Add e2e test for custom mr template

qa/qa/resource/merge_request.rb

@@ -19,7 +19,8 @@ module QA
                     :file_name,
                     :file_content
       attr_writer :no_preparation,
-                  :wait_for_merge
+                  :wait_for_merge,
+                  :template
 
       attribute :merge_when_pipeline_succeeds
       attribute :merge_status
@@ -73,7 +74,8 @@ module QA
         Page::Project::Show.perform(&:new_merge_request)
         Page::MergeRequest::New.perform do |new_page|
           new_page.fill_title(@title)
-          new_page.fill_description(@description)
+          new_page.choose_template(@template) if @template
+          new_page.fill_description(@description) unless @template
           new_page.choose_milestone(@milestone) if @milestone
           new_page.assign_to_me if @assignee == 'me'
           labels.each do |label|

qa/qa/specs/features/browser_ui/3_create/merge_request/create_merge_request_via_template_spec.rb

+# frozen_string_literal: true
+
+module QA
+  RSpec.describe 'Create' do
+    describe 'Merge request custom templates' do
+      let(:template_name) { 'custom_merge_request_template'}
+      let(:template_content) { 'This is a custom merge request template test' }
+      let(:template_project) do
+        Resource::Project.fabricate_via_api! do |project|
+          project.name = 'custom-mr-template-project'
+          project.initialize_with_readme = true
+        end
+      end
+
+      let(:merge_request_title) { 'One merge request to rule them all' }
+
+      before do
+        Flow::Login.sign_in
+
+        Resource::Repository::Commit.fabricate_via_api! do |commit|
+          commit.project = template_project
+          commit.commit_message = 'Add custom merge request template'
+          commit.add_files([
+            {
+              file_path: ".gitlab/merge_request_templates/#{template_name}.md",
+              content: template_content
+            }
+          ])
+        end
+      end
+
+      it 'creates a merge request via custom template', testcase: 'https://gitlab.com/gitlab-org/quality/testcases/-/issues/1230' do
+        Resource::MergeRequest.fabricate_via_browser_ui! do |merge_request|
+          merge_request.project = template_project
+          merge_request.title = merge_request_title
+          merge_request.template = template_name
+          merge_request.target_new_branch = false
+        end
+
+        Page::MergeRequest::Show.perform do |merge_request|
+          expect(merge_request).to have_title(merge_request_title)
+          expect(merge_request).to have_description(template_content)
+        end
+      end
+    end
+  end
+end