The document discusses various techniques for testing services in Ruby on Rails applications. It begins by defining what a service is and why testing services is important. It then covers different approaches to stubbing or mocking external services in tests to avoid making real HTTP requests, including using libraries like WebMock, VCR, and ShamRack. The document recommends stubbing or mocking services when possible for fast, reliable tests and also discusses tools for automatically recording and replaying responses like Puffing Billy.

1. Effectively
Testing Services
Neal Kemp

2. $ whoami
Iowa native
Now: Californian
Software Developer
Independent Consultant

3. What I Do
Ruby / Rails
Javascript / Angular
HTML, CSS, etc

4. what,why&how
of testing services

5. NOT
Building testable services

6. NOT
Test-driven development
(necessarily)

7. … and because I don’t want @dhh to rage

8. what

9. What is a service?
Internal “SOA”

10. Any time you make an HTTP
request to an endpoint in
another repository

11. why

12. Why are services important?
Build faster
Makes scaling easier
Use them on virtually every application
Increasingly prevalent

13. Services are critical to
modern Rails development

14. Why is testing services important?
You (should) test everything else
Services compose crucial features
You may encounter problems…

15. Internal API
Sometimes null responses
Inconsistencies
Catastrophe

16. Okay? But what about external APIs?

18. {"id": 24}
{"code": "ANA"}

19. "goals":[
{
"per":"1",
"ta":"CGY",
"et":"14:11",
"st":"Wrist Shot"
},
{
"per":"2",
"ta":"ANA",
"et":"11:12",
"st":"Backhand"
}
]
"goals": {
"per":"1",
"ta":"CGY",
"et":"14:11",
"st":"Wrist Shot"
}

20. No versioning!

22. Snapchat Client
Haphazard documentation
What are the requests?
Bizarre obfuscation
github.com/nneal/snapcat

23. how

24. What is different about services?
External network requests
You don’t own the code

26. On an airplane…
Failure is bad!
No network requests

27. Don’t interact with services from
test environment* **

28. * Includes “dummy” APIs

29. ** Using pre-recorded responses
is okay

30. Assuming: Rails, rspec

31. Timetostub!

32. Built-in Stubbing
Typhoeus
Faraday
Excon

33. Simplify.

34. gem 'webmock'

35. ENV['RAILS_ENV'] ||= 'test'
require File.expand_path('../../config/environment', __FILE__)
require 'rspec/autorun'
require 'rspec/rails’
Dir[Rails.root.join("spec/support/**/*.rb")].each { |f| require f }
ActiveRecord::Migration.check_pending! if defined?(ActiveRecord::Migration)
RSpec.configure do |config|
config.infer_base_class_for_anonymous_controllers = false
config.order = 'random’
end
WebMock.disable_net_connect!
spec/spec_helper.rb

37. module FacebookWrapper
def self.user_id(username)
user_data(username)['id']
end
def self.user_data(username)
JSON.parse(
open("https://graph.facebook.com/#{username}").read
)
end
end
lib/facebook_wrapper.rb

38. require 'facebook_wrapper'
config/intializers/facebook_wrapper.rb

39. require 'spec_helper'
describe FacebookWrapper, '.user_link' do
it 'retrieves user link' do
stub_request(:get, 'https://graph.facebook.com/arjun').
to_return(
status: 200,
headers: {},
body: '{
"id": "7901103","first_name": "Arjun",
"locale": "en_US","username": "Arjun"
}'
)
user_id = FacebookWrapper.user_id('arjun')
expect(user_id).to eq '7901103'
end
end
spec/lib/facebook_wrapper_spec.rb

40. require 'spec_helper'
describe FacebookWrapper, '.user_link' do
it 'retrieves user link' do
stub_request(:get, 'https://graph.facebook.com/arjun').
to_return(
status: 200,
headers: {},
body: '{
"id": "7901103","first_name": "Arjun",
"locale": "en_US","username": "Arjun"
}'
)
user_id = FacebookWrapper.user_id('arjun')
expect(user_id).to eq '7901103'
end
end
spec/lib/facebook_wrapper_spec.rb

41. require 'spec_helper'
describe FacebookWrapper, '.user_link' do
it 'retrieves user link' do
stub_request(:get, 'https://graph.facebook.com/arjun').
to_return(
status: 200,
headers: {},
body: '{
"id": "7901103","first_name": "Arjun",
"locale": "en_US","username": "Arjun"
}'
)
user_id = FacebookWrapper.user_id('arjun')
expect(user_id).to eq '7901103'
end
end
spec/lib/facebook_wrapper_spec.rb

42. require 'spec_helper'
describe FacebookWrapper, '.user_link' do
it 'retrieves user link' do
stub_request(:get, 'https://graph.facebook.com/arjun').
to_return(
status: 200,
headers: {},
body: '{
"id": "7901103","first_name": "Arjun",
"locale": "en_US","username": "Arjun"
}'
)
user_id = FacebookWrapper.user_id('arjun')
expect(user_id).to eq '7901103'
end
end
spec/lib/facebook_wrapper_spec.rb

43. Even Better
No network requests
Fast!
No intermittent failure

44. Mock-Services
AWS
FB graph mock
OmniAuth
Etc…

45. gem 'fb_graph-mock'

46. ENV['RAILS_ENV'] ||= 'test'
require File.expand_path('../../config/environment', __FILE__)
require 'rspec/autorun'
require 'rspec/rails’
require 'fb_graph/mock'
Dir[Rails.root.join("spec/support/**/*.rb")].each { |f| require f }
ActiveRecord::Migration.check_pending! if defined?(ActiveRecord::Migration)
RSpec.configure do |config|
config.infer_base_class_for_anonymous_controllers = false
config.order = 'random'
config.include FbGraph::Mock
end
WebMock.disable_net_connect!
spec/spec_helper.rb

