A sample guard file for Rails App, contains some code fragments from Rails Tutorial by Michael Hartl.

Guardfile

# A sample Guardfile
# More info at https://github.com/guard/guard#readme
require 'active_support/core_ext'

guard 'spork', :cucumber_env => { 'RAILS_ENV' => 'test' }, :rspec_env => { 'RAILS_ENV' => 'test' } do
  watch('config/application.rb')
  watch('config/environment.rb')
  watch(%r{^config/environments/.+\.rb$})
  watch(%r{^config/initializers/.+\.rb$})
  watch('Gemfile')
  watch('Gemfile.lock')
  watch('spec/spec_helper.rb')
  watch('test/test_helper.rb')
  watch('spec/support/')
end

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

  # Rails example
  watch(%r{^app/(.+)\.rb$})                           { |m| "spec/#{m[1]}_spec.rb" }
  watch(%r{^app/(.*)(\.erb|\.haml)$})                 { |m| "spec/#{m[1]}#{m[2]}_spec.rb" }
  watch(%r{^app/controllers/(.+)_(controller)\.rb$}) do |m|
    ["spec/routing/#{m[1]}_routing_spec.rb",
    "spec/#{m[2]}s/#{m[1]}_#{m[2]}_spec.rb",
    "spec/acceptance/#{m[1]}_spec.rb",
    (m[1][/_pages/] ? "spec/requests/#{m[1]}_spec.rb" :
      "spec/requests/#{m[1].singularize}_pages_spec.rb")]
  end

  watch(%r{^spec/support/(.+)\.rb$})                  { "spec" }
  watch('config/routes.rb')                           { "spec/routing" }
  watch('app/controllers/application_controller.rb')  { "spec/controllers" }
  
  # Capybara request specs
  watch(%r{^app/views/(.+)/}) do |m|
  "spec/requests/#{m[1].singularize}_pages_spec.rb"
  end

  # Turnip features and steps
  watch(%r{^spec/acceptance/(.+)\.feature$})
  watch(%r{^spec/acceptance/steps/(.+)_steps\.rb$})   { |m| Dir[File.join("**/#{m[1]}.feature")][0] || 'spec/acceptance' }
end