E2E discussion not dropping merge trains MR

(cherry picked from commit d20eef62)

qa/qa/specs/features/ee/browser_ui/4_verify/new_discussion_not_dropping_merge_trains_mr_spec.rb

+# frozen_string_literal: true
+
+require 'faker'
+
+module QA
+  RSpec.describe 'Verify', :docker, :runner do
+    describe 'In merge trains' do
+      context 'new thread discussions' do
+        let(:executor) { "qa-runner-#{Time.now.to_i}" }
+        let(:file_name) { 'custom_file.txt' }
+        let!(:runner) do
+          Resource::Runner.fabricate! do |runner|
+            runner.project = project
+            runner.name = executor
+            runner.tags = [executor]
+          end
+        end
+
+        let(:project) do
+          Resource::Project.fabricate_via_api! do |project|
+            project.name = 'pipeline-for-merge-trains'
+          end
+        end
+
+        let(:merge_request) do
+          Resource::MergeRequest.fabricate_via_api! do |merge_request|
+            merge_request.project = project
+            merge_request.description = Faker::Lorem.sentence
+            merge_request.target_new_branch = false
+            merge_request.file_name = file_name
+            merge_request.file_content = Faker::Lorem.sentence
+          end
+        end
+
+        before do
+          Flow::Login.sign_in
+          project.visit!
+
+          enable_merge_train
+          commit_ci_file
+
+          merge_request.visit!
+          Page::MergeRequest::Show.perform(&:try_to_merge!)
+          start_discussion
+        end
+
+        after do
+          runner.remove_via_api!
+        end
+
+        it 'do not drop MRs' do
+          # expect something magical here
+        end
+
+        private
+
+        def enable_merge_train
+          Page::Project::Menu.perform(&:go_to_general_settings)
+          Page::Project::Settings::Main.perform do |main|
+            main.expand_merge_requests_settings do |settings|
+              settings.click_pipelines_for_merged_results_checkbox
+              settings.click_save_changes
+            end
+          end
+        end
+
+        def commit_ci_file
+          Resource::Repository::Commit.fabricate_via_api! do |commit|
+            commit.project = project
+            commit.commit_message = 'Add .gitlab-ci.yml'
+            commit.add_files(
+              [
+                  {
+                      file_path: '.gitlab-ci.yml',
+                      content: <<~YAML
+                        test_merge_train:
+                          tags:
+                            - #{executor}
+                          script:
+                            - |
+                              sleep 5
+                              echo 'Yawn!'
+                          only:
+                            - merge_requests
+                      YAML
+                  }
+              ]
+            )
+          end
+        end
+
+        def start_discussion
+          Page::MergeRequest::Show.perform do |show|
+            show.click_discussions_tab
+            show.start_discussion(Faker::Lorem.sentence)
+          end
+        end
+      end
+    end
+  end
+end