add spec tests

spec/defines/instance_spec.rb

@@ -49,6 +49,22 @@ class { 'redis':
 
         it { is_expected.to contain_service('redis-server-app2.service').with_ensure(true).with_enable(true) }
       end
+
+      context 'with custom options' do
+        let(:title) { 'default' }
+        let :params do {
+          config_file_orig: '/tmp/myorig.conf',
+          custom_options: { 'myoption' => 'avalue', 'anotheroption' => 'anothervalue' },
+        }
+        end
+
+        it {
+          is_expected.to contain_file('/tmp/myorig.conf')
+            .with_content(%r{^bind 127.0.0.1})
+            .with_content(%r{^myoption avalue})
+            .with_content(%r{^anotheroption anothervalue})
+        }
+      end
     end
   end
 end