diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 3710514..dfe2c6a 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -2,34 +2,41 @@ name: build
 on:
   push:
     branches: [master]
+  pull_request:
+    branches: [master]
 jobs:
-  run:
-    runs-on: ${{ matrix.operating-system }}
+  test:
+    runs-on: ubuntu-latest
     strategy:
+      fail-fast: false
       matrix:
-        operating-system: [ubuntu-latest]
-        php-versions:
-          ["7.1", "7.2", "7.3", "7.4", "8.0", "8.1", "8.2", "8.3", "8.4"]
-    name: PHP ${{ matrix.php-versions }}
+        php-version: ["7.1", "7.2", "7.3", "7.4", "8.0", "8.1", "8.2", "8.3", "8.4"]
+    name: PHP ${{ matrix.php-version }}
     steps:
-      - uses: actions/checkout@v4
-      - name: Update advanced packaging tools
-        run: sudo apt update
+      - uses: actions/checkout@v5.0.1
+
       - name: Install Ghostscript
-        run: sudo apt install ghostscript
-      - name: Install PHP
+        run: sudo apt-get update -qq && sudo apt-get install -y ghostscript
+
+      - name: Setup PHP
         uses: shivammathur/setup-php@v2
         with:
-          php-version: ${{ matrix.php-versions }}
+          php-version: ${{ matrix.php-version }}
           coverage: xdebug
+          tools: composer:v2
+
       - name: Install dependencies
-        run: composer self-update && composer install && composer dump-autoload
-      - name: Copy .env.example to .env
+        run: composer install --no-interaction --prefer-dist
+
+      - name: Copy .env
         run: cp .env.example .env
+
       - name: Run tests
         run: composer test
+
       - name: Upload coverage to Codecov
-        uses: codecov/codecov-action@v4
+        if: matrix.php-version == '8.4'
+        uses: codecov/codecov-action@v6
         with:
           token: ${{ secrets.CODECOV_TOKEN }}
           files: ./coverage.xml
diff --git a/.gitignore b/.gitignore
index 7cb9e80..b1bda8c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,10 +5,16 @@ vendor/
 report/
 files/split/parts/
 files/merge/res.pdf
+files/merge/single.pdf
 files/to-image/images/
 composer.lock
 coverage.xml
 phpunit.xml
 .phpunit.result.cache
 .DS_Store
-.env
\ No newline at end of file
+.env
+.repomix/
+repomix-output.txt
+.claude/
+Dockerfile
+docker-compose.yml
\ No newline at end of file
diff --git a/src/Configs/Config.php b/src/Configs/Config.php
index 6f468b2..08c540d 100644
--- a/src/Configs/Config.php
+++ b/src/Configs/Config.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Ordinary9843\Configs;
 
 use Ordinary9843\Helpers\PathHelper;
diff --git a/src/Constants/GhostscriptConstant.php b/src/Constants/GhostscriptConstant.php
index 27b1aa7..f723ee5 100644
--- a/src/Constants/GhostscriptConstant.php
+++ b/src/Constants/GhostscriptConstant.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Ordinary9843\Constants;
 
 class GhostscriptConstant
diff --git a/src/Constants/ImageTypeConstant.php b/src/Constants/ImageTypeConstant.php
index 66f3518..5902527 100644
--- a/src/Constants/ImageTypeConstant.php
+++ b/src/Constants/ImageTypeConstant.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Ordinary9843\Constants;
 
 class ImageTypeConstant
diff --git a/src/Exceptions/BaseException.php b/src/Exceptions/BaseException.php
index 5a59055..fbd16c2 100644
--- a/src/Exceptions/BaseException.php
+++ b/src/Exceptions/BaseException.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Ordinary9843\Exceptions;
 
 use Exception;
@@ -18,7 +20,7 @@ class BaseException extends Exception
      * @param array $detail
      * @param BaseException $previous
      */
-    public function __construct(string $message = 'An unexpected error occurred.', int $code = self::CODE_DEFAULT, array $detail = [], BaseException $previous = null)
+    public function __construct(string $message = 'An unexpected error occurred.', int $code = self::CODE_DEFAULT, array $detail = [], ?BaseException $previous = null)
     {
         parent::__construct($message, $code, $previous);
 
diff --git a/src/Exceptions/ConfigException.php b/src/Exceptions/ConfigException.php
index 616dc93..df1e37a 100644
--- a/src/Exceptions/ConfigException.php
+++ b/src/Exceptions/ConfigException.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Ordinary9843\Exceptions;
 
 class ConfigException extends BaseException
@@ -19,7 +21,7 @@ class ConfigException extends BaseException
      * @param array $detail
      * @param BaseException $previous
      */
-    public function __construct(string $message, int $code = self::CODE_DEFAULT, array $detail = [], BaseException $previous = null)
+    public function __construct(string $message, int $code = self::CODE_DEFAULT, array $detail = [], ?BaseException $previous = null)
     {
         parent::__construct($message, $code, $detail, $previous);
     }
diff --git a/src/Exceptions/HandlerException.php b/src/Exceptions/HandlerException.php
index a26fbd9..f3a114b 100644
--- a/src/Exceptions/HandlerException.php
+++ b/src/Exceptions/HandlerException.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Ordinary9843\Exceptions;
 
