When installing RMagick you may get an error messages like this:

Version 2.13.1:

checking for Ruby version >= 1.8.5... yes
checking for gcc... yes
checking for Magick-config... no
Can't install RMagick 2.13.1. Can't find Magick-config in /home/arne/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/var/lib/gems/1.8/bin

*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers.  Check the mkmf.log file for more
d...

If you just upgraded to Bundler 10.0.10 you might get the following error when bringing up Rails:

/usr/lib/ruby/1.9.1/psych.rb:148:in `parse': couldn't parse YAML at line 17 column 14 (Psych::SyntaxError)

This is caused by Rails localization files (en.yml, de.yml, etc.) using symbols for various translation strings, and Bundler 10.0.10 defaults to a new YAML engine which cannot handle symbols.

You can switch back to the old YAML engine by ...

Note that you cannot currently use Ruby 1.9.2 with Rails 2 applications that use RSpec, so don't upgrade if that is your setup. The rspec-rails gem has a fatal bug that was only fixed for rspec-rails-2.x, which only supports Rails 3. There is no fix for the rspec-rails-1.3.x series of the gem which supports Rails 2.

Anyway, here are upgrade instructions if you only work with Rails 3 or don't use RSpec. You will lose all your gems in the process, but you can get them back easily if you h...

Specify these gem versions in your Gemfile:

gem 'cucumber', '~> 1.3.0'
gem 'cucumber-rails', '= 0.3.2' # max version for Rails 2
gem 'capybara', '< 2' # capybara 2+ requires Rails 3
gem 'mime-types', '< 2' # dependeny of capybara
gem 'nokogiri', '< 1.6' # dependency of capybara
gem 'rubyzip', '< 1' # dependency of selenium-webdriver, rubyzip 1+ requires Ruby 1.9
gem 'cucumber_factory'
gem 'database_cleaner', '< 1'
gem 'cucumber_spinner', '~> 0.2.5'
gem 'launchy', '~> 2.1.2'

With these versions set, `...

Add deprecation warnings and their solution or link to available solutions.

Global access to Rake DSL methods is deprecated. Please include Rake::DSL into classes and modules which use the Rake DSL methods.

Open your Rakefile and add the following line above YourApp::Application.load_tasks:

YourApp::Application.class_eval do
  include Rake::DSL
end

Use of ole/file_system is deprecated. Use ole/storage (the file_system api is recommended and enabled by default)...

We are maintaining some vintage projects with tests written in Test::Unit instead of RSpec. Mocks and stubs are not features of Test::Unit, but you can use the Mocha gem to add those facilities.

The following is a quick crash course to using mocks and stubs in Mocha, written for RSpec users:

|---------------------------------------------------------|
| RSpec | Mocha |
|---------------------------------------------------------|
| obj = double() | obj = mock() |
| obj.stub(:method => 'value') | `obj.stubs...

When working with large Sass files you will notice that the first request after a change to a Sass file takes quite some time. This is because the CSS files are being generated from the Sass files the moment the application answers your request (Sass looks at the files and recompiles if the timestamp changed); it takes even longer when you build sprites with the Lemonade gem.

To avoid this, have Sass watch the files for changes and compile them into CSS files immediately. Th...

You will occasionally need to clean out your database while keeping the schema intact, e.g. when someone inserted data in a migration or when you had to kill -9 a frozen test process.

Old Capybara versions already have the Database Cleaner gem as dependency. Otherwise add database_cleaner to your *Gemfile`. This lets you say this from the Rails console:

DatabaseCleaner.strategy = :truncation
DatabaseCleaner.cl...

After updating your RubyGems, you will probably not be able to run Capistrano any more, but receive an error similar to this:
can't activate net-ssh (= 2.0.22) for [], already activated net-ssh-2.1.0 for [] (Gem::LoadError)

If you have Bundler installed, you can use bundle exec to avoid this problem as follows:

Create a gemfile at ~/.capistrano/Gemfile (or at some other sensible place), that only contains these 2 lines:
source 'http://rubygems.org'
gem 'capistrano'
gem 'capistrano-ext' # You need this for multistag...

