diff --git a/lib/user.rb b/lib/user.rb
index d9ad86a..e7b9a1d 100644
--- a/lib/user.rb
+++ b/lib/user.rb
@@ -1,10 +1,26 @@
 module Application
   class User
+    attr_reader :username
     def initialize(username, name, job)
       @username = username
       @name = name
       @job = job
       @observers = []
     end
+
+    def subscribe(observer)
+      @observers << observer
+    end
+
+    def update(key, value)
+      instance_variable_set("@#{key}".to_sym, value)
+      @observers.each { |o| o.updated self }
+    end
+  end
+
+  class UserObserver
+    def updated(context)
+      print context.username
+    end
   end
 end
diff --git a/spec/anything_spec.rb b/spec/anything_spec.rb
index 860a162..4d784a5 100644
--- a/spec/anything_spec.rb
+++ b/spec/anything_spec.rb
@@ -5,17 +5,22 @@
 
 module Application
   describe User do
-    let(:user) { User.new "josemotanet", "Jose Mota", "Software Designer" }
+    let(:user) { User.new 'josemotanet', 'Jose Mota', 'Software Designer' }
 
     it 'notifies observers on changes to user' do
       observer = double
-      allow(observer).to receive(:updated).with(:username, "Josemota").and_return(nil)
-
+      allow(observer).to receive(:updated).with(user).and_return(nil)
 
       user.subscribe(observer)
       user.update(:username, "josemota")
 
-      expect(observer).to have_received(:updated).with("josemota")
+      expect(observer).to have_received(:updated).with(user)
+    end
+
+    it 'prints the changed value' do
+      observer = UserObserver.new
+      user.subscribe(observer)
+      expect{ user.update(:username, "josemota") }.to output("josemota").to_stdout
     end
   end
 end