1 files changed, 64 insertions, 0 deletions
diff --git a/spec/requests/projects/merge_requests_controller_spec.rb b/spec/requests/projects/merge_requests_controller_spec.rb
index 3b1ce569033..6580fc8b80f 100644
--- a/spec/requests/projects/merge_requests_controller_spec.rb
+++ b/spec/requests/projects/merge_requests_controller_spec.rb
@@ -3,6 +3,70 @@
 require 'spec_helper'
 
 RSpec.describe Projects::MergeRequestsController do
+  describe 'GET #discussions' do
+    let_it_be(:merge_request) { create(:merge_request) }
+    let_it_be(:project) { merge_request.project }
+    let_it_be(:user) { merge_request.author }
+    let_it_be(:discussion) { create(:discussion_note_on_merge_request, noteable: merge_request, project: project) }
+    let_it_be(:discussion_reply) { create(:discussion_note_on_merge_request, noteable: merge_request, project: project, in_reply_to: discussion) }
+    let_it_be(:state_event) { create(:resource_state_event, merge_request: merge_request) }
+    let_it_be(:discussion_2) { create(:discussion_note_on_merge_request, noteable: merge_request, project: project) }
+    let_it_be(:discussion_3) { create(:diff_note_on_merge_request, noteable: merge_request, project: project) }
+
+    before do
+      login_as(user)
+    end
+
+    context 'pagination' do
+      def get_discussions(**params)
+        get discussions_project_merge_request_path(project, merge_request, params: params.merge(format: :json))
+      end
+
+      it 'returns paginated notes and cursor based on per_page param' do
+        get_discussions(per_page: 2)
+
+        discussions = Gitlab::Json.parse(response.body)
+        notes = discussions.flat_map { |d| d['notes'] }
+
+        expect(discussions.count).to eq(2)
+        expect(notes).to match([
+          a_hash_including('id' => discussion.id.to_s),
+          a_hash_including('id' => discussion_reply.id.to_s),
+          a_hash_including('type' => 'StateNote')
+        ])
+
+        cursor = response.header['X-Next-Page-Cursor']
+        expect(cursor).to be_present
+
+        get_discussions(per_page: 1, cursor: cursor)
+
+        discussions = Gitlab::Json.parse(response.body)
+        notes = discussions.flat_map { |d| d['notes'] }
+
+        expect(discussions.count).to eq(1)
+        expect(notes).to match([
+          a_hash_including('id' => discussion_2.id.to_s)
+        ])
+      end
+
+      context 'when paginated_mr_discussions is disabled' do
+        before do
+          stub_feature_flags(paginated_mr_discussions: false)
+        end
+
+        it 'returns all discussions and ignores per_page param' do
+          get_discussions(per_page: 2)
+
+          discussions = Gitlab::Json.parse(response.body)
+          notes = discussions.flat_map { |d| d['notes'] }
+
+          expect(discussions.count).to eq(4)
+          expect(notes.count).to eq(5)
+        end
+      end
+    end
+  end
+
   context 'token authentication' do
     context 'when public project' do
       let_it_be(:public_project) { create(:project, :public) }