### Question:
ClusterRequest { @Override public String toString() { StringBuilder sb = new StringBuilder(); sb.append("{" + " clusterName=").append(clusterName) .append(", clusterId=").append(clusterId) .append(", provisioningState=").append(provisioningState) .append(", securityType=").append(securityType) .append(", stackVersion=").append(stackVersion) .append(", desired_scv=").append(serviceConfigVersionRequest) .append(", hosts=[") .append(hostNames != null ? String.join(",", hostNames) : StringUtils.EMPTY) .append("] }"); return sb.toString(); } ClusterRequest(Long clusterId, String clusterName,
      String stackVersion, Set<String> hostNames);  ClusterRequest(Long clusterId, String clusterName,
      String provisioningState, SecurityType securityType, String stackVersion, Set<String> hostNames);  ClusterRequest(Long clusterId, String clusterName,
                        String provisioningState, SecurityType securityType, String stackVersion,
                        Set<String> hostNames, Map<String, Object> sessionAttributes); @ApiModelProperty(name = ClusterResourceProvider.CLUSTER_ID) Long getClusterId(); @ApiModelProperty(name = ClusterResourceProvider.CLUSTER_NAME) String getClusterName(); @ApiModelProperty(name = ClusterResourceProvider.PROVISIONING_STATE) String getProvisioningState(); @ApiModelProperty(name = ClusterResourceProvider.SECURITY_TYPE) SecurityType getSecurityType(); @ApiModelProperty(name = ClusterResourceProvider.VERSION) String getStackVersion(); @ApiModelProperty(hidden = true) Set<String> getHostNames(); void setDesiredConfig(List<ConfigurationRequest> configRequests); @ApiModelProperty(name = ClusterResourceProvider.DESIRED_CONFIGS) List<ConfigurationRequest> getDesiredConfig(); @Override String toString(); @ApiModelProperty(name = ClusterResourceProvider.DESIRED_SERVICE_CONFIG_VERSIONS) ServiceConfigVersionRequest getServiceConfigVersionRequest(); @ApiModelProperty(hidden = true) Map<String, Object> getSessionAttributes(); void setServiceConfigVersionRequest(ServiceConfigVersionRequest serviceConfigVersionRequest);  }### Answer:
@Test public void testToString() { ClusterRequest r1 = new ClusterRequest(null, null, null, null, null, null); r1.toString(); }