFactory;
 use MonologModule\Formatter\FormatterPluginManager;
 use Monolog\Formatter\FormatterInterface;
-use PHPUnit_Framework_TestCase;
+use PHPUnit\Framework\TestCase;
 use Zend\ServiceManager\ServiceLocatorInterface;
 
-class FormatterPluginManagerFactoryTest extends PHPUnit_Framework_TestCase
+class FormatterPluginManagerFactoryTest extends TestCase
 {
     public function testRetrieveFormatterInstance()
     {
diff --git a/tests/Factory/HandlerPluginManagerFactoryTest.php b/tests/Factory/HandlerPluginManagerFactoryTest.php
index 3c8fdb8..f297e3b 100644
--- a/tests/Factory/HandlerPluginManagerFactoryTest.php
+++ b/tests/Factory/HandlerPluginManagerFactoryTest.php
@@ -4,10 +4,10 @@
 use MonologModule\Factory\HandlerPluginManagerFactory;
 use MonologModule\Handler\HandlerPluginManager;
 use Monolog\Handler\HandlerInterface;
-use PHPUnit_Framework_TestCase;
+use PHPUnit\Framework\TestCase;
 use Zend\ServiceManager\ServiceLocatorInterface;
 
-class HandlerPluginManagerFactoryTest extends PHPUnit_Framework_TestCase
+class HandlerPluginManagerFactoryTest extends TestCase
 {
     public function testRetrieveHandlerInstance()
     {
diff --git a/tests/Factory/LoggerAbstractFactoryTest.php b/tests/Factory/LoggerAbstractFactoryTest.php
index 5c01d08..e01d585 100644
--- a/tests/Factory/LoggerAbstractFactoryTest.php
+++ b/tests/Factory/LoggerAbstractFactoryTest.php
@@ -5,10 +5,10 @@
 use Monolog\Logger;
 use MonologModule\Factory\LoggerAbstractFactory;
 use MonologModule\Factory\LoggerFactory;
-use PHPUnit_Framework_TestCase;
+use PHPUnit\Framework\TestCase;
 use Zend\ServiceManager\ServiceLocatorInterface;
 
-class LoggerAbstractFactoryTest extends PHPUnit_Framework_TestCase
+class LoggerAbstractFactoryTest extends TestCase
 {
     public function canCreateServiceWithNameProvider()
     {
diff --git a/tests/Factory/LoggerFactoryTest.php b/tests/Factory/LoggerFactoryTest.php
index 6dbc4d3..f7b9b9f 100644
--- a/tests/Factory/LoggerFactoryTest.php
+++ b/tests/Factory/LoggerFactoryTest.php
@@ -8,10 +8,10 @@
 use MonologModule\Factory\LoggerFactory;
 use MonologModule\Formatter\FormatterPluginManager;
 use MonologModule\Handler\HandlerPluginManager;
-use PHPUnit_Framework_TestCase;
+use PHPUnit\Framework\TestCase;
 use Zend\ServiceManager\ServiceLocatorInterface;
 
-class LoggerFactoryTest extends PHPUnit_Framework_TestCase
+class LoggerFactoryTest extends TestCase
 {
     protected $factory;
 
diff --git a/tests/Formatter/FormatterPluginManagerTest.php b/tests/Formatter/FormatterPluginManagerTest.php
index a9e4449..a036c27 100644
--- a/tests/Formatter/FormatterPluginManagerTest.php
+++ b/tests/Formatter/FormatterPluginManagerTest.php
@@ -3,30 +3,36 @@
 
 use Monolog\Formatter\FormatterInterface;
 use MonologModule\Formatter\FormatterPluginManager;
-use PHPUnit_Framework_TestCase;
+use PHPUnit\Framework\TestCase;
 use stdClass;
+use Zend\ServiceManager\Exception\InvalidServiceException;
 use Zend\ServiceManager\ServiceLocatorInterface;
 
