Minitest in Rails without minitest_rails

Gemfile

group :test do
  gem 'minitest'
  gem 'minitest-focus'
  gem 'minispec-metadata'
  gem 'minitest-reporters'
  gem 'capybara'
  gem 'capybara-webkit'
  gem 'database_cleaner'
  gem 'factory_girl_rails'
  gem 'launchy'
  gem 'connection_pool'
  gem 'faker'
end

test_helper.rb

ENV['RAILS_ENV'] = 'test'
require File.expand_path('../../config/environment', __FILE__)
require 'minitest/autorun'
require 'minispec-metadata'
require 'rails/test_help'
require 'minitest/spec'
require 'minitest/reporters'
require 'capybara/rails'
require 'database_cleaner'

Minitest::Reporters.use! Minitest::Reporters::SpecReporter.new
Capybara.javascript_driver = :webkit

class MiniTest::Spec
  ActiveRecord::Migration.check_pending!
  DatabaseCleaner.strategy = :transaction
  include FactoryGirl::Syntax::Methods

  before :each do
    DatabaseCleaner.start
  end

  after :each do
    DatabaseCleaner.clean
  end

  class << self
    alias context describe
  end
end

class FeatureSpec < MiniTest::Spec
  include Rails.application.routes.url_helpers
  include Capybara::DSL
  include Warden::Test::Helpers

  Warden.test_mode!
  Capybara.javascript_driver = :webkit
  DatabaseCleaner.strategy   = :deletion

  before :each do
    if metadata[:js]
      Capybara.current_driver = Capybara.javascript_driver
    end
  end

  after :each do
    Warden.test_reset!
    Capybara.current_driver = Capybara.default_driver
  end

  def login!
    @user = FactoryGirl.create(:confirmed_user)
    login_as(@user, :scope => :user)
  end

  def last_email
    ActionMailer::Base.deliveries.last
  end
end
MiniTest::Spec.register_spec_type /feature/i, FeatureSpec

# Forces all threads to share the same connection. This works on
# Capybara because it starts the web server in a thread.
# https://gist.github.com/mperham/3049152
class ActiveRecord::Base
  mattr_accessor :shared_connection
  @@shared_connection = nil

  def self.connection
    @@shared_connection || ConnectionPool::Wrapper.new(:size => 1) { retrieve_connection }
  end
end
ActiveRecord::Base.shared_connection = ActiveRecord::Base.connection