Integrando una API en Rails

Gemfile

gem 'faraday'
gem 'faraday_middleware'

group :test do
  gem 'rspec-rails'
  gem 'webmock'
end

holidays_fetcher.rb

# app/services/external/holidays_fetcher.rb
class External::HolidaysFetcher
  URL = 'http://nolaborables.com.ar'.freeze

  def initialize
    @connection = Faraday.new(url: URL) do |faraday|
      faraday.request  :url_encoded
      faraday.response :json, content_type: 'application/json'
      faraday.adapter  Faraday.default_adapter
    end
  end

  def call(year: Date.current.year, with_optional: true)
    parameters = with_optional ? {incluir: :opcional} : {}
    response   = @connection.get("/api/v2/feriados/#{year}", parameters)

    return false unless response.success?

    build_holidays(response)
  end

  private

  def build_holidays(response)
    response.body.map do |holiday|
      External::Holiday.new(holiday)
    end
  end
end

holidays_fetcher_spec.rb

# spec/services/external/holidays_fetcher_spec.rb
require 'rails_helper'
require 'mocks/holidays_mock'

describe External::HolidaysFetcher do
  subject(:fetcher) { described_class.new }

  describe '#call' do
    shared_examples 'External::Holiday builder' do
      it 'returns External::Holiday records' do
        holidays = subject

        expect(holidays).not_to be_empty

        holidays.each do |holiday|
          expect(holiday).to be_an_instance_of(External::Holiday)
        end
      end
    end

    shared_examples 'Optional External::Holiday builder' do
      it 'builds optional External::Holiday' do
        expect(subject.any?(&:optional?)).to be true
      end
    end

    shared_examples 'HTTP connection to external API' do
      it 'makes an HTTP request to the external API' do
        subject
        expect(api_mock).to have_been_requested
      end
    end

    shared_examples 'Current year holidays fetcher' do
      it 'uses current year as part of the URI' do
        subject
        uri_regex = /nolaborables\.com\.ar\/api\/v2\/feriados\/#{Date.current.year}/

        expect(WebMock.stub_request(:get, uri_regex))
          .to have_been_requested
      end
    end

    context "when 'with_optional' argument is not received" do
      let!(:api_mock) { HolidaysMock.mock(:all) }

      subject { fetcher.call }

      it_behaves_like 'External::Holiday builder'
      it_behaves_like 'Optional External::Holiday builder'
      it_behaves_like 'HTTP connection to external API'
      it_behaves_like 'Current year holidays fetcher'
    end

    context  "when 'year' argument is received" do
      let(:year) { Date.current.year - 1 }
      let!(:api_mock) do
        HolidaysMock.mock(
          :all,
          /nolaborables\.com\.ar\/api\/v2\/feriados\/#{year}/
        )
      end

      subject { fetcher.call(year: year) }

      it_behaves_like 'External::Holiday builder'
      it_behaves_like 'Optional External::Holiday builder'
      it_behaves_like 'HTTP connection to external API'
    end

    context 'when requesting holidays with optional ones' do
      let!(:api_mock) { HolidaysMock.mock(:all) }

      subject { fetcher.call(with_optional: true) }

      it_behaves_like 'External::Holiday builder'
      it_behaves_like 'Optional External::Holiday builder'
      it_behaves_like 'HTTP connection to external API'
      it_behaves_like 'Current year holidays fetcher'
    end

    context 'when requesting holidays without optional ones' do
      let!(:api_mock) { HolidaysMock.mock(:all_except_optional) }

      subject { fetcher.call(with_optional: false) }

      it_behaves_like 'External::Holiday builder'
      it_behaves_like 'HTTP connection to external API'
      it_behaves_like 'Current year holidays fetcher'

      it 'does not build any optional External::Holiday' do
        expect(subject.any?(&:optional?)).to be false
      end
    end

    context 'when there is a connection error' do
      let!(:api_mock) { HolidaysMock.mock(:connection_error) }

      subject { fetcher.call }

      it { is_expected.to be false }
    end
  end
end

holidays_mock.rb

# spec/mocks/holidays_mock.rb
require 'webmock'

class HolidaysMock
  include WebMock::API

  URI = /nolaborables\.com\.ar\/api\/v2\/feriados\/\d{4}/.freeze
  URI_WITHOUT_OPTIONAL = /nolaborables\.com\.ar\/api\/v2\/feriados\/\d{4}$/.freeze
  URI_WITH_OPTIONAL = /nolaborables\.com\.ar\/api\/v2\/feriados\/\d{4}\?incluir=opcional$/.freeze

  def self.mock(method, *args)
    mock_object.send(method, *args)
  end

  def all(uri = nil)
    stub_holidays(
      uri || URI_WITH_OPTIONAL,
      File.read('spec/mocks/data/holidays_with_optional.json')
    )
  end

  def all_except_optional
    stub_holidays(
      URI_WITHOUT_OPTIONAL,
      File.read('spec/mocks/data/holidays_without_optional.json')
    )
  end

  def connection_error
    stub_request(:get, URI).to_return(
      body:    '{"error": "Error de conexión"}',
      status:  500,
      headers: {'Content-Type' => 'application/json'}
    )
  end

  class << self
    private

    def mock_object
      @mock_object ||= HolidaysMock.new
    end
  end

  private

  def stub_holidays(uri, response)
    stub_request(:get, uri)
      .to_return(
        body:    response,
        status:  200,
        headers: {'Content-Type' => 'application/json'}
      )
  end
end

spec_helper.rb

# spec/spec_helper.rb
require 'webmock/rspec'

RSpec.configure do |config|
  # ...
end