-class FormatterPluginManagerTest extends PHPUnit_Framework_TestCase
+class FormatterPluginManagerTest extends TestCase
 {
-    public function testValidatePlugin()
+    public function testRetrievePlugin()
     {
+        $formatter = $this->createMock(FormatterInterface::class);
+
         $serviceLocator = $this->createMock(ServiceLocatorInterface::class);
-        $handlerPluginManager = new FormatterPluginManager($serviceLocator);
+        $formatterPluginManager = new FormatterPluginManager($serviceLocator, [
+            'services' => [
+                FormatterInterface::class => $formatter,
+            ],
+        ]);
 
-        $handler = $this->createMock(FormatterInterface::class);
-        $handlerPluginManager->validatePlugin($handler);
+        $formatterReturned = $formatterPluginManager->get(FormatterInterface::class);
+        $this->assertSame($formatter, $formatterReturned);
     }
 
-    /**
-     * @expectedException \Zend\ServiceManager\Exception\InvalidServiceException
-     */
     public function testValidateInvalidPlugin()
     {
         $serviceLocator = $this->createMock(ServiceLocatorInterface::class);
-        $handlerPluginManager = new FormatterPluginManager($serviceLocator);
+        $formatterPluginManager = new FormatterPluginManager($serviceLocator);
+
+        $this->expectException(InvalidServiceException::class);
 
-        $handler = new stdClass;
-        $handlerPluginManager->validatePlugin($handler);
+        $formatter = new stdClass;
+        $formatterPluginManager->validatePlugin($formatter);
     }
 }
diff --git a/tests/Handler/Factory/GelfHandlerFactoryTest.php b/tests/Handler/Factory/GelfHandlerFactoryTest.php
index 7b350f5..3e2c1b4 100644
--- a/tests/Handler/Factory/GelfHandlerFactoryTest.php
+++ b/tests/Handler/Factory/GelfHandlerFactoryTest.php
@@ -3,10 +3,10 @@
 
 use MonologModule\Handler\Factory\GelfHandlerFactory;
 use Monolog\Handler\GelfHandler;
-use PHPUnit_Framework_TestCase;
+use PHPUnit\Framework\TestCase;
 use Zend\ServiceManager\ServiceLocatorInterface;
 
-class GelfHandlerFactoryTest extends PHPUnit_Framework_TestCase
+class GelfHandlerFactoryTest extends TestCase
 {
     public function testInstantiateGelfHandler()
     {
diff --git a/tests/Handler/HandlerPluginManagerTest.php b/tests/Handler/HandlerPluginManagerTest.php
index 142daed..9a49d37 100644
--- a/tests/Handler/HandlerPluginManagerTest.php
+++ b/tests/Handler/HandlerPluginManagerTest.php
@@ -3,29 +3,35 @@
 
 use Monolog\Handler\HandlerInterface;
 use MonologModule\Handler\HandlerPluginManager;
-use PHPUnit_Framework_TestCase;
+use PHPUnit\Framework\TestCase;
 use stdClass;
+use Zend\ServiceManager\Exception\InvalidServiceException;
 use Zend\ServiceManager\ServiceLocatorInterface;
 
-class HandlerPluginManagerTest extends PHPUnit_Framework_TestCase
+class HandlerPluginManagerTest extends TestCase
 {
-    public function testValidatePlugin()
+    public function testRetrievePlugin()
     {
+        $handler = $this->createMock(HandlerInterface::class);
+
         $serviceLocator = $this->createMock(ServiceLocatorInterface::class);
-        $handlerPluginManager = new HandlerPluginManager($serviceLocator);
+        $handlerPluginManager = new HandlerPluginManager($serviceLocator, [
+            'services' => [
+                HandlerInterface::class => $handler,
+            ],
+        ]);
 
-        $handler = $this->createMock(HandlerInterface::class);
-        $handlerPluginManager->validatePlugin($handler);
+        $handlerReturned = $handlerPluginManager->get(HandlerInterface::class);
+        $this->assertSame($handler, $handlerReturned);
     }
 
-    /**
-     * @expectedException \Zend\ServiceManager\Exception\InvalidServiceException
-     */
     public function testValidateInvalidPlugin()
     {
         $serviceLocator = $this->createMock(ServiceLocatorInterface::class);
         $handlerPluginManager = new HandlerPluginManager($serviceLocator);
 
+        $this->expectException(InvalidServiceException::class);
+
         $handler = new stdClass;
         $handlerPluginManager->validatePlugin($handler);
     }