Serves a rack app based on paths/responses defined in a cucumber feature

fake_endpoints.rb

require 'gherkin/parser/parser'
require 'gherkin/formatter/json_formatter'
#This is intended to be mounted on top of a rails app with 
#mount FakeEndpoints => "/fake_api"
#this allows clients to play around with an intended implementation of the API without it being actually coded at all
#the features look like
# Given I GET /an/endpoint; Then the JSON response is:
class FakeEndpoints
  def initialize
    @routes = gather_routes
  end

  def call(env)
    payload = @routes[env["PATH_INFO"]]
    if payload
      [200, {"Content-Type" => "application/hal+json"}, [payload]]
    else
      [404, {"Content-Type" => "application/json"}, ['{"message": "these are not the bytes you are looking for"}']
    end
  end

  private
  def gather_routes
    Walker.texas_ranger
  end

  class Walker
    def self.texas_ranger
      chuck = Walker.new
      chuck.visit("#{Rails.root}/features/api_endpoints.feature")
      chuck.gathered
    end

    attr_reader :gathered

    def initialize
      @gathered = {}
    end


    def visit(path)
      io = StringIO.new
      formatter = Gherkin::Formatter::JSONFormatter.new(io)
      parser = Gherkin::Parser::Parser.new(formatter)
      parser.parse(IO.read(path), path, 0)
      formatter.done

      parsed = JSON.parse(io.string)
      feature = parsed.first
      feature["elements"].each do |scenario|
        next if scenario["steps"].nil?
        next unless scenario["steps"].size == 2
        route = scenario["steps"].first["name"].match(/I GET "(.*)"/)[1]
        payload = scenario["steps"].last["doc_string"]["value"].gsub(/\s+/, " ")
        gathered.merge!({route => payload})
      end
    end
  end
end