Testing HTTP APIs in Ruby - @shaiguitar - RailsConf 2013

gistfile1.md

Testing HTTP APIs in Ruby

@shaiguitar

• Everything as a service
• Test it!
• Problem statement: Testing a server/client HTTP API
• Good plan:
  • Create API
  • Build client lib that can be used in confusmer apps
  • Make it easy for consumer apps to test w/ our client library
• How?

Isolation

• Test server, code server, test client, code client
• Have to use FakeWeb to mimic the server
  • Not testing the whole thing
  • No integration
  • non-representative tests

Sandboxes

• Running server that clients can test against
• Server dev the same
• Test client against real server
• If server API changes, test fail (good!)
• But...
• Setting up sandbox takes time
• Server API changes require releases to sandbox
• Real requests to sandbox slow down client tests
• Unique data conflicts
• Complex tests setup/teardown
• No fixtures shipped with client
• Still better than Isolation!

Fake Servers

• Create a fake server to use in the client
• Ship a fake_server.rb in the client
• Mirror of API from the outside, doesn't do all internal stuff

module MyAPI
  class FakeServer < Sinatra::Base
  end
end

• Fake server mimics API

• Slim code, Keep it simple

• Fast/in-memory

• Ensure low dependencies

• Run client tests against both real AND fake server

  • Local dev runs against just fake, CI runs against real (or both)

• Fake is validated by 'real' run mode

• Full integration

• Local dev of client is quick

• (fog & zendesk can do @client.mock!)

• (Look up github.com/lanej/cistern)

• More steps for client in making server code changes (mostly for client library developer)

Mapper style

• Share more code!
• Consolidate fake + real into one repo
• Only EngineYard does this
• Create a repo to hol
• Mappers in both API repos which maps between fake/real
• On rack you can mount shared API definitions together
• mount RealOrFake::Server, :at => 'api'
• Consumer apps using lib use fake mapper
• Still have full integration
• Less duplication of API definition code
• Specific lib dependencies (Rack and Faraday)
• Must be familiar w/ the concepts, it can be hard to maintain and enhance

Conclusions

• This bubble is all about APIs
• Consider using client to test server (sensical to couple server/client)
• Validated fake API is great for local client dev

Questions/Comments

• VCR could come in handy (use cached response locally, make fresh requests on CI)

Woah, we should have given the talk together! ;)

The slides are here:

github.com/shaiguitar/ruby_apis_and_clients