We tend to use database transactions as a magic bullet to get rid of all our concurrency problems. When things get really bad, we might even throw in some locking mechanism, but then are usually done with it.

Unfortunately, transactions semantics in databases are actually very complicated, and chances are, your making some incorrect assumptions.

The MySQL innodb engine actually has [four different modes](ht...

Consul 0.9 comes with many new features to optimize powers that only check access to a given record. e.g. Power.current.post?(Post.last). See below for details.

Powers that only check a given object

Sometimes it is not convenient to define powers as a collection. Sometimes you only want to store a method that
checks whether a given object is accessible.

To do so, simply define a power that ends in a question mark:

class Power
  ...

  power :upd...

I recently encountered the error above when I was running selenium tests.

Thanks to a post on stackoverflow I found out that clearing all files in tmp/cache in my project folder made the issue go away.

Similar to closing an opened browser window, spreewald now supports the I switch to the new browser tab step.

Info

See the Spreewald README for more cool features.

You can use it to test links that were opened with a link_to(..., :target => '_blank') link or other ways that create new tabs or windows.

Important

This only works with Selenium ...

Rails 4.0 is finally ready after a thorough process of betas and release candidates. It's an amazing new version packed with new goodies and farewells to old features past their expiration date.

This card shows how to upgrade a Rails 2 application from Rails 2.3.8 through every single patch level up to 2.3.18, and then, hopefully, Rails LTS.

2.3.8 to 2.3.9

This release has many minor changes and fixes to prepare your application for Rails 3.

Step-by-step upgrade instructions:

0. Upgrade rails gem
1. Change your environment.rb so it says RAILS_GEM_VERSION = '2.3.9'
2. Change your ...

Merge requests are often rejected for similar reasons.

To avoid this, before you send a merge request, please confirm that your code ...

• has been reviewed by yourself beforehand
• fulfills every requirement defined as an acceptance criterion
• does not have any log or debugging statements like console.log(...), byebug etc.
• has green tests
• has tests...

Essential backports that enable many of the nice features of Ruby 1.8.7 up to 2.0.0 for earlier versions.

Capybara drivers will usually delete all cookies after each scenario. If you need to lose cookie data in the middle of a scenario, you can do this:

browser = Capybara.current_session.driver.browser
if browser.respond_to?(:clear_cookies)
  # Rack::MockSession
  browser.clear_cookies
elsif browser.respond_to?(:manage) and browser.manage.respond_to?(:delete_all_cookies)
  # Selenium::WebDriver
  browser.manage.delete_all_cookies
else
  raise "Don't know how to clear cookies. Weird driver?"
end

You have multiple options:

1. Just don't have a type column. All STI magic will be disabled automatically.
2. If you have a type column but want to use it for something else (WAT?), you can set self.inheritance_column = :_non_existing_column in the class definition
3. (Untested) In the parent class, set self.abstract_class = true

This technique is useful to implement form models / presenters, where you want all the goodness of Ac...

Sometimes you need a piece of code to do something different for specs than for features. If you don't have separate environments, you can't check your Rails.env.

I managed to distinguish between specs and features by asking Capybara.

Note that this only works when you do not use Capybara in specs.

if defined?(Capybara) and Capybara.respond_to?(:current_driver)
  # you're in a Cucumber scenario
else
  # you're probably in a spec
end

You could omit the defined?(Capybara) condition, if you are sure that Capybara...

When you want to do a git diff but do not care about the full diff and just want to know which files changed, use the --name-only switch:

$ git diff --name-only
app/controllers/sessions_controller.rb
app/models/user.rb
features/sign_in.feature

To include some brief information about changed lines, use the --stat switch:

$ git diff --stat
app/controllers/sessions_controller.rb |    8 +-
app/models/user.rb                     |   30 ++++
features/sign_in.feature               |  136 +++++++++++++++++

T...

All Rubyists should be familiar with the common definitions for include and extend. You include a module to add instance methods to a class and extend to add class methods. Unfortunately, this common definition isn’t entirely accurate. It fails to explain why we use instance.extend(Module) to add methods to an instance. Shouldn’t it be instance.include(Module)? To figure this out we’re going to start by discussing where methods are stored.

• include: Adds methods from the provided Module to the object
• extend: Calls include on the single...

Note: This technique is confusing and slows down your test suite.

