add test

app/models/comment.rb

@@ -34,13 +34,13 @@ def self.counts_for(commentables)
   # @return [Hash] Hash of counts indexed by request_id
   #
   def self.counts_for_requests(requests) # rubocop:todo Metrics/AbcSize
-    all_commentables = requests.flat_map { |request| [request, request.try(:asset), request.try(:asset).try(:labware)] }
+    all_commentables = requests.flat_map { |request| [request, request.asset, request.asset&.labware] }
     counts = where(commentable: all_commentables.compact).group(:commentable_type, :commentable_id).count
 
     requests.each_with_object({}) do |request, counter_cache|
       request_count = counts.fetch(['Request', request.id], 0)
-      receptacle_count = counts.fetch(['Receptacle', request.try(:asset_id)], 0)
-      labware_count = counts.fetch(['Labware', request.try(:asset).try(:labware_id)], 0)
+      receptacle_count = counts.fetch(['Receptacle', request.asset_id], 0)
+      labware_count = counts.fetch(['Labware', request.asset&.labware_id], 0)
       counter_cache[request.id] = request_count + receptacle_count + labware_count
     end
   end

spec/models/comment_spec.rb

@@ -18,17 +18,29 @@
   end
 
   describe '#counts_for_requests' do
-    let(:request) { create :sequencing_request, asset: tube }
+    let(:request1) { create :sequencing_request, asset: tube }
     let(:tube) { create :multiplexed_library_tube }
 
-    before do
-      create :comment, commentable: tube, description: 'An excellent tube'
-      create :comment, commentable: tube.receptacle, description: 'A good receptacle'
-      create :comment, commentable: request, description: 'A reasonable request'
+    let(:request2) { create :sequencing_request }
+
+    context 'when request has asset' do
+      before do
+        create :comment, commentable: tube, description: 'An excellent tube'
+        create :comment, commentable: tube.receptacle, description: 'A good receptacle'
+        create :comment, commentable: request1, description: 'A reasonable request1'
+      end
+
+      it 'counts comments on requests, their assets and receptacles' do
+        expect(described_class.counts_for_requests([request1])).to eq({ request1.id => 3 })
+      end
     end
 
-    it 'counts comments on requests, their assets and receptacles' do
-      expect(described_class.counts_for_requests([request])).to eq({ request.id => 3 })
+    context 'when request has no asset' do
+      before { create :comment, commentable: request2, description: 'A reasonable request2' }
+
+      it 'counts comments on requests only' do
+        expect(described_class.counts_for_requests([request2])).to eq({ request2.id => 1 })
+      end
     end
   end