Library for stubbing HTTP requests and setting expectations on HTTP requests in Ruby.
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Library for stubbing and setting expectations on HTTP requests in Ruby.


  • Stubbing HTTP requests at low http client lib level (no need to change tests when you change HTTP library)
  • Setting and verifying expectations on HTTP requests
  • Matching requests based on method, URI, headers and body
  • Smart matching of the same URIs in different representations (also encoded and non encoded forms)
  • Smart matching of the same headers in different representations.
  • Support for Test::Unit
  • Support for RSpec 1.x and RSpec 2.x
  • Support for Net::HTTP and other http libraries based on Net::HTTP (i.e RightHttpConnection, rest-client, HTTParty)
  • Support for HTTPClient library (both sync and async requests)
  • Support for Patron library
  • Easy to extend to other HTTP libraries


gem install webmock --source

In your test/test_helper.rb add these two lines:

require 'webmock/test_unit'

class Test::Unit::TestCase
  include WebMock

or if you use RSpec add these lines to spec/spec_helper:

require 'webmock/rspec'

Spec::Runner.configure do |config|
  config.include WebMock

You can also use WebMock without RSpec or Test::Unit support:

require 'webmock'

include WebMock



Stubbed request based on uri only and with the default response

 stub_request(:any, "")

 Net::HTTP.get("", "/")    # ===> Success

Stubbing requests based on method, uri, body and headers

stub_request(:post, "").with(:body => "abc", :headers => { 'Content-Length' => 3 })

uri = URI.parse("")
req =
req['Content-Length'] = 3
res = Net::HTTP.start(, uri.port) {|http|
  http.request(req, "abc")
}    # ===> Success

Matching request body and headers against regular expressions

stub_request(:post, "").
  with(:body => /^.*world$/, :headers => {"Content-Type" => /image\/.+/}).to_return(:body => "abc")

uri = URI.parse('')
req =
req['Content-Type'] = 'image/png'
res = Net::HTTP.start(, uri.port) {|http|
  http.request(req, 'hello world')
}    # ===> Success

Matching custom request headers

stub_request(:any, "").with(:headers=>{ 'Header-Name' => 'Header-Value' })

uri = URI.parse('')
req =
req['Header-Name'] = 'Header-Value'
res = Net::HTTP.start(, uri.port) {|http|
  http.request(req, 'abc')
}    # ===> Success

Matching multiple headers with the same name

stub_http_request(:get, '').with(:headers => {'Accept' => ['image/jpeg', 'image/png'] })

req ="/")  
req['Accept'] = ['image/png']
req.add_field('Accept', 'image/jpeg')
Net::HTTP.start("") {|http|  http.request(req) } # ===> Success

Matching requests against provided block

stub_request(:post, "").with { |request| request.body == "abc" }'', 'abc')    # ===> Success

Request with basic authentication

stub_request(:get, "")

Net::HTTP.start('') {|http|
  req ='/')
  req.basic_auth 'user', 'pass'
}  # ===> Success

Matching uris using regular expressions

 stub_request(:any, /.*example.*/)

 Net::HTTP.get('', '/') # ===> Success	

Stubbing with custom response

stub_request(:any, "").to_return(:body => "abc", :status => 200,  :headers => { 'Content-Length' => 3 } )

Net::HTTP.get("", '/')    # ===> "abc"

Response with body specified as IO object'/tmp/response_body.txt', 'w') { |f| f.puts 'abc' }

stub_request(:any, "").to_return(:body =>'/tmp/response_body.txt'), :status => 200)

Net::HTTP.get('', '/')    # ===> "abc\n"

Response with custom status message

stub_request(:any, "").to_return(:status => [500, "Internal Server Error"])

req ="/")
Net::HTTP.start("") { |http| http.request(req) }.message # ===> "Internal Server Error"

Replaying raw responses recorded with curl -is

`curl -is > /tmp/example_curl_-is_output.txt`
raw_response_file ="/tmp/example_curl_-is_output.txt")

from file

stub_request(:get, "").to_return(raw_response_file)

or string

stub_request(:get, "").to_return(

Responses dynamically evaluated from block

stub_request(:any, '').
  to_return { |request| {:body => request.body} }'', 'abc')    # ===> "abc\n"

Responses dynamically evaluated from lambda

stub_request(:any, '').
  to_return(lambda { |request| {:body => request.body} })'', 'abc')    # ===> "abc\n"	       

Responses with dynamically evaluated parts

stub_request(:any, '').
  to_return(:body => lambda { |request| request.body })'', 'abc')    # ===> "abc\n"	

Raising errors

stub_request(:any, '').to_raise(StandardError)'', 'abc')    # ===> StandardError

Raising timeout errors

stub_request(:any, '').to_timeout'', 'abc')    # ===> RestClient::RequestTimeout	

Multiple responses for repeated requests

stub_request(:get, "").to_return({:body => "abc"}, {:body => "def"})
Net::HTTP.get('', '/')    # ===> "abc\n"
Net::HTTP.get('', '/')    # ===> "def\n"

#after all responses are used the last response will be returned infinitely

Net::HTTP.get('', '/')    # ===> "def\n" 

Multiple responses using chained to_return(), to_raise() or to_timeout declarations

stub_request(:get, "").
	to_return({:body => "abc"}).then.  #then() is just a syntactic sugar
	to_return({:body => "def"}).then.
Net::HTTP.get('', '/')    # ===> "abc\n"
Net::HTTP.get('', '/')    # ===> "def\n"
Net::HTTP.get('', '/')    # ===> MyException raised

Specifying number of times given response should be returned

stub_request(:get, "").
	to_return({:body => "abc"}).times(2).then.
	to_return({:body => "def"})

Net::HTTP.get('', '/')    # ===> "abc\n"
Net::HTTP.get('', '/')    # ===> "abc\n"
Net::HTTP.get('', '/')    # ===> "def\n"

Real requests to network can be allowed or disabled


stub_request(:any, "").to_return(:body => "abc")

Net::HTTP.get('', '/')    # ===> "abc"

Net::HTTP.get('', '/') # ===> /.+Something.+/


Net::HTTP.get('', '/')    # ===> Failure

External requests can be disabled while allowing localhost

WebMock.disable_net_connect!(:allow_localhost => true)

Net::HTTP.get('', '/')   # ===> Failure

Net::HTTP.get('localhost:9887', '/')      # ===> Allowed. Perhaps to Selenium?

