diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..3673c10
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,74 @@
+name: CI
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: [master]
+
+jobs:
+  tests:
+    name: Tests (PHP ${{ matrix.php }}, Symfony ${{ matrix.symfony }})
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - php: '7.4'
+            symfony: '5.4.*'
+            phpunit: '^9.6'
+          - php: '8.1'
+            symfony: '5.4.*'
+          - php: '8.1'
+            symfony: '6.4.*'
+          - php: '8.2'
+            symfony: '6.4.*'
+          - php: '8.2'
+            symfony: '7.2.*'
+          - php: '8.3'
+            symfony: '7.2.*'
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php }}
+          coverage: none
+
+      - name: Lock Symfony version
+        run: |
+          composer require --no-update \
+            symfony/config:"${{ matrix.symfony }}" \
+            symfony/dependency-injection:"${{ matrix.symfony }}" \
+            symfony/http-kernel:"${{ matrix.symfony }}" \
+            symfony/yaml:"${{ matrix.symfony }}"
+
+      - name: Lock PHPUnit version
+        if: matrix.phpunit
+        run: composer require --dev --no-update phpunit/phpunit:"${{ matrix.phpunit }}"
+
+      - name: Install dependencies
+        run: composer update --prefer-dist --no-progress
+
+      - name: Run tests
+        run: vendor/bin/phpunit
+
+  phpstan:
+    name: PHPStan
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: '8.2'
+          coverage: none
+
+      - name: Install dependencies
+        run: composer install --prefer-dist --no-progress
+
+      - name: Run PHPStan
+        run: vendor/bin/phpstan analyse
diff --git a/.phpunit.result.cache b/.phpunit.result.cache
index ac82fc9..a602b27 100644
--- a/.phpunit.result.cache
+++ b/.phpunit.result.cache
@@ -1 +1 @@
-{"version":2,"defects":{"RedjanYm\\FCMBundle\\Tests\\DependencyInjection\\RedjanYmFCMExtensionTest::testLoadRegistersServicesAndParameters":8,"RedjanYm\\FCMBundle\\Tests\\DependencyInjection\\RedjanYmFCMExtensionTest::testClientServiceIsPublic":8,"RedjanYm\\FCMBundle\\Tests\\DependencyInjection\\RedjanYmFCMExtensionTest::testNotificationFactoryServiceIsPublic":8},"times":{"RedjanYm\\FCMBundle\\Tests\\DependencyInjection\\ConfigurationTest::testValidConfiguration":0.004,"RedjanYm\\FCMBundle\\Tests\\DependencyInjection\\ConfigurationTest::testServiceAccountFileIsRequired":0,"RedjanYm\\FCMBundle\\Tests\\DependencyInjection\\ConfigurationTest::testServiceAccountFileCannotBeEmpty":0,"RedjanYm\\FCMBundle\\Tests\\DependencyInjection\\RedjanYmFCMExtensionTest::testLoadRegistersServicesAndParameters":0.007,"RedjanYm\\FCMBundle\\Tests\\DependencyInjection\\RedjanYmFCMExtensionTest::testClientServiceIsPublic":0,"RedjanYm\\FCMBundle\\Tests\\DependencyInjection\\RedjanYmFCMExtensionTest::testNotificationFactoryServiceIsPublic":0,"RedjanYm\\FCMBundle\\Tests\\NotificationFactoryTest::testCreateDeviceNotification":0,"RedjanYm\\FCMBundle\\Tests\\NotificationFactoryTest::testCreateDeviceNotificationWithMinimalArgs":0,"RedjanYm\\FCMBundle\\Tests\\NotificationFactoryTest::testCreateTopicNotification":0,"RedjanYm\\FCMBundle\\Tests\\NotificationFactoryTest::testCreateTopicNotificationWithMinimalArgs":0,"RedjanYm\\FCMBundle\\Tests\\NotificationFactoryTest::testTopicNotificationSerializesWithTopicKey":0.001,"RedjanYm\\FCMBundle\\Tests\\NotificationFactoryTest::testDeviceNotificationSerializesWithTokenKey":0,"RedjanYm\\FCMBundle\\Tests\\DependencyInjection\\RedjanYmFCMExtensionTest::testAutowiringAliases":0}}
\ No newline at end of file
