fix(test): add tests on node_exporter service

test/integration/default/controls/service_spec.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+control 'prometheus services' do
+  title 'should be running'
+
+  describe service('node_exporter') do
+    it { should be_enabled }
+    it { should be_running }
+  end
+
+  # node_exporter port
+  describe port(9100) do
+    it { should be_listening }
+  end
+end