diff --git a/.scrutinizer.yml b/.scrutinizer.yml
index 28afb6e..41fdf94 100644
--- a/.scrutinizer.yml
+++ b/.scrutinizer.yml
@@ -11,10 +11,13 @@ build:
     environment:
         php:
             version: "7.0.4"
-#    tests:
-#        override:
-#            -
-#                command: "php bin/phpunit -c phpunit.xml --colors=always --verbose --coverage-clover=coverage.xml"
-#                coverage:
-#                    file: "coverage.xml"
-#                    format: "php-clover"
+    tests:
+        override:
+            -
+                command: "composer validate"
+        override:
+            -
+                command: "php bin/phpunit -c phpunit.xml --colors=always --verbose --coverage-clover=coverage.xml"
+                coverage:
+                    file: "coverage.xml"
+                    format: "php-clover"
diff --git a/composer.json b/composer.json
index 4c5663d..f6d9c17 100644
--- a/composer.json
+++ b/composer.json
@@ -19,8 +19,11 @@
     },
     "autoload-dev": {
         "psr-4": {
-            "EM\\Tests\\CssCompiler\\": "tests/"
-        }
+            "EM\\Tests\\PHPUnit\\": "tests/phpunit"
+        },
+        "classmap": [
+            "tests/shared-enviroment/IntegrationTestSuite.php"
+        ]
     },
     "config": {
         "bin-dir": "bin/"
diff --git a/src/Container/File.php b/src/Container/File.php
index 4918c1e..9569cc7 100644
--- a/src/Container/File.php
+++ b/src/Container/File.php
@@ -11,7 +11,7 @@ class File
     const TYPE_SASS       = 'sass';
     const TYPE_SCSS       = 'scss';
     const TYPE_LESS       = 'less';
-    const SUPPORTED_TYPES = [
+    static $supportedTypes = [
         self::TYPE_COMPASS,
         self::TYPE_SASS,
         self::TYPE_SCSS,
@@ -179,7 +179,7 @@ protected function detectSourceTypeFromPath($path)
     {
         $extension = strtolower(pathinfo($path, PATHINFO_EXTENSION));
 
-        return in_array($extension, static::SUPPORTED_TYPES)
+        return in_array($extension, static::$supportedTypes)
             ? $extension
             : static::TYPE_UNKNOWN;
     }
diff --git a/src/Processor/Processor.php b/src/Processor/Processor.php
index 0983bd9..dc949c0 100644
--- a/src/Processor/Processor.php
+++ b/src/Processor/Processor.php
@@ -16,7 +16,7 @@ class Processor
     const FORMATTER_EXPANDED   = 'expanded';
     const FORMATTER_NESTED     = 'nested';
     const FORMATTER_COMPACT    = 'compact';
-    const SUPPORTED_FORMATTERS = [
+    static $supportedFormatters = [
         self::FORMATTER_COMPRESSED,
         self::FORMATTER_CRUNCHED,
         self::FORMATTER_EXPANDED,
@@ -167,8 +167,8 @@ public function processFile(File $file)
      */
     protected function getFormatterClass($formatter)
     {
-        if (!in_array($formatter, static::SUPPORTED_FORMATTERS)) {
-            throw new \InvalidArgumentException('unknown formatter, available options are: ' . print_r(static::SUPPORTED_FORMATTERS, true));
+        if (!in_array($formatter, static::$supportedFormatters)) {
+            throw new \InvalidArgumentException('unknown formatter, available options are: ' . print_r(static::$supportedFormatters, true));
         }
 
         return 'Leafo\\ScssPhp\\Formatter\\' . ucfirst($formatter);
diff --git a/tests/phpunit/ProcessorTest.php b/tests/phpunit/ProcessorTest.php
new file mode 100644
index 0000000..7edeec2
--- /dev/null
+++ b/tests/phpunit/ProcessorTest.php
@@ -0,0 +1,105 @@
+<?php
+
+namespace EM\Tests\PHPUnit;
+
+use Composer\IO\IOInterface;
+use EM\CssCompiler\Container\File;
+use EM\CssCompiler\Processor\Processor;
+use EM\Tests\Environment\IntegrationTestSuite;
+
+/**
+ * @see Processor
+ */
+class ProcessorTest extends IntegrationTestSuite
+{
+    protected $event;
+    protected $io;
+    protected $package;
+
+    protected function setUp()
+    {
+        $this->io = $this->getMockBuilder(IOInterface::class)->getMock();
+    }
+
+    /**
+     * @see Processor::attachFiles
+     * @test
+     */
+    public function attachFiles()
+    {
+        $paths = [
+            static::getSharedFixturesDirectory() . '/sass',
+            static::getSharedFixturesDirectory() . '/compass'
+        ];
+        $cacheDir = dirname(dirname(__DIR__)) . '/var/cache';
+
+        foreach ($paths as $path) {
+            $processor = new Processor($this->io);
+            $processor->attachFiles($path, $cacheDir);
+
+            $this->assertCount(2, $processor->getFiles());
+        }
+    }
+
+    /**
+     * @see Processor::attachFiles
+     * @test
+     *