Copy the attached code to features/support. This gets you a new Cucumber tag @no_parallel which ensures that the tagged scenario does not run in parallel with other scenarios that are tagged with @no_parallel. Other scenarios not tagged will @no_parallel can still run in parallel with the tagged test. Please read the previous sentence again.

This can help when multiple test processes that access a single resource that is hard to shar...

yaml4r is a juxtaposition of yaml documents and their Ruby couterpart. Thus, it does a great job as YAML-doc, e.g. when writing Rails locale files. Did you know that ...

• << is a merge key (similar to & in SASS)
• there are variables, called aliases. Definition: &alias Some content, usage: *alias.

Caveats

Specifying a key twice does not merge the sub keys, but override the first definition, e.g.

de:
  car: # overridden
    door: Tür
 ...

The User-Agent HTTP header identifies the client and is sent by "regular" browsers, search engine crawlers, or other web client software.

Cucumber

In Rack::Test, you can set your user agent like this on Capybara:

Given /^my user agent is "(.+)"$/ do |agent|
  page.driver.browser.header('User-Agent', agent)
  # Or, for older Capybaras:
  # page.driver.header('User-Agent', agent)
end

For Selenium tests with Firefox, it seems you can set the general.useragent.override profile setting to your preferred value. [See StackOver...

Ever wondered about the difference between def and define_method? Turns out there are three implicit contexts in Ruby. def and define_method differ in which one they use.

def

• Ruby keyword, starts a method definition
• Opens a new, isolated scope. Variables defined outside are not accessible inside and vice versa.
• Defines an instance method on the receiver (specified before the method name, e.g. def object.foo); implicit receiver is the default definee

The default definee is not self and...

When a controller action redirects to an external URL (like http://somehost.com/some/path) you will find that this is hard to test with Cucumber and Capybara:

• A non-Javascript Rack::Test scenario will just ignore the host and try to open /some/path in your local application
• A Selenium test will actually follow the redirect, which you probably don't want either

There are two workarounds for this. You can use either, or a combination of both.

1. Write a controller spec

Controller specs can test if a resp...

Unfortunately, Capybara does not offer a switch to disable cookies in your test browser. However, you can work around that by using a tiny Rack middleware -- it works for both Selenium and non-Selenium tests.

Wouldn't it be nice to say something like this?

Given cookies are disabled
When I try to sign in
Then I should see "Can't sign you in. Please enable cookies."

You can! Put the code below into some place like lib/rack/cookie_stripper.rb.

module Rack
  class CookieStripper
    
    ENABLED = false

...

To set a cookie in your test browser for cucumber tests, you need to know which driver you are using. Use the step below according to your driver.

Rack::Test

Given /^I have a "([^\"]+)" cookie set to "([^\"]+)"$/ do |key, value|
  headers = {}
  Rack::Utils.set_cookie_header!(headers, key, value)
  cookie_string = headers['Set-Cookie']

  Capybara.current_session.driver.browser.set_cookie(cookie_string)
end

Note that Rack::Utils is only used to find out the correct cookie header string (you don't want to generate it yours...

The following code doesn't work like expected:

page.find(css_selector).find(other_css_selector)

The second .find will search the whole dom instead of a scope.

Rumor has it this is fixed in Capybara 0.4.1.

If you open a pop-up window [1] in your Selenium tests and you want to close it, you can do this:

# Find our target window
handle = page.driver.find_window("My window title")

# Close it
page.driver.browser.switch_to.window(handle)
page.driver.browser.close

# Have the Selenium driver point to another window
last_handle = page.driver.browser.window_handles.last
page.driver.browser.switch_to.window(last_handle)

Mind these:

• find_window returns a window handle, which is something like `"{485fa8bd-fa99-...

If you need to capture signatures on an IPad or similar device, you can use Thomas J Bradley's excellent Signature Pad plugin for jQuery.

To implement, just follow the steps on the Github page.

The form

If you have a model Signature with name: string, signature: text, you can use it with regular rails form like this:

- form_for @signature, :html => { :class => 'signature_form' } do |form|
  %dl
    %dt
      = form...

Counters are an awesome CSS feature you didn't know about. It is supported in all browsers and IE8+.

CSS counters are an implementation of Automatic counters and numbering in CSS 2.1. The value of a counter is manipulated through the use of counter-reset and counter-increment and is displayed on a page using the counter() or counters() function of the content property.