diff --git a/Observer/Observer.php b/Observer/User.php
similarity index 64%
rename from Observer/Observer.php
rename to Observer/User.php
index 1cb07dc..3b41867 100644
--- a/Observer/Observer.php
+++ b/Observer/User.php
@@ -1,30 +1,16 @@
 <?php
 
-namespace DesignPatterns;
+namespace DesignPatterns\Observer;
 
 /**
- * Observer pattern
- *
- * Purpose:
- * to implement a publish/subscribe behaviour to an object, whenever a "Subject" object changes it's state, the attached
- * "Observers" will be notified. It is used to shorten the amount of coupled objects and uses loose coupling instead
- *
- * Examples:
- * - a message queue system is observed to show the progress of a job in a GUI
- *
- * PHP already defines two interfaces that can help to implement this pattern: SplObserver and SplSubject
+ * Observer pattern : The observed object (the subject)
+ * 
+ * The subject maintains a list of Observers and sends notifications.
  *
  */
-class UserObserver implements \SplObserver
-{
-    public function update(\SplSubject $subject)
-    {
-        echo get_class($subject) . ' has been updated';
-    }
-}
-
 class User implements \SplSubject
 {
+
     protected $_data = array();
 
     /**
@@ -86,9 +72,6 @@ class User implements \SplSubject
         // notify the observers, that user has been updated
         $this->notify();
     }
+
 }
 
-$user = new User();
-$user->attach(new UserObserver());
-
-$user->notify();
diff --git a/Observer/UserObserver.php b/Observer/UserObserver.php
new file mode 100644
index 0000000..3cb8b9a
--- /dev/null
+++ b/Observer/UserObserver.php
@@ -0,0 +1,32 @@
+<?php
+
+namespace DesignPatterns\Observer;
+
+/**
+ * Observer pattern
+ *
+ * Purpose:
+ * to implement a publish/subscribe behaviour to an object, whenever a "Subject" object changes it's state, the attached
+ * "Observers" will be notified. It is used to shorten the amount of coupled objects and uses loose coupling instead
+ *
+ * Examples:
+ * - a message queue system is observed to show the progress of a job in a GUI
+ *
+ * PHP already defines two interfaces that can help to implement this pattern: SplObserver and SplSubject
+ *
+ */
+class UserObserver implements \SplObserver
+{
+
+    /**
+     * This is the only method to implement as an observer.
+     * It is called by the Subject (usually by SplSubject::notify() )
+     * 
+     * @param \SplSubject $subject
+     */
+    public function update(\SplSubject $subject)
+    {
+        echo get_class($subject) . ' has been updated';
+    }
+
+}
diff --git a/Tests/Observer/ObserverTest.php b/Tests/Observer/ObserverTest.php
new file mode 100644
index 0000000..7c12bc8
--- /dev/null
+++ b/Tests/Observer/ObserverTest.php
@@ -0,0 +1,62 @@
+<?php
+
+namespace DesignPatterns\Tests\Observer;
+
+use DesignPatterns\Observer\UserObserver;
+use DesignPatterns\Observer\User;
+
+/**
+ * ObserverTest tests the Observer pattern
+ */
+class ObserverTest extends \PHPUnit_Framework_TestCase
+{
+
+    protected $observer;
+
+    protected function setUp()
+    {
+        $this->observer = new UserObserver();
+    }
+
+    /**
+     * Tests the notification
+     */
+    public function testNotify()
+    {
+        $this->expectOutputString('DesignPatterns\Observer\User has been updated');
+        $subject = new User();
+
+        $subject->attach($this->observer);
+        $subject->property = 123;
+    }
+
+    /**
+     * Tests the subscribing
+     */
+    public function testAttachDetach()
+    {
+        $subject = new User();
+        $this->assertAttributeEmpty('_observers', $subject);
+        $subject->attach($this->observer);
+        $this->assertAttributeNotEmpty('_observers', $subject);
+        $subject->detach($this->observer);
+        $this->assertAttributeEmpty('_observers', $subject);
+    }
+
+    /**
+     * Tests the update() invocation on a mockup
+     */
+    public function testUpdateCalling()
+    {
+        $subject = new User();
+        $observer = $this->getMock('SplObserver');
+        $subject->attach($observer);
+
+        $observer->expects($this->once())
+                ->method('update')
+                ->with($subject);
+
+        $subject->notify();
+    }
+
+}
\ No newline at end of file