+{"version":2,"defects":{"RedjanYm\\FCMBundle\\Tests\\DependencyInjection\\RedjanYmFCMExtensionTest::testLoadRegistersServicesAndParameters":8,"RedjanYm\\FCMBundle\\Tests\\DependencyInjection\\RedjanYmFCMExtensionTest::testClientServiceIsPublic":8,"RedjanYm\\FCMBundle\\Tests\\DependencyInjection\\RedjanYmFCMExtensionTest::testNotificationFactoryServiceIsPublic":8},"times":{"RedjanYm\\FCMBundle\\Tests\\DependencyInjection\\ConfigurationTest::testValidConfiguration":0.007,"RedjanYm\\FCMBundle\\Tests\\DependencyInjection\\ConfigurationTest::testServiceAccountFileIsRequired":0.001,"RedjanYm\\FCMBundle\\Tests\\DependencyInjection\\ConfigurationTest::testServiceAccountFileCannotBeEmpty":0,"RedjanYm\\FCMBundle\\Tests\\DependencyInjection\\RedjanYmFCMExtensionTest::testLoadRegistersServicesAndParameters":0.012,"RedjanYm\\FCMBundle\\Tests\\DependencyInjection\\RedjanYmFCMExtensionTest::testClientServiceIsPublic":0,"RedjanYm\\FCMBundle\\Tests\\DependencyInjection\\RedjanYmFCMExtensionTest::testNotificationFactoryServiceIsPublic":0,"RedjanYm\\FCMBundle\\Tests\\NotificationFactoryTest::testCreateDeviceNotification":0.001,"RedjanYm\\FCMBundle\\Tests\\NotificationFactoryTest::testCreateDeviceNotificationWithMinimalArgs":0,"RedjanYm\\FCMBundle\\Tests\\NotificationFactoryTest::testCreateTopicNotification":0,"RedjanYm\\FCMBundle\\Tests\\NotificationFactoryTest::testCreateTopicNotificationWithMinimalArgs":0,"RedjanYm\\FCMBundle\\Tests\\NotificationFactoryTest::testTopicNotificationSerializesWithTopicKey":0.001,"RedjanYm\\FCMBundle\\Tests\\NotificationFactoryTest::testDeviceNotificationSerializesWithTokenKey":0,"RedjanYm\\FCMBundle\\Tests\\DependencyInjection\\RedjanYmFCMExtensionTest::testAutowiringAliases":0}}
\ No newline at end of file
diff --git a/DependencyInjection/Configuration.php b/DependencyInjection/Configuration.php
index 6cf36bf..5f260dc 100644
--- a/DependencyInjection/Configuration.php
+++ b/DependencyInjection/Configuration.php
@@ -18,7 +18,7 @@ class Configuration implements ConfigurationInterface
     public function getConfigTreeBuilder(): TreeBuilder
     {
         $treeBuilder = new TreeBuilder('redjan_ym_fcm');
-        $rootNode = method_exists(TreeBuilder::class, 'getRootNode') ? $treeBuilder->getRootNode() : $treeBuilder->root('redjan_ym_fcm');
+        $rootNode = $treeBuilder->getRootNode();
 
         $rootNode
             ->children()
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..2f389a2
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,7 @@
+.PHONY: test phpstan
+
+test:
+	vendor/bin/phpunit
+
+phpstan:
+	vendor/bin/phpstan analyse
diff --git a/NotificationFactory.php b/NotificationFactory.php
index 94831fc..8f3fdd9 100644
--- a/NotificationFactory.php
+++ b/NotificationFactory.php
@@ -10,6 +10,8 @@ class NotificationFactory
 {
     /**
      * Create a notification targeted at a specific device token.
+     *
+     * @param array<string, mixed> $data
      */
     public function createDeviceNotification(string $token, string $title, ?string $body = null, array $data = []): Notification
     {
@@ -18,6 +20,8 @@ public function createDeviceNotification(string $token, string $title, ?string $
 
     /**
      * Create a notification targeted at a topic.
+     *
+     * @param array<string, mixed> $data
      */
     public function createTopicNotification(string $topic, string $title, ?string $body = null, array $data = []): Notification
     {
diff --git a/composer.json b/composer.json
index b11a9bf..b91d269 100644
--- a/composer.json
+++ b/composer.json
@@ -17,7 +17,8 @@
     "redjanym/php-firebase-cloud-messaging": "^2.1"
   },
   "require-dev": {
-    "phpunit/phpunit": "^9.5 || ^10.0",
+    "phpstan/phpstan": "^1.10",
+    "phpunit/phpunit": "^9.6 || ^10.0",
     "symfony/dependency-injection": "^5.4 || ^6.0 || ^7.0",
     "symfony/config": "^5.4 || ^6.0 || ^7.0",
     "symfony/http-kernel": "^5.4 || ^6.0 || ^7.0",
diff --git a/phpstan.neon b/phpstan.neon
new file mode 100644
index 0000000..94fa794
--- /dev/null
+++ b/phpstan.neon
@@ -0,0 +1,6 @@
+parameters:
+    level: 6
+    paths:
+        - DependencyInjection
+        - NotificationFactory.php
+        - RedjanYmFCMBundle.php