Tiny Rails + Teaspoon setup (uses mocha by default). A good place to start with a small coffeescript project.

config.ru

require 'rubygems'
require 'bundler/setup'
require 'action_controller/railtie'
require 'sprockets/railtie'

Bundler.require

module App
  class Application < Rails::Application
    config.session_store :cookie_store, :key => '_app_session'
    config.secret_token = '30dd9731a121fb4a3425fb528ffed853'
    config.active_support.deprecation = :log
    config.consider_all_requests_local = true
    config.encoding = 'utf-8'

    config.assets.enabled = true
    config.assets.version = '1.0'
    config.assets.debug = true

    config.assets.paths = []
    config.assets.paths << 'lib/dependencies'
    config.assets.paths << 'lib/javascripts'
    config.assets.paths << 'lib/stylesheets'
  end

  Teaspoon.configure do |config|
    config.asset_paths      = ['spec']
    config.fixture_path     = 'spec/fixtures'

    config.suite do |suite|
      suite.matcher      = 'spec/**/*_spec.{js,js.coffee,coffee}'
      suite.helper       = 'spec_helper'
      suite.javascripts  = ['teaspoon-mocha', 'support/chai', 'support/sinon', 'support/sinon-chai']
    end
  end
end

class ApplicationController < ActionController::Base
  prepend_view_path Rails.application.root
  prepend_view_path Rails.application.root.join('/dependencies/three/examples')
  def page
    render template: params[:page] || 'index'
  end
end

Rails.application.initialize!
Rails.application.routes.draw do
  # rendering pages
  match '/(:page)' => 'application#page', via: :get
end

run App::Application rescue nil

Gemfile

source 'https://rubygems.org'

gem 'rails'
gem 'haml-rails'
gem 'coffee-rails'
gem 'sass-rails'

# Build process dependencies
gem 'uglifier'                  # javascript compression
gem 'yui-compressor'            # css compression

# Test dependencies
gem 'teaspoon'