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Rack::Test is a layer on top of Rack's MockRequest similar to Merb's RequestHelper
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Latest commit a2f762d Feb 28, 2019


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Rack::Test is a small, simple testing API for Rack apps. It can be used on its own or as a reusable starting point for Web frameworks and testing libraries to build on.


  • Maintains a cookie jar across requests
  • Easily follow redirects when desired
  • Set request headers to be used by all subsequent requests
  • Small footprint. Approximately 200 LOC

Supported platforms

  • 2.2.2+
  • 2.3
  • 2.4
  • JRuby 9.1.+

If you are using Ruby 1.8, 1.9 or JRuby 1.7, use rack-test 0.6.3.

Known incompatibilites

  • rack-test >= 0.71 does not work with older Capybara versions (< 2.17). See #214 for more details.


(The examples use Test::Unit but it's equally possible to use rack-test with other testing frameworks like rspec.)

require "test/unit"
require "rack/test"

class HomepageTest < Test::Unit::TestCase
  include Rack::Test::Methods

  def app
    app = lambda { |env| [200, {'Content-Type' => 'text/plain'}, ['All responses are OK']] }
    builder = app

  def test_response_is_ok
    get '/'

    assert last_response.ok?
    assert_equal last_response.body, 'All responses are OK'

  def set_request_headers
    header 'Accept-Charset', 'utf-8'
    get '/'

    assert last_response.ok?
    assert_equal last_response.body, 'All responses are OK'

  def test_response_is_ok_for_other_paths
    get '/other_paths'

    assert last_response.ok?
    assert_equal last_response.body, 'All responses are OK'

  def post_with_json
    # No assertion in this, we just demonstrate how you can post a JSON-encoded string.
    # By default, Rack::Test will use HTTP form encoding if you pass in a Hash as the
    # parameters, so make sure that `json` below is already a JSON-serialized string.
    post(uri, json, { 'CONTENT_TYPE' => 'application/json' })

  def delete_with_url_params_and_body
    delete '/?foo=bar', JSON.generate('baz' => 'zot')

If you want to test one app in isolation, you just return that app as shown above. But if you want to test the entire app stack, including middlewares, cascades etc. you need to parse the app defined in

OUTER_APP = Rack::Builder.parse_file("").first

class TestApp < Test::Unit::TestCase
  include Rack::Test::Methods

  def app

  def test_root
    get "/"
    assert last_response.ok?


To install the latest release as a gem:

gem install rack-test

Or via Bundler:

gem 'rack-test'

Or to install unreleased version via Bundler:

gem 'rack-test', github: 'rack-test', branch: 'master'


  • Contributions from Bryan Helmkamp, Simon Rozet, Pat Nakajima and others
  • Much of the original code was extracted from Merb 1.0's request helper


rack-test is released under the MIT License.


Contributions are welcome. Please make sure to:

  • Use a regular forking workflow
  • Write tests for the new or changed behaviour
  • Provide an explanation/motivation in your commit message / PR message
  • Ensure is updated


  • Ensure is up-to-date
  • Bump VERSION in lib/rack/test/version.rb
  • git commit . -m 'Release 1.1.0'
  • git push
  • bundle exec thor :release
  • Updated the GitHub releases page
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