EM with Redis tests

em_test.rb

def em(redis_url=REDIS_URL, &block)
  EM.run do
    redis = EM::Hiredis.connect(redis_url)
    block.call(redis)
  end
end

# ...
# fluffyness
# ...

it "returns keys for sources" do
  em do |redis|
    collector = VisitorsSources.new(redis)
    collector.sources.callback do |sources|
      @sources = sources
      EM.stop
    end
  end
  @sources.size.must_be :>, 0
end