Add feture spec for Merge Train

Adding feature spec

ee/spec/features/merge_trains/user_adds_merge_request_to_merge_train_spec.rb

+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe 'User adds a merge request to a merge train', :js do
+  let(:project) { create(:project, :repository) }
+  let(:user) { create(:user) }
+
+  let!(:merge_request) do
+    create(:merge_request, :with_merge_request_pipeline,
+      source_project: project, source_branch: 'feature',
+      target_project: project, target_branch: 'master')
+  end
+
+  let(:ci_yaml) do
+    { test: { stage: 'test', script: 'echo', only: ['merge_requests'] } }
+  end
+
+  before do
+    stub_licensed_features(merge_pipelines: true, merge_trains: true)
+    project.add_maintainer(user)
+    project.update!(merge_pipelines_enabled: true, merge_trains_enabled: true)
+    merge_request.all_pipelines.first.succeed!
+    merge_request.update_head_pipeline
+    stub_ci_pipeline_yaml_file(YAML.dump(ci_yaml))
+
+    sign_in(user)
+  end
+
+  it "shows 'Start merge train' button" do
+    visit project_merge_request_path(project, merge_request)
+
+    expect(page).to have_button('Start merge train')
+  end
+
+  context 'when merge_trains EEP license is not available' do
+    before do
+      stub_licensed_features(merge_trains: false)
+    end
+
+    it 'does not show Start merge train' do
+      visit project_merge_request_path(project, merge_request)
+
+      expect(page).not_to have_button('Start merge train')
+    end
+  end
+
+  context "when user clicks 'Start merge train' button" do
+    before do
+      visit project_merge_request_path(project, merge_request)
+      click_button 'Start merge train'
+      wait_for_requests
+    end
+
+    it 'informs merge request that auto merge is enabled' do
+      within('.mr-widget-section') do
+        expect(page).to have_content("Added to the merge train by #{user.name}")
+        expect(page).to have_content('The source branch will not be deleted')
+        expect(page).to have_link('Remove from merge train')
+        expect(page).to have_link('Delete source branch')
+      end
+    end
+
+    context "when user clicks 'Remove from merge train' button" do
+      before do
+        click_link 'Remove from merge train'
+      end
+
+      it 'cancels automatic merge' do
+        within('.mr-widget-section') do
+          expect(page).not_to have_content("Added to the merge train by #{user.name}")
+          expect(page).to have_button('Start merge train')
+        end
+      end
+    end
+
+    context "when user clicks 'Delete source branch" do
+      before do
+        click_link 'Delete source branch'
+      end
+
+      it 'updates the merge option' do
+        within('.mr-widget-section') do
+          expect(page).to have_content('The source branch will be deleted')
+        end
+      end
+    end
+  end
+
+  context 'when the merge request is not the first queue on the train' do
+    before do
+      create(:merge_request, :on_train,
+        source_project: project, source_branch: 'signed-commits',
+        target_project: project, target_branch: 'master')
+    end
+
+    it "shows 'Add to merge train' button" do
+      visit project_merge_request_path(project, merge_request)
+
+      expect(page).to have_button('Add to merge train')
+    end
+  end
+end

ee/spec/features/merge_trains/user_adds_to_merge_train_when_pipeline_succeeds_spec.rb

+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe 'User adds to merge train when pipeline succeeds', :js do
+  let(:project) { create(:project, :repository) }
+  let(:user) { create(:user) }
+
+  let!(:merge_request) do
+    create(:merge_request, :with_merge_request_pipeline,
+      source_project: project, source_branch: 'feature',
+      target_project: project, target_branch: 'master')
+  end
+
+  before do
+    stub_licensed_features(merge_pipelines: true, merge_trains: true)
+    project.add_maintainer(user)
+    project.update!(merge_pipelines_enabled: true, merge_trains_enabled: true)
+    merge_request.update_head_pipeline
+
+    sign_in(user)
+  end
+
+  it 'shows Start merge train when pipeline succeeds button' do
+    visit project_merge_request_path(project, merge_request)
+
+    expect(page).to have_button('Start merge train when pipeline succeeds')
+  end
+
+  context 'when merge_trains EEP license is not available' do
+    before do
+      stub_licensed_features(merge_trains: false)
+    end
+
+    it 'does not show Start merge train when pipeline succeeds button' do
+      visit project_merge_request_path(project, merge_request)
+
+      expect(page).not_to have_button('Start merge train when pipeline succeeds')
+    end
+  end
+
+  context "when user clicks 'Start merge train when pipeline succeeds' button" do
+    before do
+      visit project_merge_request_path(project, merge_request)
+      click_button 'Start merge train when pipeline succeeds'
+    end
+
+    it 'informs merge request that auto merge is enabled' do
+      within('.mr-widget-section') do
+        expect(page).to have_content("Set by #{user.name} to start a merge train when the pipeline succeeds")
+        expect(page).to have_content('The source branch will not be deleted')
+        expect(page).to have_link('Cancel automatic merge')
+        expect(page).to have_link('Delete source branch')
+      end
+    end
+
+    context "when user clicks 'Cancel automatic merge' button" do
+      before do
+        click_link 'Cancel automatic merge'
+      end
+
+      it 'cancels automatic merge' do
+        within('.mr-widget-section') do
+          expect(page).not_to have_content("Set by #{user.name} to start a merge train when the pipeline succeeds")
+          expect(page).to have_button('Start merge train when pipeline succeeds')
+        end
+      end
+    end
+
+    context "when user clicks 'Delete source branch" do
+      before do
+        click_link 'Delete source branch'
+      end
+
+      it 'updates the merge option' do
+        within('.mr-widget-section') do
+          expect(page).to have_content('The source branch will be deleted')
+        end
+      end
+    end
+  end
+
+  context 'when the merge request is not the first queue on the train' do
+    before do
+      create(:merge_request, :on_train,
+        source_project: project, source_branch: 'signed-commits',
+        target_project: project, target_branch: 'master')
+    end
+
+    it 'shows Add to merge train when pipeline succeeds button' do
+      visit project_merge_request_path(project, merge_request)
+
+      expect(page).to have_button('Add to merge train when pipeline succeeds')
+    end
+  end
+end