assert-response: sugar around Rack::Test

When it comes to Rack::Test there are two things that I don't like:

  • If your rack app raises an error, it is not exposed as an error but hidden in last_response.errors
  • Most of the time a status 404 should be considered as an error - the only exeption being that we expect a 404 status
  • It's annoying to test for content-types

assert-response is there to address these issues:

  • an error that occurs in your rack app will be raised (with original backtrace)
  • you may test the error class and message
  • a status 404 will raise an error everywhere execept from testing 404 responses
  • you get a shortcut for all content-types that come with Rack::Mime and may register your own
  • you get a little DSL to be able to do several test against the same response in a DRY way


assert-response has been tested with ruby 1.8.7 and 1.9.2. It should be usable with every testing library and has been tested with test/unit and minitest.

Install it as a gem:

sudo gem install assert-response

or in rvm:

gem install assert-response


require 'minitest'
require 'rack/test'
require 'assert-reponse'

include Rack::Test::Methods

def app

(for usage without the inclusion of Rack::Test::Methods or with Test::Unit, see AssertResponse::Methods)

And then in your test something like this:

get '/myroute'
assert_response_html 'my body'

This will

# raise the error, if an error occures in MyApp
raise AssertResponse::Status404 if last_response.status is not 404
assert_equal200, last_response.status
assert "test/html", last_response.headers['Content-Type']
assert_match /my\ body/, last_response.body

But you may also want to... check just the mime type:

get '/myroute'

check for a 404 page:

get '/myroute'
assert_response_not_found_html "Not found!"

This one does:

assert 404, last_response.status
assert "test/html", last_response.headers['Content-Type']
assert_match /Not\ found!/, last_response.body

For all mime types in Rack::Mime you get 3 methods, where [shortcut] is the file extension

assert_response_[shortcut] # checks for status 200, content-type and body matching
assert_response_is_[shortcut] # checks for content-type and status 200
assert_response_not_found_[shortcut] # checks for content-type, status 404 and body matching

You may define your own content-type with

AssertResponse.add_content_type :my_shortcut, "text/mymimetype"

# later...
assert_response_my_shortcut "here the body"
assert_response_not_found_my_shortcut "Not found but correct content-type"

There is some additional sugar like


Everything after assert_response_ is the called method of AssertResponse, look them up in the documentation.

When using the assert_response_ methods always the last_response object is checked.

If you want to check a saved response instead, you may use the little DSL

get '/myroute'
my_response = last_response
get '/other'
assert_response my_response do
  is_html  # checks content-type
  body 'my body' # same as 'body /my\ body/' 

Now inside the code block you may use the methods of AssertResponse (but without the assert_response_ prefixes).


Maybe add some sugar for cookie testing.

Contributing to assert-response

  • Check out the latest master to make sure the feature hasn't been implemented or the bug hasn't been fixed yet
  • Check out the issue tracker to make sure someone already hasn't requested it and/or contributed it
  • Fork the project
  • Start a feature/bugfix branch
  • Commit and push until you are happy with your contribution
  • Make sure to add tests for it. This is important so I don't break it in a future version unintentionally.
  • Please try not to mess with the Rakefile, version, or history. If you want to have your own version, or is otherwise necessary, that is fine, but please isolate to its own commit so I can cherry-pick around it.


Copyright (c) 2011 Marc Rene Arns. See LICENSE.txt for further details.