ActiveRecord Validation not working

you should get the error when you try to save, something like so:

def create
  @model = MyModel.new(params[:my_model])
  if @model.save
    flash[:notice] = 'Success'
    redirect_to :some_action
  else
    flash[:error] = 'Error'
    render :action => :new
  end
end

then typically in your view you'd show the errors:
<%= error_messages_for :my_model %>