 class HandlerException extends BaseException
@@ -16,7 +18,7 @@ class HandlerException extends BaseException
      * @param array $detail
      * @param BaseException $previous
      */
-    public function __construct(string $message, int $code = self::CODE_DEFAULT, array $detail = [], BaseException $previous = null)
+    public function __construct(string $message, int $code = self::CODE_DEFAULT, array $detail = [], ?BaseException $previous = null)
     {
         parent::__construct($message, $code, $detail, $previous);
     }
diff --git a/src/Exceptions/InvalidException.php b/src/Exceptions/InvalidException.php
index f760a79..526f685 100644
--- a/src/Exceptions/InvalidException.php
+++ b/src/Exceptions/InvalidException.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Ordinary9843\Exceptions;
 
 class InvalidException extends BaseException
@@ -22,7 +24,7 @@ class InvalidException extends BaseException
      * @param array $detail
      * @param BaseException $previous
      */
-    public function __construct(string $message, int $code = self::CODE_DEFAULT, array $detail = [], BaseException $previous = null)
+    public function __construct(string $message, int $code = self::CODE_DEFAULT, array $detail = [], ?BaseException $previous = null)
     {
         parent::__construct($message, $code, $detail, $previous);
     }
diff --git a/src/Exceptions/NotFoundException.php b/src/Exceptions/NotFoundException.php
index 645f0fe..24f83b9 100644
--- a/src/Exceptions/NotFoundException.php
+++ b/src/Exceptions/NotFoundException.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Ordinary9843\Exceptions;
 
 class NotFoundException extends BaseException
@@ -19,7 +21,7 @@ class NotFoundException extends BaseException
      * @param array $detail
      * @param BaseException $previous
      */
-    public function __construct(string $message, int $code = self::CODE_DEFAULT, array $detail = [], BaseException $previous = null)
+    public function __construct(string $message, int $code = self::CODE_DEFAULT, array $detail = [], ?BaseException $previous = null)
     {
         parent::__construct($message, $code, $detail, $previous);
     }
diff --git a/src/Factories/HandlerFactory.php b/src/Factories/HandlerFactory.php
index 868f9a3..7948d98 100644
--- a/src/Factories/HandlerFactory.php
+++ b/src/Factories/HandlerFactory.php
@@ -1,26 +1,46 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Ordinary9843\Factories;
 
+use Ordinary9843\Handlers\BaseHandler;
+use Ordinary9843\Handlers\ConvertHandler;
+use Ordinary9843\Handlers\GetTotalPagesHandler;
+use Ordinary9843\Handlers\GuessHandler;
+use Ordinary9843\Handlers\MergeHandler;
+use Ordinary9843\Handlers\SplitHandler;
+use Ordinary9843\Handlers\ToImageHandler;
 use Ordinary9843\Interfaces\HandlerInterface;
 use Ordinary9843\Exceptions\NotFoundException;
 
 class HandlerFactory
 {
+    private const HANDLER_MAP = [
+        'base'          => BaseHandler::class,
+        'convert'       => ConvertHandler::class,
+        'guess'         => GuessHandler::class,
+        'getTotalPages' => GetTotalPagesHandler::class,
+        'merge'         => MergeHandler::class,
+        'split'         => SplitHandler::class,
+        'toImage'       => ToImageHandler::class,
+    ];
+
     /**
      * @param string $type
-     * 
+     *
      * @return HandlerInterface
-     * 
+     *
      * @throws NotFoundException
      */
     public function create(string $type): HandlerInterface
     {
-        $class = 'Ordinary9843\\Handlers\\' . ucfirst($type) . 'Handler';
-        if (!class_exists($class)) {
-            throw new NotFoundException('Class "' . $class . '" does not exist.', NotFoundException::CODE_CLASS);
+        if (!isset(self::HANDLER_MAP[$type])) {
+            throw new NotFoundException('Handler "' . $type . '" does not exist.', NotFoundException::CODE_CLASS);
         }
 
+        $class = self::HANDLER_MAP[$type];
+
         return new $class();
     }
 }
diff --git a/src/Ghostscript.php b/src/Ghostscript.php
index 4d44e95..01f1175 100644
--- a/src/Ghostscript.php
+++ b/src/Ghostscript.php
@@ -1,27 +1,15 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Ordinary9843;
 
 use Ordinary9843\Configs\Config;
 use Ordinary9843\Factories\HandlerFactory;
 use Ordinary9843\Exceptions\InvalidException;
 use Ordinary9843\Interfaces\HandlerInterface;
+use Ordinary9843\Constants\ImageTypeConstant;
 
-/**
- * @method string convert(string $file, float $version)
- * @method float guess(string $file)
- * @method string merge(string $path, string $filename, array $files, bool $isAutoConvert = true)
- * @method array split(string $file, string $path)
- * @method array toImage(string $file, string $path, string $type = 'jpeg')
- * @method int getTotalPages(string $file)
- * @method void clearTmpFiles(bool $isForceClear = false, int $days = 7)
- * @method void setBinPath(string $binPath)
- * @method string getBinPath()
- * @method void setTmpPath(string $tmpPath)
- * @method string getTmpPath()
- * @method void setOptions(array $options)
- * @method array getOptions()
- */
 class Ghostscript
 {
     /** @var HandlerInterface[] */
@@ -44,53 +32,90 @@ public function __construct(string $binPath = '', string $tmpPath = '')
         Config::initialize($this->arguments);
     }
 
