diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 8ad070b..fa89286 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        php-versions: ['8.2', '8.3']
+        php-versions: ['8.2', '8.3', '8.4']
 
     steps:
       # Checkout the repository
@@ -30,7 +30,7 @@ jobs:
       - run: php --version
 
       # Print Composer version
-      - run: composer --version 
+      - run: composer --version
 
       # Validate composer.json syntax
       - name: Validate composer.json syntax
@@ -46,4 +46,4 @@ jobs:
       # Run PHPUnit tests
       - name: Run PHPUnit
         run: vendor/bin/phpunit
-          --no-progress
\ No newline at end of file
+          --no-progress
diff --git a/composer.json b/composer.json
index 8b26f18..60b6721 100644
--- a/composer.json
+++ b/composer.json
@@ -18,7 +18,7 @@
     "php-http/httplug": "^2.4",
     "php-http/client-common": "^2.7",
     "psr/http-message": "^2.0",
-    "jumbojett/openid-connect-php": "^1.0",
+    "jumbojett/openid-connect-php": "dev-master",
     "symfony/serializer": "^7.2",
     "symfony/property-access": "^7.2",
     "json-mapper/json-mapper": "^2.22",
@@ -36,13 +36,14 @@
   },
   "require-dev": {
     "phpunit/phpunit": "^11.3",
-    "phpstan/phpstan": "^1.12",
+    "phpstan/phpstan": "^2.1",
     "mockery/mockery": "^1.6",
     "squizlabs/php_codesniffer": "^3.10",
     "phpcompatibility/php-compatibility": "^9.3",
     "symfony/var-dumper": "^7.1",
     "guzzlehttp/guzzle": "^7.9",
-    "vlucas/phpdotenv": "^5.6"
+    "vlucas/phpdotenv": "^5.6",
+    "rector/rector": "^2.0"
   },
   "scripts": {
     "analyze": "vendor/bin/phpstan",
diff --git a/rector.php b/rector.php
new file mode 100644
index 0000000..5daf004
--- /dev/null
+++ b/rector.php
@@ -0,0 +1,8 @@
+<?php
+
+return Rector\Config\RectorConfig::configure()
+    ->withPaths([__DIR__ . '/src', __DIR__ . '/tests', __DIR__ . '/examples'])
+    ->withPhpVersion(Rector\ValueObject\PhpVersion::PHP_84)
+    ->withRules([
+         Rector\Php84\Rector\Param\ExplicitNullableParamTypeRector::class,
+    ]);
diff --git a/src/Apis/AbstractCollection.php b/src/Apis/AbstractCollection.php
index 3e26ab4..acbfba1 100644
--- a/src/Apis/AbstractCollection.php
+++ b/src/Apis/AbstractCollection.php
@@ -26,11 +26,9 @@ public function __construct(AbstractResponse ...$items)
      * @param AbstractResponse $item The item
      * @return void
      */
-    public function add(mixed $item): void
+    public function add(AbstractResponse $item): void
     {
-        if ($item instanceof AbstractResponse) {
-            $this->items[] = $item;
-        }
+        $this->items[] = $item;
     }
 
     /**
diff --git a/src/EnvironmentManager.php b/src/EnvironmentManager.php
index 4b47316..798a8a8 100644
--- a/src/EnvironmentManager.php
+++ b/src/EnvironmentManager.php
@@ -67,6 +67,6 @@ public function getIdpUrl(): string
 
     private function validateEnvironment(?string $environment): bool
     {
-        return isset($environment) && $environment !== null && in_array($environment, ApiEnvironment::asArray());
+        return isset($environment) && in_array($environment, ApiEnvironment::asArray());
     }
 }
diff --git a/src/HttpClient/Builder.php b/src/HttpClient/Builder.php
index 6657e13..33317d9 100644
--- a/src/HttpClient/Builder.php
+++ b/src/HttpClient/Builder.php
@@ -33,10 +33,10 @@ class Builder
     private array $plugins = [];
 
     public function __construct(
-        ClientInterface $httpClient = null,
-        RequestFactoryInterface $requestFactory = null,
-        StreamFactoryInterface $streamFactory = null,
-        UriFactoryInterface $uriFactory = null
+        ?ClientInterface $httpClient = null,
+        ?RequestFactoryInterface $requestFactory = null,
+        ?StreamFactoryInterface $streamFactory = null,
+        ?UriFactoryInterface $uriFactory = null
     ) {
         $this->httpClient = $httpClient ?? Psr18ClientDiscovery::find();
         $this->requestFactory = $requestFactory ?? Psr17FactoryDiscovery::findRequestFactory();
diff --git a/tests/Endpoints/BaseEndpointTestCase.php b/tests/Endpoints/BaseEndpointTestCase.php
index b0dc8da..96ccdac 100644
--- a/tests/Endpoints/BaseEndpointTestCase.php
+++ b/tests/Endpoints/BaseEndpointTestCase.php
@@ -14,10 +14,10 @@ class BaseEndpointTestCase extends TestCase
 {
     private DataProviderInterface $provider;
 
-    public function __construct(string $name)
+    protected function setUp(): void
     {
+        parent::setUp();
         $this->initDataProvider();
-        parent::__construct($name);
     }
 
     private function initDataProvider(): void
diff --git a/tests/Endpoints/DataProvider.php b/tests/Endpoints/DataProvider.php
index d56054b..5c37b86 100644
--- a/tests/Endpoints/DataProvider.php
+++ b/tests/Endpoints/DataProvider.php
@@ -51,7 +51,7 @@ public function getData(mixed $param = null): array
     /**
      * @param array<int, mixed>|null $requests
      */
-    public function createClientHandler(?array $requests = [], ?MockHandler &$mock = null): SeravoApiClient
+    public function createClientHandler(?array $requests = [], ?MockHandler $mock = null): SeravoApiClient
     {
         $mock = new MockHandler($requests);
         return new SeravoApiClient(