diff --git a/Tests/Observer/ObserverTest.php b/Tests/Observer/ObserverTest.php
new file mode 100644
index 0000000..79bf61a
--- /dev/null
+++ b/Tests/Observer/ObserverTest.php
@@ -0,0 +1,53 @@
+<?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();
+    }
+
+    public function testNotify()
+    {
+        $this->expectOutputString('DesignPatterns\Observer\User has been updated');
+        $subject = new User();
+
+        $subject->attach($this->observer);
+        $subject->property = 123;
+    }
+
+    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);
+    }
+
+    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