Testing joins, as recommended by Sean

https://github.com/paper-trail-gem/paper_trail/pull/1143#issuecomment-415132567

.rubocop.yml

@@ -95,6 +95,10 @@ Naming/PredicateName:
 Naming/UncommunicativeMethodParamName:
   Enabled: false
 
+# This cop does not seem to work in rubocop-rspec 1.28.0
+RSpec/DescribeClass:
+  Enabled: false
+
 # Yes, ideally examples would be short. Is it possible to pick a limit and say,
 # "no example will ever be longer than this"? Hard to say. Sometimes they're
 # quite long.

spec/dummy_app/app/models/management.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+# Note that there is no `type` column for this subclassed model, so changes to
+# Management objects should result in Versions which have an item_type of
+# Customer.
+class Management < Customer
+end

spec/models/family/celebrity_family_spec.rb

@@ -4,6 +4,18 @@ require "spec_helper"
 
 module Family
   RSpec.describe CelebrityFamily, type: :model, versioning: true do
+    describe "#joins" do
+      it "works on an STI model" do
+        described_class.create!
+        result = described_class.
+          joins(:versions).
+          select("families.id, max(versions.event) as event").
+          group("families.id").
+          first
+        expect(result.event).to eq("create")
+      end
+    end
+
     describe "#create" do
       it "creates version with item_subtype == class.name, not base_class" do
         carter = described_class.create(

spec/models/management_spec.rb

@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+require "spec_helper"
+
+::RSpec.describe(::Management, type: :model, versioning: true) do
+  it "utilises the base_class for STI classes having no type column" do
+    expect(Management.inheritance_column).to eq("type")
+    expect(Management.columns.map(&:name)).not_to include("type")
+
+    # Create, update, and destroy a Management and a Customer
+    customer1 = Customer.create(name: "Cust 1")
+    customer2 = Management.create(name: "Cust 2")
+    customer1.update(name: "Cust 1a")
+    customer2.update(name: "Cust 2a")
+    customer1.destroy
+    customer2.destroy
+
+    # All versions end up with an `item_type` of Customer
+    expect(
+      PaperTrail::Version.where(item_type: "Customer").count
+    ).to eq(6)
+    expect(
+      PaperTrail::Version.where(item_type: "Management").count
+    ).to eq(0)
+
+    # The item_subtype, on the other hand, is 3 and 3
+    expect(
+      PaperTrail::Version.where(item_subtype: "Customer").count
+    ).to eq(3)
+    expect(
+      PaperTrail::Version.where(item_subtype: "Management").count
+    ).to eq(3)
+  end
+end

spec/models/person_spec.rb

@@ -5,7 +5,7 @@ require "spec_helper"
 # The `Person` model:
 #
 # - has a dozen associations of various types
-# - has a custome serializer, TimeZoneSerializer, for its `time_zone` attribute
+# - has a custom serializer, TimeZoneSerializer, for its `time_zone` attribute
 RSpec.describe Person, type: :model, versioning: true do
   describe "#time_zone" do
     it "returns an ActiveSupport::TimeZone" do

spec/models/song_spec.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+require "spec_helper"
+
+::RSpec.describe(::Song, type: :model, versioning: true) do
+  describe "#joins" do
+    it "works" do
+      described_class.create!
+      result = described_class.
+        joins(:versions).
+        select("songs.id, max(versions.event) as event").
+        group("songs.id").
+        first
+      expect(result.event).to eq("create")
+    end
+  end
+end