AnyFixture: make DB fixtures from blocks

any_fixture.rb

module AnyFixture
  INSERT_RXP = /^INSERT INTO ([\S]+)/

  class Cache
    attr_reader :store

    delegate :clear, to: :store

    def initialize
      @store = {}
    end

    def fetch(key)
      return store[key] if store.key?(key)
      return unless block_given?
      store[key] = yield
    end
  end

  class << self
    def add(id)
      cache.fetch(id) do
        ActiveSupport::Notifications.subscribed(method(:subscriber), "sql.active_record") do
          yield
        end
      end
    end

    def subscriber(_event, _start, _finish, _id, data)
      matches = data.fetch(:sql).match(INSERT_RXP)
      tables_cache[matches[1]] = true if matches
    end

    def clean
      tables_cache.keys.each do |table|
        ActiveRecord::Base.connection.execute %(
          DELETE FROM #{table}
        )
      end
      tables_cache.clear
      cache.clear
    end

    private

    def cache
      @cache ||= Cache.new
    end

    def tables_cache
      @tables_cache ||= {}
    end
  end
end

RSpec.configure do |config|
  after(:suite) { AnyFixture.clean }  
end