### Question:
WlsDomainConfig implements WlsDomain { @Override @Nonnull public String[] getClusterNames() { return getClusterConfigs().keySet().toArray(new String[0]); } WlsDomainConfig();  WlsDomainConfig(String name);  WlsDomainConfig(
      String name,
      String adminServerName,
      Map<String, WlsClusterConfig> wlsClusterConfigs,
      Map<String, WlsServerConfig> wlsServerConfigs,
      Map<String, WlsServerConfig> wlsServerTemplates,
      Map<String, WlsMachineConfig> wlsMachineConfigs); static WlsDomainConfig create(String jsonResult); static String getRetrieveServersSearchUrl(); static String getRetrieveServersSearchPayload(); String getClusterName(String serverName); String getName(); String getAdminServerName(); void setAdminServerName(String adminServerName); synchronized Map<String, WlsClusterConfig> getClusterConfigs(); List<WlsClusterConfig> getConfiguredClusters(); void setConfiguredClusters(List<WlsClusterConfig> configuredClusters); synchronized Map<String, WlsServerConfig> getServerConfigs(); List<WlsServerConfig> getServers(); void setServers(List<WlsServerConfig> servers); List<WlsServerConfig> getServerTemplates(); void setServerTemplates(List<WlsServerConfig> serverTemplates); synchronized Map<String, WlsMachineConfig> getMachineConfigs(); synchronized WlsClusterConfig getClusterConfig(String clusterName); synchronized WlsServerConfig getServerConfig(String serverName); synchronized boolean containsCluster(String clusterName); synchronized boolean containsServer(String serverName); synchronized WlsMachineConfig getMachineConfig(String machineName); @Override @Nonnull String[] getClusterNames(); @Override int getReplicaLimit(String clusterName); WlsDomainConfig withAdminServer(String adminServerName, String listenAddress, int port); WlsDomainConfig addWlsServer(String name, String listenAddress, int port); WlsDomainConfig withCluster(WlsClusterConfig clusterConfig); Map<String, Object> toTopology(); @Override String toString(); @Override int hashCode(); @Override boolean equals(Object other); void processDynamicClusters();  }### Answer:
@Test public void whenTwoClustersDefined_returnBothNames() { WlsDomainConfigSupport support = new WlsDomainConfigSupport("test-domain"); support.addWlsCluster("cluster1", "ms1", "ms2", "ms3"); support.addWlsCluster("cluster2", "ms4", "ms5"); assertThat( support.createDomainConfig().getClusterNames(), arrayContainingInAnyOrder("cluster1", "cluster2")); }