Create a simple mock server from API Blueprint document for testing

blueprint_mock_server.rb

require "addressable/template"
require "redsnow"
require "sinatra"

class BlueprintMockServer
  def initialize(base_url, blueprint)
    @mocks = {}
    api = RedSnow.parse(File.read(blueprint.to_s))
    api.ast.resource_groups.flat_map(&:resources).each do |resource|
      uri_template = Addressable::Template.new(base_url + resource.uri_template)
      @mocks[uri_template] = Hash[resource.actions.map { |a| [a.method, a] }]
    end
  end

  def call(env)
    request = Rack::Request.new(env)
    action = match request
    return [404, {}, []] unless action
    responses(action).first || [500, {}, []]
  end

  def match(request)
    template = @mocks.keys.find { |uri| uri.match(request.url) }
    @mocks[template][request.request_method] if template
  end

  def responses(action)
    action.examples.flat_map(&:responses).map do |response|
      [response.name.to_i, headers(response), [response.body]]
    end
  end

  def headers(response)
    Hash[response.headers.collection.map { |item| [item[:name], item[:value]] }]
  end
end

test_helper.rb

require "webmock"
require "blueprint_mock_server"

base_url = "http://my-api-host"
blueprint = Rails.root.join("doc", "my-api-doc.apib")
app = BlueprintMockServer.new(base_url, path_to_blueprint)
WebMock::StubRegistry.instance.register_request_stub(
  WebMock::RequestStub.new(:any, /#{base_url}/)
).to_rack(app)

As a gem: https://github.com/karnov/apib-mock_server