diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..ee965d5
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,21 @@
+name: CI
+
+on: [push]
+
+jobs:
+  build-test:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - uses: php-actions/composer@v5
+
+      - name: PHPUnit Tests
+        uses: php-actions/phpunit@v9
+        env:
+          TEST_NAME: PHPUNIT
+        with:
+          bootstrap: vendor/autoload.php
+          configuration: phpunit.xml
+          args: --coverage-text
diff --git a/.github/workflows/php.yml b/.github/workflows/php.yml
new file mode 100644
index 0000000..066ac59
--- /dev/null
+++ b/.github/workflows/php.yml
@@ -0,0 +1,36 @@
+name: PHP Composer
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Validate composer.json and composer.lock
+      run: composer validate --strict
+
+    - name: Cache Composer packages
+      id: composer-cache
+      uses: actions/cache@v2
+      with:
+        path: vendor
+        key: ${{ runner.os }}-php-${{ hashFiles('**/composer.lock') }}
+        restore-keys: |
+          ${{ runner.os }}-php-
+
+    - name: Install dependencies
+      run: composer install --prefer-dist --no-progress
+
+    # Add a test script to composer.json, for instance: "test": "vendor/bin/phpunit"
+    # Docs: https://getcomposer.org/doc/articles/scripts.md
+
+    - name: Run test suite
+      run: composer run-script test
diff --git a/DependencyInjection/Configuration.php b/DependencyInjection/Configuration.php
index 90bbdfa..3d5900a 100644
--- a/DependencyInjection/Configuration.php
+++ b/DependencyInjection/Configuration.php
@@ -12,11 +12,10 @@ class Configuration implements ConfigurationInterface
      *
      * @return TreeBuilder
      */
-    public function getConfigTreeBuilder()
+    public function getConfigTreeBuilder(): TreeBuilder
     {
         $treeBuilder = new TreeBuilder('knp_markdown');
-        // BC layer for symfony/config < 4.2
-        $rootNode = method_exists($treeBuilder, 'getRootNode') ? $treeBuilder->getRootNode() : $treeBuilder->root('knp_markdown');
+        $rootNode = $treeBuilder->getRootNode();
 
         $rootNode
             ->addDefaultsIfNotSet()
@@ -27,37 +26,6 @@ class Configuration implements ConfigurationInterface
                         ->scalarNode('service')->cannotBeEmpty()->defaultValue('markdown.parser.max')->end()
                     ->end()
                 ->end()
-                ->arrayNode('sundown')
-                    ->addDefaultsIfNotSet()
-                    ->children()
-                        ->arrayNode('extensions')
-                            ->addDefaultsIfNotSet()
-                            ->children()
-                                ->booleanNode('fenced_code_blocks')->defaultFalse()->end()
-                                ->booleanNode('no_intra_emphasis')->defaultFalse()->end()
-                                ->booleanNode('tables')->defaultFalse()->end()
-                                ->booleanNode('autolink')->defaultFalse()->end()
-                                ->booleanNode('strikethrough')->defaultFalse()->end()
-                                ->booleanNode('lax_html_blocks')->defaultFalse()->end()
-                                ->booleanNode('space_after_headers')->defaultFalse()->end()
-                                ->booleanNode('superscript')->defaultFalse()->end()
-                            ->end()
-                        ->end()
-                        ->arrayNode('render_flags')
-                            ->addDefaultsIfNotSet()
-                            ->children()
-                                ->booleanNode('filter_html')->defaultFalse()->end()
-                                ->booleanNode('no_images')->defaultFalse()->end()
-                                ->booleanNode('no_links')->defaultFalse()->end()
-                                ->booleanNode('no_styles')->defaultFalse()->end()
-                                ->booleanNode('safe_links_only')->defaultFalse()->end()
-                                ->booleanNode('with_toc_data')->defaultFalse()->end()
-                                ->booleanNode('hard_wrap')->defaultFalse()->end()
-                                ->booleanNode('xhtml')->defaultFalse()->end()
-                            ->end()
-                        ->end()
-                    ->end()
-                ->end()
             ->end()
         ->end();
 
