diff --git a/composer.json b/composer.json
index 961801c..8c6a04e 100644
--- a/composer.json
+++ b/composer.json
@@ -18,14 +18,15 @@
     ],
 
     "require": {
-        "php":                      "^7.1.3|^8.0",
-        "symfony/framework-bundle": "~3.4|^4.0|^5.0",
-        "symfony/dependency-injection": "~3.4|^4.0|^5.0",
+        "php":                      ">= 7.4",
+        "symfony/framework-bundle": "^4.0|^5.0|^6.0",
+        "symfony/dependency-injection": "^4.0|^5.0|^6.0",
         "michelf/php-markdown":     "~1.4"
     },
     "require-dev": {
-        "symfony/phpunit-bridge": "^4.4.0 || ^5.0",
-        "symfony/templating": "~3.4|^4.0|^5.0"
+        "symfony/phpunit-bridge": "^4.4.0 || ^5.0 || ^6.0",
+        "symfony/templating": "^4.0|^5.0|^6.0",
+        "phpunit/phpunit": "^9.5"
     },
     "suggest": {
         "symfony/twig-bundle": "to use the Twig markdown filter",
@@ -38,6 +39,12 @@
         }
     },
 
+    "autoload-dev": {
+        "psr-4": {
+            "App\\Tests\\": "tests/"
+        }
+    },
+
     "autoload": {
         "psr-4": {
             "Knp\\Bundle\\MarkdownBundle\\": ""
diff --git a/Tests/EscapingTest.php b/tests/EscapingTest.php
similarity index 89%
rename from Tests/EscapingTest.php
rename to tests/EscapingTest.php
index a2d396f..92f49b0 100644
--- a/Tests/EscapingTest.php
+++ b/tests/EscapingTest.php
@@ -2,13 +2,15 @@
 
 namespace Knp\Bundle\MarkdownBundle\Tests;
 
+use PHPUnit\Framework\TestCase;
+
 use Knp\Bundle\MarkdownBundle\Parser\MarkdownParser as Parser;
 
-class EscapingTest extends \PHPUnit_Framework_TestCase
+class EscapingTest extends TestCase
 {
     protected $parser;
 
-    public function setUp()
+    public function setUp(): void
     {
         $this->parser = new Parser();
     }
diff --git a/Tests/FeatureTest.php b/tests/FeatureTest.php
similarity index 97%
rename from Tests/FeatureTest.php
rename to tests/FeatureTest.php
index 7c0d099..a2291d7 100644
--- a/Tests/FeatureTest.php
+++ b/tests/FeatureTest.php
@@ -3,8 +3,9 @@
 namespace Knp\Bundle\MarkdownBundle\Tests;
 
 use Knp\Bundle\MarkdownBundle\Parser\MarkdownParser as Parser;
+use PHPUnit\Framework\TestCase;
 
-class FeatureTest extends \PHPUnit_Framework_TestCase
+class FeatureTest extends TestCase
 {
     public function testParser()
     {
@@ -754,10 +755,10 @@ EOF;
         // asserting a few things instead of comparing full final HTML
         // because a few minor things have changed over versions of Michelf
         // With assertContains(), tests will pass across all versions
-        $this->assertContains('<p>That\'s some text with a footnote.<sup id="fnref:1"><a href="#fn:1"', $actualHtml);
-        $this->assertContains('<div class="footnotes"', $actualHtml);
-        $this->assertContains('<li id="fn:1"', $actualHtml);
-        $this->assertContains('<p>And that\'s the footnote.&#160;<a href="#fnref:1" class="footnote-backref"', $actualHtml);
+        $this->assertStringContainsString('<p>That\'s some text with a footnote.<sup id="fnref:1"><a href="#fn:1"', $actualHtml);
+        $this->assertStringContainsString('<div class="footnotes"', $actualHtml);
+        $this->assertStringContainsString('<li id="fn:1"', $actualHtml);
+        $this->assertStringContainsString('<p>And that\'s the footnote.&#160;<a href="#fnref:1" class="footnote-backref"', $actualHtml);
     }
 
     /**
diff --git a/Tests/IntegrationTest.php b/tests/IntegrationTest.php
similarity index 78%
rename from Tests/IntegrationTest.php
rename to tests/IntegrationTest.php
index 4586e54..7c88445 100644
--- a/Tests/IntegrationTest.php
+++ b/tests/IntegrationTest.php
@@ -4,14 +4,16 @@ namespace Knp\Bundle\MarkdownBundle\Tests;
 
 use Knp\Bundle\MarkdownBundle\KnpMarkdownBundle;
 use Knp\Bundle\MarkdownBundle\Parser\MarkdownParser;
+use PHPUnit\Framework\TestCase;
 use Symfony\Bundle\FrameworkBundle\FrameworkBundle;
 use Symfony\Bundle\FrameworkBundle\Kernel\MicroKernelTrait;
 use Symfony\Component\Config\Loader\LoaderInterface;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\HttpKernel\Kernel;
+use Symfony\Component\Routing\Loader\Configurator\RoutingConfigurator;
 use Symfony\Component\Routing\RouteCollectionBuilder;
 
