spec_rack_logger.rb

require 'rack/logger'
require 'rack/lint'
require 'stringio'

context "Rack::Logger" do
  specify "logs to rack.errors" do
    app = lambda { |env|
      log = env['rack.logger']
      log.debug("Created logger")
      log.info("Program started")
      log.warn("Nothing to do!")

      [200, {'Content-Type' => 'text/plain'}, ["Hello, World!"]]
    }

    errors = StringIO.new
    Rack::Logger.new(app).call({'rack.errors' => errors})
    errors.string.should.match "Program started"
    errors.string.should.match "Nothing to do"
  end
end