+     * @expectedException \Exception
+     */
+    public function attachFilesExpectedException()
+    {
+        $path = static::getSharedFixturesDirectory() . '/do-not-exists';
+        $cacheDir = dirname(dirname(__DIR__)) . '/var/cache';
+
+        $processor = new Processor($this->io);
+        $processor->attachFiles($path, $cacheDir);
+
+        $this->assertCount(2, $processor->getFiles());
+    }
+
+    /**
+     * @see Processor::processFile
+     * @test
+     */
+    public function processFileSASS()
+    {
+        $file = (new File(static::getSharedFixturesDirectory() . '/compass/sass/layout.scss', ''))
+            ->setSourceContentFromSourcePath();
+
+        (new Processor($this->io))->processFile($file);
+
+        $this->assertNotEquals($file->getParsedContent(), $file->getSourceContent());
+    }
+
+    /**
+     * @see Processor::processFile
+     * @test
+     *
+     * @expectedException \EM\CssCompiler\Exception\CompilerException
+     */
+    public function processFileExpectedException()
+    {
+        $file = (new File(static::getSharedFixturesDirectory() . '/compass/sass/', ''))
+            ->setSourceContentFromSourcePath()
+            ->setType(File::TYPE_UNKNOWN);
+
+        (new Processor($this->io))->processFile($file);
+    }
+
+    /**
+     * @see Processor::getFormatterClass
+     * @test
+     */
+    public function getFormatterClass()
+    {
+        foreach (Processor::$supportedFormatters as $formatter) {
+            $expected = 'Leafo\\ScssPhp\\Formatter\\' . ucfirst($formatter);
+
+            $this->assertEquals(
+                $expected,
+                $this->invokeMethod(new Processor($this->io), 'getFormatterClass', [$formatter])
+            );
+        }
+    }
+}
diff --git a/tests/shared-enviroment/IntegrationTestSuite.php b/tests/shared-enviroment/IntegrationTestSuite.php
new file mode 100644
index 0000000..557ae00
--- /dev/null
+++ b/tests/shared-enviroment/IntegrationTestSuite.php
@@ -0,0 +1,57 @@
+<?php
+
+namespace EM\Tests\Environment;
+
+/**
+ * @since 0.1
+ */
+abstract class IntegrationTestSuite extends \PHPUnit_Framework_TestCase
+{
+    /**
+     * able to invoke any non-static of object and return the result and throws exceptions if so
+     *
+     * useful to used to invoke non-public method of the class
+     *
+     * @param mixed  $object
+     * @param string $methodName
+     * @param array  $methodArguments
+     *
+     * @return mixed
+     * @throws \Exception
+     */
+    protected function invokeMethod($object, $methodName, array $methodArguments = [])
+    {
+        $method = (new \ReflectionClass(get_class($object)))->getMethod($methodName);
+        $method->setAccessible(true);
+
+        return $method->invokeArgs($object, $methodArguments);
+    }
+
+    /**
+     * @return string
+     */
+    public static function getRootDirectory()
+    {
+        return dirname(__DIR__);
+    }
+
+    /**
+     * @return string
+     */
+    public static function getSharedFixturesDirectory()
+    {
+        return static::getRootDirectory() . '/shared-fixtures';
+    }
+
+    /**
+     * return content of the file in located in tests/shared-fixtures directory
+     *
+     * @param string $filename
+     *
+     * @return string
+     */
+    public static function getSharedFixtureContent(string $filename)
+    {
+        return file_get_contents(static::getSharedFixturesDirectory() . "/$filename");
+    }
+}
diff --git a/tests/shared-fixtures/composer.phpunit.json b/tests/shared-fixtures/composer.phpunit.json
new file mode 100644
index 0000000..e7e11de
--- /dev/null
+++ b/tests/shared-fixtures/composer.phpunit.json
@@ -0,0 +1,35 @@
+{
+    "name": "eugene-matvejev/css-compiler",
+    "description": "compiles SASS and LESS assets on composer's callback",
+    "type": "lib",
+    "license": "MIT",
+    "authors": [
+        {
+            "name": "Eugene Matvejev",
+            "email": "eugene.matvejev@gmail.com"
+        }
+    ],
+    "autoload": {
+        "psr-4": {
+            "EM\\CssCompiler\\": "src/"
+        },
+        "classmap": [
+            "ScriptHandler.php"
+        ]
+    },
+    "autoload-dev": {
+        "psr-4": {
+            "EM\\Tests\\CssCompiler\\": "tests/"
+        }
+    },
+    "require": {
+        "php": ">= 5.6",
+        "leafo/lessphp": "^0.5",
+        "leafo/scssphp": "@dev",
+        "leafo/scssphp-compass": "@dev"
+    },
+    "require-dev": {
+        "composer/composer": "^1.1",
+        "phpunit/phpunit": "^5.3"
+    }
+}