diff --git a/.travis.yml b/.travis.yml
index 3dccb0c09..9ce1c2496 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -30,7 +30,7 @@ before_script:
     - cd tests
 
 # run unit tests, create result file
-script: ../vendor/bin/phpunit --configuration phpunit.xml --coverage-text --coverage-clover=coverage.clover
+script: ../vendor/bin/phpunit --verbose --debug  --configuration phpunit.xml --coverage-text --coverage-clover=coverage.clover
 
 # gets tools from Scrutinizer, uploads unit tests results to Scrutinizer (?)
 after_script:
diff --git a/application/core/Auth.php b/application/core/Auth.php
index 10430b14a..84761fe7d 100644
--- a/application/core/Auth.php
+++ b/application/core/Auth.php
@@ -72,7 +72,7 @@ public static function checkAdminAuthentication()
      */
     public static function checkSessionConcurrency(){
         if(Session::userIsLoggedIn()){
-            if(Session::isConcurrentSessionExists()){
+            if(Session::isSessionBroken()){
                 LoginModel::logout();
                 Redirect::home();
                 exit();
diff --git a/application/core/Session.php b/application/core/Session.php
index 89d64c6ef..a489a6ec5 100644
--- a/application/core/Session.php
+++ b/application/core/Session.php
@@ -84,8 +84,10 @@ public static function updateSessionId($userId, $sessionId = null)
     }
 
     /**
-     * checks for session concurrency
-     *
+     * checks for broken session 
+     * Session could be broken by Session concurrency or when user is deleted / suspended
+     * 
+     * - Session concurrency is done as the following:
      * This is done as the following:
      * UserA logs in with his session id('123') and it will be stored in the database.
      * Then, UserB logs in also using the same email and password of UserA from another PC,
@@ -94,6 +96,9 @@ public static function updateSessionId($userId, $sessionId = null)
      * Now, Whenever UserA performs any action,
      * You then check the session_id() against the last one stored in the database('456'),
      * If they don't match then log both of them out.
+     * 
+     * - Check for deleted / suspended users:
+     * Suspended/deleted users have no userSessionId anymore stored in database
      *
      * @access public
      * @static static method
@@ -101,7 +106,7 @@ public static function updateSessionId($userId, $sessionId = null)
      * @see Session::updateSessionId()
      * @see http://stackoverflow.com/questions/6126285/php-stop-concurrent-user-logins
      */
-    public static function isConcurrentSessionExists()
+    public static function isSessionBroken()
     {
         $session_id = session_id();
         $userId     = Session::get('user_id');
@@ -117,7 +122,7 @@ public static function isConcurrentSessionExists()
             $result = $query->fetch();
             $userSessionId = !empty($result)? $result->session_id: null;
 
-            return $session_id !== $userSessionId;
+            return empty($userSessionId) || $session_id !== $userSessionId;
         }
 
         return false;
diff --git a/tests/core/ConfigTest.php b/tests/core/ConfigTest.php
index 11dae0508..fe20047d4 100644
--- a/tests/core/ConfigTest.php
+++ b/tests/core/ConfigTest.php
@@ -23,9 +23,14 @@ public function tearDown()
 
     /**
      * Checks if the correct config file for an EXISTING environment / config is called.
+	 * 
+     * @runInSeparateProcess
      */
 	public function testGetDefaultEnvironment()
 	{
+		// for testing
+		header_remove(); 
+
         // manually set environment to "development"
 		putenv('APPLICATION_ENV=development');
 
@@ -33,8 +38,14 @@ public function testGetDefaultEnvironment()
 		$this->assertEquals('index', Config::get('DEFAULT_ACTION'));
 	}
 
+    /**
+     * @runInSeparateProcess
+     */
 	public function testGetFailingEnvironment()
 	{
+		// for testing
+		header_remove(); 
+
         // manually set environment to "foobar" (and non-existing environment)
 		putenv('APPLICATION_ENV=foobar');
 
diff --git a/tests/core/EnvironmentTest.php b/tests/core/EnvironmentTest.php
index a6d32cf72..462144b85 100644
--- a/tests/core/EnvironmentTest.php
+++ b/tests/core/EnvironmentTest.php
@@ -4,14 +4,12 @@ class EnvironmentTest extends PHPUnit_Framework_TestCase
 {
 	public function testGetDefault()
 	{
-		// call for environment should return "development"
-		$this->assertEquals('development', Environment::get());
-	}
+		// call for environment should return "testing" like set in .travis.yml
+		$this->assertEquals('testing', Environment::get());
 
-	public function testGetDevelopment()
-	{
-		putenv('APPLICATION_ENV=development');
-		// call for environment should return "development"
+		putenv('APPLICATION_ENV=');
+
+		// call for environment should now return "development", the default value
 		$this->assertEquals('development', Environment::get());
 	}
 
@@ -20,4 +18,12 @@ public function testGetProduction()
 		putenv('APPLICATION_ENV=production');
 		$this->assertEquals('production', Environment::get());
 	}
+
+	public function testGetDevelopment()
+	{
+		putenv('APPLICATION_ENV=development');
+		// call for environment should return "development"
+		$this->assertEquals('development', Environment::get());
+	}
+	
 }