Add RSpec test case for #404

spec/models/animal_spec.rb

@@ -0,0 +1,19 @@
+require 'rails_helper'
+
+describe Animal, :type => :model do
+  it { is_expected.to be_versioned }
+
+  describe "STI", :versioning => true do
+    it { expect(Animal.inheritance_column).to eq('species') }
+
+    describe "updates to the `inheritance_column`" do
+      subject { Cat.create!(name: 'Leo') }
+
+      it "should be allowed" do
+        subject.update_attributes(:name => 'Spike', :species => 'Dog')
+        dog = Animal.find(subject.id)
+        expect(dog).to be_instance_of(Dog)
+      end
+    end
+  end
+end