For more detail, look at http://github.com/leshill/fast_specs

fast_spec_helper.rb

# Fast specs
#
# To run from the command line for my_model in your app:
#
#     rspec -Ifast_specs fast_specs/models/my_model
#
require 'rspec'

RSpec.configure do |config|
  config.mock_with :rspec
end

# Load required files from the app
#
#   app_require 'app/model/profile'
#
def app_require(file)
  require File.expand_path(file)
end

# Load required support files
#
#   support_require 'database'
#   support_require 'database_cleaner'
#
def support_require(file)
  require "support/#{file}"
end

File.join(File.dirname(__FILE__), "fast_support/**/*.rb")

why?

"#{File.dirname(__FILE__)}/fast_support/**/*.rb"

Habit. Thx.