[Rails 3.2] validation on create not working

[Erwin]

class Place < ActiveRecord::Base

  validates :description, :presence => true

  validates :description, :uniqueness => {:case_sensitive => true, :on => :create }

  # also tried 

  # validates :description, :uniqueness => {:case_sensitive => true },  :on => :create

On update  ( in form fields, updated label,  same description )

params

{"event"=>{"place_attributes"=>{"label"=>"a very beautiful place", "description"=>"where you should go..."}}

@event.errors debugging

@messages={:"place.description"=>["has already been taken"]}>   !! uniqueness should not be checked ¿

thanks for any clue ..

[Colin Law]

I don't understand what is happening that is not as you expect.
Please try and explain in more detail.

Colin

[Erwin]

 the[SOLVED]   I thought uniqueness of :description was checked on record update even with :on => :create condition for validate...   

it was , but my functional  test was not an update ...

I was using 

post :update, :locale => I18n.locale, :id => @event_0[:id]

it MUST be

put :update, :locale => I18n.locale, :id => @event_0[:id]