style(test): improve Ruby style

test/integration/repo/controls/packages_spec.rb

@@ -1,23 +1,24 @@
 # frozen_string_literal: true
 
-case platform[:family]
-when 'redhat'
-  packages = %w[
-    prometheus2
-    alertmanager
-    node_exporter
-  ]
-when 'debian'
-  packages = %w[
-    prometheus
-    prometheus-alertmanager
-    prometheus-node-exporter
-  ]
-end
-
 control 'prometheus packages' do
   title 'should be installed'
 
+  packages =
+    case platform[:family]
+    when 'redhat'
+      %w[
+        prometheus2
+        alertmanager
+        node_exporter
+      ]
+    when 'debian'
+      %w[
+        prometheus
+        prometheus-alertmanager
+        prometheus-node-exporter
+      ]
+    end
+
   packages.each do |p|
     describe package(p) do
       it { should be_installed }