47. describe FacebookWrapper, '.user_link' do
it 'retrieves user link' do
mock_graph :get, 'arjun', 'users/arjun_public' do
user_id = FacebookWrapper.user_id('arjun')
expect(user_id).to eq '7901103'
end
end
end
spec/lib/facebook_wrapper_spec.rb

48. describe FacebookWrapper, '.user_link' do
it 'retrieves user link' do
mock_graph :get, 'arjun', 'users/arjun_public' do
user_id = FacebookWrapper.user_id('arjun')
expect(user_id).to eq '7901103'
end
end
end
spec/lib/facebook_wrapper_spec.rb

49. Even Better
Already stubbed for you
Pre-recorded responses (sometimes)
Don’t need to know API endpoints

50. gem 'sham_rack'

51. gem 'sinatra'

52. ENV['RAILS_ENV'] ||= 'test'
require File.expand_path('../../config/environment', __FILE__)
require 'rspec/autorun'
require 'rspec/rails’
Dir[Rails.root.join("spec/support/**/*.rb")].each { |f| require f }
ActiveRecord::Migration.check_pending! if defined?(ActiveRecord::Migration)
RSpec.configure do |config|
config.infer_base_class_for_anonymous_controllers = false
config.order = 'random’
end
WebMock.disable_net_connect!
spec/spec_helper.rb

53. ShamRack.at('graph.facebook.com', 443).sinatra do
get '/:username' do
%Q|{
"id": "7901103",
"name": "Arjun Banker",
"first_name": "Arjun",
"last_name": "Banker",
"link": "http://www.facebook.com/#{params[:username]}",
"location": {
"id": 114952118516947,
"name": "San Francisco, California"
},
"gender": "male"
}|
end
end
spec/support/fake_facebook.rb

54. ShamRack.at('graph.facebook.com', 443).sinatra do
get '/:username' do
%Q|{
"id": "7901103",
"name": "Arjun Banker",
"first_name": "Arjun",
"last_name": "Banker",
"link": "http://www.facebook.com/#{params[:username]}",
"location": {
"id": 114952118516947,
"name": "San Francisco, California"
},
"gender": "male"
}|
end
end
spec/support/fake_facebook.rb

55. ShamRack.at('graph.facebook.com', 443).sinatra do
get '/:username' do
%Q|{
"id": "7901103",
"name": "Arjun Banker",
"first_name": "Arjun",
"last_name": "Banker",
"link": "http://www.facebook.com/#{params[:username]}",
"location": {
"id": 114952118516947,
"name": "San Francisco, California"
},
"gender": "male"
}|
end
end
spec/support/fake_facebook.rb

56. ShamRack.at('graph.facebook.com', 443).sinatra do
get '/:username' do
%Q|{
"id": "7901103",
"name": "Arjun Banker",
"first_name": "Arjun",
"last_name": "Banker",
"link": "http://www.facebook.com/#{params[:username]}",
"location": {
"id": 114952118516947,
"name": "San Francisco, California"
},
"gender": "male"
}|
end
end
spec/support/fake_facebook.rb

57. describe FacebookWrapper, '.user_link' do
it 'retrieves user link' do
user_id = FacebookWrapper.user_id('arjun')
expect(user_id).to eq '7901103’
end
end
spec/lib/facebook_wrapper_spec.rb

58. Even Better
Dynamic
Expressive
Readable

59. gem 'vcr'

60. ENV['RAILS_ENV'] ||= 'test'
require File.expand_path('../../config/environment', __FILE__)
require 'rspec/autorun'
require 'rspec/rails’
Dir[Rails.root.join("spec/support/**/*.rb")].each { |f| require f }
ActiveRecord::Migration.check_pending! if defined?(ActiveRecord::Migration)
RSpec.configure do |config|
config.infer_base_class_for_anonymous_controllers = false
config.order = 'random’
end
WebMock.disable_net_connect!
VCR.configure do |c|
c.cassette_library_dir = 'spec/fixtures/vcr_cassettes'
c.hook_into :webmock
end
spec/spec_helper.rb

61. describe FacebookWrapper, '.user_link' do
it 'retrieves user link' do
VCR.use_cassette('fb_user_arjun') do
user_id = FacebookWrapper.user_id('arjun')
expect(user_id).to eq '7901103'
end
end
end
spec/lib/facebook_wrapper_spec.rb

62. describe FacebookWrapper, '.user_link' do
it 'retrieves user link' do
VCR.use_cassette('fb_user_arjun') do
user_id = FacebookWrapper.user_id('arjun')
expect(user_id).to eq '7901103'
end
end
end
spec/lib/facebook_wrapper_spec.rb

63. Even Better
Record API automatically
Replay responses without network
Verify responses

64. Additional Build Process
Runs outside normal test mode
Rechecks cassettes for diffs
Avoids versioning issues

65. gem 'puffing-billy'

66. Puffing-Billy
Built for in-browser requests
Allowed to record and reuse (like VCR)

67. Be brave, venture
out of ruby

68. I also like…

69. Chrome Dev Tools

70. Postman

71. HTTPie

72. Charles

73. Additional Reading
martinfowler.com/bliki/IntegrationContractTest.html
robots.thoughtbot.com/how-to-stub-external-services-in-tests
joblivious.wordpress.com/2009/02/20/handling-intermittence-how-to-
survive-test-driven-development
railscasts.com/episodes/291-testing-with-vcr

74. Bringing it all together
Testing services is crucial
If in doubt, stub it out
Determine the flexibility you want
Record responses to save time

75. Next Up
Eliminating Inconsistent Test Failures
with Austin Putman

76. Thank you!
me@nealke.mp
(I like emails)
@neal_kemp
(I tweet)