-class IntegrationTest extends \PHPUnit_Framework_TestCase
+class IntegrationTest extends TestCase
 {
     public function testServicesAvailable()
     {
@@ -37,13 +39,17 @@ class IntegrationKernel extends Kernel
         ];
     }
 
-    protected function configureRoutes(RouteCollectionBuilder $routes)
+    protected function configureRoutes(RoutingConfigurator $routes)
     {
     }
 
     protected function configureContainer(ContainerBuilder $c, LoaderInterface $loader)
     {
-        $c->setParameter('kernel.secret', '1234');
+
+            $c->loadFromExtension('framework', [
+                'secret' => 'F00',
+                'router' => ['utf8' => true]
+            ]);
     }
 
     public function getCacheDir()
diff --git a/Tests/Parser/ParserManagerTest.php b/tests/Parser/ParserManagerTest.php
similarity index 92%
rename from Tests/Parser/ParserManagerTest.php
rename to tests/Parser/ParserManagerTest.php
index 9285ea8..7357c1e 100644
--- a/Tests/Parser/ParserManagerTest.php
+++ b/tests/Parser/ParserManagerTest.php
@@ -5,8 +5,9 @@ namespace Knp\Bundle\MarkdownBundle\Tests\Parser;
 use Knp\Bundle\MarkdownBundle\Helper\MarkdownHelper;
 use Knp\Bundle\MarkdownBundle\Tests\fixtures\app\TestKernel;
 use Knp\Bundle\MarkdownBundle\Parser\ParserManager;
+use PHPUnit\Framework\TestCase;
 
-class ParserManagerTest extends \PHPUnit_Framework_TestCase
+class ParserManagerTest extends TestCase
 {
     public function testIntegration()
     {
diff --git a/Tests/Performance/.htaccess b/tests/Performance/.htaccess
similarity index 100%
rename from Tests/Performance/.htaccess
rename to tests/Performance/.htaccess
diff --git a/Tests/Performance/Base.php b/tests/Performance/Base.php
similarity index 100%
rename from Tests/Performance/Base.php
rename to tests/Performance/Base.php
diff --git a/Tests/Performance/Light.php b/tests/Performance/Light.php
similarity index 100%
rename from Tests/Performance/Light.php
rename to tests/Performance/Light.php
diff --git a/Tests/Performance/Max.php b/tests/Performance/Max.php
similarity index 100%
rename from Tests/Performance/Max.php
rename to tests/Performance/Max.php
diff --git a/Tests/Performance/Medium.php b/tests/Performance/Medium.php
similarity index 100%
rename from Tests/Performance/Medium.php
rename to tests/Performance/Medium.php
diff --git a/Tests/Performance/Min.php b/tests/Performance/Min.php
similarity index 100%
rename from Tests/Performance/Min.php
rename to tests/Performance/Min.php
diff --git a/Tests/Performance/index.php b/tests/Performance/index.php
similarity index 100%
rename from Tests/Performance/index.php
rename to tests/Performance/index.php
diff --git a/Tests/Performance/run b/tests/Performance/run
similarity index 100%
rename from Tests/Performance/run
rename to tests/Performance/run
diff --git a/Tests/PresetTest.php b/tests/PresetTest.php
similarity index 94%
rename from Tests/PresetTest.php
rename to tests/PresetTest.php
index cc7aaf0..224cb31 100644
--- a/Tests/PresetTest.php
+++ b/tests/PresetTest.php
@@ -3,8 +3,9 @@
 namespace Knp\Bundle\MarkdownBundle\Tests;
 
 use Knp\Bundle\MarkdownBundle\Parser\Preset as Preset;
+use PHPUnit\Framework\TestCase;
 
-class PresetTest extends \PHPUnit_Framework_TestCase
+class PresetTest extends TestCase
 {
     public function testMax()
     {
diff --git a/Tests/fixtures/app/TestKernel.php b/tests/fixtures/app/TestKernel.php
similarity index 100%
rename from Tests/fixtures/app/TestKernel.php
rename to tests/fixtures/app/TestKernel.php
diff --git a/Tests/fixtures/big_text.html b/tests/fixtures/big_text.html
similarity index 100%
rename from Tests/fixtures/big_text.html
rename to tests/fixtures/big_text.html
diff --git a/Tests/fixtures/big_text.markdown b/tests/fixtures/big_text.markdown
similarity index 100%
rename from Tests/fixtures/big_text.markdown
rename to tests/fixtures/big_text.markdown