diff --git a/composer.json b/composer.json
index 7210d41a..f3b7cd0c 100644
--- a/composer.json
+++ b/composer.json
@@ -32,9 +32,10 @@
     "require-dev": {
         "phpunit/phpunit": "~9.3.0",
         "monolog/monolog": "1.*|2.*",
-        "phpstan/phpstan": "^0.12.81",
+        "phpstan/phpstan": "^2.1.22",
         "friendsofphp/php-cs-fixer": "^3.5",
-        "php-http/mock-client": "^1.5"
+        "php-http/mock-client": "^1.5",
+        "rector/rector": "^2.1"
     },
     "suggest": {
         "monolog/monolog": "Allows to handle logs",
diff --git a/composer.lock b/composer.lock
index 4cc3e1e7..2a5cff26 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "fc7d0cfb157d28568ea5453c2ece4a54",
+    "content-hash": "61dd5ee073d8375252d4c1122e48d372",
     "packages": [
         {
             "name": "nyholm/psr7",
@@ -1994,20 +1994,20 @@
         },
         {
             "name": "phpstan/phpstan",
-            "version": "0.12.100",
+            "version": "2.1.22",
             "source": {
                 "type": "git",
                 "url": "https://github.com/phpstan/phpstan.git",
-                "reference": "48236ddf823547081b2b153d1cd2994b784328c3"
+                "reference": "41600c8379eb5aee63e9413fe9e97273e25d57e4"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/phpstan/phpstan/zipball/48236ddf823547081b2b153d1cd2994b784328c3",
-                "reference": "48236ddf823547081b2b153d1cd2994b784328c3",
+                "url": "https://api.github.com/repos/phpstan/phpstan/zipball/41600c8379eb5aee63e9413fe9e97273e25d57e4",
+                "reference": "41600c8379eb5aee63e9413fe9e97273e25d57e4",
                 "shasum": ""
             },
             "require": {
-                "php": "^7.1|^8.0"
+                "php": "^7.4|^8.0"
             },
             "conflict": {
                 "phpstan/phpstan-shim": "*"
@@ -2017,11 +2017,6 @@
                 "phpstan.phar"
             ],
             "type": "library",
-            "extra": {
-                "branch-alias": {
-                    "dev-master": "0.12-dev"
-                }
-            },
             "autoload": {
                 "files": [
                     "bootstrap.php"
@@ -2032,9 +2027,16 @@
                 "MIT"
             ],
             "description": "PHPStan - PHP Static Analysis Tool",
+            "keywords": [
+                "dev",
+                "static analysis"
+            ],
             "support": {
+                "docs": "https://phpstan.org/user-guide/getting-started",
+                "forum": "https://github.com/phpstan/phpstan/discussions",
                 "issues": "https://github.com/phpstan/phpstan/issues",
-                "source": "https://github.com/phpstan/phpstan/tree/0.12.100"
+                "security": "https://github.com/phpstan/phpstan/security/policy",
+                "source": "https://github.com/phpstan/phpstan-src"
             },
             "funding": [
                 {
@@ -2044,13 +2046,9 @@
                 {
                     "url": "https://github.com/phpstan",
                     "type": "github"
-                },
-                {
-                    "url": "https://tidelift.com/funding/github/packagist/phpstan/phpstan",
-                    "type": "tidelift"
                 }
             ],
-            "time": "2022-11-01T09:52:08+00:00"
+            "time": "2025-08-04T19:17:37+00:00"
         },
         {
             "name": "phpunit/php-code-coverage",
@@ -3103,6 +3101,66 @@
             ],
             "time": "2024-06-11T12:45:25+00:00"
         },
+        {
+            "name": "rector/rector",
+            "version": "2.1.2",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/rectorphp/rector.git",
+                "reference": "40a71441dd73fa150a66102f5ca1364c44fc8fff"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/rectorphp/rector/zipball/40a71441dd73fa150a66102f5ca1364c44fc8fff",
+                "reference": "40a71441dd73fa150a66102f5ca1364c44fc8fff",
+                "shasum": ""
+            },
+            "require": {
+                "php": "^7.4|^8.0",
+                "phpstan/phpstan": "^2.1.18"
+            },
+            "conflict": {
+                "rector/rector-doctrine": "*",
+                "rector/rector-downgrade-php": "*",
+                "rector/rector-phpunit": "*",
+                "rector/rector-symfony": "*"
+            },
+            "suggest": {
+                "ext-dom": "To manipulate phpunit.xml via the custom-rule command"
+            },
+            "bin": [
+                "bin/rector"
+            ],
+            "type": "library",
+            "autoload": {
+                "files": [
+                    "bootstrap.php"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "description": "Instant Upgrade and Automated Refactoring of any PHP code",
+            "homepage": "https://getrector.com/",
+            "keywords": [
+                "automation",
+                "dev",
+                "migration",
+                "refactoring"
+            ],
+            "support": {
+                "issues": "https://github.com/rectorphp/rector/issues",
+                "source": "https://github.com/rectorphp/rector/tree/2.1.2"
+            },
+            "funding": [
+                {
+                    "url": "https://github.com/tomasvotruba",
+                    "type": "github"
+                }
+            ],
+            "time": "2025-07-17T19:30:06+00:00"
+        },
         {
             "name": "sebastian/cli-parser",
             "version": "1.0.2",
diff --git a/phpstan.neon.dist b/phpstan.neon.dist
new file mode 100644
index 00000000..4d08f439
--- /dev/null
+++ b/phpstan.neon.dist
@@ -0,0 +1,7 @@
+parameters:
+    errorFormat: table
+    level: 5
+    paths:
+        - %currentWorkingDirectory%/src
+    bootstrapFiles:
+        - %currentWorkingDirectory%/vendor/autoload.php
diff --git a/rector.php b/rector.php
new file mode 100644
index 00000000..2bb5054d
--- /dev/null
+++ b/rector.php
@@ -0,0 +1,16 @@
+<?php
+
+declare(strict_types=1);
+
+use Rector\Config\RectorConfig;
+use Rector\Php84\Rector\Param\ExplicitNullableParamTypeRector;
+use Rector\ValueObject\PhpVersion;
+
+return RectorConfig::configure()
+    ->withPaths([
+        __DIR__ . '/src',
+    ])
+    ->withPhpVersion(PhpVersion::PHP_84)
+    ->withRules([
+        ExplicitNullableParamTypeRector::class,
+    ]);
diff --git a/tests/FeedIo/SpecificationTest.php b/tests/FeedIo/SpecificationTest.php
index 0b43e951..2dcdef60 100644
--- a/tests/FeedIo/SpecificationTest.php
+++ b/tests/FeedIo/SpecificationTest.php
@@ -5,7 +5,7 @@
 use FeedIo\Rule\DateTimeBuilder;
 use FeedIo\Standard\Atom;
 use FeedIo\Standard\Json;
-use PHPStan\Testing\TestCase;
+use PHPUnit\Framework\TestCase;
 use Psr\Log\NullLogger;
 
 class SpecificationTest extends TestCase