+    public function convert(string $file, float $version): string
+    {
+        return $this->createHandler('convert')->execute($file, $version);
+    }
+
+    public function guess(string $file): float
+    {
+        return $this->createHandler('guess')->execute($file);
+    }
+
+    public function merge(string $path, string $filename, array $files, bool $isAutoConvert = true): string
+    {
+        return $this->createHandler('merge')->execute($path, $filename, $files, $isAutoConvert);
+    }
+
+    public function split(string $file, string $path): array
+    {
+        return $this->createHandler('split')->execute($file, $path);
+    }
+
+    public function toImage(string $file, string $path, string $type = ImageTypeConstant::JPEG): array
+    {
+        return $this->createHandler('toImage')->execute($file, $path, $type);
+    }
+
+    public function getTotalPages(string $file): int
+    {
+        return $this->createHandler('getTotalPages')->execute($file);
+    }
+
+    public function clearTmpFiles(bool $isForceClear = false, int $days = 7): void
+    {
+        $this->createBaseHandler()->clearTmpFiles($isForceClear, $days);
+    }
+
+    public function setBinPath(string $binPath): void
+    {
+        $this->createBaseHandler()->setBinPath($binPath);
+    }
+
+    public function getBinPath(): string
+    {
+        return $this->createBaseHandler()->getBinPath();
+    }
+
+    public function setTmpPath(string $tmpPath): void
+    {
+        $this->createBaseHandler()->setTmpPath($tmpPath);
+    }
+
+    public function getTmpPath(): string
+    {
+        return $this->createBaseHandler()->getTmpPath();
+    }
+
+    public function setOptions(array $options): void
+    {
+        $this->createBaseHandler()->setOptions($options);
+    }
+
+    public function getOptions(): array
+    {
+        return $this->createBaseHandler()->getOptions();
+    }
+
     /**
      * @param string $name
      * @param array $arguments
-     * 
+     *
      * @return mixed
-     * 
+     *
      * @throws InvalidException
      */
     public function __call(string $name, array $arguments)
     {
-        switch ($name) {
-            case 'convert':
-            case 'guess':
-            case 'merge':
-            case 'split':
-            case 'toImage':
-            case 'getTotalPages':
-                $handler = $this->createHandler($name);
-
-                return $handler->execute(...$arguments);
-            case 'getBinPath':
-            case 'getTmpPath':
-            case 'getOptions':
-            case 'clearTmpFiles':
-                $handler = $this->createBaseHandler();
-
-                return $handler->{$name}();
-            case 'setBinPath':
-            case 'setTmpPath':
-                $handler = $this->createBaseHandler();
-
-                return $handler->{$name}(current($arguments));
-            case 'setOptions':
-                $handler = $this->createBaseHandler();
-
-                return $handler->{$name}(...$arguments);
-            default:
-                throw new InvalidException('Invalid method: "' . $name . '".', InvalidException::CODE_METHOD, [
-                    'name' => $name,
-                    'arguments' => $arguments
-                ]);
-        }
+        throw new InvalidException('Invalid method: "' . $name . '".', InvalidException::CODE_METHOD, [
+            'name' => $name,
+            'arguments' => $arguments
+        ]);
     }
 
     /**
      * @param string $name
-     * 
+     *
      * @return HandlerInterface
      */
     private function createHandler(string $name): HandlerInterface
diff --git a/src/Handlers/BaseHandler.php b/src/Handlers/BaseHandler.php
index 8276680..68ee6c0 100644
--- a/src/Handlers/BaseHandler.php
+++ b/src/Handlers/BaseHandler.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Ordinary9843\Handlers;
 
 use Ordinary9843\Configs\Config;
@@ -151,6 +153,10 @@ public function optionsToCommand(string $command): string
      */
     public function isPdf(string $file): bool
     {
+        if (!$this->isFile($file)) {
+            return false;
+        }
+
         if (strcasecmp(pathinfo($file, PATHINFO_EXTENSION), 'pdf') !== 0) {
             return false;
         }
diff --git a/src/Handlers/ConvertHandler.php b/src/Handlers/ConvertHandler.php
index 14f91da..57b60d5 100644
--- a/src/Handlers/ConvertHandler.php
+++ b/src/Handlers/ConvertHandler.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Ordinary9843\Handlers;
 
 use Ordinary9843\Helpers\PathHelper;
diff --git a/src/Handlers/GetTotalPagesHandler.php b/src/Handlers/GetTotalPagesHandler.php
index 1971193..69a7598 100644
--- a/src/Handlers/GetTotalPagesHandler.php
+++ b/src/Handlers/GetTotalPagesHandler.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Ordinary9843\Handlers;
 
 use Ordinary9843\Helpers\PathHelper;
@@ -26,6 +28,8 @@ public function execute(...$arguments): int
         $this->validateBinPath();
         $this->mapArguments($arguments);
 