On 32bit systems, the maximum representable Time is 2038-01-19 03:14:07 in UTC or 2038-01-19 04:14:07 in CET. If you try to instantiate a Time with any later value, Ruby will raise an ArgumentError.

If you need to represent later time values, use the DateTime class. This is also what Rails does when it loads a record from the database that has a DATETIME value which Time cannot represent. Note that there are some [subtle differences](http://stackoverflow.com/quest...

This tool is used on our application servers (and called when deploying) but it also works locally.
Just call dumple development from your project directory to dump your database.

This script is part of our geordi gem on github.

The code below shows a method #validate which uses Nokogiri to validate an XML document against an XSD schema. It returns an array of Nokogiri::XML::SyntaxError objects.

require 'rubygems'
gem 'nokogiri'
require 'nokogiri'

def validate(document_path, schema_path, root_element)
  schema = Nokogiri::XML::Schema(File.read(schema_path))
  document = Nokogiri::XML(File.read(document_path))
  schema.validate(document.xpath("//#{root_element}").to_s)
end

v...

When defining a trait using the Modularity gem, you must take extra steps to define constants to avoid caveats (like when defining subclasses through traits).

tl;dr

In traits, always define constants with explicit self.

If your trait defines a constant inside the as_trait block, it will be bound to the trait module, not the class including the trait.
While this may seem unproblematic at first glance, it becomes a problem when including trai...

In case https://www.rubydoc.info/ is to slow or offline, you can also read a gem documentation offline.

Start a server with gem server and go to http://0.0.0.0:8808/. Here you will find a list of all installed gems and it is possible to navigate to the documentation if installed e.g. http://0.0.0.0:8808/doc_root/rubocop-0.77.0/

In case you set the configured RubyGems to not install documentation by default, you need to add generate the documentation for the specific gem.

gem install rubocop --document
`...

Are you adding a "Then show me the page" and re-run Cucumber whenever there is a failing scenario? Don't be that guy!

Save time with the shiny new version of our cucumber_spinner gem. It comes with a Cucumber formatter that not only displays an awesome progress bar, and shows failing scenarios immediately, it will also open the current page in your browser whenever a scenario step fails.

After you installed the gem, use the formatter like this:

cucumber --format CucumberSpinner::Curiou...

Call geordi clean from a project root to remove unused and unnecessary files inside it.

This script is part of our geordi gem on github. In Geordi > 1.2 you can call geordi clean.

You can usually just use the eq matched to compare two numbers:

expect(deal.total).to eq(120)

If the actual value is a BigDecimal, you might have issues when you match it against a Float:

expect(deal.total_price).to eq(1200.99)

In these cases, try matching it against another BigDecimal:

expect(deal.total_price).to eq BigDecimal(1200.99)

If you don't like the syntax, our rspec_candy gem has a matcher that will compare Fixnums (integers), Floats and `BigDecima...

Use the htmlentities gem.

Encoding works like this:

require 'htmlentities'
coder = HTMLEntities.new
string = "<élan>"
coder.encode(string)               # => "&lt;élan&gt;"
coder.encode(string, :named)       # => "&lt;&eacute;lan&gt;"
coder.encode(string, :decimal)     # => "&#60;&#233;lan&#62;"
coder.encode(string, :hexadecimal) # => "&#x3c;&#xe9;lan&#x3e;"

Decoding works like this:

require 'htmlentities'
coder = HTMLEntities.new
string = "élan"
cod...

Use the Launchy gem:

Launchy.open('http://www.ruby-lang.org/')

When a has_many association basically serves to store a list of associated strings (tags, categories, ...), it can be convenient to represent this association as a string array in the containing model. Here is an example for this pattern from the acts-as-taggable-on gem:

post = Post.last
p post.tag_list # ['foo', 'bar', 'baz']
post.tag_list = ['bam']
p post.tag_list # ['bam']

This string array tag_list is magical in several ways:

• It is read from and written to a `has...