attribute_normalizer_spec.rb

#...
# Added in your example and it passed without your pull request.
describe 'will perform its actions before type cast' do

  before do
    User.class_eval do
      normalize_attribute :price do |value|
        value.to_s.gsub(",",".").to_f
      end
    end
  end

  { '44,8' => 44.8 }.each do |key, value|
    it "should normalize '#{key}' to '#{value}'" do
      user = User.new(:price => key)
      user.price.should == value
    end
  end

end

test_helper.rb

#...
# Added in the price column
ActiveRecord::Schema.define do
  create_table :users, :force => true do |t|
    t.string :name
    t.float  :price
  end
end
#...