+        $file = '';
+
         try {
             $file = PathHelper::convertPathSeparator($arguments['file']);
             if (!$this->isFile($file)) {
diff --git a/src/Handlers/GuessHandler.php b/src/Handlers/GuessHandler.php
index 418cdda..7806bc4 100644
--- a/src/Handlers/GuessHandler.php
+++ b/src/Handlers/GuessHandler.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Ordinary9843\Handlers;
 
 use Ordinary9843\Exceptions\BaseException;
diff --git a/src/Handlers/MergeHandler.php b/src/Handlers/MergeHandler.php
index 15c4081..fa8c9a5 100644
--- a/src/Handlers/MergeHandler.php
+++ b/src/Handlers/MergeHandler.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Ordinary9843\Handlers;
 
 use Ordinary9843\Helpers\PathHelper;
@@ -25,6 +27,7 @@ class MergeHandler extends BaseHandler implements HandlerInterface
 
     public function __construct()
     {
+        parent::__construct();
         $this->convertHandler = (new HandlerFactory())->create('convert');
         $this->guessHandler = (new HandlerFactory())->create('guess');
     }
@@ -42,6 +45,8 @@ public function execute(...$arguments): string
         $this->validateBinPath();
         $this->mapArguments($arguments);
 
+        $file = '';
+
         try {
             $path = PathHelper::convertPathSeparator($arguments['path']);
             $filename = PathHelper::convertPathSeparator($arguments['filename']);
@@ -59,6 +64,11 @@ public function execute(...$arguments): string
 
                 return true;
             });
+
+            if (empty($files)) {
+                throw new HandlerException('No valid PDF files to merge.', HandlerException::CODE_EXECUTE);
+            }
+
             $output = shell_exec(
                 $this->optionsToCommand(
                     sprintf(
@@ -77,7 +87,9 @@ public function execute(...$arguments): string
 
             return $file;
         } catch (BaseException $exception) {
-            $this->delete($file);
+            if ($file !== '') {
+                $this->delete($file);
+            }
 
             throw new HandlerException($exception->getMessage(), HandlerException::CODE_EXECUTE, [
                 'arguments' => $arguments
diff --git a/src/Handlers/SplitHandler.php b/src/Handlers/SplitHandler.php
index ad03a99..f138f3d 100644
--- a/src/Handlers/SplitHandler.php
+++ b/src/Handlers/SplitHandler.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Ordinary9843\Handlers;
 
 use Ordinary9843\Helpers\PathHelper;
@@ -20,14 +22,15 @@ class SplitHandler extends BaseHandler implements HandlerInterface
 
     public function __construct()
     {
+        parent::__construct();
         $this->getTotalPagesHandler = (new HandlerFactory())->create('getTotalPages');
     }
 
     /**
      * @param array ...$arguments
-     * 
+     *
      * @return array
-     * 
+     *
      * @throws HandlerException
      * @throws InvalidException
      */
@@ -49,7 +52,7 @@ public function execute(...$arguments): array
 
             return array_map(function ($i) use ($path, $pdfFormatPath) {
                 return $path . sprintf($pdfFormatPath, $i);
-            }, range(0, $totalPages - 1));
+            }, range(1, $totalPages));
         } catch (BaseException $exception) {
             throw new HandlerException($exception->getMessage(), HandlerException::CODE_EXECUTE, [
                 'arguments' => $arguments
diff --git a/src/Handlers/ToImageHandler.php b/src/Handlers/ToImageHandler.php
index 797a192..98959fb 100644
--- a/src/Handlers/ToImageHandler.php
+++ b/src/Handlers/ToImageHandler.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Ordinary9843\Handlers;
 
 use Ordinary9843\Helpers\PathHelper;
@@ -16,19 +18,23 @@ class ToImageHandler extends BaseHandler implements HandlerInterface
     /** @var array */
     protected $argumentsMapping = ['file', 'path', 'type'];
 
+    /** @var string[] */
+    private const ALLOWED_TYPES = [ImageTypeConstant::JPEG, ImageTypeConstant::PNG];
+
     /** @var GetTotalPagesHandler */
     protected $getTotalPagesHandler = null;
 
     public function __construct()
     {
+        parent::__construct();
         $this->getTotalPagesHandler = (new HandlerFactory())->create('getTotalPages');
     }
 
     /**
      * @param array ...$arguments
-     * 
+     *
      * @return array
-     * 
+     *
      * @throws HandlerException
      * @throws InvalidException
      */
@@ -41,6 +47,14 @@ public function execute(...$arguments): array
             $file = PathHelper::convertPathSeparator($arguments['file']);
             $path = PathHelper::convertPathSeparator($arguments['path']);
             $type = $arguments['type'] ? $arguments['type'] : ImageTypeConstant::JPEG;
+
+            if (!in_array($type, self::ALLOWED_TYPES, true)) {
+                throw new InvalidException(
+                    'Invalid image type "' . $type . '". Allowed: ' . implode(', ', self::ALLOWED_TYPES) . '.',
+                    InvalidException::CODE_FILE_TYPE
+                );
+            }
+
             $totalPages = $this->getTotalPagesHandler->execute($file);
             (!$this->isDir($path)) && $this->makeDir($path);
             $imageFormatPath = ($totalPages > 1) ? '/image_%d.' . $type : '/' . pathinfo($file, PATHINFO_FILENAME) . '.' . $type;
diff --git a/src/Helpers/PathHelper.php b/src/Helpers/PathHelper.php
index fa7b4cd..3b9ecd1 100644
--- a/src/Helpers/PathHelper.php
+++ b/src/Helpers/PathHelper.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Ordinary9843\Helpers;
 
