Betamax

Betamax allows for the recording and playback of arbitrary Ruby objects to simplify testing external dependencies. Think of it like the VCR gem, but for any complicated object, not just HTTP interactions. This gem was originally developed to write a test suite for a MiniDisc NetMD Walkman library, where the recording and playback of real USB traffic was desired.

Install the gem and add to the application's Gemfile by executing:

bundle add betamax

If bundler is not being used to manage dependencies, install the gem by executing:

gem install betamax

Currently this gem supports testing with RSpec or Minitest.

First, require the gem in your spec helper:

# File: spec/spec_helper.rb

require 'betamax'

Then, record an object. The first time you run your test, a recording will be created in spec/betamax_tapes/. Subsequent test runs will playback from your recording. Make sure to tag your example as :betamax to enable recording and playback.

RSpec.describe 'a MiniDisc device' do
  let(:walkman) do
    usb_device = LibUSB::Context.devices(idProduct: 0x0084).first

    MiniDisc::Device.new usb_device: Betamax.record(usb_device)
  end

  it 'has a tracklist', :betamax do
    walkman.open do |disc|
      disc.tracks.first.title.should == 'Song of the Highwire Shrimper'
    end
  end
end

In the above example, the test will continue to work even if the USB device is no longer present. If for some reason changes to your code change the interaction with your recorded object, your test will fail. This could be because methods were called in a different order, block arguments changed, method calls were expected but did not take place, etc.

Include Betamax::Minitest in your test class and surround the recorded interaction with with_betamax. Tapes are named after the test class and method and stored in test/betamax_tapes/ (override with tapes_folder:).

class WalkmanTest < Minitest::Test
  include Betamax::Minitest

  def test_tracklist
    with_betamax do
      usb_device = LibUSB::Context.devices(idProduct: 0x0084).first
      walkman = MiniDisc::Device.new usb_device: Betamax.record(usb_device)

      walkman.open do |disc|
        assert_equal 'Song of the Highwire Shrimper', disc.tracks.first.title
      end
    end
  end
end

After checking out the repo, run bin/setup to install dependencies. Then, run bundle exec rake to run the RSpec and Minitest suites and RuboCop. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/Aesthetikx/betamax.