VCR

Record your test suite's HTTP interactions and replay them during future test runs for fast, deterministic, accurate tests.

Synopsis

require 'rubygems'
require 'test/unit'
require 'vcr'

VCR.config do |c|
  c.cassette_library_dir = 'fixtures/vcr_cassettes'
  c.stub_with :webmock # or :fakeweb
end

class VCRTest < Test::Unit::TestCase
  def test_example_dot_com
    VCR.use_cassette('synopsis') do
      response = Net::HTTP.get_response(URI('http://www.iana.org/domains/example/'))
      assert_match /Example Domains/, response.body
    end
  end
end

Run this test once, and VCR will record the http request to fixtures/vcr_cassettes/synopsis.yml. Run it again, and VCR will replay the response from iana.org when the http request is made. This test is now fast (no real HTTP requests are made anymore), deterministic (the test will continue to pass, even if you are offline, or iana.org goes down for maintenance) and accurate (the response will contain the same headers and body you get from a real request).

Features

• Automatically records and replays your HTTP interactions with minimal setup/configuration code.
• Supports and works with the HTTP stubbing facilities of multiple libraries. Currently, the following are supported:
  • FakeWeb
  • WebMock
  • Typhoeus
  • Faraday
  • Excon
• Supports multiple HTTP libraries:
  • Patron (when using WebMock)
  • Curb (when using WebMock -- only supports Curl::Easy at the moment)
  • HTTPClient (when using WebMock)
  • em-http-request (when using WebMock)
  • Net::HTTP (when using FakeWeb and WebMock)
  • Typhoeus (Typhoeus::Hydra, but not Typhoeus::Easy or Typhoeus::Multi)
  • Excon
  • Faraday
  • And of course any library built on Net::HTTP, such as Mechanize, HTTParty or Rest Client.
• Request matching is configurable based on HTTP method, URI, host, path, body and headers.
• The same request can receive different responses in different tests--just use different cassettes.
• The recorded requests and responses are stored on disk as YAML and can easily be inspected and edited.
• Dynamic responses are supported using ERB.
• Automatically re-records cassettes on a configurable regular interval to keep them fresh and current.
• Disables all HTTP requests that you don't explicitly allow.
• Simple cucumber integration is provided using tags.
• Includes convenient RSpec macro.
• Known to work well with many popular ruby libraries including RSpec 1 & 2, Cucumber, Test::Unit, Capybara, Mechanize, Rest-Client and HTTParty.
• Extensively tested on 7 different ruby interpretters.
• Includes Rack and Faraday middleware.

Usage

Browse the documentation for usage info.

The VCR talk given at Philly.rb also contains good usage info.

Release Policy

VCR follows the principles of semantic versioning. The cucumber features define VCR's public API. Patch level releases contain only bug fixes. Minor releases contain backward-compatible new features. Major new releases contain backwards-incompatible changes to the public API.

Ruby Interpreter Compatibility

VCR has been tested on the following ruby interpreters:

• MRI 1.8.7
• MRI 1.9.2
• REE 1.8.7
• JRuby 1.5.6
• Rubinius 1.2.1

Known Issues

• VCR uses YAML to serialize the HTTP interactions to disk in a human-readable, human-editable format. Unfortunately there are bugs in Syck, Ruby's default YAML engine, that cause it to modify strings when serializing them. It appears the the bug is limited to entire lines of whitespace. A string such as "1\n \n2" will get changed to "1\n\n2" (see this gist for example code). In practice, this usually isn't so bad, but it can occassionally cause problems, especially when the recorded response includes a content_length header and you are using an HTTP client that relies on this. Mechanize will raise an EOFError when the content_length header does not match the response body length. One solution is to use Psych, the new YAML engine included in Ruby 1.9. VCR attempts to use Psych if possible, but you may have to re-compile ruby 1.9 to use it. See this issue for more info. You can also use the :update_content_length_header cassette option to ensure the header has the correct value.

Development

• Source hosted on GitHub.
• Direct questions and discussions to the mailing list.
• Report issues on GitHub Issues.
• Pull requests are very welcome! Please include spec and/or feature coverage for every patch, and create a topic branch for every separate change you make.

If you find VCR useful, please recommend me on working with rails.

Thanks

• Aslak Hellesøy for Cucumber.
• Bartosz Blimke for WebMock.
• Chris Kampmeier for FakeWeb.
• Chris Young for NetRecorder, the inspiration for VCR.
• David Balatero for help with Typhoeus support.
• Wesley Beary for help with Excon support.

Thanks also to the following people who have contributed patches or helpful suggestions:

• Aaron Brethorst
• Bartosz Blimke
• Ben Hutton
• Bradley Isotope
• Eric Allam
• Justin Smestad
• Karl Baum
• Nathaniel Bibler
• Oliver Searle-Barnes
• Wesley Beary

Copyright

Copyright (c) 2010-2011 Myron Marston. See LICENSE for details.