test.rb

require "bundler/inline"

gemfile(true) do
  source "https://rubygems.org"

  gem "rails", '5.1.6.2'
  gem 'pg'
  gem 'turbostreamer'
  gem 'oj'
end

require 'rails/all'
require "active_record"
require "action_controller/railtie"
require 'action_view/testing/resolvers'

require "turbostreamer"
ActionView::Template.register_template_handler :streamer, TurboStreamer::Handler

ActiveRecord::Base.establish_connection(adapter: "postgresql", database: "railstest")
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :users, force: true do |t|
    t.string :name
    t.timestamps
  end

  create_table :roles, force: true do |t|
    t.integer :user_id
    t.string :name
    t.timestamps
  end

end

class User < ActiveRecord::Base
  has_many :roles
end

class Role < ActiveRecord::Base
  belongs_to :user
end

class TestApp < Rails::Application
  secrets.secret_token    = "secret_token"
  secrets.secret_key_base = "secret_key_base"

  config.action_controller.perform_caching = true
  config.action_controller.enable_fragment_cache_logging = true
  config.cache_store = :memory_store, { size: 64.megabytes }

  config.logger = Logger.new($stdout)
  Rails.logger = config.logger

  routes.draw do
    resources :pools, only: :index
  end
end

class PoolsController < ActionController::Base
  include Rails.application.routes.url_helpers
  self.view_paths = [ActionView::FixtureResolver.new(
    "layouts/application.html.erb" => '<%= yield %>',
    "pools/index.json.streamer"=> <<-RB
      json.object! do
        json.cache! @users do
          json.users @users do |user|
          end
        end
      end
    RB
  )]

  def index
    @users = User.includes(:roles).where("roles.name IN ('a', 'b')").references(:roles)
    render layout: false
  end
end

Rails.backtrace_cleaner.remove_silencers!
require "minitest/autorun"

class PoolTest < Minitest::Test
  include Rack::Test::Methods

  def setup
    @app = Rails.application
    Rails.cache = ActiveSupport::Cache::MemoryStore.new
  end

  def test_index
    get "/pools.json"

    assert last_response.ok?
    assert_equal last_response.body, "# of primary categories: 1"
  end

  private

  def app
    @app
  end
end