Poision the exhibit cache value when a document is updated

app/models/spotlight/solr_document_sidecar.rb

@@ -8,7 +8,8 @@ class SolrDocumentSidecar < ActiveRecord::Base
 
     acts_as_taggable
 
-    belongs_to :exhibit, optional: false
+    # The "touch: true" ensures the exhibit's cache is invalidated when the document is updated
+    belongs_to :exhibit, optional: false, touch: true
     belongs_to :resource, optional: true
     belongs_to :document, optional: false, polymorphic: true
     serialize :data, Hash

spec/models/spotlight/solr_document_sidecar_spec.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-describe Spotlight::SolrDocumentSidecar, type: :model do
+RSpec.describe Spotlight::SolrDocumentSidecar, type: :model do
   let(:exhibit) { FactoryBot.create(:exhibit) }
 
   before do
@@ -45,4 +45,15 @@
       its(:to_solr) { is_expected.to include 'a_multivalued_field_with_some_blanks' => ['a'] }
     end
   end
+
+  describe '#update' do
+    before do
+      subject.save
+    end
+
+    it 'poisions the exhibit cache' do
+      expect { subject.update(data: { 'a_tesim' => 1, 'b_tesim' => 2, 'c_tesim' => 3 }) }
+        .to(change { subject.exhibit.updated_at })
+    end
+  end
 end