 class PathHelper
diff --git a/src/Interfaces/BaseInterface.php b/src/Interfaces/BaseInterface.php
index 60acf35..b526bca 100644
--- a/src/Interfaces/BaseInterface.php
+++ b/src/Interfaces/BaseInterface.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Ordinary9843\Interfaces;
 
 interface BaseInterface
diff --git a/src/Interfaces/HandlerInterface.php b/src/Interfaces/HandlerInterface.php
index f8df816..d263448 100644
--- a/src/Interfaces/HandlerInterface.php
+++ b/src/Interfaces/HandlerInterface.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Ordinary9843\Interfaces;
 
 interface HandlerInterface extends BaseInterface
diff --git a/src/Traits/ConfigTrait.php b/src/Traits/ConfigTrait.php
index 3c44bf4..7a29c07 100755
--- a/src/Traits/ConfigTrait.php
+++ b/src/Traits/ConfigTrait.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Ordinary9843\Traits;
 
 use Ordinary9843\Configs\Config;
@@ -25,8 +27,8 @@ public function getBinPath(): string
     }
 
     /**
-     * @param int $tmpPath
-     * 
+     * @param string $tmpPath
+     *
      * @return void
      */
     public function setTmpPath(string $tmpPath): void
diff --git a/src/Traits/FileSystemTrait.php b/src/Traits/FileSystemTrait.php
index ad251d9..d449eaa 100644
--- a/src/Traits/FileSystemTrait.php
+++ b/src/Traits/FileSystemTrait.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Ordinary9843\Traits;
 
 trait FileSystemTrait
diff --git a/tests/Factories/HandlerFactoryTest.php b/tests/Factories/HandlerFactoryTest.php
index 37c6d65..316ca6d 100644
--- a/tests/Factories/HandlerFactoryTest.php
+++ b/tests/Factories/HandlerFactoryTest.php
@@ -9,6 +9,7 @@
 use Ordinary9843\Handlers\SplitHandler;
 use Ordinary9843\Handlers\ConvertHandler;
 use Ordinary9843\Handlers\ToImageHandler;
+use Ordinary9843\Handlers\GetTotalPagesHandler;
 use Ordinary9843\Factories\HandlerFactory;
 use Ordinary9843\Exceptions\NotFoundException;
 
