Add a spec for concurrent process

spec/features/merge_requests/pipelines_spec.rb

 require 'spec_helper'
 
 feature 'Pipelines for Merge Requests', js: true do
+  describe 'pipeline tab' do
     given(:user) { create(:user) }
     given(:merge_request) { create(:merge_request) }
     given(:project) { merge_request.target_project }
@@ -28,7 +29,7 @@ feature 'Pipelines for Merge Requests', js: true do
         end
         wait_for_requests
 
-      expect(page).to have_selector('.stage-cell')
+        expect(page).to have_selector('.sssssssss')
       end
     end
 
@@ -43,4 +44,44 @@ feature 'Pipelines for Merge Requests', js: true do
         end
       end
     end
+  end
+
+  describe 'race condition' do
+    given(:project) { create(:project, :repository) }
+    given(:user) { create(:user) }
+    given(:build_push_data) { { ref: 'feature', checkout_sha: TestEnv::BRANCH_SHA['feature'] } }
+
+    given(:merge_request_params) do
+       { "source_branch" => "feature", "source_project_id" => project.id,
+         "target_branch" => "master", "target_project_id" => project.id, "title" => "A" }
+    end
+
+    background do
+      project.add_master(user)
+      sign_in user
+    end
+
+    context 'when pipeline and merge request were created simultaneously' do
+      background do
+        stub_ci_pipeline_to_return_yaml_file
+
+        threads = []
+        threads << Thread.new do
+          @merge_request = MergeRequests::CreateService.new(project, user, merge_request_params).execute
+        end
+
+        threads << Thread.new do
+          @pipeline = Ci::CreatePipelineService.new(project, user, build_push_data).execute(:push)
+        end
+
+        threads.each { |thr| thr.join }
+      end
+
+      scenario 'user sees pipeline in merge request widget' do
+        visit project_merge_request_path(project, @merge_request)
+        expect(page.find(".ci-widget")).to have_content(TestEnv::BRANCH_SHA['feature'])
+        expect(page.find(".ci-widget")).to have_content("##{@pipeline.id}")
+      end
+    end
+  end
 end