diff --git a/composer.json b/composer.json
index 48a8c4f..122e2d2 100644
--- a/composer.json
+++ b/composer.json
@@ -28,7 +28,8 @@
         "symfony/expression-language": "^2.7"
     },
     "require-dev": {
-        "phpunit/phpunit": "4.8.*"
+        "phpunit/phpunit": "4.8.*",
+        "mikey179/vfsStream": "^1.0"
     },
     "bin": ["bin/deprecation-detector"],
     "autoload": {
diff --git a/composer.lock b/composer.lock
index 47f7c65..3124a7c 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,9 +4,55 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#composer-lock-the-lock-file",
         "This file is @generated automatically"
     ],
-    "hash": "9e6c3b0f18e1265f8887eac427da82fc",
-    "content-hash": "13a91fb9ffa68f2ba28c400a08e6baed",
+    "hash": "2fd97b5f4aab66649dd2d818e5d51a5b",
+    "content-hash": "6e15ef62add11bbfee0cbe056d7f67f0",
     "packages": [
+        {
+            "name": "mikey179/vfsStream",
+            "version": "v1.6.0",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/mikey179/vfsStream.git",
+                "reference": "73bcb605b741a7d5044b47592338c633788b0eb7"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/mikey179/vfsStream/zipball/73bcb605b741a7d5044b47592338c633788b0eb7",
+                "reference": "73bcb605b741a7d5044b47592338c633788b0eb7",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=5.3.0"
+            },
+            "require-dev": {
+                "phpunit/phpunit": "~4.5"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "1.6.x-dev"
+                }
+            },
+            "autoload": {
+                "psr-0": {
+                    "org\\bovigo\\vfs\\": "src/main/php"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "BSD-3-Clause"
+            ],
+            "authors": [
+                {
+                    "name": "Frank Kleine",
+                    "homepage": "http://frankkleine.de/",
+                    "role": "Developer"
+                }
+            ],
+            "description": "Virtual file system to mock the real file system in unit tests.",
+            "homepage": "http://vfs.bovigo.org/",
+            "time": "2015-10-06 16:59:57"
+        },
         {
             "name": "nikic/php-parser",
             "version": "v1.4.1",
diff --git a/tests/RuleSet/Loader/FileLoaderTest.php b/tests/RuleSet/Loader/FileLoaderTest.php
index 6a39d08..232e736 100644
--- a/tests/RuleSet/Loader/FileLoaderTest.php
+++ b/tests/RuleSet/Loader/FileLoaderTest.php
@@ -2,14 +2,14 @@
 
 namespace SensioLabs\DeprecationDetector\Tests\RuleSet\Loader;
 
+use org\bovigo\vfs\vfsStream;
+use SensioLabs\DeprecationDetector\RuleSet\RuleSet;
+
 class FileLoaderTest extends \PHPUnit_Framework_TestCase
 {
     public function testClassIsInitializable()
     {
-        $dispatcher = $this->prophesize('Symfony\Component\EventDispatcher\EventDispatcher');
-        $loader = new \SensioLabs\DeprecationDetector\RuleSet\Loader\FileLoader($dispatcher->reveal());
-
-        $this->assertInstanceOf('SensioLabs\DeprecationDetector\RuleSet\Loader\FileLoader', $loader);
+        $this->assertInstanceOf('SensioLabs\DeprecationDetector\RuleSet\Loader\FileLoader', $this->getInstance());
     }
 
     /**
@@ -18,15 +18,44 @@ public function testClassIsInitializable()
      */
     public function testLoadingNotExistingFileThrowsAnException()
     {
-        $dispatcher = $this->prophesize('Symfony\Component\EventDispatcher\EventDispatcher');
-        $loader = new \SensioLabs\DeprecationDetector\RuleSet\Loader\FileLoader($dispatcher->reveal());
-
-        $loader->loadRuleSet('no_such.file');
+        $this->getInstance()->loadRuleSet('no_such.file');
     }
 
+    /**
+     * @expectedException \RuntimeException
+     * @expectedExceptionMessage Rule set file is not valid.
+     */
     public function testLoadRuleSetThrowsExceptionIfCachedIsNotAnInstanceOfRuleset()
     {
-        //@TODO: file_get_contents is untestable
-        $this->markTestSkipped();
+        $dummy = 'This is not a RuleSet';
+
+        $root = vfsStream::setup();
+        $virtualFile = vfsStream::newFile('dummy')
+            ->withContent(serialize($dummy))
+            ->at($root);
+
+        $this->getInstance()->loadRuleSet($virtualFile->url());
+    }
+
+    public function testLoadRuleSetSuccess()
+    {
+        $ruleSet = new RuleSet();
+
+        $root = vfsStream::setup();
+        $virtualFile = vfsStream::newFile('ruleSet')
+            ->withContent(serialize($ruleSet))
+            ->at($root);
+
+        $loader = $this->getInstance();
+
+        $actualRuleSet = $loader->loadRuleSet($virtualFile->url());
+
+        $this->assertInstanceOf('\SensioLabs\DeprecationDetector\RuleSet\RuleSet', $actualRuleSet);
+    }
+
+    protected function getInstance()
+    {
+        $dispatcher = $this->prophesize('Symfony\Component\EventDispatcher\EventDispatcher');
+        return new \SensioLabs\DeprecationDetector\RuleSet\Loader\FileLoader($dispatcher->reveal());
     }
 }