Add spec to confirm CTEs work as expected

spec/chrono_model/time_machine/with_cte_spec.rb

@@ -0,0 +1,62 @@
+require 'spec_helper'
+
+RSpec.describe ChronoModel::TimeMachine do
+  include ChronoTest::TimeMachine::Helpers
+
+  adapter.create_table 'posts', temporal: true do |t|
+    t.string :title
+    t.references :author
+    t.timestamps
+  end
+
+  adapter.create_table 'authors', temporal: true do |t|
+    t.string :name
+    t.timestamps
+  end
+
+  class Post < ActiveRecord::Base
+    include ChronoModel::TimeMachine
+
+    belongs_to :author
+  end
+
+  class Author < ActiveRecord::Base
+    include ChronoModel::TimeMachine
+  end
+
+  describe '.with CTE' do
+    let(:author1) { Author.create(name: author1_name_as_of_post1) }
+    let(:post1) { Post.create(title: 'Post 1', author: author1) }
+    let(:author2) { Author.create(name: 'Author 2') }
+    let(:post2) { Post.create(title: 'Post 2', author: author2) }
+
+    let(:author1_name_as_of_post1) { 'Author 1.1' }
+    let(:author1_name_as_of_post2) { 'Author 1.2' }
+    let(:author1_name_as_of_now) { 'Author 1.3' }
+
+    before do
+      post1
+      sleep(0.05)
+      author1.update(name: author1_name_as_of_post2)
+      post2
+      sleep(0.05)
+      author1.update(name: author1_name_as_of_now)
+    end
+
+    it 'works' do
+      # it does not automatically add as_of to CTE
+      scope = Post.as_of(post2.created_at)
+                  .with(authors_cte: Author.all)
+                  .joins("inner join authors_cte on authors_cte.id = posts.author_id")
+      expect(scope.where(authors_cte: { name: author1_name_as_of_now }).count).to eq(1)
+      expect(scope.where(authors_cte: { name: author1_name_as_of_post2 }).count).to eq(0)
+
+      # it produces an as_of CTE
+      scope = Post.as_of(post2.created_at)
+                  .with(authors_cte: Author.as_of(post2.created_at).all)
+                  .joins("inner join authors_cte on authors_cte.id = posts.author_id")
+      expect(scope.where(authors_cte: { name: author1_name_as_of_now }).count).to eq(0)
+      expect(scope.where(authors_cte: { name: author1_name_as_of_post2 }).count).to eq(1)
+    end
+  end
+end