diff --git a/Parser/SundownParser.php b/Parser/SundownParser.php
deleted file mode 100644
index 572bc7d..0000000
--- a/Parser/SundownParser.php
+++ /dev/null
@@ -1,30 +0,0 @@
-<?php
-
-namespace Knp\Bundle\MarkdownBundle\Parser;
-
-use Knp\Bundle\MarkdownBundle\MarkdownParserInterface;
-
-use Sundown\Markdown;
-
-/**
- * SundownParser
- *
- * This class wraps the original Sundown parser to implement the KnpMardownBundle interface
- */
-class SundownParser implements MarkdownParserInterface
-{
-    private $parser;
-
-    public function __construct(Markdown $parser)
-    {
-        $this->parser = $parser;
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function transformMarkdown($text)
-    {
-        return $this->parser->render($text);
-    }
-}
diff --git a/README.markdown b/README.markdown
index 715d6ad..398d3a7 100644
--- a/README.markdown
+++ b/README.markdown
@@ -2,6 +2,9 @@ Provide markdown conversion (based on [Michel Fortin work](https://github.com/mi
 
 [![Build Status](https://secure.travis-ci.org/KnpLabs/KnpMarkdownBundle.svg)](http://travis-ci.org/KnpLabs/KnpMarkdownBundle)
 
+![ci.yml](https://github.com/tacman/KnpMarkdownBundle/actions/workflows/ci.yml/badge.svg)
+![php.yml](https://github.com/tacman/KnpMarkdownBundle/actions/workflows/php.yml/badge.svg)
+
 ## INSTALLATION
 
 Add KnpMarkdownBundle to your project via [Composer](https://getcomposer.org/):
diff --git a/Resources/config/sundown.xml b/Resources/config/sundown.xml
deleted file mode 100644
index ea1f81d..0000000
--- a/Resources/config/sundown.xml
+++ /dev/null
@@ -1,26 +0,0 @@
-<?xml version="1.0" ?>
-<container xmlns="http://symfony.com/schema/dic/services"
-           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-           xsi:schemaLocation="http://symfony.com/schema/dic/services http://symfony.com/schema/dic/services/services-1.0.xsd">
-
-    <parameters>
-        <parameter key="markdown.parser.sundown.class">Knp\Bundle\MarkdownBundle\Parser\SundownParser</parameter>
-        <parameter key="markdown.sundown.base_parser.class">Sundown\Markdown</parameter>
-        <parameter key="markdown.sundown.renderer.class">Sundown\Render\HTML</parameter>
-    </parameters>
-
-    <services>
-        <service id="markdown.parser.sundown" class="%markdown.parser.sundown.class%" public="false">
-            <argument type="service" id="markdown.sundown.base_parser" />
-        </service>
-
-        <service id="markdown.sundown.base_parser" public="false" class="%markdown.sundown.base_parser.class%">
-            <argument type="service" id="markdown.sundown.renderer" />
-            <argument>%markdown.sundown.extensions%</argument>
-        </service>
-
-        <service id="markdown.sundown.renderer" public="false" class="%markdown.sundown.renderer.class%">
-            <argument>%markdown.sundown.render_flags%</argument>
-        </service>
-    </services>
-</container>
diff --git a/composer.json b/composer.json
index df598c7..a071716 100644
--- a/composer.json
+++ b/composer.json
@@ -18,20 +18,18 @@
     ],
 
     "require": {
-        "php":                      "^7.1.3|^8.0",
-        "symfony/framework-bundle": "~3.4|^4.0|^5.0|^6.0",
-        "symfony/dependency-injection": "~3.4|^4.0|^5.0|^6.0",
+        "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": {
-        "phpunit/phpunit": "^9.5",
         "symfony/phpunit-bridge": "^4.4.0 || ^5.0 || ^6.0",
-        "symfony/templating": "~3.4|^4.0|^5.0|^6.0",
-        "symfony/test-pack": "^1.0"
+        "symfony/templating": "^4.0|^5.0|^6.0",
+        "phpunit/phpunit": "^9.5"
     },
     "suggest": {
-        "symfony/twig-bundle": "to use the Twig markdown filter",
-        "ext-sundown": "to use optional support for php-sundown extension instead of php implementation"
+        "symfony/twig-bundle": "to use the Twig markdown filter"
     },
 
     "extra": {
@@ -40,6 +38,18 @@
         }
     },
 
+    "scripts": {
+        "test": [
+            "php ./vendor/bin/phpunit"
+        ]
+    },
+
+    "autoload-dev": {
+        "psr-4": {
+            "Knp\\Bundle\\MarkdownBundle\\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