diff --git a/spec/mailers/notify_spec.rb b/spec/mailers/notify_spec.rb
index 978118ed1b17aff6f083c29495598eca56baae46..8b564841cffb15fa5709fd82c89330cd2c7d2de3 100644
--- a/spec/mailers/notify_spec.rb
+++ b/spec/mailers/notify_spec.rb
@@ -2072,6 +2072,10 @@ def invite_to_group(group, inviter:, user: nil, tasks_to_be_done: [])
           )
         end
       end
+
+      it 'includes only one link to the highlighted_diff_email' do
+          expect(subject.html_part.body.raw_source).to include('assets/mailers/highlighted_diff_email').once
+      end
     end
 
     it 'contains review author name' do