How to test if some specific rack middleware is being used?

Question

To be more particular, I'm talking about sentry-raven and sinatra here. I saw examples testing sinatra applications, or middlewares. But I didn't see ones testing if some particular middleware is present. Or should I be testing behavior, not configuration (or how should I call it)?

Answer 1

With help from ruby-raven guys, we've got this:

ENV['RACK_ENV'] = 'test'

# the app: start

require 'sinatra'
require 'sentry-raven'

Raven.configure(true) do |config|
  config.dsn = '...'
end

use Raven::Rack

get '/' do
  'Hello, world!'
end

# the app: end

require 'rspec'
require 'rack/test'

Raven.configure do |config|
  logger = ::Logger.new(STDOUT)
  logger.level = ::Logger::WARN
  config.logger = logger
end

describe 'app' do
  include Rack::Test::Methods

  def app
    @app || Sinatra::Application
  end

  class TestRavenError < StandardError; end

  it 'sends errors to sentry' do
    @app = Class.new Sinatra::Application do
      get '/' do
        raise TestRavenError
      end
    end
    allow(Raven.client).to receive(:send).and_return(true)
    begin
      get '/'
    rescue TestRavenError
    end
    expect(Raven.client).to have_received(:send)
  end
end

Or if raven sending requests is in the way (when tests fail because of raven sending requests, and not because of the underlying error), one can disable them:

Raven.configure(true) do |config|
  config.should_send = Proc.new { false }
end

And mock Raven.send_or_skip instead:

...
allow(Raven).to receive(:send_or_skip).and_return(true)
begin
  get '/'
rescue TestRavenError
end
expect(Raven).to have_received(:send_or_skip)
...