@@ -77,4 +78,33 @@ public function testCreateBaseHandlerShouldThrowNotFoundException(): void
         $this->expectExceptionCode(NotFoundException::CODE_CLASS);
         (new HandlerFactory)->create('');
     }
+
+    /**
+     * @return void
+     */
+    public function testCreateGetTotalPagesHandlerShouldSucceed(): void
+    {
+        $handler = (new HandlerFactory())->create('getTotalPages');
+        $this->assertInstanceOf(GetTotalPagesHandler::class, $handler);
+    }
+
+    /**
+     * @return void
+     */
+    public function testCreateWithUppercaseTypeShouldThrowNotFoundException(): void
+    {
+        $this->expectException(NotFoundException::class);
+        $this->expectExceptionCode(NotFoundException::CODE_CLASS);
+        (new HandlerFactory())->create('Convert');
+    }
+
+    /**
+     * @return void
+     */
+    public function testCreateWithUnknownTypeShouldThrowNotFoundException(): void
+    {
+        $this->expectException(NotFoundException::class);
+        $this->expectExceptionCode(NotFoundException::CODE_CLASS);
+        (new HandlerFactory())->create('nonExistentHandler');
+    }
 }
diff --git a/tests/Handlers/BaseHandlerTest.php b/tests/Handlers/BaseHandlerTest.php
index 0d48ca8..53350e6 100644
--- a/tests/Handlers/BaseHandlerTest.php
+++ b/tests/Handlers/BaseHandlerTest.php
@@ -200,4 +200,108 @@ public function testArgumentsMappingWhenProvidedInputs()
             'arg2' => 'value2'
         ], $arguments);
     }
+
+    /**
+     * @return void
+     */
+    public function testIsPdfReturnsFalseForNonExistentFile(): void
+    {
+        $handler = new BaseHandler();
+        $this->assertFalse($handler->isPdf('/nonexistent/path/file.pdf'));
+    }
+
+    /**
+     * @return void
+     */
+    public function testIsPdfReturnsFalseForEmptyString(): void
+    {
+        $handler = new BaseHandler();
+        $this->assertFalse($handler->isPdf(''));
+    }
+
+    /**
+     * @return void
+     */
+    public function testIsPdfReturnsFalseForDirectoryPath(): void
+    {
+        $handler = new BaseHandler();
+        $this->assertFalse($handler->isPdf(sys_get_temp_dir()));
+    }
+
+    /**
+     * @return void
+     */
+    public function testGetTmpFileContainsTmpPath(): void
+    {
+        $handler = new BaseHandler();
+        $tmpFile = $handler->getTmpFile();
+        $this->assertStringStartsWith($handler->getTmpPath(), $tmpFile);
+    }
+
+    /**
+     * @return void
+     */
+    public function testGetTmpFileWithCustomFilenameContainsPrefix(): void
+    {
+        $handler = new BaseHandler();
+        $tmpFile = $handler->getTmpFile('custom');
+        $this->assertStringContainsString('ghostscript_tmp_file_custom', $tmpFile);
+        $this->assertStringEndsWith('.pdf', $tmpFile);
+    }
+
+    /**
+     * @return void
+     */
+    public function testForceClearDeletesTmpPrefixedFiles(): void
+    {
+        $handler = new BaseHandler();
+        $tmpFile = tempnam($handler->getTmpPath(), BaseHandler::TMP_FILE_PREFIX);
+        @rename($tmpFile, $tmpFile . '.pdf');
+        $tmpFile .= '.pdf';
+        $handler->clearTmpFiles(true);
+        $this->assertFalse(file_exists($tmpFile));
+    }
+
+    /**
+     * @return void
+     */
+    public function testOptionsToCommandWithKeyValuePairs(): void
+    {
+        $handler = new BaseHandler();
+        $handler->setOptions(['-dCompatibilityLevel' => '1.4']);
+        $result = $handler->optionsToCommand('gs');
+        $this->assertEquals('gs -dCompatibilityLevel=1.4', $result);
+    }
+
+    /**
+     * @return void
+     */
+    public function testOptionsToCommandWithNumericKeys(): void
+    {
+        $handler = new BaseHandler();
+        $handler->setOptions(['-dSAFER', '-dBATCH']);
+        $result = $handler->optionsToCommand('gs');
+        $this->assertEquals('gs -dSAFER -dBATCH', $result);
+    }
+
+    /**
+     * @return void
+     */
+    public function testOptionsToCommandWithEmptyOptionsReturnsOriginal(): void
+    {
+        $handler = new BaseHandler();
+        $this->assertEquals('gs -sDEVICE=pdfwrite', $handler->optionsToCommand('gs -sDEVICE=pdfwrite'));
+    }
+
+    /**
+     * @return void
+     */
+    public function testValidateBinPathThrowsForNonExistentPath(): void
+    {
+        $this->expectException(InvalidException::class);
+        $this->expectExceptionCode(InvalidException::CODE_FILEPATH);
+        $handler = new BaseHandler();
+        $handler->setBinPath('/nonexistent/gs');
+        $handler->validateBinPath();
+    }
 }
diff --git a/tests/Handlers/ConvertHandlerTest.php b/tests/Handlers/ConvertHandlerTest.php
index 5b6aea7..75c622c 100644
--- a/tests/Handlers/ConvertHandlerTest.php
+++ b/tests/Handlers/ConvertHandlerTest.php
@@ -91,4 +91,29 @@ public function testExecuteFailedShouldThrowHandlerException(): void
         ]);
         $handler->execute($file, 1.5);
     }
+
+    /**
+     * @return void
+     */
+    public function testExecuteReturnsSameFilePathOnSuccess(): void
+    {
+        $file = dirname(__DIR__, 2) . '/files/convert/test.pdf';
+        $handler = new ConvertHandler();
+        $handler->setBinPath($this->getEnv('GS_BIN_PATH'));
+        $result = $handler->execute($file, 1.4);
+        $this->assertEquals($file, $result);
+        $this->assertFileExists($result);
+    }