Setting Expectations

Setting expectations in Test::Unit

require 'webmock/test_unit'

stub_request(:any, "")

uri = URI.parse('')
req =
req['Content-Length'] = 3
res = Net::HTTP.start(, uri.port) {|http|
  http.request(req, 'abc')

assert_requested :post, "",
  :headers => {'Content-Length' => 3}, :body => "abc", :times => 1    # ===> Success

assert_not_requested :get, ""    # ===> Success

assert_requested(:post, "", :times => 1) { |req| req.body == "abc" }

Expecting real (not stubbed) requests


Net::HTTP.get('', '/')    # ===> Success

assert_requested :get, ""    # ===> Success

Setting expectations in RSpec

This style is borrowed from fakeweb-matcher

require 'webmock/rspec'

WebMock.should have_requested(:get, "").with(:body => "abc", :headers => {'Content-Length' => 3}).twice

WebMock.should_not have_requested(:get, "")

WebMock.should have_requested(:post, "").with { |req| req.body == "abc" }

Different way of setting expectations in RSpec

request(:post, "").with(:body => "abc", :headers => {'Content-Length' => 3}).should have_been_made.once

request(:post, "").should have_been_made.times(3)

request(:any, "").should_not have_been_made

request(:post, "").with { |req| req.body == "abc" }.should have_been_made

Clearing stubs and request history

If you want to reset all current stubs and history of requests use WebMock.reset_webmock

stub_request(:any, "")

Net::HTTP.get('', '/')    # ===> Success


Net::HTTP.get('', '/')    # ===> Failure

assert_not_requested :get, ""    # ===> Success

Matching requests

An executed request matches stubbed request if it passes following criteria:

When request URI matches stubbed request URI string or Regexp pattern
And request method is the same as stubbed request method or stubbed request method is :any
And request body is the same as stubbed request body or stubbed request body is not specified
And request headers match stubbed request headers, or stubbed request headers match a subset of request headers, or stubbed request headers are not specified
And request matches provided block or block is not provided

Precedence of stubs

Always the last declared stub matching the request will be applied i.e:

stub_request(:get, "").to_return(:body => "abc")
stub_request(:get, "").to_return(:body => "def")

Net::HTTP.get('', '/')   # ====> "def"

Matching URIs

WebMock will match all different representations of the same URI.

I.e all the following representations of the URI are equal:


The following URIs with basic authentication are also equal for WebMock


or these

" path/?a=my param&b=c"
" path/?a=my param&b=c"
" path/?a=my param&b=c"
" path/?a=my param&b=c"

If you provide Regexp to match URI, WebMock will try to match it against every valid form of the same url.

I.e /.*my param.*/ will match because it is equivalent of path

Matching headers

WebMock will match request headers against stubbed request headers in the following situations:

  1. Stubbed request has headers specified and request headers are the same as stubbed headers
    i.e stubbed headers: { 'Header1' => 'Value1', 'Header1' => 'Value1' }, requested: { 'Header1' => 'Value1', 'Header1' => 'Value1' }

  2. Stubbed request has headers specified and stubbed request headers are a subset of request headers
    i.e stubbed headers: { 'Header1' => 'Value1' }, requested: { 'Header1' => 'Value1', 'Header1' => 'Value1' }

  3. Stubbed request has no headers
    i.e stubbed headers: nil, requested: { 'Header1' => 'Value1', 'Header1' => 'Value1' }

WebMock normalises headers and treats all forms of same headers as equal: i.e the following two sets of headers are equal:

{ "Header1" => "value1", :content_length => 123, :X_CuStOm_hEAder => :value }

{ :header1 => "value1", "Content-Length" => 123, "x-cuSTOM-HeAder" => "value" }

Recording real requests and responses and replaying them later

To record your application's real HTTP interactions and replay them later in tests you can use VCR with WebMock.

Bugs and Issues

Please submit them here


If you have any suggestions on how to improve WebMock please send an email to the mailing list

I'm particularly interested in how the DSL could be improved.


The initial lines of this project were written during New Bamboo Hack Day Thanks to my fellow Bambinos for all the great suggestions!

People who submitted patches and new features or suggested improvements. Many thanks to these people:

  • Ben Pickles
  • Mark Evans
  • Ivan Vega
  • Piotr Usewicz
  • Nick Plante
  • Nick Quaranto
  • Diego E. "Flameeyes" Pettenò
  • Niels Meersschaert
  • Mack Earnhardt
  • Arvicco
  • Sergio Gil
  • Jeffrey Jones
  • Tekin Suleyman
  • Tom Ward
  • Nadim Bitar
  • Myron Marston
  • Sam Phillips
  • Jose Angel Cortinas
  • Razic
  • Steve Tooke


Thank you Fakeweb! This library was inspired by FakeWeb. I imported some solutions from that project to WebMock. I also copied some code i.e Net:HTTP adapter. Fakeweb architecture unfortunately didn't allow me to extend it easily with the features I needed. I also preferred some things to work differently i.e request stub precedence.


Copyright (c) 2009-2010 Bartosz Blimke. See LICENSE for details.