E2E discussion not dropping merge trains MR

(cherry picked from commit d20eef6250476c217fd796b557f67559bb50059e)

app/views/projects/_merge_request_merge_checks_settings.html.haml

@@ -21,6 +21,6 @@
         .text-secondary
           = s_('ProjectSettings|This introduces the risk of merging changes that will not pass the pipeline.')
   .form-check.mb-2
-    = form.check_box :only_allow_merge_if_all_discussions_are_resolved, class: 'form-check-input'
+    = form.check_box :only_allow_merge_if_all_discussions_are_resolved, class: 'form-check-input', data: { qa_selector: 'allow_merge_if_all_discussions_are_resolved_checkbox' }
     = form.label :only_allow_merge_if_all_discussions_are_resolved, class: 'form-check-label' do
       = s_('ProjectSettings|All discussions must be resolved')

qa/qa/ee/page/project/settings/merge_request.rb

@@ -23,6 +23,11 @@ module QA
             def click_pipelines_for_merged_results_checkbox
               check_element :merged_results_pipeline_checkbox
             end
+
+            def enable_merge_train
+              click_pipelines_for_merged_results_checkbox
+              click_save_changes
+            end
           end
         end
       end

qa/qa/page/project/settings/merge_request.rb

@@ -15,6 +15,10 @@ module QA
             element :radio_button_merge_ff
           end
 
+          view 'app/views/projects/_merge_request_merge_checks_settings.html.haml' do
+            element :allow_merge_if_all_discussions_are_resolved_checkbox
+          end
+
           def click_save_changes
             click_element :save_merge_request_changes
           end
@@ -23,6 +27,11 @@ module QA
             click_element :radio_button_merge_ff
             click_save_changes
           end
+
+          def enable_merge_if_all_disscussions_are_resolved
+            click_element :allow_merge_if_all_discussions_are_resolved_checkbox
+            click_save_changes
+          end
         end
       end
     end

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 discussion' do
+        let(:executor) { "qa-runner-#{Faker::Alphanumeric.alphanumeric(8)}" }
+        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 = 'custom_file.txt'
+            merge_request.file_content = Faker::Lorem.sentence
+          end
+        end
+
+        before do
+          Flow::Login.sign_in
+          project.visit!
+
+          Page::Project::Menu.perform(&:go_to_general_settings)
+          Page::Project::Settings::Main.perform(&:expand_merge_requests_settings)
+          Page::Project::Settings::MergeRequest.perform do |setting|
+            setting.enable_merge_train
+            setting.enable_merge_if_all_disscussions_are_resolved
+          end
+
+          commit_ci_file
+
+          merge_request.visit!
+          Page::MergeRequest::Show.perform do |show|
+            show.has_pipeline_status?('passed')
+            show.try_to_merge!
+          end
+        end
+
+        after do
+          runner.remove_via_api!
+        end
+
+        it 'does not drop MR', testcase: 'https://gitlab.com/gitlab-org/quality/testcases/-/issues/1010' do
+          start_discussion
+
+          Page::MergeRequest::Show.perform do |show|
+            show.has_pipeline_status?('passed')
+            expect(show).to be_merged
+          end
+        end
+
+        private
+
+        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: echo 'OK!'
+                          only:
+                            - merge_requests
+                      YAML
+                  }
+              ]
+            )
+          end
+        end
+
+        def start_discussion
+          Page::MergeRequest::Show.perform do |show|
+            show.wait_until(reload: false) do
+              show.has_content? 'started a merge train'
+            end
+            show.click_discussions_tab
+            show.start_discussion(Faker::Lorem.sentence)
+          end
+        end
+      end
+    end
+  end
+end