Learning Ruby reimplementing it: attr_writer

This is how attr_writer may be (re)implemented:

module Kernel
  def attribute_writer(attribute)
    define_method("#{attribute}=".to_sym) do |value|
      instance_variable_set("@#{attribute}", value)

class MyClass
  attribute_writer :my_attribute

m = MyClass.new
m.my_attribute = 23

puts m.instance_variable_get "@my_attribute" # => 23

Learning Ruby reimplementing it: attr_reader

How handy is the attr_reader method? Very handy indeed.

Never asked yourself how it may be implemented? Just do it!

This is my take:

module Kernel
  def attribute_reader(attribute)
    define_method(attribute) do

class MyClass
  attribute_reader :my_attribute

m = MyClass.new
m.instance_variable_set("@my_attribute", 42)

puts m.my_attribute # => 42

What’s yours?

Have fun!

A Rails project file for Sublime Text 2

The simplest thing that you can do to open up the Sublime Text 2 editor on your Rails project is to just type in

$ subl .

on the Rails root directory¹.

A slightly better solution is to create a .sublime-project file in your project root directory, so that you may launch the editor with something like

$ subl --project my_rails_project.sublime-project

A question then arises, “How do I exclude useless directories as tmp or log from the project file?”

Answer: just edit the sublime-project file this way:

     "path": ".",
     "folder_exclude_patterns": ["tmp", "log"],
     "file_exclude_patterns": [".tmtags"]

(and of course you should adapt it to your actual preferences on what to exclude from your project).

Note that you can also specify a “file_exclude_patterns” property to filter out some files (in my case I wanted to exclude the ctag index file).

  1. to install the command line tool, just follow the docs here.

A review of “Great Bash” video by Carl Albing (O’Reilly Media)

Shell programming is a topic that every professional programmer should care about, and keep improving on, for several reasons.
Here are the first two I can think about:

  1. Because is essential in order to promote the automation of many manual processes (and automation is damn important!).
  2. Because I like to be a programmer as much as a devop, and I want to be able to deploy what I develop, and take care of all the operational and system stuff related to the system I contribute to build.

Me myself made the mistake of underestimate the relevance of this topic for way too time in the past: don’t make my same mistake :-)

Carl Albing’s “Great Bash” by O’Reilly Media is a collection of several short video lessons on the basics of the shell programming.

I watch the “Great Bash” lessons hoping to learn more about shell programming, but unfortunately Carl Albing’s video lessons are too introductory (IMHO).

It was nevertheless great to recap many things I learned here and there, and so my time watching it was not wasted at all, but I would recommend this video only to shell programmer beginners.

There are also some (really) minor defects in the technical way the video is recorded: the audio quality may be improved and sometimes the speaker take some long inexplicable pauses. But, that said, the overall quality is really good.

In the end I recommend to watch this video if you are a shell programmer beginner and you want to start understanding more about this topic.

Dynamically add data accessor methods on “static” Rails data model

An useful metaprogramming spell I recently played with is the Module#define_method(), which dynamically adds an instance method to the class on which is called.


I found it particularly useful to add data accessor methods on “static” Rails data model: suppose I’m working an e-commerce Rails webapp, and I have a Country model which maps the countries suitable for shipping, or a PaymentType model which represents all the possible payment types.

For these kind of models (and tables), which are typically static (they don’t change often), you often have to access specific values, say Country.italy or PaymentType.credit_card.

In these cases, defining dynamically an accessor method may be useful and more clear than always perform a find_by_name("my value").

So, for example, I open up my country.rb model class and add these lines

class << self
  Country.all.each do |each_country|
    define_method(each_country.name.downcase.gsub('.', '').gsub(' ', '_')) do

And then opening the Rails console I will be able to type

1.8.7@epistore > Country.sri_lanka
# {
                :id => 59,
              :zone => "U9",
           :enabled => true,
        :created_at => Tue, 20 Apr 2010 17:01:45 CEST +02:00,
        :updated_at => Tue, 20 Apr 2010 17:01:45 CEST +02:00,
          :iso_code => "LK",
    :country_set_id => nil

Just a note: as I said, Module#define_method() will add an instance method on the class. To add a class method, which is what I want, we have to use a different approach, using the class << self syntax to add a singleton method in the receiver.

I may also add a query method on each Country instance to check that country against another country (for example, I may ask my_country.italy?)

  Country.all.each do |each_country|
    define_method(each_country.name.downcase.gsub('.', '').gsub(' ', '_').concat('?')) do
      has_iso_code? each_country.iso_code

And then, after issuing a reload! command in the Rails console, I may type:

1.8.7@epistore > Country.usa.usa?
1.8.7@epistore > Country.usa.italy?
1.8.7@epistore > Country.usa.south_korea?
1.8.7@epistore > Country.south_korea.south_korea?

