☑️ Add test to clarify expected configuration

With Knapsack, we're noticing that load path issues can be a subtle
problem.

With this commit, I'm testing the configuration to ensure that we have
the expected and correct lamba for generating IIIF Page's file titles.

Related to:

- https://github.com/scientist-softserv/adventist-dl/issues/628

app/services/iiif_print/manifest_builder_service_behavior_decorator.rb

@@ -1,19 +1,10 @@
 # frozen_string_literal: true
 
-# OVERRIDE IiifPrint v1.0.0 to not render thumbnail files in the UV
-IiifPrint::ManifestBuilderServiceBehavior.module_eval do
+module HykuKnapsack::ManifestBuilderServiceDecorator
   def build_manifest(presenter:)
-    manifest = manifest_factory.new(presenter).to_h
-    hash = JSON.parse(manifest.to_json)
-    parent_and_child_solr_hits = parent_and_child_solr_hits(presenter) if @child_works.present?
-    hash = send("sanitize_v#{@version}", hash: hash, presenter: presenter, solr_doc_hits: parent_and_child_solr_hits)
-    if @child_works.present? && IiifPrint.config.sort_iiif_manifest_canvases_by
-      send("sort_canvases_v#{@version}",
-           hash: hash,
-           sort_field: IiifPrint.config.sort_iiif_manifest_canvases_by)
-    end
-    hash['rendering'] = rendering(presenter: presenter)
-    hash
+    returning_hash = super
+    returning_hash['rendering'] = rendering(presenter: presenter)
+    returning_hash
   end
 
   def rendering(presenter:)
@@ -51,3 +42,5 @@ def sanitize_label(label)
   end
 end
 # rubocop:enable Metrics/BlockLength
+
+Hyrax::ManifestBuilderService.prepend(HykuKnapsack::ManifestBuilderServiceDecorator)

spec/config/initializers/iiif_print_spec.rb

@@ -0,0 +1,44 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe IiifPrint do
+  describe '.config' do
+    describe '.unique_child_title_generator_function' do
+      subject { described_class.config.unique_child_title_generator_function }
+
+      it 'is defined in HykuKnapsack::Engine' do
+        # Verifying that we're using the configured title generator for PDFs.
+        # Triage for: https://github.com/scientist-softserv/adventist-dl/issues/628
+        expect(subject.source_location[0]).to(
+          eq(HykuKnapsack::Engine.root.join('config', 'initializers', 'iiif_print.rb').to_s)
+        )
+      end
+    end
+    describe '.sort_iiif_manifest_canvases_by' do
+      it do
+        # require 'byebug'; byebug
+      end
+    end
+  end
+
+  describe 'decoration of Hyrax::ManifestBuilderService' do
+    describe '#manifest_for method' do
+      subject { Hyrax::ManifestBuilderService.instance_method(:manifest_for).source_location[0] }
+
+      # Verifying that we're using the IIIF Print provided source_location; in particular we're not
+      # using the undecorated Hyrax version.
+      it { is_expected.to start_with(IiifPrint::Engine.root.to_s) }
+    end
+
+    describe '#build_manifest' do
+      subject { Hyrax::ManifestBuilderService.instance_method(:build_manifest).source_location[0] }
+
+      it do
+        is_expected.to(
+          eq(HykuKnapsack::Engine.root.join('app', 'services', 'iiif_print', 'manifest_builder_service_behavior_decorator.rb').to_s)
+        )
+      end
+    end
+  end
+end