+
+    /**
+     * @return void
+     */
+    public function testExecuteWithEmptyFilePathThrowsHandlerException(): void
+    {
+        $this->expectException(HandlerException::class);
+        $this->expectExceptionCode(HandlerException::CODE_EXECUTE);
+        $handler = new ConvertHandler();
+        $handler->setBinPath($this->getEnv('GS_BIN_PATH'));
+        $handler->execute('', 1.4);
+    }
 }
diff --git a/tests/Handlers/GetTotalPagesHandlerTest.php b/tests/Handlers/GetTotalPagesHandlerTest.php
index 11186ac..4169150 100644
--- a/tests/Handlers/GetTotalPagesHandlerTest.php
+++ b/tests/Handlers/GetTotalPagesHandlerTest.php
@@ -74,4 +74,28 @@ public function testExecuteWhenFileTypeNotMatchShouldThrowHandlerException(): vo
         $handler->setBinPath($this->getEnv('GS_BIN_PATH'));
         $handler->execute($file);
     }
+
+    /**
+     * @return void
+     */
+    public function testExecuteWithEmptyFilePathThrowsHandlerException(): void
+    {
+        $this->expectException(HandlerException::class);
+        $this->expectExceptionCode(HandlerException::CODE_EXECUTE);
+        $handler = new GetTotalPagesHandler();
+        $handler->setBinPath($this->getEnv('GS_BIN_PATH'));
+        $handler->execute('');
+    }
+
+    /**
+     * @return void
+     */
+    public function testExecuteWithNonExistentFileThrowsHandlerException(): void
+    {
+        $this->expectException(HandlerException::class);
+        $this->expectExceptionCode(HandlerException::CODE_EXECUTE);
+        $handler = new GetTotalPagesHandler();
+        $handler->setBinPath($this->getEnv('GS_BIN_PATH'));
+        $handler->execute('/nonexistent/file.pdf');
+    }
 }
diff --git a/tests/Handlers/GuessHandlerTest.php b/tests/Handlers/GuessHandlerTest.php
index 71c06ad..7e970b5 100644
--- a/tests/Handlers/GuessHandlerTest.php
+++ b/tests/Handlers/GuessHandlerTest.php
@@ -47,4 +47,33 @@ public function testExecuteShouldThrowInvalidException(): void
         $handler->setBinPath($this->getEnv('GS_BIN_PATH'));
         $handler->execute($file);
     }
+
+    /**
+     * @return void
+     */
+    public function testExecuteReturnsZeroForPdfWithoutVersionHeader(): void
+    {
+        $file = tempnam(sys_get_temp_dir(), 'test');
+        @rename($file, $file .= '.pdf');
+        @file_put_contents($file, 'This is not a real PDF, no version header.');
+        $handler = new GuessHandler();
+
+        try {
+            $version = $handler->execute($file);
+            $this->assertEquals(0.0, $version);
+        } finally {
+            @unlink($file);
+        }
+    }
+
+    /**
+     * @return void
+     */
+    public function testExecuteWithEmptyFilePathThrowsHandlerException(): void
+    {
+        $this->expectException(HandlerException::class);
+        $this->expectExceptionCode(HandlerException::CODE_EXECUTE);
+        $handler = new GuessHandler();
+        $handler->execute('');
+    }
 }
diff --git a/tests/Handlers/MergeHandlerTest.php b/tests/Handlers/MergeHandlerTest.php
index 2ea7d7a..e625cdd 100644
--- a/tests/Handlers/MergeHandlerTest.php
+++ b/tests/Handlers/MergeHandlerTest.php
@@ -124,4 +124,46 @@ public function testExecuteFailedShouldThrowHandlerException(): void
             dirname(__DIR__, 2) . '/files/merge/part_3.pdf'
         ]);
     }
+
+    /**
+     * @return void
+     */
+    public function testExecuteWithEmptyFilesArrayThrowsHandlerException(): void
+    {
+        $this->expectException(HandlerException::class);
+        $this->expectExceptionCode(HandlerException::CODE_EXECUTE);
+        $handler = new MergeHandler();
+        $handler->setBinPath($this->getEnv('GS_BIN_PATH'));
+        $handler->execute(dirname(__DIR__, 2) . '/files/merge', 'res.pdf', []);
+    }
+
+    /**
+     * @return void
+     */
+    public function testExecuteWithAllInvalidFilesThrowsHandlerException(): void
+    {
+        $this->expectException(HandlerException::class);
+        $this->expectExceptionCode(HandlerException::CODE_EXECUTE);
+        $handler = new MergeHandler();
+        $handler->setBinPath($this->getEnv('GS_BIN_PATH'));
+        $handler->execute(dirname(__DIR__, 2) . '/files/merge', 'res.pdf', [
+            dirname(__DIR__, 2) . '/files/merge/nonexistent1.pdf',
+            dirname(__DIR__, 2) . '/files/merge/nonexistent2.pdf',
+        ]);
+    }
+
+    /**
+     * @return void
+     */
+    public function testExecuteWithOnlyOneValidFileMergesSuccessfully(): void
+    {
+        $path = dirname(__DIR__, 2) . '/files/merge';
+        $handler = new MergeHandler();
+        $handler->setBinPath($this->getEnv('GS_BIN_PATH'));
+        $result = $handler->execute($path, 'single.pdf', [
+            dirname(__DIR__, 2) . '/files/merge/part_1.pdf',
+            dirname(__DIR__, 2) . '/files/merge/nonexistent.pdf',
+        ]);
+        $this->assertFileExists($result);
+    }
 }
diff --git a/tests/Handlers/SplitHandlerTest.php b/tests/Handlers/SplitHandlerTest.php
index ad35fc1..e217850 100644
--- a/tests/Handlers/SplitHandlerTest.php
+++ b/tests/Handlers/SplitHandlerTest.php
@@ -42,4 +42,58 @@ public function testExecuteFailedShouldShouldThrowHandlerException(): void
         ]);
         $handler->execute(dirname(__DIR__, 2) . '/files/split/test.pdf', '/tmp/mock/files');
     }
+
+    /**
+     * @return void
+     */
