Webmock and VCR are tools for stubbing and recording HTTP requests in tests. Webmock allows fine-grained control over stubbing but requires the remote server, while VCR records and replays requests without the server through cassettes. The document provides information on setting up and using both tools to stub or record HTTP requests in different testing frameworks for reliable and isolated tests.

1. Testing HTTP calls
Kerry Buckley
IPRUG lightning talk, 5 March 2013

2. Why?
Your tests
Your app
Webby stuff

3. Webmock
Test::Unit Minitest RSpec Cucumber
Your app
EM-HTTP-
Net::HTTP HTTPclient Patron
request
Curb Typhoeus Excon
Webmock

4. Setup
group :test do
gem "webmock"
end
require 'webmock/rspec'
require 'webmock/minitest'
require 'webmock/test_unit'
require 'webmock/cucumber'

5. Basic stub
stub_request :any,
"www.example.com"
Net::HTTP.get "www.example.com", "/"
# => 200 OK, body = ""

6. Filtering requests
stub_request(:post, "www.example.com").
with(body: "abc",
headers: {'Content-Length' => 3})
stub_http_request(:post, "www.example.com").
with(body: {data: {a: "1", b: "five"}})
stub_request(:post, "www.example.com").
with {|request| some_checks(request) }

7. Response
stub_request(:any, "www.example.com").
to_return(body: "abc",
status: 200,
headers: {'Content-Length' => 3} )
stub_request(:any, 'www.example.net').
to_return {|request| {body: request.body} }

8. Raising exceptions
stub_request(:any, 'www.example.net').
to_raise("some error")
stub_request(:any, 'www.example.net').
to_raise(Errno::ECONNRESET.new("some error"))
stub_request(:any, 'www.example.net').
to_raise(Errno::ETIMEDOUT)
stub_request(:any, 'www.example.net').to_timeout

9. Stubbing with Rack
class MyRackApp
def self.call(env)
[200, {}, ["Hello"]]
end
end
stub_request(:get, "www.example.com").
to_rack(MyRackApp)

10. Allow real requests
WebMock.allow_net_connect!
WebMock.disable_net_connect!(
allow_localhost: true)
WebMock.disable_net_connect!(
allow: "www.example.org:8080")

11. Expectations
require 'webmock/rspec'
WebMock.should_not have_requested(:get,
"www.something.com")
WebMock.should have_requested(:get,
"www.example.com").
with(body: "abc",
headers: {'Content-Length' => 3}).twice
WebMock.should have_requested(:get,
"www.example.com").
with(query: {"a" => ["b", "c"]})

12. Replaying curl
`curl -is www.example.com > /tmp/example.txt`
raw_response_file = File.new("/tmp/example.txt")
stub_request(:get, "www.example.com").
to_return(raw_response_file)
stub_request(:get, "www.example.com").
to_return(raw_response_file.read)

13. VCR
Your tests
Your app
Webby stuff

14. Setup
group :test do
gem "vcr"
end
VCR.configure do |c|
c.cassette_library_dir = "vcr_cassettes"
c.hook_into :webmock
end
VCR.use_cassette("example-dot-com-index") do
Net::HTTP.get "www.example.com", "/"
end

15. Library support
Test::Unit Minitest RSpec Cucumber
VCR
Webmock Fakeweb Faraday Excon
Typhoeus

16. RSpec
RSpec.configure do |c|
c.extend VCR::RSpec::Macros
end
describe "something" do
use_vcr_cassette
it "does something" do
...
end
end

17. Cucumber
VCR.cucumber_tags do |t|
t.tag '@example-dot-com-index'
t.tag '@example-dot-com-another-request'
end
Feature: VCR stuff
@example-dot-com-index
Scenario: Do something
Given foo
When bar
Then baz

18. Cassettes
---
http_interactions:
- request:
method: get
uri: http://example.com/
body: ''
headers: {}
response:
status:
code: 200
message: OK
headers:
Content-Type:
- text/html;charset=utf-8
Content-Length:
- '26'
body: This is the response body
http_version: '1.1'
recorded_at: Tue, 01 Nov 2011 04:58:44 GMT
recorded_with: VCR 2.0.0

19. Request matching
VCR.configure do |c|
c.default_cassette_options = {
match_requests_on: [:method, :uri]}
end
Also available:
• :host
• :path
• :query
• :body
• :headers

20. Ignoring requests
VCR.configure do |c|
c.ignore_request do |request|
URI(request.uri).port == 7777
end
c.ignore_hosts "foo.com", "bar.com"
c.ignore_localhost = true
end

21. Summary
Use Webmock (or Fakeweb)
• For fine-grained control
• If remote server isn’t available
Use VCR
• When record/replay is enough
• For an easy life