An example of bundler's inline feature used with rspec

rspec-single-file-scaffold.rb

begin
  require 'bundler/inline'
rescue LoadError => e
  $stderr.puts 'Bundler version 1.10 or later is required. Please update your Bundler'
  raise e
end

gemfile do
  source 'https://rubygems.org'
  gem 'rspec'
end

require 'rspec/autorun'

class HelloWorld
  def say_hello
    'Hello World!'
  end
end

describe HelloWorld do
  it 'says hello' do
    expect(subject.say_hello).to eq 'Hello World!'
  end
end

Output of this in use:

09:37 $ ruby ./scaffold.rb 
.

Finished in 0.00116 seconds (files took 0.04594 seconds to load)
1 example, 0 failures