Ruby on Rails: Best way to test a failed call to a third party API

Question

I call a third party web service right now as part of my application. I am using the RestClient gem in order to do this. There are a ton of tools available to do the same thing, so that should not matter.

What I'm curious about is having good enough tests, nothing too fancy, where I can simulate how my application responds when the third party web service is unavailable for whatever reason. Be it that I exceeded a rate limit or a timeout due to network latency/complications, I just want to be able to take something like an HTTP status code and test what my application does in that event.

What's the best way to do this with Test::Unit? Right now the call to the third party service is encapsulated inside of one of my controllers. I have a simple module with some wrapper methods for the different end points of the remote service. I just want to make sure that my application does the right things when the service is or isn't available.

Is using an additional framework next to Test::Unit that can 'stub' the right way to go about doing this? Obviously I can't force a network timeout and starting to hack with things like IPtables just for tests is not worth the time. I'm sure this problem has been solved a million times as integrating things such as Facebook and Twitter into web applications is so popular these days. How do you test for failure when reaching those APIs in a robust/controlled format?

Answer 1

I would recommend using something like webmock to mock all of your http requests (not just to mock a failed request); it'll greatly speed up your test suite instead of having to actually hit the third party service every time you run the tests.

Webmock supports Rest Client and Test::Unit. Just put this code in your test/test_helper.rb file:

require 'webmock/test_unit' 

As an example, to test a network timeout:

stub_request(:any, 'www.example.net').to_timeout
RestClient.post('www.example.net', 'abc')    # ===> RestClient::RequestTimeout

Answer 2

railscast: 291 (subscriber only) talks about testing with VCR and rspec (i know, not it's not Test:Unit)

anyway you could look into using VCR for this sort of thing