public static String appendSuffix(String serviceName, String serviceNameSuffix) {
    if (serviceNameSuffix == null) throw new NullPointerException("serviceNameSuffix == null");
    if (serviceNameSuffix.isEmpty()) return serviceName;
    return serviceName + "_" + serviceNameSuffix;
  }
Reuse a builder as it is significantly slows tests to create 100000 of these!
zipkin/src/test/java/zipkin2/TestObjects.java