Include additional test case

spec/services/tables/discomfort_calculator_spec.rb

@@ -125,6 +125,20 @@ module Tables
           expect(calculator.send(:cohesion_penalty)).to eq(8)
         end
       end
+
+      context 'when the table contains six guests of three evenly split groups' do
+        let(:table) do
+          [
+            create_list(:guest, 2, affinity_group_list: ['family']),
+            create_list(:guest, 2, affinity_group_list: ['friends']),
+            create_list(:guest, 2, affinity_group_list: ['work'])
+          ].flatten
+        end
+
+        it 'returns the sum of the penalties for each pair of guests' do
+          expect(calculator.send(:cohesion_penalty)).to eq(4 * 1 + 4 * Rational(1, 2) + 4 * Rational(2, 3))
+        end
+      end
     end
   end
 end