Add feature scenario for Newsletter admin section, including email zip download

spec/features/admin/newsletters_spec.rb

@@ -0,0 +1,22 @@
+require 'rails_helper'
+
+feature 'Admin newsletters emails' do
+
+  let(:download_button_text) { 'Download zip with users list' }
+
+  background do
+    @admin = create(:administrator)
+    login_as(@admin.user)
+    visit admin_newsletters_path
+  end
+
+  scenario 'Index' do
+    expect(page).to have_content download_button_text
+  end
+
+  scenario 'Download newsletter email zip' do
+    click_link download_button_text
+    expect( Zip::InputStream.open(StringIO.new(page.body)).get_next_entry.get_input_stream {|is| is.read } ).to include @admin.user.email
+  end
+end
+