1 files changed, 57 insertions, 8 deletions

diff --git a/spec/serializers/member_serializer_spec.rb b/spec/serializers/member_serializer_spec.rb
index af209c0191f..f7415214e95 100644
--- a/spec/serializers/member_serializer_spec.rb
+++ b/spec/serializers/member_serializer_spec.rb
@@ -7,28 +7,77 @@ RSpec.describe MemberSerializer do
 
   let_it_be(:current_user) { create(:user) }
 
-  subject { described_class.new.represent(members, { current_user: current_user, group: group, source: source }) }
+  subject(:representation) do
+    described_class.new.represent(members, { current_user: current_user, group: group, source: source }).to_json
+  end
 
   shared_examples 'members.json' do
-    it 'matches json schema' do
-      expect(subject.to_json).to match_schema('members')
-    end
+    it { is_expected.to match_schema('members') }
   end
 
   context 'group member' do
-    let(:group) { create(:group) }
+    let_it_be(:group) { create(:group) }
+    let_it_be(:members) { present_members(create_list(:group_member, 1, group: group)) }
+
     let(:source) { group }
-    let(:members) { present_members(create_list(:group_member, 1, group: group)) }
 
     it_behaves_like 'members.json'
+
+    it 'handles last group owner assignment' do
+      group_member = members.last
+
+      expect { representation }.to change(group_member, :last_owner)
+                                     .from(nil).to(true)
+                                     .and change(group_member, :last_blocked_owner).from(nil).to(false)
+    end
+
+    context "with LastGroupOwnerAssigner query improvements" do
+      it "avoids N+1 database queries for last group owner assignment in MembersPresenter" do
+        group_member = create(:group_member, group: group)
+        control_count = ActiveRecord::QueryRecorder.new { member_last_owner_with_preload([group_member]) }.count
+        group_members = create_list(:group_member, 3, group: group)
+
+        expect { member_last_owner_with_preload(group_members) }.not_to exceed_query_limit(control_count)
+      end
+
+      it "avoids N+1 database queries for last blocked owner assignment in MembersPresenter" do
+        group_member = create(:group_member, group: group)
+        control_count = ActiveRecord::QueryRecorder.new { member_last_blocked_owner_with_preload([group_member]) }.count
+        group_members = create_list(:group_member, 3, group: group)
+
+        expect { member_last_blocked_owner_with_preload(group_members) }.not_to exceed_query_limit(control_count)
+      end
+
+      def member_last_owner_with_preload(members)
+        assigner_with_preload(members)
+        members.map { |m| group.member_last_owner?(m) }
+      end
+
+      def member_last_blocked_owner_with_preload(members)
+        assigner_with_preload(members)
+        members.map { |m| group.member_last_blocked_owner?(m) }
+      end
+
+      def assigner_with_preload(members)
+        MembersPreloader.new(members).preload_all
+        Members::LastGroupOwnerAssigner.new(group, members).execute
+      end
+    end
   end
 
   context 'project member' do
-    let(:project) { create(:project) }
+    let_it_be(:project) { create(:project) }
+    let_it_be(:members) { present_members(create_list(:project_member, 1, project: project)) }
+
     let(:source) { project }
     let(:group) { project.group }
-    let(:members) { present_members(create_list(:project_member, 1, project: project)) }
 
     it_behaves_like 'members.json'
+
+    it 'does not invoke group owner assignment' do
+      expect(Members::LastGroupOwnerAssigner).not_to receive(:new)
+
+      representation
+    end
   end
 end