Using Webmock to Stub to a Rack App

Posted on 17 Jan 2013 by Eric Oestrich

I have been integrating with outside services recently and decided to use webmock to stub the requests. Instead of creating a bunch of stub_request for each section of the service you want to stub, you can just stub the entire domain to a rack app. It's a lesser known feature of webmock because it's just briefly mentioned in their readme.

You just have to call #to_rack at the end of a stub_request instead of #to_return. In the rack app you can also validate that the requests you are sending contain the correct headers, are authenticated correctly, etc.

spec/spec_helper.rb
RSpec.configure do |config|
  config.before do
    stub_request(:any, /outsideservice\.com/).to_rack(OutsideServiceApp.new)
  end
end
spec/support/outsideserviceapp.rb
class OutsideServiceApp
  def call(env)
    validate_request(env)

    case [env["REQUEST_METHOD"], env["PATH_INFO"]]
    when ["GET", "/orders"]
      [200, {}, [File.read("spec/fixtures/orders.json")]]
    else
      [404, {}, []]
    end
  end

  ...
end
spec/outsideservicecaller_spec.rb
describe OutsideServceCaller do
  it "should load orders" do
    OutsideServiceCaller.orders.should == File.read("spec/fixtures/orders.json")
  end
end
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