Depending on the kind of Rails app you have, these may be a useful tip.

assert_select_rjs reloaded!

If you ever dared to unit-test a Rails RJS action, for example something like this:
def my_ajax_action
   render(:update) do |page|
     page.replace_html 'shoppinglist', :partial => 'cart'
     page.replace_html 'items', :partial => 'layouts/items', :locals => { :cart => @cart }
you may already know and use the assert_select_rjs testing helper, which basically will verify the structure of your RJS response.

This testing method may really help you shortening the TDD feedback loop in an AJAX-based Rails webapp, and then you’ll may even be confident enough and save one or two brittle Selenium tests.

The only problem with assert_select_rjs is that is (IMHO) poorly documented and rarely googled about.
So, this is my turn to give back what we discovered.

If you have a Rails webapp using jQuery as javascript framework, you may have a hard time using assert_select_rjs correctly, and this is why:

for jQuery, this is the correct way to use assert_select_rjs:
assert_select_rjs :replace_html, '#shoppinglist'
it’s important the ‘#’ prefix here to refer to DOM element IDs, since the notation without ‘#’ will work only if your app uses Prototype.
Another nice thing to know is the way to make assertion on the selection matched by the assert_select_rjs.
For example, this code
assert_select_rjs :replace_html, '#shoppinglist' do
    assert_select '#shipping_cost_description', /Shipping costs for France/
    assert_select '#shipping_cost_value', /&euro; 12,30/
will verify that the section replaced inside the ‘shoppinglist’ element will match the two followings assetions.

My first test using webdriver (aka Selenium 2.0)!

As many say, a good solution to selenese flu is Webdriver (see more at http://code.google.com/p/selenium).

Webdriver has been accepted by the Selenium guys as the new approach to web application testing, opposed to the classical “selenium 1.0” approach, based on a javascript driver, which suffers from way too many issues.
Unfortunately, Selenium 2.0, which plan to fully support Webdriver, is still on an alpha release, and actually is very difficult to find ruby-based web testing tools supporting this alpha version of selenium 2.0.
One of those tools is actually Watir (though Webrat too is planning to support Selenium 2.0 sooner or later), and more precisely this project is quite stable to allow a first test drive.

So this is what I did:

First: installed required gems

  sudo gem install selenium-webdriver
  sudo gem install watir-webdriver --pre

Second: configure my Rails testing configuration to use watir

  config.gem "watir-webdriver"
  require 'test_help'
  require 'watir-webdriver'

Third: write a test

require 'test_helper'

class PaypalIntegrationTest < ActionController::IntegrationTest
  include LocaleHelper
  self.use_transactional_fixtures = false

  def setup
    ... some setup stuff here ...   
    @browser = Watir::Browser.new(:firefox)

  def teardown

  test "something interesting" do
    @browser.goto "https://developer.paypal.com/"
    @browser.text_field(:name, "login_email").set "my_test_account@sourcesense.com"
    @browser.text_field(:name, "login_password").set "mysecret"
    @browser.button(:name, "submit").click

    @browser.goto "https://localhost"

    @browser.link(:id, 'loginlink').click
    @browser.text_field(:name, "email").set @user.email
    @browser.text_field(:name, "password").set @user.password
    @browser.button(:text, "Login").click

    # add_a_product_to_cart
    product = Factory(:product, :code => "a code", :categories => [@juve_store])
    Factory(:product_variant, :code => "03", :availability => 99, :product => product)
    @browser.goto "https://localhost/frontend/products/show/#{product.id}"
    @browser.button(:id, "add_to_cart").click

    @browser.link(:text, "Checkout").click
    @browser.link(:id, "gotobuy").click

    # choose "Paypal"

    @browser.link(:id, "gotobuy").click

    sleep 5
    assert @browser.text.include?("Payment for order #{last_order_number()}")

    @browser.text_field(:name, "login_email").set "my_test_buyer@sourcesense.com"
    @browser.text_field(:name, "login_password").set "yetanothersecrethere"
    @browser.button(:text, "Accedi").click
    @browser.button(:text, "Paga ora").click

    sleep 5
    assert @browser.text.include?("Il pagamento è stato inviato")

    @browser.button(:id, "merchantReturn").click
    assert_contain_waiting("Your purchase")



  def last_order_number
    Order.last ? Order.last.number : ""


Some comments here:

  • This is a spike, so please don’t say this test is too long and not well refactored
  • I had to put two sleep calls in two places (I gotta say that this specific test, involving paypal sandbox, is really slow due to the slowness in the paypal response time).
  • Anyway, this alpha version of webdriver is still lacking: I cannot say wheather this is a problem I’ll have even with future (possibly more stable) version of Webdriver.

Some references:

A (still brief) experience on using Selenium to test a Rails + ajax app

This is a note to make a point on our (mine and my team’s) current use of Selenium to test the ajax behaviour in the Rails webapp we’re currently developing. Ajax replacing of part of the page is growing, and with it we have to face the classical question: “how do we test (I mean automatically :-) the ajax/javascript behaviours in our webapp?”.

