Fasten your TDD red-green-refactor cycles

Having recently been bit by the TDD bug, I’ve been researching a lot about best practices when it comes to testing and speeding up the red-green-refactor process and I recently came across a really neat way to fasten the cycles further.

Guard - is a command line tool that allows you to handle events on file modifications. What that means is you can essentially configure it to monitor for modifications to specific files on your file system and perform corresponding actions. It is a great utility and can be used for carrying out a wide variety of actions.

There is a big list of ‘Guards’ available, which are essentially extensions for guard to guard specific types of files, you can find the list here in the Guard Wiki

Installation :

I would recommend you to use bundler to maintain your gem dependies, if you are doing so, simply add the following in your Gemfile

gem 'guard'
gem 'guard-rspec'
gem 'guard-cucumber'

gem 'rb-inotify'
gem 'libnotify' # This is optional for notifications on linux, for other OS' please look at for details for other OS'

Or if you’re not using bundler, simply install the above mentioned gems
manually. After having done that you can perform the following steps to setup
guard and configure it for both rspec & cucumber

    $ guard init          # This creates an empty Guardfile in the project's root, which it uses for configurations.
    $ guard init rspec    # This adds rspec guard to the Guardfile
    $ guard init cucumber # This adds cucumber guard to the Guardfile

If you now look at your Guardfile, you will see something like this :

    # A sample Guardfile
    # More info at

    guard 'cucumber' do
      watch(%r{^features/support/.+$}) { 'features' }
      watch(%r{^features/step_definitions/(.+)_steps\.rb$}) { |m| Dir[File.join("**/#{m[1]}.feature")][0] || 'features' }

    guard 'rspec', :version => 2 do
      watch(%r{^lib/(.+)\.rb$}) { |m| "spec/lib/#{m[1]}_spec.rb" }
      watch('spec/spec_helper.rb') { "spec" }

      # Rails example
      watch(%r{^app/(.+)\.rb$}) { |m| "spec/#{m[1]}_spec.rb" }
      watch(%r{^lib/(.+)\.rb$}) { |m| "spec/lib/#{m[1]}_spec.rb" }
      watch(%r{^app/controllers/(.+)_(controller)\.rb$})  { |m| ["spec/routing/#{m[1]}_routing_spec.rb", "spec/#{m[2]}s/#{m[1]}_#{m[2]}_spec.rb", "spec/acceptance/#{m[1]}_spec.rb"] }
      watch(%r{^spec/support/(.+)\.rb$}) { "spec" }
      watch('spec/spec_helper.rb') { "spec" }
      watch('config/routes.rb') { "spec/routing" }
      watch('app/controllers/application_controller.rb') { "spec/controllers" } # Capybara request specs
      watch(%r{^app/views/(.+)/.*\.(erb|haml)$}) { |m| "spec/requests/#{m[1]}_spec.rb" }

The Guardfile is quite self-explanatory, but you can have a look at for more details.

After having done that, all you need to do is start guard by issuing :

guard [start] # start is optional

Now whenever you create or modify either your spec or cucumber feature files, guard will automatically run the tests for your for the individual file that has been modified / added. This is really cool since all you need to do is write your tests and save the files and it will automatically run your tests.

If you have installed the library for notifications (libnotify in linux), you will see a cool notification of the tests instantly, indicating with the help of an icon whether the tests passed or failed. This is indeed a faster approach to following the red-green-refactor TDD cycles.

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