diff --git a/pm-convert b/pm-convert
index 1168f11..6a9ae06 100755
--- a/pm-convert
+++ b/pm-convert
@@ -1,7 +1,7 @@
 #!/usr/bin/env php
 <?php
 
-declare(strict_types = 1);
+declare(strict_types=1);
 
 use PmConverter\Processor;
 
@@ -20,8 +20,13 @@ foreach ($paths as $path) {
 
 is_null($file) && throw new RuntimeException('Unable to locate autoload.php file.');
 
+$processor = new Processor($argv);
 try {
-    (new Processor($argv))->convert();
+    $processor->convert();
+} catch (InvalidArgumentException $e) {
+    fwrite(STDERR, sprintf('ERROR: %s%s', $e->getMessage(), PHP_EOL));
+    print(implode(PHP_EOL, $processor->usage()));
+    die(1);
 } catch (Exception $e) {
     fwrite(STDERR, sprintf('ERROR: %s%s', $e->getMessage(), PHP_EOL));
     die(1);
diff --git a/src/FileSystem.php b/src/FileSystem.php
index c137425..1a63685 100644
--- a/src/FileSystem.php
+++ b/src/FileSystem.php
@@ -1,6 +1,6 @@
 <?php
 
-declare(strict_types = 1);
+declare(strict_types=1);
 
 namespace PmConverter;
 
diff --git a/src/Processor.php b/src/Processor.php
index b99a4d4..df720b4 100644
--- a/src/Processor.php
+++ b/src/Processor.php
@@ -22,7 +22,7 @@ class Processor
     /**
      * Converter version
      */
-    public const VERSION = '1.2.0';
+    public const VERSION = '1.2.1';
 
     /**
      * @var string[] Paths to collection files
@@ -167,6 +167,9 @@ class Processor
         if (empty($this->collectionPaths)) {
             throw new InvalidArgumentException('there are no collections to convert');
         }
+        if (empty($this->outputPath)) {
+            throw new InvalidArgumentException('-o is required');
+        }
         if (empty($this->formats)) {
             $this->formats = [ConvertFormat::Http->name => ConvertFormat::Http];
         }
@@ -285,7 +288,7 @@ class Processor
     /**
      * @return string[]
      */
-    protected function version(): array
+    public function version(): array
     {
         return ["Postman collection converter v" . self::VERSION];
     }
@@ -293,7 +296,7 @@ class Processor
     /**
      * @return string[]
      */
-    protected function copyright(): array
+    public function copyright(): array
     {
         return [
             'Anthony Axenov (c) ' . date('Y') . ", MIT license",
@@ -304,7 +307,7 @@ class Processor
     /**
      * @return array
      */
-    protected function usage(): array
+    public function usage(): array
     {
         return array_merge($this->version(), [
             'Usage:',