Add spec test for sensitive regtoken parameter

spec/functions/register_to_file_spec.rb

@@ -59,6 +59,14 @@
 
       it { is_expected.to run.with_params(url, regtoken, runner_name, {}, nil, '/path/to/ca_file').and_return('Specified CA file doesn\'t exist, not attempting to create authtoken') }
     end
+
+    context 'with sensitive token value' do
+      before do
+        allow(PuppetX::Gitlab::Runner).to receive(:register).with(url, { 'token' => regtoken }, nil, '/tmp').and_return(return_hash)
+      end
+
+      it { is_expected.to run.with_params(url, sensitive(regtoken), runner_name, {}, nil, '/tmp').and_return(return_hash['token']) }
+    end
   end
 
   context 'noop does not register runner and returns dummy token' do