Have stubbed service emulate failures

fake_github.rb

require 'sinatra/base'

class FakeGitHub < Sinatra::Base
  cattr_reader :emulate_failure
  
  def self.reset!
    @@emulate_failure = false
  end
  
  def self.emulate_failure!
    @@emulate_failure = true
  end
  
  get '/repos/:organization/:project/contributors' do
    if emulate_failure
      json_response 400, 'error.json'
    else
      json_response 200, 'contributors.json'
    end
  end

  private

  def json_response(response_code, file_name)
    content_type :json
    status response_code
    File.open(File.dirname(__FILE__) + '/fixtures/' + file_name, 'rb').read
  end
end

some_spec.rb

require 'spec_helper'

feature 'External request' do
  after do
    FakeGitHub.reset!
  end
  
  it 'queries FactoryGirl contributors on Github' do
    FakeGitHub.emulate_failure!
    
    uri = URI('https://api.github.com/repos/thoughtbot/factory_girl/contributors')

    expect(response).to have_http_status(:bad_request)
  end
end