+    public function testSplitOutputFilesStartAtPartOne(): void
+    {
+        $handler = new SplitHandler();
+        $handler->setBinPath($this->getEnv('GS_BIN_PATH'));
+        $outputPath = sys_get_temp_dir() . '/gs_split_test_' . uniqid();
+        $parts = $handler->execute(dirname(__DIR__, 2) . '/files/split/test.pdf', $outputPath);
+
+        $this->assertCount(3, $parts);
+        $this->assertStringEndsWith('/part_1.pdf', $parts[0]);
+        $this->assertStringEndsWith('/part_2.pdf', $parts[1]);
+        $this->assertStringEndsWith('/part_3.pdf', $parts[2]);
+    }
+
+    /**
+     * @return void
+     */
+    public function testSplitOutputFilesAreCreated(): void
+    {
+        $handler = new SplitHandler();
+        $handler->setBinPath($this->getEnv('GS_BIN_PATH'));
+        $outputPath = sys_get_temp_dir() . '/gs_split_test_' . uniqid();
+        $parts = $handler->execute(dirname(__DIR__, 2) . '/files/split/test.pdf', $outputPath);
+
+        foreach ($parts as $part) {
+            $this->assertFileExists($part);
+        }
+    }
+
+    /**
+     * @return void
+     */
+    public function testExecuteWithNonExistentFileThrowsHandlerException(): void
+    {
+        $this->expectException(HandlerException::class);
+        $this->expectExceptionCode(HandlerException::CODE_EXECUTE);
+        $handler = new SplitHandler();
+        $handler->setBinPath($this->getEnv('GS_BIN_PATH'));
+        $handler->execute('/nonexistent/file.pdf', sys_get_temp_dir());
+    }
+
+    /**
+     * @return void
+     */
+    public function testExecuteWithEmptyFilePathThrowsHandlerException(): void
+    {
+        $this->expectException(HandlerException::class);
+        $handler = new SplitHandler();
+        $handler->setBinPath($this->getEnv('GS_BIN_PATH'));
+        $handler->execute('', sys_get_temp_dir());
+    }
 }
diff --git a/tests/Handlers/ToImageHandlerTest.php b/tests/Handlers/ToImageHandlerTest.php
index af50a34..e575654 100644
--- a/tests/Handlers/ToImageHandlerTest.php
+++ b/tests/Handlers/ToImageHandlerTest.php
@@ -63,4 +63,43 @@ public function testExecuteFailedShouldThrowHandlerException(): void
         ]);
         $handler->execute(dirname(__DIR__, 2) . '/files/to-image/test.pdf', '/tmp/mock/files');
     }
+
+    /**
+     * @return void
+     */
+    public function testExecuteWithInvalidImageTypeThrowsHandlerException(): void
+    {
+        $this->expectException(HandlerException::class);
+        $this->expectExceptionCode(HandlerException::CODE_EXECUTE);
+        $handler = new ToImageHandler();
+        $handler->setBinPath($this->getEnv('GS_BIN_PATH'));
+        $handler->execute(
+            dirname(__DIR__, 2) . '/files/to-image/test.pdf',
+            sys_get_temp_dir(),
+            'bmp'
+        );
+    }
+
+    /**
+     * @return void
+     */
+    public function testExecuteWithEmptyFilePathThrowsHandlerException(): void
+    {
+        $this->expectException(HandlerException::class);
+        $handler = new ToImageHandler();
+        $handler->setBinPath($this->getEnv('GS_BIN_PATH'));
+        $handler->execute('', sys_get_temp_dir(), 'jpeg');
+    }
+
+    /**
+     * @return void
+     */
+    public function testExecuteWithNonExistentFileThrowsHandlerException(): void
+    {
+        $this->expectException(HandlerException::class);
+        $this->expectExceptionCode(HandlerException::CODE_EXECUTE);
+        $handler = new ToImageHandler();
+        $handler->setBinPath($this->getEnv('GS_BIN_PATH'));
+        $handler->execute('/nonexistent/file.pdf', sys_get_temp_dir(), 'jpeg');
+    }
 }
diff --git a/tests/Helpers/PathHelperTest.php b/tests/Helpers/PathHelperTest.php
index f7b58ea..03e1964 100644
--- a/tests/Helpers/PathHelperTest.php
+++ b/tests/Helpers/PathHelperTest.php
@@ -14,4 +14,48 @@ public function testPathShouldEqualOriginPathAfterConversion(): void
     {
         $this->assertEquals(implode(DIRECTORY_SEPARATOR, ['usr', 'bin', 'gs']), PathHelper::convertPathSeparator('usr/bin/gs'));
     }
+
+    /**
+     * @return void
+     */
+    public function testEmptyStringReturnsEmptyString(): void
+    {
+        $this->assertEquals('', PathHelper::convertPathSeparator(''));
+    }
+
+    /**
+     * @return void
+     */
+    public function testBackslashesAreConverted(): void
+    {
+        $result = PathHelper::convertPathSeparator('usr\\bin\\gs');
+        $this->assertEquals(implode(DIRECTORY_SEPARATOR, ['usr', 'bin', 'gs']), $result);
+    }
+
+    /**
+     * @return void
+     */
+    public function testMixedSeparatorsAreNormalized(): void
+    {
+        $result = PathHelper::convertPathSeparator('usr/bin\\gs');
+        $this->assertEquals(implode(DIRECTORY_SEPARATOR, ['usr', 'bin', 'gs']), $result);
+    }
+
+    /**
+     * @return void
+     */
+    public function testAlreadyNormalizedPathIsUnchanged(): void
+    {
+        $path = implode(DIRECTORY_SEPARATOR, ['usr', 'bin', 'gs']);
+        $this->assertEquals($path, PathHelper::convertPathSeparator($path));
+    }
+
+    /**
+     * @return void
+     */
+    public function testPathWithSpacesIsPreserved(): void
+    {
+        $result = PathHelper::convertPathSeparator('path/with spaces/file.pdf');
+        $this->assertEquals(implode(DIRECTORY_SEPARATOR, ['path', 'with spaces', 'file.pdf']), $result);
+    }
 }