private String createProtonIndexedVespaServices(List<String> sdNames) {
        String pre = "<?xml version='1.0' encoding='utf-8' ?>" +
                "<services version='1.0'>" +
                "  <admin version='2.0'>" +
                "    <adminserver hostalias='node0'/>" +
                "  </admin>" +
                "  <container version='1.0'>" +
                "    <search/>" +
                "    <nodes>" +
                "      <node hostalias='node0'/>" +
                "    </nodes>" +
                "  </container>" +
                "  <content version='1.0' id='test'>" +
                "     <redundancy>1</redundancy>" +
                "     <engine>" +
                "        <proton>" +
                "           <visibility-delay>34</visibility-delay>" +
                "        </proton>" +
                "     </engine>" +
                "     <documents>";

        String post = "         </documents>" +
                "     <group>" +
                "       <node hostalias='node0' distribution-key='3' />" +
                "     </group>" +
                "</content>" +
                "</services>";
        return createVespaServices(pre, sdNames, post, "index");
    }
Test for using the content model to create indexed search clusters.
config-model/src/test/java/com/yahoo/vespa/model/content/IndexedTest.java