Testing http calls with Webmock and VCR

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

Why?
Your tests

Your app

Webby stuff

Webmock
Test::Unit Minitest RSpec Cucumber

Your app

EM-HTTP-
Net::HTTP HTTPclient Patron
request

Curb Typhoeus Excon

Webmock

Setup
group :test do
gem "webmock"
end

require 'webmock/rspec'

require 'webmock/minitest'

require 'webmock/test_unit'

require 'webmock/cucumber'

Basic stub

stub_request :any,
"www.example.com"

Net::HTTP.get "www.example.com", "/"

# => 200 OK, body = ""

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) }

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} }

Raising exceptions
to_raise("some error")

to_raise(Errno::ECONNRESET.new("some error"))

to_raise(Errno::ETIMEDOUT)

stub_request(:any, 'www.example.net').to_timeout

Stubbing with Rack
class MyRackApp
def self.call(env)
[200, {}, ["Hello"]]
end
end

stub_request(:get, "www.example.com").
to_rack(MyRackApp)

Allow real requests
WebMock.allow_net_connect!

WebMock.disable_net_connect!(
allow_localhost: true)

WebMock.disable_net_connect!(
allow: "www.example.org:8080")

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"]})

Replaying curl
`curl -is www.example.com > /tmp/example.txt`
raw_response_file = File.new("/tmp/example.txt")

to_return(raw_response_file)

to_return(raw_response_file.read)

VCR
Your tests

Your app

Webby stuff

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

Library support
Test::Unit Minitest RSpec Cucumber

VCR

Webmock Fakeweb Faraday Excon

Typhoeus

RSpec
RSpec.configure do |c|
c.extend VCR::RSpec::Macros
end

describe "something" do
use_vcr_cassette

it "does something" do
...
end
end

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

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

Request matching
c.default_cassette_options = {
match_requests_on: [:method, :uri]}
end

Also available:

• :host
• :path
• :query
• :body
• :headers

Ignoring requests
c.ignore_request do |request|
URI(request.uri).port == 7777
end

c.ignore_hosts "foo.com", "bar.com"

c.ignore_localhost = true
end

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

Testing http calls with Webmock and VCR

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