Testing Ruby modules included on and making use of ActiveRecrord Model functionality in RSpec

ar_module_spec.rb

# Recently I had need to work on an ActiveRecord model
# that gained much of its functionality through the
# inclusion of a Ruby Module. Over the course of the
# work, I found that many of the models that include
# the module also included duplicated specs to cover
# the inherited behavior.
#
# Of course, this isn't ideal.
#
# In a perfect world, the module's behavior would be
# exercised in isolation. It would have its own spec
# file and specs and allow removal of all the similar
# specs on the including models. Unfortunately, most
# Rails apps don't have a generic model just lying
# around to function as a stand-in in testing
# situations such as this.
#
# The solution: Build an ActiveRecord model with the
# required attributes and methods at spec runtime.
#
# Thanks to Foraker Labs and user hjing on
# StackOverflow for filling in the gaps!
# 
# https://www.foraker.com/blog/testing-activerecord-modules
# https://stackoverflow.com/questions/14431723/activemodelvalidations-on-anonymous-class
#
require "spec_helper_rails"

describe SomeNamespace::SomeModuleToTest do

  let(:mock_class) { build_mock_class }
  let!(:record) { mock_class.create(some_required_attribute: 1) }

  before(:all) { create_table }
  after(:all) { drop_table }
  
  describe "some behavior" do
    it "does a thing" do
      # ...
    end
  end

  def build_mock_class
    Class.new(ActiveRecord::Base) do
      self.table_name = "mock_table"
      reset_column_information

      include SomeNamespace::SomeModuleToTest

      # Required to prevent ArgumentError within AR
      def self.name 
        "MockClass"
      end
    end
  end

  def create_table
    ActiveRecord::Base.connection.create_table :mock_table do |t|
      t.integer :some_required_attribute
    end
  end

  def drop_table
    ActiveRecord::Base.connection.drop_table :mock_table
  end
end