private static String clusterXmlWithNodeDistributionKey(int key) {
        return "<content version=\"1.0\" id=\"mockcluster\">" +
               "  <redundancy>1</redundancy>" +
               "  <documents/>" +
               "  <group>" +
               "    <node distribution-key=\"%d\" hostalias=\"mockhost\"/>".formatted(key) +
               "  </group>" +
               "</content>";
    }
Here there is no good choice.
config-model/src/test/java/com/yahoo/vespa/model/content/ContentClusterTest.java