Testing ActiveRecord Concerns

README.md

Testing ActiveRecord Concerns

This gist illustrates the full spec suite of the example used in Testing ActiveRecord Concerns

Copy the testing-concerns.rb file and run rspec testing-concerns.rb

The output should look something like

... bundling ...
... some database logs ...

Finished in 0.04126 seconds (files took 6.61 seconds to load)
10 examples, 0 failures

This gist is available as open-source under the terms of the MIT License.

testing-concerns.rb

# frozen_string_literal: true

# -- RAILS SETUP (ignore) --

require "bundler/inline"

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

  git_source(:github) { |repo| "https://github.com/#{repo}.git" }

  gem "rails", github: "rails/rails", branch: "main"
  gem 'rspec-rails', '~> 4.0.2'
  gem "sqlite3"
  gem 'byebug'
end

require 'byebug'
require "active_record"
require "minitest/autorun"
require "logger"
require 'rails/all'

# This connection will do for database-independent bug reports.
ActiveRecord::Base.configurations = { "test" => { adapter: "sqlite3", database: "database.sqlite" } }
ActiveRecord::Base.establish_connection ActiveRecord::Base.configurations['test']
ActiveRecord::Base.logger = Logger.new(STDOUT)

# -- RAILS APP --

ActiveRecord::Schema.define do
  create_table :posts, force: true do |t|
    t.datetime :reviewed_at
    t.string :title, null: false
  end
end

# requires #reviewed_at:datetime column
module Reviewable
  extend ActiveSupport::Concern

  included do
    scope :reviewed, -> { where.not(reviewed_at: nil) }
    scope :unreviewed, -> { where(reviewed_at: nil) }
  end

  def reviewed?
    reviewed_at.present?
  end

  def review(time = DateTime.current)
    update(reviewed_at: time)
  end
end

class Post < ActiveRecord::Base
  include Reviewable

  validates_presence_of :title
end

# -- RAILS SPEC HELPER --

module InMemoryDatabaseHelpers
  extend ActiveSupport::Concern

  class_methods do
    def switch_to_SQLite(&block)
      before(:all) { switch_to_in_memory_database(&block) }
      after(:all) { switch_back_to_test_database }
    end
  end

  private

  def switch_to_in_memory_database(&block)
    raise 'No migration given' unless block_given?

    ActiveRecord::Migration.verbose = false
    ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:")
    ActiveRecord::Schema.define(version: 1, &block)
  end

  def switch_back_to_test_database
    ActiveRecord::Base.establish_connection(ActiveRecord::Base.configurations['test'])
  end
end

# -- RAILS SPEC SUITE --

# requires a :reviewable object
shared_examples 'reviewable'do
  describe 'the interface' do
    subject { described_class.new }

    it 'has the correct interface' do
      expect(subject).to respond_to(:reviewed?)
      expect(subject).to respond_to(:review)
      expect(described_class).to respond_to(:reviewed)
      expect(described_class).to respond_to(:unreviewed)
    end
  end

  describe 'scopes' do
    let!(:records) { described_class.where(id: [reviewed, unreviewed]) }

    before do
      expect(reviewed.reviewed?).to eql true
      expect(unreviewed.reviewed?).to eql false
    end

    describe '.reviewed' do
      subject { records.reviewed }

      it { is_expected.to eq [reviewed] }
    end

    describe '.unreviewed' do
      subject { records.unreviewed }

      it { is_expected.to eq [unreviewed] }
    end
  end

  describe '#reviewed?' do
    subject { described_class.new }

    it 'returns the correct boolean based on #reviewed_at' do
      subject.reviewed_at = nil
      expect(subject.reviewed?).to eql false

      subject.reviewed_at = DateTime.current
      expect(subject.reviewed?).to eql true
    end
  end

  describe '#review' do
    let(:time) { DateTime.current }

    subject { unreviewed.review(time) }

    it 'updates the reviewed_at attribute' do
      expect { subject }.to change { unreviewed.reload.reviewed_at }.from(nil).to(time)
    end
  end
end

class FakeReviewable < ActiveRecord::Base
  include Reviewable
end

describe Reviewable do
  include InMemoryDatabaseHelpers

  switch_to_SQLite do
    create_table :fake_reviewables do |t|
      t.datetime :reviewed_at
    end
  end

  describe FakeReviewable, type: :model do
    include_examples 'reviewable' do
      let(:reviewed)   { FakeReviewable.create! reviewed_at: DateTime.current }
      let(:unreviewed) { FakeReviewable.create! reviewed_at: nil }
    end
  end
end

# This example is at the end to show that the Rails app went back to the current testing database configuration defined in the setup
describe Post do
  include_examples 'reviewable' do
    let(:reviewed)   { Post.create! title: 'title1', reviewed_at: DateTime.current }
    let(:unreviewed) { Post.create! title: 'title2', reviewed_at: nil }
  end
end