diff --git a/test/integration/default/controls/backend_spec.rb b/test/integration/default/controls/backend_spec.rb
index f27673a..0c8e4d9 100644
--- a/test/integration/default/controls/backend_spec.rb
+++ b/test/integration/default/controls/backend_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 describe package('nftables') do
   it { should be_installed }
 end
diff --git a/test/integration/default/controls/firewalld_spec.rb b/test/integration/default/controls/firewalld_spec.rb
index ef81e55..99b9861 100644
--- a/test/integration/default/controls/firewalld_spec.rb
+++ b/test/integration/default/controls/firewalld_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 describe package('firewalld') do
   it { should be_installed }
 end
diff --git a/test/integration/default/controls/ipset_spec.rb b/test/integration/default/controls/ipset_spec.rb
index 3a45f32..7ee5022 100644
--- a/test/integration/default/controls/ipset_spec.rb
+++ b/test/integration/default/controls/ipset_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 describe package('ipset') do
   it { should be_installed }
 end