diff --git a/spec/models/user_spec.rb b/spec/models/user_spec.rb
--- a/spec/models/user_spec.rb
+++ b/spec/models/user_spec.rb
@@ -48,7 +48,48 @@
   it "should not accept invalid activation key" do
     @john.verify_activation_key("12345").should == false
   end
-  
+end
+
+describe User, "when re-register with the same e-mail" do
+
+  before(:each) do
+    @mary_email = 'mary@in.th'
+    
+    @time_first_register = Time.local(2008,5,10,9,00).gmtime
+
+    @mary_first = mock_model(User, 
+                             :login => 'mary1', 
+                             :password => 'hello', 
+                             :email => @mary_email,
+                             :created_at => @time_first_register)
+    @mary_second = User.new(:login => 'mary2', 
+                            :password => 'hello', 
+                            :email => @mary_email)
+    User.stub!(:find_by_email).
+      with(@mary_email, {:order => "created_at DESC"}).
+      and_return(@mary_first)
+  end
+
+  class User
+    public :enough_time_interval_between_same_email_registrations
+  end
+
+  it "should not be allowed if the time interval is less than 5 mins" do
+    time_now = @time_first_register + 4.minutes
+    Time.stub!(:now).and_return(time_now)
+
+    @mary_second.enough_time_interval_between_same_email_registrations
+    @mary_second.errors.length.should_not be_zero
+  end
+
+  it "should be allowed if the time interval is more than 5 mins" do
+    time_now = @time_first_register + 6.minutes
+    Time.stub!(:now).and_return(time_now)
+
+    @mary_second.enough_time_interval_between_same_email_registrations
+    @mary_second.errors.length.should be_zero
+  end
+
 end
 
 describe User, "as a class" do