Add specs to detect reindexing UI issues

ee/spec/controllers/admin/application_settings_controller_spec.rb

@@ -11,6 +11,26 @@ RSpec.describe Admin::ApplicationSettingsController do
     stub_env('IN_MEMORY_APPLICATION_SETTINGS', 'false')
   end
 
+  describe 'GET #general' do
+    before do
+      sign_in(admin)
+    end
+
+    context 'zero-downtime elasticsearch reindexing' do
+      render_views
+
+      let!(:task) { create(:elastic_reindexing_task) }
+
+      it 'assigns elasticsearch reindexing task' do
+        get :general
+
+        expect(assigns(:elasticsearch_reindexing_task)).to eq(task)
+        expect(response.body).to include('Reindexing status')
+        expect(response.body).to include("State: #{task.state}")
+      end
+    end
+  end
+
   describe 'PUT #update' do
     before do
       sign_in(admin)

ee/spec/views/admin/application_settings/_elasticsearch_form.html.haml_spec.rb

@@ -75,6 +75,56 @@ RSpec.describe 'admin/application_settings/_elasticsearch_form' do
     end
   end
 
+  context 'zero-downtime elasticsearch reindexing' do
+    let(:application_setting) { build(:application_setting) }
+
+    before do
+      assign(:elasticsearch_reindexing_task, task)
+    end
+
+    context 'without extended details' do
+      let(:task) { build(:elastic_reindexing_task) }
+
+      it 'renders the task' do
+        render
+
+        expect(rendered).to include("State: #{task.state}")
+        expect(rendered).not_to include("Task ID:")
+        expect(rendered).not_to include("Error:")
+        expect(rendered).not_to include("Expected documents:")
+        expect(rendered).not_to include("Documents reindexed:")
+      end
+    end
+
+    context 'with extended details' do
+      let(:task) { build(:elastic_reindexing_task, state: :reindexing, elastic_task: 'elastic-task-id', error_message: 'error-message', documents_count_target: 5, documents_count: 10) }
+
+      it 'renders the task' do
+        render
+
+        expect(rendered).to include("State: #{task.state}")
+        expect(rendered).to include("Task ID: #{task.elastic_task}")
+        expect(rendered).to include("Error: #{task.error_message}")
+        expect(rendered).to include("Expected documents: #{task.documents_count}")
+        expect(rendered).to include("Documents reindexed: #{task.documents_count_target} (50.0%)")
+      end
+    end
+
+    context 'with extended details, but without documents_count_target' do
+      let(:task) { build(:elastic_reindexing_task, state: :reindexing, elastic_task: 'elastic-task-id', documents_count: 10) }
+
+      it 'renders the task' do
+        render
+
+        expect(rendered).to include("State: #{task.state}")
+        expect(rendered).to include("Task ID: #{task.elastic_task}")
+        expect(rendered).to include("Expected documents: #{task.documents_count}")
+        expect(rendered).not_to include("Error:")
+        expect(rendered).not_to include("Documents reindexed:")
+      end
+    end
+  end
+
   context 'when there are elasticsearch indexed namespaces' do
     let(:application_setting) { build(:application_setting, elasticsearch_limit_indexing: true) }