diff --git a/Tests/Functional/ServiceInstantiationTest.php b/Tests/Functional/ServiceInstantiationTest.php
index ebbfff42..1bd5abd9 100644
--- a/Tests/Functional/ServiceInstantiationTest.php
+++ b/Tests/Functional/ServiceInstantiationTest.php
@@ -6,13 +6,18 @@
 
 class ServiceInstantiationTest extends WebTestCase
 {
-    public static function setUpBeforeClass()
+    public function testHttpClient()
     {
         static::bootKernel();
+        $container = static::$kernel->getContainer();
+        $this->assertTrue($container->has('httplug.client'));
+        $client = $container->get('httplug.client');
+        $this->assertInstanceOf('Http\Client\HttpClient', $client);
     }
 
-    public function testHttpClient()
+    public function testHttpClientNoDebug()
     {
+        static::bootKernel(['debug' => false]);
         $container = static::$kernel->getContainer();
         $this->assertTrue($container->has('httplug.client'));
         $client = $container->get('httplug.client');
diff --git a/Tests/Unit/DependencyInjection/HttplugExtensionTest.php b/Tests/Unit/DependencyInjection/HttplugExtensionTest.php
index b88d795b..54a2bd8f 100644
--- a/Tests/Unit/DependencyInjection/HttplugExtensionTest.php
+++ b/Tests/Unit/DependencyInjection/HttplugExtensionTest.php
@@ -7,6 +7,7 @@
 
 /**
  * @author David Buchmann <mail@davidbu.ch>
+ * @author Tobias Nyholm <tobias.nyholm@gmail.com>
  */
 class HttplugExtensionTest extends AbstractExtensionTestCase
 {
@@ -52,4 +53,78 @@ public function testConfigLoadService()
             $this->assertContainerBuilderHasAlias("httplug.$type", "my_{$type}_service");
         }
     }
+
+    public function testNoProfilingWhenToolbarIsDisabled()
+    {
+        $this->load(
+            [
+                'toolbar' => [
+                    'enabled' => false,
+                ],
+                'clients' => [
+                    'acme' => [
+                        'factory' => 'httplug.factory.curl',
+                        'plugins' => ['foo'],
+                    ],
+                ],
+            ]
+        );
+
+        $this->verifyProfilingDisabled();
+    }
+
+    public function testNoProfilingWhenNotInDebugMode()
+    {
+        $this->setParameter('kernel.debug', false);
+        $this->load(
+            [
+                'clients' => [
+                    'acme' => [
+                        'factory' => 'httplug.factory.curl',
+                        'plugins' => ['foo'],
+                    ],
+                ],
+            ]
+        );
+
+        $this->verifyProfilingDisabled();
+    }
+
+    public function testProfilingWhenToolbarIsSpecificallyOn()
+    {
+        $this->setParameter('kernel.debug', false);
+        $this->load(
+            [
+                'toolbar' => [
+                    'enabled' => true,
+                ],
+                'clients' => [
+                    'acme' => [
+                        'factory' => 'httplug.factory.curl',
+                        'plugins' => ['foo'],
+                    ],
+                ],
+            ]
+        );
+
+        $def = $this->container->findDefinition('httplug.client');
+        $arguments = $def->getArguments();
+
+        $this->assertTrue(isset($arguments[3]));
+        $this->assertTrue(isset($arguments[3]['debug_plugins']));
+        $this->assertFalse(empty($arguments[3]['debug_plugins']));
+    }
+
+    private function verifyProfilingDisabled()
+    {
+        $def = $this->container->findDefinition('httplug.client');
+        $arguments = $def->getArguments();
+
+        if (isset($arguments[3])) {
+            $this->assertEmpty(
+                $arguments[3],
+                'Parameter 3 to the PluginClient must not contain any debug_plugin information when profiling is disabled'
+            );
+        }
+    }
 }
diff --git a/Tests/Unit/Discovery/ConfiguredClientsStrategyTest.php b/Tests/Unit/Discovery/ConfiguredClientsStrategyTest.php
new file mode 100644
index 00000000..ecf3dbc7
--- /dev/null
+++ b/Tests/Unit/Discovery/ConfiguredClientsStrategyTest.php
@@ -0,0 +1,62 @@
+<?php
+
+namespace Http\HttplugBundle\Tests\Unit\Discovery;
+
+use Http\Client\HttpAsyncClient;
+use Http\Client\HttpClient;
+use Http\HttplugBundle\Discovery\ConfiguredClientsStrategy;
+
+class ConfiguredClientsStrategyTest extends \PHPUnit_Framework_TestCase
+{
+    public function testGetCandidates()
+    {
+        $httpClient = $this->getMock(HttpClient::class);
+        $httpAsyncClient = $this->getMock(HttpAsyncClient::class);
+        $strategy = new ConfiguredClientsStrategy($httpClient, $httpAsyncClient);
+
+        $candidates = $strategy::getCandidates(HttpClient::class);
+        $candidate = array_shift($candidates);
+        $this->assertEquals($httpClient, $candidate['class']());
+
+        $candidates = $strategy::getCandidates(HttpAsyncClient::class);
+        $candidate = array_shift($candidates);
+        $this->assertEquals($httpAsyncClient, $candidate['class']());
+    }
+
+    public function testGetCandidatesEmpty()
+    {
+        $strategy = new ConfiguredClientsStrategy(null, null);
+
+        $candidates = $strategy::getCandidates(HttpClient::class);
+        $this->assertEquals([], $candidates);
+
+        $candidates = $strategy::getCandidates(HttpAsyncClient::class);
+        $this->assertEquals([], $candidates);
+    }
+
+    public function testGetCandidatesEmptyAsync()
+    {
+        $httpClient = $this->getMock(HttpClient::class);
+        $strategy = new ConfiguredClientsStrategy($httpClient, null);
+
+        $candidates = $strategy::getCandidates(HttpClient::class);
+        $candidate = array_shift($candidates);
+        $this->assertEquals($httpClient, $candidate['class']());
+
+        $candidates = $strategy::getCandidates(HttpAsyncClient::class);
+        $this->assertEquals([], $candidates);
+    }
+
+    public function testGetCandidatesEmptySync()
+    {
+        $httpAsyncClient = $this->getMock(HttpAsyncClient::class);
+        $strategy = new ConfiguredClientsStrategy(null, $httpAsyncClient);
+
+        $candidates = $strategy::getCandidates(HttpClient::class);
+        $this->assertEquals([], $candidates);
+
+        $candidates = $strategy::getCandidates(HttpAsyncClient::class);
+        $candidate = array_shift($candidates);
+        $this->assertEquals($httpAsyncClient, $candidate['class']());
+    }
+}
diff --git a/composer.json b/composer.json
index 0808a51f..0ca830a4 100644
--- a/composer.json
+++ b/composer.json
@@ -31,7 +31,7 @@
         "twig/twig": "^1.18 || ^2.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "^4.5",
+        "phpunit/phpunit": "^4.5 || ^5.4",
         "php-http/curl-client": "^1.0",
         "php-http/socket-client": "^1.0",
         "php-http/guzzle6-adapter": "^1.1.1",
@@ -39,7 +39,7 @@
         "php-http/buzz-adapter": "^0.3",
         "symfony/symfony": "^2.7 || ^3.0",
         "polishsymfonycommunity/symfony-mocker-container": "^1.0",
-        "matthiasnoback/symfony-dependency-injection-test": "^0.7"
+        "matthiasnoback/symfony-dependency-injection-test": "^1.0"
     },
     "conflict": {
         "php-http/guzzle6-adapter": "<1.1"