1 files changed, 83 insertions, 0 deletions
diff --git a/spec/finders/resource_milestone_event_finder_spec.rb b/spec/finders/resource_milestone_event_finder_spec.rb
new file mode 100644
index 00000000000..ff4508996e2
--- /dev/null
+++ b/spec/finders/resource_milestone_event_finder_spec.rb
@@ -0,0 +1,83 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe ResourceMilestoneEventFinder do
+  let_it_be(:user) { create(:user) }
+  let_it_be(:issue_project) { create(:project) }
+  let_it_be(:issue) { create(:issue, project: issue_project) }
+
+  describe '#execute' do
+    subject { described_class.new(user, issue).execute }
+
+    it 'returns events with milestones accessible by user' do
+      milestone = create(:milestone, project: issue_project)
+      event = create_event(milestone)
+      issue_project.add_guest(user)
+
+      expect(subject).to eq [event]
+    end
+
+    it 'filters events with public project milestones if issues and MRs are private' do
+      project = create(:project, :public, :issues_private, :merge_requests_private)
+      milestone = create(:milestone, project: project)
+      create_event(milestone)
+
+      expect(subject).to be_empty
+    end
+
+    it 'filters events with project milestones not accessible by user' do
+      project = create(:project, :private)
+      milestone = create(:milestone, project: project)
+      create_event(milestone)
+
+      expect(subject).to be_empty
+    end
+
+    it 'filters events with group milestones not accessible by user' do
+      group = create(:group, :private)
+      milestone = create(:milestone, group: group)
+      create_event(milestone)
+
+      expect(subject).to be_empty
+    end
+
+    it 'paginates results' do
+      milestone = create(:milestone, project: issue_project)
+      create_event(milestone)
+      create_event(milestone)
+      issue_project.add_guest(user)
+
+      paginated = described_class.new(user, issue, per_page: 1).execute
+
+      expect(subject.count).to eq 2
+      expect(paginated.count).to eq 1
+    end
+
+    context 'when multiple events share the same milestone' do
+      it 'avoids N+1 queries' do
+        issue_project.add_developer(user)
+
+        milestone1 = create(:milestone, project: issue_project)
+        milestone2 = create(:milestone, project: issue_project)
+
+        control_count = ActiveRecord::QueryRecorder.new { described_class.new(user, issue).execute }.count
+        expect(control_count).to eq(1) # 1 events query
+
+        create_event(milestone1, :add)
+        create_event(milestone1, :remove)
+        create_event(milestone1, :add)
+        create_event(milestone1, :remove)
+        create_event(milestone2, :add)
+        create_event(milestone2, :remove)
+
+        # 1 events + 1 milestones + 1 project + 1 user + 4 ability
+        expect { described_class.new(user, issue).execute }.not_to exceed_query_limit(control_count + 7)
+      end
+    end
+
+    def create_event(milestone, action = :add)
+      create(:resource_milestone_event, issue: issue, milestone: milestone, action: action)
+    end
+  end
+end