diff --git a/test/integration/default/controls/config_spec.rb b/test/integration/default/controls/config_spec.rb
index 0131bb4..bfe12b5 100644
--- a/test/integration/default/controls/config_spec.rb
+++ b/test/integration/default/controls/config_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 control 'Vsftpd configuration' do
   title 'should match desired lines'
 
diff --git a/test/integration/default/controls/package_spec.rb b/test/integration/default/controls/package_spec.rb
index a424660..70e7121 100644
--- a/test/integration/default/controls/package_spec.rb
+++ b/test/integration/default/controls/package_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 control 'Vsftpd package' do
   title 'should be installed'
 
diff --git a/test/integration/default/controls/service_spec.rb b/test/integration/default/controls/service_spec.rb
index bd957d1..e6bd956 100644
--- a/test/integration/default/controls/service_spec.rb
+++ b/test/integration/default/controls/service_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 control 'Vsftpd service' do
   title 'should be running and enabled'