Shared examples spec'ing JSON API of a RESTful model backed by Ohm (Redis), for RSpec 3

spec_support_restful_ohm_resource.rb

# Shared examples take a model class as parameters, and expect:
# 1. ``create_attrs`` and ``update_attrs`` to be available in the context.
# 2. ``user`` method to be available in the context, representing currently logged in user.
# 3. Factory to be defined for the model, and ``build`` method to be included into examples.
#
# EXAMPLE
# -------
#
# 1. factories.rb:
#     FactoryGirl.define do
#       factory :jaeger do
#         id { SecureRandom::uuid }
#         name { Faker::Name.name }
#         year { Faker::Number.number(4) }
#       end
#     end
#
# 2. jaeger_spec.rb:
#   
#   # ... bootstrapping, API setup etc
#   context 'Jaeger API' do
#     let(:create_attrs) { { name: 'Striker Eureka', year: '2019' } }
#     let(:update_attrs) { { name: 'Chrome Brutus', year: '2017' } }
#
#     it_behaves_like 'a RESTful Ohm resource', Jaeger
#   end
#
# This spec also assumes that all requests and responses are JSON data, with model name as the root key, e.g.:
#   { jaeger: { name: 'Striker Eureka' } }
#

RSpec.shared_examples "a RESTful Ohm resource" do |model|
  let(:path) { '/' + model.to_s.underscore.pluralize }
  let(:class_str) { model.to_s.underscore }
  let(:class_sym) { class_str.to_sym }

  describe 'POST' do
    subject(:create_resource) { post path, class_sym => create_attrs }

    it 'creates new resource' do
      expect { create_resource }.to change { model.all.size }.by(1)
    end

    describe 'created resource' do
      let!(:new_resource) do
        old_ids = model.all.ids
        create_resource
        id = (model.all.ids - old_ids).last
        expect(id).to_not be_nil
        model[id]
      end

      it 'returned in the response' do
        expect(last_response.status).to eq 201
        expect(
          JSON.parse(last_response.body)[class_str]
        ).to represent_entity_of(new_resource)
      end

      it 'is assigned to the current user' do
        expect(new_resource.user).to eq user
      end

      it 'is given a UUID' do
        expect(new_resource.id).to_not be_nil
      end
    end
  end

  describe "#{model.to_s.underscore.pluralize}/:id" do
    let(:resource) { build(class_sym, user: user).tap(&:save) }

    describe 'GET' do
      before { get "#{path}/#{resource.id}" }

      it 'returns resource data' do
        expect(last_response.status).to eq 200
        expect(
          JSON.parse(last_response.body)[class_str]
        ).to represent_entity_of(resource)
      end
    end

    describe 'PUT' do
      before { put "#{path}/#{resource.id}", class_sym => update_attrs }

      it 'updates resource' do
        expect(resource.load!.attributes).to include update_attrs
      end

      it 'returns updated resource data' do
        expect(last_response.status).to eq 200
        expect(
          JSON.parse(last_response.body)[class_str]
        ).to represent_entity_of(resource.load!)
      end
    end

    describe 'DELETE' do
      before { delete "#{path}/#{resource.id}" }

      it 'deletes resource' do
        expect(model[resource.id]).to be_nil
      end

      it 'returns deleted resource data' do
        expect(last_response.status).to eq 200
        expect(
          JSON.parse(last_response.body)[class_str]
        ).to represent_entity_of(resource)
      end
    end

  end

end