This is how we are trying to manage this issue now, after some days of spiking on Selenium, Watir and BlueRidge (I hope to write more on Watir and BlueRidge in some future post, because these two tools are worth speaking).

Actually we are giving a try to the combination of Webrat + Selenium, since we already have a big test suite of integration test using Webrat, and have a good knowledge of the Webrat API.

We added the selenium-client gem to be able to drive Selenium through the Webrat API.
This is extracted from our test environment configuration file:

config.gem 'selenium-client', :lib => 'selenium/client'
config.gem "webrat", :version => '>= 0.6.0'

Then, we defined a class from which all the selenium test cases will inherit.
This class basically is used to

  • disable the transactional fixtures in Rails, to allow the browser process where Selenium runs to access the data prepared in the tests
  • configure Webrat with the “selenium” mode
  • be the place to collect helper methods as “login” or “logout”, used in many tests.
class SeleniumIntegrationTest < ActionController::IntegrationTest
  self.use_transactional_fixtures = false

  setup :switch_webrat_to_selenium
  def switch_webrat_to_selenium
    Webrat.configure do |config|
      config.mode = :selenium
      config.application_environment = :test

    selenium.set_speed(100)       # default is 0 ms
    selenium.set_timeout(10000)   # default is 30000 ms

  teardown :delete_cookies
  def delete_cookies

 [other helper methods here, like login, logout, and so on...]


We also added a rake task to be able to launch all the selenium tests

namespace :test do

  desc "Run Selenium Test"
  Rake::TestTask.new(:selenium) do |t|
    t.libs << "test"
    t.test_files = FileList['test/selenium/*test.rb']
    t.verbose = true

One thing we learned through several repeated mistakes is that the Webrat API is different when called in the “selenium” mode then the one we were used to when using Webrat in the classical “rails” mode.
For example, the “assert_have_selector” method for selenium only takes one argument, that is the CSS selector, while in the classical webrat mode, the same method takes another parameter to specify the expected content to match with (see this rdoc: http://gitrdoc.com/brynary/webrat/tree/master). So we had to define helper methods based on “assert_have_xpath” method using xpath to express the same intent of a method like assert_have_selector(css_selector, expected_content)

Here is our helper method

  def assert_has_id id, text_content
    assert_have_xpath "//*[@id='#{id}'][1][text()='#{text_content}']"

Fixing SeleniumRC to work with Firefox 3.6

The brand new release of Firefox 3.6 brings, together with some improvements in the browser, also some headaches for all selenium users: actually the latest selenium RC jar (selenium-server.jar) won’t work with Firefox 3.6.

The problem is related to the addons that Selenium will pretend to have in the Firefox instance fired up when Selenium RC server starts. As a matter of fact, those two addons are not declared to be compatible with 3.6.

The simple fix is then to edit the addons’ install.rdf files in the selenium-server.jar to manually set the compatibility to 3.6.

Alternatively, you can download this patched jar from this repository, rename it to selenium-server.jar and replace the previous jar with this.

The actual steps to fix my webrat gem (I use Selenium through Webrat) were

  1. download the above mentioned file (http://github.com/saucelabs/saucelenium/blob/master/selenium-sauce.jar)
  2. rename it to selenium-server.jar
  3. replace the previous file in the vendor folder of your webrat gem (mine was /usr/local/lib/ruby/gems/1.8/gems/webrat-0.7.0/vendor/selenium-server.jar)

One (and a half) useful thing to know when using DeepTest gem with MySQL

DeepTest currently won’t work if you’ve configured MySQL with no password (in other words, if you are able to connect to mysql with a simple “mysql -u root”).
To fix this, you have to patch DeepTest (I know, asap I’ll go through the whole process to propose the patch to the original project leader).
Actually, you have to comment out a line, in the DeepTest:Database:MysqlSetupListener#grant_privileges method:

def grant_privileges(connection)
sql = %{grant all on #{worker_database}.*
to %s@'localhost';} % [
connection.quote(worker_database_config[:username])# ,
# connection.quote(worker_database_config[:password])  <-- mysql with no password won't work
connection.execute sql

Another tip (the “half” in the blog post title):
Don’t forget to edit the “pattern” option in your DeepTest rake task, to be able to grab all the testcases you want.
In my case, I want to skip a whole folder containing selenium tests, so I have to write my Deep Test rake file this way:
(in /lib/tasks/test.rake)

require "deep_test/rake_tasks"

DeepTest::TestTask.new "deep" do |t|
t.number_of_workers = 2
t.pattern = "test/{unit,functional,integration}/**/*_test.rb"
t.libs << "test"
t.worker_listener = "DeepTest::Database::MysqlSetupListener"