Rails validations running against original record during update

I'm trying to figure out an inconsistency between what's happening in a functional test and what is happening in my development environment. I have a custom validation method unique_entry that is essentially a specialized version of validates_uniqueness_of. It looks like this:

def unique_entry
  matched_entry = Entry.first(:conditions => ['LOWER(field_one)开发者_运维技巧 = LOWER(?) AND LOWER(field_two) = LOWER(?)', self.field_one, self.field_two])
  errors.add_to_base('Duplicate detected') if matched_entry && (matched_entry.id != self.id)
end

The update action in the controller is very basic:

def update
  if @entry.update_attributes(params[:entry])
    flash.now[:success] = 'Success'
    render :action => 'show'
  else
    flash.now[:error] = 'Error'
    render :action => 'edit'
  end
end

This works just fine when I'm creating a new record. When I update a record, however, I get inconsistent behavior. If I test it from a browser in my development environment, it correctly renders the edit action with an error message, but in my functional test, it accepts the update as successful. Here is the test:

test "should not update entry and should render edit view if invalid update" do
  put :update, { :id => 1, :field_one => 'new_value', :field_two => 'new_value' } # 'new values' are the same as another existing record to trigger the duplication check
  assert_template :edit
  assert_not_nil flash[:error]
end

I looked at the test log and discovered that the values unique_entry is using are the record's original values instead of the values it should be attempting to update with. That is, the first line of unique_entry generates an SQL query like this:

SELECT * FROM "entries" WHERE (LOWER(field_one) = LOWER('original_value_of_field_one') AND LOWER(field_two) = LOWER('original_value_of_field_two')) LIMIT 1

What am I missing here? Why do my validations seem to be running against the original record instead of the new values only in the test environment?

In your test, shouldn't there be some reference to :entry, since that is what you are looking for in the controller params[:entry] ?