diff --git a/.github/workflows/rector.yaml b/.github/workflows/rector.yaml
new file mode 100644
index 00000000..bf4f407e
--- /dev/null
+++ b/.github/workflows/rector.yaml
@@ -0,0 +1,35 @@
+# github action that checks code with Rector
+name: Rector
+
+on:
+    pull_request: null
+
+jobs:
+    rector:
+        runs-on: ubuntu-latest
+        if: github.event.pull_request.head.repo.full_name == 'TomasVotruba/lines'
+        steps:
+            -
+                if: github.event.pull_request.head.repo.full_name == github.repository
+                uses: actions/checkout@v3
+                with:
+                    # Must be used to trigger workflow after push
+                    token: ${{ secrets.ACCESS_TOKEN }}
+
+            -
+                uses: shivammathur/setup-php@v2
+                with:
+                    php-version: 8.1
+                    coverage: none
+
+            -   uses: "ramsey/composer-install@v2"
+
+            -   run: vendor/bin/rector --ansi
+
+            -
+                # commit only to core contributors who have repository access
+                uses: stefanzweifel/git-auto-commit-action@v4
+                with:
+                    commit_message: '[rector] Rector fixes'
+                    commit_author: 'GitHub Action <actions@github.com>'
+                    commit_user_email: 'action@github.com'
diff --git a/rector.php b/rector.php
index adbf9d7b..0d520a08 100644
--- a/rector.php
+++ b/rector.php
@@ -5,7 +5,9 @@
 use Rector\CodeQuality\Rector\Class_\InlineConstructorDefaultToPropertyRector;
 use Rector\Config\RectorConfig;
 use Rector\PHPUnit\CodeQuality\Rector\Class_\YieldDataProviderRector;
+use Rector\PHPUnit\Set\PHPUnitSetList;
 use Rector\Set\ValueObject\LevelSetList;
+use Rector\Set\ValueObject\SetList;
 
 return static function (RectorConfig $rectorConfig): void {
     $rectorConfig->importNames();
@@ -16,15 +18,21 @@
 
     $rectorConfig->paths([
         __DIR__ . '/src',
-        __DIR__ . '/tests/unit',
+        __DIR__ . '/tests',
+    ]);
+
+    $rectorConfig->skip([
+        '*/Fixture/*',
     ]);
 
     $rectorConfig->sets([
         LevelSetList::UP_TO_PHP_81,
-        \Rector\Set\ValueObject\SetList::CODE_QUALITY,
-        \Rector\Set\ValueObject\SetList::CODING_STYLE,
-        \Rector\Set\ValueObject\SetList::TYPE_DECLARATION,
-        \Rector\PHPUnit\Set\PHPUnitSetList::PHPUNIT_100,
-        \Rector\PHPUnit\Set\PHPUnitSetList::PHPUNIT_CODE_QUALITY,
+        SetList::CODE_QUALITY,
+        SetList::CODING_STYLE,
+        SetList::TYPE_DECLARATION,
+        SetList::PRIVATIZATION,
+        SetList::DEAD_CODE,
+        PHPUnitSetList::PHPUNIT_100,
+        PHPUnitSetList::PHPUNIT_CODE_QUALITY,
     ]);
 };
diff --git a/src/Analyser.php b/src/Analyser.php
index 506f5b02..4c322bb4 100644
--- a/src/Analyser.php
+++ b/src/Analyser.php
@@ -11,7 +11,7 @@
  */
 final class Analyser
 {
-    private Collector $collector;
+    private readonly Collector $collector;
 
     public function __construct()
     {
diff --git a/src/CLI/Application.php b/src/CLI/Application.php
index 3d0e7243..b5a550eb 100644
--- a/src/CLI/Application.php
+++ b/src/CLI/Application.php
@@ -4,6 +4,7 @@
 
 namespace TomasVotruba\Lines\CLI;
 
+use Throwable;
 use SebastianBergmann\FileIterator\Facade;
 use TomasVotruba\Lines\Analyser;
 use TomasVotruba\Lines\Enum\StatusCode;
@@ -22,7 +23,7 @@ public function run(array $argv): int
 
         try {
             $arguments = $argumentsBuilder->build($argv);
-        } catch (\Throwable $throwable) {
+        } catch (Throwable $throwable) {
             print PHP_EOL . $throwable->getMessage() . PHP_EOL;
 
             return StatusCode::ERROR;
@@ -40,7 +41,7 @@ public function run(array $argv): int
 
         foreach ($arguments->directories() as $directory) {
             $currentFiles = (new Facade())->getFilesAsArray($directory, $arguments->suffixes(), '', $arguments->exclude());
-            $files = array_merge($files, $currentFiles);
+            $files = [...$files, ...$currentFiles];
         }
 
         if ($files === []) {
diff --git a/src/CLI/ArgumentsBuilder.php b/src/CLI/ArgumentsBuilder.php
index cbc58109..f9fdfc35 100644
--- a/src/CLI/ArgumentsBuilder.php
+++ b/src/CLI/ArgumentsBuilder.php
@@ -29,7 +29,7 @@ public function build(array $argv): Arguments
         } catch (CliParserException $cliParserException) {
             throw new ShouldNotHappenException(
                 $cliParserException->getMessage(),
-                (int) $cliParserException->getCode(),
+                $cliParserException->getCode(),
                 $cliParserException
             );
         }
diff --git a/src/Collector.php b/src/Collector.php
index d849ee91..cfc66630 100644
--- a/src/Collector.php
+++ b/src/Collector.php
@@ -25,7 +25,7 @@ public function getPublisher(): Publisher
     public function addFile(string $filename): void
     {
         $this->increment('files');
-        $this->addUnique('directories', dirname((string) $filename));
+        $this->addUnique('directories', dirname($filename));
     }
 
     public function incrementLines(int $number): void